INOVIO PHARMACEUTICALS, INC., 10-K filed on 3/6/2024
Annual Report
v3.24.0.1
Cover Page - USD ($)
$ in Millions
 12 Months Ended
Dec. 31, 2023
Mar. 01, 2024
Jun. 30, 2023
Cover [Abstract]      
Document Type 10-K    
Document Annual Report true    
Document Period End Date Dec. 31, 2023    
Current Fiscal Year End Date --12-31    
Document Transition Report false    
Entity File Number 001-14888    
Entity Registrant Name INOVIO PHARMACEUTICALS, INC.    
Entity Incorporation, State or Country Code DE    
Entity Tax Identification Number 33-0969592    
Entity Address, Address Line One 660 W. Germantown Pike    
Entity Address, Address Line Two Suite 110    
Entity Address, City or Town Plymouth Meeting    
Entity Address, State or Province PA    
Entity Address, Postal Zip Code 19462    
City Area Code 267    
Local Phone Number 440-4200    
Title of 12(b) Security COMMON STOCK, $0.001 PAR VALUE    
Trading Symbol INO    
Security Exchange Name NASDAQ    
Entity Well-known Seasoned Issuer No    
Entity Voluntary Filers No    
Entity Current Reporting Status Yes    
Entity Interactive Data Current Yes    
Entity Filer Category Non-accelerated Filer    
Entity Small Business true    
Entity Emerging Growth Company false    
ICFR Auditor Attestation Flag false    
Document Financial Statement Error Correction false    
Entity Shell Company false    
Entity Public Float     $ 119.7
Entity Common Stock, Shares Outstanding   23,370,365  
Documents Incorporated by Reference
DOCUMENTS INCORPORATED BY REFERENCE
Portions of the registrant’s definitive proxy statement to be filed with the Commission pursuant to Regulation 14A in connection with the registrant’s 2024 Annual Meeting of Stockholders (the “Proxy Statement’) are incorporated by reference into Part III of this Report. Such Proxy Statement will be filed with the Commission not later than 120 days after the conclusion of the registrant’s fiscal year ended December 31, 2023.
    
Amendment Flag false    
Document Fiscal Year Focus 2023    
Document Fiscal Period Focus FY    
Entity Central Index Key 0001055726    
v3.24.0.1
Audit Information
 12 Months Ended
Dec. 31, 2023
Audit Information [Abstract]  
Auditor Location San Diego, California
Auditor Name Ernst & Young LLP
Auditor Firm ID 42
v3.24.0.1
Consolidated Balance Sheets - USD ($)
Dec. 31, 2023
Dec. 31, 2022
Current assets:    
Cash and cash equivalents $ 14,310,862 $ 46,329,359
Short-term investments 130,982,913 206,669,397
Prepaid expenses and other current assets 5,393,665 50,130,481
Prepaid expenses and other current assets from affiliated entities 20,432 375,227
Total current assets 153,113,100 315,242,680
Fixed assets, net 4,960,986 7,727,997
Investments in affiliated entity 2,780,287 2,007,142
Intangible assets, net 0 2,129,861
Goodwill 0 10,513,371
Operating lease right-of-use assets 9,491,735 10,228,207
Other assets 605,315 684,044
Total assets 170,951,423 348,533,302
Current liabilities:    
Accrued clinical trial expenses 2,365,382 10,594,073
Operating lease liability 2,406,522 2,803,973
Grant funding liability 87,489 2,475,031
Grant funding liability from affiliated entities 21,918 87,673
Convertible senior notes 16,770,654 0
Total current liabilities 42,570,228 96,868,074
Convertible senior notes 0 16,614,840
Operating lease liability, net of current portion 11,032,066 12,655,586
Deferred tax liabilities 0 32,046
Total liabilities 53,602,294 126,170,546
Commitments and contingencies
Inovio Pharmaceuticals, Inc. stockholders’ equity:    
Preferred stock—par value $0.001; Authorized shares: 10,000,000, issued and outstanding shares: 9 at December 31, 2023 and 2022 0 0
Common stock—par value $0.001; Authorized shares: 600,000,000 at December 31, 2023 and 2022, issued and outstanding: 22,793,075 at December 31, 2023 and 21,090,938 at December 31, 2022 [1] 22,792 21,090
Additional paid-in capital 1,740,954,074 1,710,888,191
Accumulated deficit (1,622,965,136) (1,487,847,784)
Accumulated other comprehensive loss (662,601) (698,741)
Total Inovio Pharmaceuticals, Inc. stockholders’ equity 117,349,129 222,362,756
Total liabilities and stockholders’ equity 170,951,423 348,533,302
Nonrelated Party    
Current assets:    
Accounts receivable 0 1,701,726
Current liabilities:    
Accounts payable and accrued expenses 19,847,744 79,686,885
Related Party    
Current assets:    
Accounts receivable 2,405,228 10,036,490
Current liabilities:    
Accounts payable and accrued expenses $ 1,070,519 $ 1,220,439
[1]
(1) The Company effected a reverse stock split of its outstanding shares of common stock on January 24, 2024 where every twelve shares of its common stock issued and outstanding was converted into one share of common stock. Any fractional post-split shares as a result of the reverse split were paid in cash. Shareholders of the Company authorized the Board of Directors to approve the reverse stock split at a special meeting of stockholders held on January 12, 2024. Outstanding share amounts have been restated to reflect the reverse stock split on a retroactive basis for all periods presented.
v3.24.0.1
Consolidated Balance Sheets (Parenthetical)
Dec. 31, 2023
$ / shares
shares
Dec. 31, 2022
$ / shares
shares
Statement of Financial Position [Abstract]    
Preferred stock, par value (in dollars per share) | $ / shares $ 0.001 $ 0.001
Preferred stock, shares authorized (in shares) 10,000,000 10,000,000
Preferred stock, shares issued (in shares) 9 9
Preferred stock, shares outstanding (in shares) 9 9
Common stock, par value (in USD per share) | $ / shares [1] $ 0.001 $ 0.001
Common stock, shares authorized (in shares) [1] 600,000,000 600,000,000
Common stock, shares issued (in shares) [1] 22,793,075 21,090,938
Common stock, shares outstanding (in shares) [1] 22,793,075 21,090,938
[1]
(1) The Company effected a reverse stock split of its outstanding shares of common stock on January 24, 2024 where every twelve shares of its common stock issued and outstanding was converted into one share of common stock. Any fractional post-split shares as a result of the reverse split were paid in cash. Shareholders of the Company authorized the Board of Directors to approve the reverse stock split at a special meeting of stockholders held on January 12, 2024. Outstanding share amounts have been restated to reflect the reverse stock split on a retroactive basis for all periods presented.
v3.24.0.1
Consolidated Statements of Operations - USD ($)
 12 Months Ended
Dec. 31, 2023
Dec. 31, 2022
Dec. 31, 2021
Revenues [Abstract]      
Revenue from collaborative arrangements and other contracts, including affiliated entity $ 832,010 $ 10,262,268 $ 1,774,758
Operating expenses:      
Research and development 86,676,563 187,650,503 249,240,324
General and administrative 47,582,104 90,185,285 53,752,353
Impairment of goodwill 10,513,371 0 0
Total operating expenses 144,772,038 277,835,788 302,992,677
Loss from operations (143,940,028) (267,573,520) (301,217,919)
Other income (expense):      
Interest income 8,133,290 4,782,030 3,363,080
Interest expense (1,222,789) (1,253,952) (1,936,447)
Gain (loss) on investment in affiliated entity 773,145 (1,899,654) (553,570)
Net unrealized gain (loss) on available-for-sale equity securities 5,850,626 (7,846,172) (3,222,838)
Other (expense) income, net (4,711,596) (3,861,584) 343,371
Net loss before share in net loss of Geneos (135,117,352) (277,652,852) (303,224,323)
Share in net loss of Geneos 0 (2,165,213) (434,387)
Net loss $ (135,117,352) $ (279,818,065) $ (303,658,710)
Net loss per share      
Basic (in dollars per share) [1] $ (6.09) $ (14.07) $ (17.45)
Diluted (in dollars per share) [1] $ (6.09) $ (14.07) $ (17.45)
Weighted average number of common shares outstanding      
Basic (in shares) [1] 22,173,662 19,885,182 17,402,483
Diluted (in shares) [1] 22,173,662 19,885,182 17,402,483
[1]
(1) Share and per share amounts have been restated to reflect the 1-for-12 reverse stock split effected in January 2024 on a retroactive basis for all periods presented.
v3.24.0.1
Consolidated Statements of Operations (Parenthetical)
Jan. 24, 2024
Subsequent Event  
Stock split, conversion ratio 0.083333
v3.24.0.1
Consolidated Statements of Comprehensive Loss - USD ($)
 12 Months Ended
Dec. 31, 2023
Dec. 31, 2022
Dec. 31, 2021
Statement of Comprehensive Income [Abstract]      
Net loss $ (135,117,352) $ (279,818,065) $ (303,658,710)
Other comprehensive loss:      
Foreign currency translation (3,920) (25,556) (30,134)
Unrealized (loss) gain on short-term investments, net of tax 40,060 (390,949) 4,048
Comprehensive loss attributable to Inovio Pharmaceuticals, Inc. $ (135,081,212) $ (280,234,570) $ (303,684,796)
v3.24.0.1
Consolidated Statements of Stockholders' Equity - USD ($)
Total
Adjustment
Preferred stock
Common stock
Additional paid-in capital
Additional paid-in capital
Adjustment
Accumulated deficit
Accumulated deficit
Adjustment
Accumulated other comprehensive loss
Beginning balance (in shares) at Dec. 31, 2020     9 15,570,957 [1]          
Beginning balance at Dec. 31, 2020 $ 461,140,758   $ 0 $ 15,571 [1] $ 1,367,578,149   $ (906,196,812)   $ (256,150)
Increase (Decrease) in Stockholders' Equity [Roll Forward]                  
Issuance of common stock for cash, net of financing costs (in shares) [1]       2,275,861          
Issuance of common stock for cash, net of financing costs 209,441,410     $ 2,276 [1] 209,439,134        
Conversion of preferred stock/senior notes to common stock (in shares) [1]       84,120          
Conversion of preferred stock/senior notes to common stock 4,377,892     $ 84 [1] 4,377,808        
Exercise of stock options and warrants for cash and vesting of RSUs, net of tax payments (in shares) [1]       184,299          
Exercise of stock options for cash and vesting of RSUs, net of tax payments 2,057,393     $ 184 [1] 2,057,209        
Stock-based compensation 26,336,764       26,336,764        
Net loss (303,658,710)           (303,658,710)    
Unrealized gain (loss) on short-term investments, net of tax 4,048               4,048
Foreign currency translation (30,134)               (30,134)
Ending balance at Dec. 31, 2021 399,669,421 $ (1,468,216) $ 0 $ 18,115 [1] 1,609,789,064 $ (3,294,019) (1,209,855,522) $ 1,825,803 (282,236)
Ending balance (in shares) at Dec. 31, 2021     9 18,115,237 [1]          
Increase (Decrease) in Stockholders' Equity [Roll Forward]                  
Issuance of common stock for cash, net of financing costs (in shares) [1]       2,870,478          
Issuance of common stock for cash, net of financing costs 82,955,311     $ 2,870 [1] 82,952,441        
Exercise of stock options and warrants for cash and vesting of RSUs, net of tax payments (in shares) [1]       105,223          
Exercise of stock options for cash and vesting of RSUs, net of tax payments (1,114,609)     $ 105 [1] (1,114,714)        
Stock-based compensation 22,555,419       22,555,419        
Net loss (279,818,065)           (279,818,065)    
Unrealized gain (loss) on short-term investments, net of tax (390,949)               (390,949)
Foreign currency translation (25,556)               (25,556)
Ending balance at Dec. 31, 2022 222,362,756   $ 0 $ 21,090 [1] 1,710,888,191   (1,487,847,784)   (698,741)
Ending balance (in shares) at Dec. 31, 2022     9 21,090,938 [1]          
Increase (Decrease) in Stockholders' Equity [Roll Forward]                  
Issuance of common stock for legal settlement (in shares) [1]       760,083          
Issuance of common stock for legal settlement 14,000,000     $ 760 [1] 13,999,240        
Issuance of common stock for cash, net of financing costs (in shares) [1]       875,305          
Issuance of common stock for cash, net of financing costs 5,461,745     $ 875 [1] 5,460,870        
Exercise of stock options and warrants for cash and vesting of RSUs, net of tax payments (in shares) [1]       66,749          
Exercise of stock options for cash and vesting of RSUs, net of tax payments (466,646)     $ 67 [1] (466,713)        
Stock-based compensation 11,072,486       11,072,486        
Net loss (135,117,352)           (135,117,352)    
Unrealized gain (loss) on short-term investments, net of tax 40,060               40,060
Foreign currency translation (3,920)               (3,920)
Ending balance at Dec. 31, 2023 $ 117,349,129   $ 0 $ 22,792 [1] $ 1,740,954,074   $ (1,622,965,136)   $ (662,601)
Ending balance (in shares) at Dec. 31, 2023     9 22,793,075 [1]          
[1]
(1) All share amounts in this column, including appropriate reclassifications between common stock and additional paid-in capital, have been restated to reflect the 1-for-12 reverse stock split effected in January 2024 on a retroactive basis for all periods presented.
v3.24.0.1
Consolidated Statements of Stockholders' Equity (Parenthetical)
 12 Months Ended
Dec. 31, 2021
Statement of Stockholders' Equity [Abstract]  
Accounting Standards Update [Extensible Enumeration] Accounting Standards Update 2020-06
v3.24.0.1
Consolidated Statements of Cash Flows - USD ($)
 12 Months Ended
Dec. 31, 2023
Dec. 31, 2022
Dec. 31, 2021
Cash flows from operating activities:      
Net loss $ (135,117,352) $ (279,818,065) $ (303,658,710)
Adjustments to reconcile net loss to net cash used in operating activities:      
Depreciation 2,621,649 3,656,713 3,040,096
Amortization of intangible assets 145,417 496,494 520,415
Amortization of operating lease right-of-use assets 736,472 1,342,819 1,170,270
Impairment of goodwill 10,513,371 0 0
Impairment of intangible assets 1,984,444 0 0
Deferred taxes (32,046) 0 0
Non-cash stock-based compensation 11,072,486 22,555,419 26,336,764
Non-cash interest on senior convertible notes 155,814 186,977 858,644
Amortization of (discounts) premiums on investments (4,686,144) (1,320,546) 1,633,286
Realized loss on sales of short-term investments 4,805,804 4,029,961 5,397
Gain on remeasurement of investment in Geneos 0 (165,215) 0
Net loss on disposal of fixed assets 317,997 1,074,830 0
(Gain) loss on equity investment in affiliated entity (773,145) 1,899,654 553,570
Share of net loss in Geneos 0 2,165,213 434,387
Net unrealized (gain) loss on available-for-sale equity securities (5,850,626) 7,846,172 3,222,838
Unrealized transaction (gain) loss on foreign-currency denominated debt 0 0 (176,927)
Changes in operating assets and liabilities:      
Accounts receivable, including from affiliated entities 9,332,988 (3,706,172) 11,031,705
Prepaid expenses and other current assets, including from affiliated entities 39,020,611 (5,336,525) (6,343,632)
Other assets 78,729 741,750 24,531,654
Accounts payable and accrued expenses, including due to affiliated entities (45,989,061) 32,606,581 26,140,970
Accrued clinical trial expenses (8,228,691) 267,807 375,921
Deferred revenue, including from affiliated entity 0 (85,989) (39,853)
Operating lease right-of-use assets and liabilities, net (2,020,971) (2,603,956) (2,329,394)
Grant funding liability, including from affiliated entity (2,453,297) (2,034,517) (2,973,089)
Other liabilities 0 (14,826) (42,837)
Net cash used in operating activities (124,365,551) (216,215,421) (215,708,525)
Cash flows from investing activities:      
Purchases of investments (203,475,052) (248,528,843) (348,953,236)
Proceeds from sale or maturity of investments 284,932,562 361,083,850 174,839,758
Purchases of capital assets (320,898) (969,153) (1,231,006)
Proceeds from sale of capital assets 6,219,263 0 0
Investment in Geneos 0 (1,999,998) 0
Net cash provided by (used in) investing activities 87,355,875 109,585,856 (175,344,484)
Cash flows from financing activities:      
Proceeds from issuance of common stock, net of issuance costs 5,461,745 82,955,311 209,441,410
Proceeds from stock option exercises 0 283,022 6,668,741
Taxes paid related to net share settlement of equity awards (466,646) (1,397,631) (4,611,348)
Net cash provided by financing activities 4,995,099 81,840,702 211,498,803
Effect of exchange rate changes on cash and cash equivalents (3,920) (25,556) (30,134)
Decrease in cash and cash equivalents (32,018,497) (24,814,419) (179,584,340)
Cash and cash equivalents, beginning of period 46,329,359 71,143,778 250,728,118
Cash and cash equivalents, end of period 14,310,862 46,329,359 71,143,778
Supplemental disclosure:      
Amounts accrued for purchases of fixed assets 0 108,181 204,815
Interest paid 1,066,975 1,066,975 1,077,803
Change in prepaid expenses and other current assets related to fixed assets 0 6,071,000 7,709,337
Issuance of common stock as part of litigation settlement $ 14,000,000 $ 0 $ 0
v3.24.0.1
The Company
 12 Months Ended
Dec. 31, 2023
Organization, Consolidation and Presentation of Financial Statements [Abstract]  
The Company The Company
Inovio Pharmaceuticals, Inc. (the “Company” or “INOVIO”) is a clinical-stage biotechnology company focused on developing and commercializing DNA medicines to help treat and protect people from diseases associated with human papillomavirus (HPV), cancer, and infectious diseases. INOVIO's platform harnesses the power of in vivo protein production, featuring optimized design and delivery of DNA medicines that teach the body to manufacture its own disease-fighting tools.
INOVIO uses proprietary technology to design DNA plasmids, which are small circular DNA molecules that work like software the body’s cells can download to produce specific proteins to target and fight disease. The Company's proprietary investigational CELLECTRA® delivery devices help its DNA medicines enter the body’s cells for optimal effect.
INOVIO's lead candidate is INO-3107 for the treatment of recurrent respiratory papillomatosis (RRP), a rare and debilitating disease of the respiratory tract caused by HPV infection. In its completed Phase 1/2 clinical trial of INO-3107 for the treatment of HPV-6 and HPV-11-associated RRP, 81.3% of patients experienced a reduction in the number of surgical interventions in the year following administration of INO-3107, when compared with the year prior to treatment.
In addition to its development efforts with INO-3107, INOVIO is actively developing or planning to develop DNA medicines for other indications, including HPV-related anal dysplasia and oropharyngeal squamous cell carcinoma (OPSCC); glioblastoma multiforme (GBM), a deadly form of brain cancer; and a potential vaccine booster to protect against the Ebola virus. The Company was previously conducting clinical trials of a DNA medicine candidate for the treatment of HPV-related cervical high-grade squamous intraepithelial lesions (HSIL) but announced in August 2023 that it was ceasing development for this indication in the United States. However, its collaborator ApolloBio Corporation continues to conduct a Phase 3 clinical trial of this candidate in China and plans to seek regulatory approval for and potentially commercialize the candidate in that jurisdiction.
The Company's partners and collaborators include Advaccine Biopharmaceuticals Suzhou Co, ApolloBio Corporation, AstraZeneca, The Bill & Melinda Gates Foundation (Gates), Coalition for Epidemic Preparedness Innovations (CEPI), Coherus Biosciences, Defense Advanced Research Projects Agency (DARPA), The U.S. Department of Defense (DoD), HIV Vaccines Trial Network, International Vaccine Institute (IVI), Kaneka Eurogentec, National Cancer Institute (NCI), National Institutes of Health (NIH), National Institute of Allergy and Infectious Diseases (NIAID), Plumbline Life Sciences, Regeneron Pharmaceuticals, Richter-Helm BioLogics, Thermo Fisher Scientific, the University of Pennsylvania, the Walter Reed Army Institute of Research, and The Wistar Institute.
INOVIO was incorporated in Delaware in 2001 and has its principal executive offices in Plymouth Meeting, Pennsylvania.
v3.24.0.1
Summary of Significant Accounting Policies
 12 Months Ended
Dec. 31, 2023
Accounting Policies [Abstract]  
Summary of Significant Accounting Policies Summary of Significant Accounting Policies
Basis of Presentation and Liquidity
The Company incurred a net loss of $135.1 million for the year ended December 31, 2023. The Company had working capital of $110.5 million and an accumulated deficit of $1.6 billion as of December 31, 2023. The Company has incurred losses in each year since its inception and expects to continue to incur significant expenses and operating losses for the foreseeable future in connection with the research and preclinical and clinical development of its product candidates. The Company’s cash, cash equivalents and short-term investments of $145.3 million as of December 31, 2023 are sufficient to support the Company's operations for a period of at least 12 months from the date it is issuing these financial statements.
In order to continue to fund future research and development activities, the Company will need to seek additional capital. This may occur through strategic alliance and licensing arrangements, grant agreements and/or future public or private debt or equity financings, including under At-the-Market Equity Offering Sales Agreements (“Sales Agreements”). The Company has a history of conducting debt and equity financings, including the receipt of net proceeds of $5.5 million, $83.0 million and $47.7 million from equity offerings under Sales Agreements during the years ending December 31, 2023, 2022 and 2021, respectively, and $162.1 million from a January 2021 underwritten public offering of common stock. However, sufficient funding may not be available in the future, or if available, may be on terms that significantly dilute or otherwise adversely affect the rights of existing stockholders. If adequate funds are not available, the Company may need to delay, reduce the scope of or put on hold one or more of its clinical and/or preclinical programs.
The Company is and, from time to time, may in the future be subject to various legal proceedings and claims arising in the ordinary course of business. The Company assesses contingencies to determine the degree of probability and range of possible loss for potential accrual in its consolidated financial statements. An estimated loss contingency is accrued in the consolidated financial statements if it is probable that a liability has been incurred and the amount of the loss can be reasonably estimated. Legal proceedings, including litigation, government investigations and enforcement actions, could result in material costs,
occupy significant management resources and entail civil and criminal penalties, even if the Company ultimately prevails. Any of the foregoing consequences could result in serious harm to the Company’s business, results of operations and financial condition.
Reverse Stock Split
On January 24, 2024, the Company filed with the Secretary of State of the State of Delaware a certificate of amendment to its certificate of incorporation, as previously amended, to effect a 1-for-12 reverse stock split of our common stock (the “Reverse Stock Split”). As a result of the Reverse Stock Split, every 12 issued and outstanding shares of the Company's common stock were automatically combined into one issued and outstanding share of common stock. The reverse stock split was reflected on the Nasdaq Capital Market beginning with the opening of trading on January 25, 2024. Accordingly, an amount equal to the par value of the decreased shares resulting from the reverse stock split was reclassified from "Additional paid-in capital" to "Common stock" on the balance sheet and statement of changes in stockholders’ equity. Any fractional post-split shares as a result of the reverse stock split were eliminated by the payment of cash for the value of such fractional share. As a result of the Reverse Stock Split, proportionate adjustments were made to the number of shares underlying, and the exercise or conversion prices of, the Company's outstanding stock options and outstanding shares of Series C Cumulative Convertible Preferred Stock and to the number of shares of common stock issuable under the Company's equity incentive plans. The reverse stock split did not change the par value of the Company's common stock or the authorized number of shares of the Company's common stock. All share amounts and per share amounts disclosed in this Annual Report on Form 10-K have been restated to reflect the reverse stock split on a retroactive basis for all periods presented.
Consolidation
The consolidated financial statements include the accounts of Inovio Pharmaceuticals, Inc. and its wholly-owned subsidiary Inovio Asia LLC.
Segment Reporting
Operating segments are identified as components of an enterprise about which separate discrete financial information is available for evaluation by the chief operating decision-maker in making decisions regarding resource allocation and assessing performance. The Company views its operations and manages its business as one segment operating primarily within the United States.
Use of Estimates
The preparation of consolidated financial statements in conformity with U.S. GAAP requires management to make estimates and assumptions that affect the reported amounts of assets and liabilities, disclosures of contingent assets and liabilities at the date of the consolidated financial statements and the reported amounts of revenues and expenses during the reporting period. Actual results could differ from those estimates.
Concentration of Credit Risk
Financial instruments that potentially subject the Company to concentrations of credit risk consist primarily of cash and short-term investments. The Company limits its exposure to credit loss by placing its cash and investments with high credit quality financial institutions. Additionally, the Company has established guidelines regarding diversification of its investments and their maturities which are designed to maintain principal and maximize liquidity.
The Company has contracts with certain of its customers that have represented more than 10% of the Company's total revenues, as discussed in Note 3.
Fair Value Measurements
The guidance regarding fair value measurements establishes a three-tier fair value hierarchy which prioritizes the inputs used in measuring fair value. These tiers include: Level 1, defined as observable inputs such as quoted prices in active markets that are accessible at the measurement date; Level 2, defined as inputs other than quoted prices in active markets that are either directly or indirectly observable; and Level 3, defined as unobservable inputs in which little or no market data exists, therefore requiring an entity to develop its own assumptions.
The Company’s financial instruments include cash equivalents, short-term investments, investments in affiliated entity, accounts receivable, prepaid expenses and other assets, accounts payable and accrued expenses, and convertible senior notes. The carrying amounts of cash equivalents, accounts receivable, prepaid expenses and other assets, accounts payable and accrued expenses approximate the related fair values due to the short-term maturities of these instruments. Short-term investments are recorded at fair value on a recurring basis, based on current market valuations. The Company carries convertible senior notes at face value less unamortized debt discount and issuance costs on its consolidated balance sheet, and it presents the fair value of such convertible notes for disclosure purposes only.
Cash and Cash Equivalents
Cash equivalents are considered by the Company to be highly liquid investments purchased with original maturities of three months or less from the date of purchase. Cash and cash equivalents included certain mutual funds and U.S. treasury securities at December 31, 2023 and 2022.
Short-term Investments
The Company defines investments as income-yielding securities that can be readily converted into cash or equity investments classified as available-for-sale. Investments included mutual funds, U.S. treasury securities, certificates of deposit, U.S. agency mortgage-backed securities and an equity investment in the Company’s affiliated entity, PLS, at December 31, 2023 and 2022.
Short-term investments are recorded at fair value, based on current market valuations. Unrealized gains and losses on the Company's short-term debt investments are excluded from earnings and reported as a separate component of other comprehensive loss until realized. Realized gains and losses and unrealized gains and losses on available-for-sale equity securities are included in non-operating other income (expense) on the consolidated statements of operations and are derived using the specific identification method for determining the cost of the securities sold.
Accounts Receivable
Accounts receivable are recorded at invoiced amounts and do not bear interest. The Company performs ongoing credit evaluations of its customers’ financial condition. Credit is extended to customers as deemed necessary and generally does not require collateral. Management believes that the risk of loss is significantly reduced due to the quality and financial position of the Company's customers. There was no allowance for doubtful accounts for potential credit losses as of December 31, 2023 and 2022.
Fixed Assets
Fixed assets include property and equipment and leasehold improvements. Property and equipment are stated at cost and depreciated using the straight-line method over the estimated useful life of the assets, generally three to five years. Leasehold improvements are amortized over the shorter of the remaining term of the related leases or the estimated economic useful lives of the improvements. Repairs and maintenance are expensed as incurred.
The Company evaluates the carrying value of long-lived assets, which includes fixed assets and right-of-use assets, for impairment whenever events or changes in circumstances indicate that the carrying amounts of the asset may not be fully recoverable. No impairment losses have been recognized related to long-lived assets for the year ended December 31, 2023 and 2022.
Goodwill and Intangible Assets
Goodwill represents the excess of acquisition cost over the fair value of the net assets of acquired businesses. Goodwill is reviewed for impairment at least annually, or more frequently if an event occurs indicating the potential for impairment. The Company evaluates intangible assets for impairment whenever events or changes in circumstances indicate the carrying amounts of the assets may not be recoverable.
During its goodwill impairment review, the Company may assess qualitative factors to determine whether it is likely that the fair value of its reporting unit is less than its carrying amount, including goodwill. The qualitative factors include, but are not limited to, macroeconomic conditions, industry and market considerations, and the overall financial performance of the Company. If, after assessing the totality of these qualitative factors, the Company determines that it is not likely that the fair value of its reporting unit is less than its carrying amount, then no additional assessment is deemed necessary. Otherwise, the Company will proceed to perform the impairment test in which the fair value of the reporting unit is compared with its carrying amount, and an impairment charge will be recorded for the amount by which the carrying amount exceeds the reporting unit's fair value, if any.
Calculating the fair value of a reporting unit, an asset group and an individual asset involves significant estimates and assumptions. These estimates and assumptions include, among others, projected future cash flows, risk-adjusted discount rates, future economic and market conditions, and the determination of appropriate market comparables. Changes in these factors and assumptions used can materially affect the amount of impairment loss recognized in the period the asset was considered impaired.
During 2023, the Company experienced a decline in its market capitalization as a result of a sustained decrease in the Company’s stock price. This sustained decrease was considered to represent a triggering event requiring management to perform a quantitative goodwill impairment test as of September 30, 2023. The Company first tested its long-lived assets for impairment. The Company determined that all of its long-lived assets, which include property and equipment, leasehold improvements and right-of-use assets, represented one asset group for purposes of its long-lived asset impairment assessment. The Company concluded that the long-lived assets were not impaired, as their carrying values were not in excess of their fair value. Next, the Company determined that the fair value of its reporting unit was less than its carrying value and the Company recorded a loss on impairment of goodwill of $10.5 million.
During 2023, the Company also recorded an impairment charge of $2.0 million to research and development expense for the remaining book value of intangible assets acquired in 2016 from Bioject Medical Technologies, as the Company had no plans to further develop or utilize this technology.
Refer to Note 8 for further information regarding Goodwill and Intangible Assets.
Income Taxes
The Company recognizes deferred tax assets and liabilities for temporary differences between the financial reporting basis and the tax basis of the Company’s assets and liabilities along with net operating loss and tax credit carry forwards. The Company records a valuation allowance against its deferred tax assets to reduce the net carrying value to an amount that it believes is more likely than not to be realized. When the Company establishes or reduces the valuation allowance against its deferred tax assets, its provision for income taxes will increase or decrease, respectively, in the period such determination is made.
Valuation allowances against the Company’s deferred tax assets were $327.5 million and $299.1 million at December 31, 2023 and 2022, respectively. Changes in the valuation allowances, when they are recognized in the provision for income taxes, are included as a component of the estimated annual effective tax rate.
Collaboration Agreements and Revenue Recognition
The Company assesses whether its collaboration agreements are subject to Accounting Standards Codification ("ASC") Topic 808: Collaborative Arrangements (“Topic 808”) based on whether they involve joint operating activities and whether both parties have active participation in the arrangement and are exposed to significant risks and rewards. To the extent that the arrangement falls within the scope of Topic 808 and the Company concludes that its collaboration partner is not a customer, the Company presents such payments as a reduction of research and development expense. If payments from the collaboration partner to the Company represent consideration from a customer, then the Company accounts for those payments within the scope of Accounting Standards Update (“ASU”) 2014-09, Revenue from Contracts with Customers (“Topic 606”).
Grants
The Company accounts for various grant agreements under the contributions guidance under Subtopic 958-605, Not-for-Profit Entities-Revenue Recognition, which is outside the scope of Topic 606, as the government agencies granting the Company funds are not receiving reciprocal value for their contributions. All contributions received from current grant agreements are recorded as a contra-research and development expense as opposed to revenue on the consolidated statement of operations.
Foreign Currency Transactions
The functional and presentation currency of the Company is the U.S. dollar. Transactions denominated in a currency other than the functional currency are recorded on the initial recognition at the exchange rate at the date of the transaction. After initial recognition, monetary assets and liabilities denominated in foreign currency are translated at the end of each reporting period into the functional currency at the exchange rate at that date. The cumulative translation adjustment is included in the accumulated other comprehensive income (loss) within the statement of stockholders' equity. Exchange differences are included in general and administrative expenses in the consolidated statement of operations. Non-monetary assets and liabilities measured at cost are remeasured at the exchange rate at the date of the transaction.
Variable Interest Entities (VIE)
The Company evaluates its ownership, contractual and other interests in entities that are not wholly-owned to determine if these entities are VIEs, and, if so, whether the Company is the primary beneficiary of the VIE. In determining whether the Company is the primary beneficiary of a VIE and therefore required to consolidate the VIE, the Company applies a qualitative approach that determines whether it has both (1) the power to direct the activities of the VIE that most significantly impact the VIE’s economic performance and (2) the obligation to absorb losses of, or the rights to receive benefits from, the VIE that could potentially be significant to that VIE. The Company will continuously perform this assessment, as changes to existing relationships or future transactions may result in the consolidation or deconsolidation of a VIE.
Equity Investments
Under ASC Topic 321, Investments - Equity Securities, the Company must measure equity investments (except those accounted for under the equity method, those that result in consolidation of the investee and certain other investments) at fair value and recognize any changes in fair value in the consolidated statement of operations. The Company can elect a measurement alternative for equity investments that do not have readily determinable fair values and do not qualify for the practical expedient in ASC Topic 820, Fair Value Measurement, to estimate fair value using the net asset value per share (or its equivalent). The Company's equity investments that do not have readily determinable fair values and do not qualify for the net asset value practical expedient for estimating fair value are measured at cost, less any impairments, plus or minus changes resulting from observable price changes in orderly transactions for identifiable or similar investments of the same issuer. 
Research and Development Expenses - Clinical Trial Accruals
The Company's activities have largely consisted of research and development efforts related to developing its proprietary device technology and DNA medicine candidates. For clinical trial expenses, judgements used in estimating accruals rely on estimates of total costs incurred based on participant enrollment, completion of studies and other events. Accrued clinical trial costs are subject to revisions as trials progress. Revisions are charged to expense in the period in which the facts that give rise to the revision become known. Historically, revisions have not resulted in material changes to research and development expense; however, a modification in the protocol of a clinical trial or cancellation of a trial could result in a charge to the Company's results of operations.
Net Loss Per Share
Basic net loss per share is computed by dividing the net loss for the year by the weighted average number of shares of common stock outstanding during the year. Diluted net loss per share is calculated in accordance with the treasury stock method for the outstanding stock options and restricted stock units ("RSUs") and reflects the potential dilution that would occur if securities or other contracts to issue common stock were exercised or converted to common stock. The dilutive impact of the outstanding Notes issued by the Company (discussed in Note 9) has been considered using the "if-converted" method. The calculation of diluted net loss per share requires that, to the extent the average market price of the underlying shares for the reporting period exceeds the exercise price of the options or other securities and the presumed exercise of such securities are dilutive to net loss per share for the period, an adjustment to net loss used in the calculation is required to remove the change in fair value of such securities from the numerator for the period. Likewise, an adjustment to the denominator is required to reflect the related dilutive shares, if any. For the years ended December 31, 2023, 2022 and 2021, basic and diluted net loss per share are the same, as the assumed exercise or settlement of stock options, RSUs and the potentially dilutive shares issuable upon conversion of the Notes would have been anti-dilutive.
The following table summarizes potential shares of common stock that were excluded from diluted net loss per share calculation because of their anti-dilutive effect:
Year Ended December 31,
202320222021
Options to purchase common stock1,128,864 1,018,095 874,082 
Service-based restricted stock units274,794 212,964 204,005 
Performance-based restricted stock units— 9,328 55,279 
Convertible preferred stock275 275 275 
Convertible notes254,165 254,165 254,165 
Total1,658,098 1,494,827 1,387,806 

Leases
For its long-term operating leases, the Company recognized an operating lease right-of-use asset and an operating lease liability on its consolidated balance sheets. The lease liability is determined as the present value of future lease payments using an estimated rate of interest that the Company would pay to borrow equivalent funds on a collateralized basis at the lease commencement date. The right-of-use asset is based on the liability adjusted for any prepaid or deferred rent. The Company determines the lease term at the commencement date by considering whether renewal options and termination options are reasonably assured of exercise.
Fixed rent expense for the Company's operating leases is recognized on a straight-line basis over the term of the lease and is included in operating expenses on the consolidated statements of operations. Variable lease payments including lease operating expenses are recorded as incurred.
Stock-Based Compensation
The Company incurs stock-based compensation expense related to RSUs and stock options. The fair value of restricted stock is determined by the closing price of the Company's common stock reported on the Nasdaq Global Select Market on the date of grant. The Company estimates the fair value of stock options granted using the Black-Scholes option pricing model. The Black-Scholes option pricing model was developed for use in estimating the fair value of traded options, which have no vesting restrictions and are fully transferable. In addition, option valuation models require the input of subjective assumptions, including the expected stock price volatility and expected option life. The Company amortizes the fair value of the awards on a straight-line basis over the requisite vesting period of the awards. Expected volatility is based on historical volatility. The expected life of options granted is based on historical expected life. The risk-free interest rate is based on the U.S. Treasury yield in effect at the time of grant. The dividend yield is based on the fact that no dividends have been paid historically and none are currently expected to be paid in the foreseeable future. The Company recognizes forfeitures as they occur.
The weighted average assumptions used in the Black-Scholes model for option grants to employees and directors are presented below:
 Year Ended December 31,
 202320222021
Risk-free interest rate4.05%2.05%0.91%
Expected volatility100%94%93%
Expected life in years5.55.76
Dividend yield———

The weighted average assumptions used in the Black-Scholes model for option grants to non-employees are presented below:
 Year Ended December 31,
 202320222021
Risk-free interest rate3.90%1.96%1.45%
Expected volatility89%87%87%
Expected life in years101010
Dividend yield———

Recent Accounting Pronouncements
The recent accounting pronouncements below may have a significant effect on the Company's financial statements. Recent accounting pronouncements that are not anticipated to have an impact on or are unrelated to the Company's financial condition, results of operations, or related disclosures are not discussed.
ASU No. 2023-07. In November 2023, the Financial Accounting Standards Board (FASB) issued Accounting Standards Update (ASU) 2023-07, Segment Reporting (Topic 280): Improvements to Reportable Segment Disclosures. The ASU expands public entities’ segment disclosures by requiring disclosure of significant segment expenses that are regularly reviewed by the Chief Operating Decision Maker (CODM) and included within each reported measure of segment profit or loss, an amount and description of its composition for other segment items, and interim disclosures of a reportable segment’s profit or loss and assets. The ASU also allows, in addition to the measure that is most consistent with U.S. GAAP, the disclosure of additional measures of segment profit or loss that are used by the CODM in assessing segment performance and deciding how to allocate resources. All disclosure requirements under ASU 2023-07 are also required for public entities with a single reportable segment. The ASU is effective for fiscal years beginning after December 15, 2023, and interim periods within fiscal years beginning after December 15, 2024, on a retrospective basis, with early adoption permitted. The Company is currently evaluating the impact of this standard on its consolidated financial statements and disclosures.
ASU No. 2023-09. In December 2023, the FASB issued ASU No. 2023-09, Income Taxes (Topic 740): Improvements to Income Tax Disclosures. ASU 2023-09 requires disaggregated information about a reporting entity’s effective tax rate reconciliation as well as information on income taxes paid. ASU 2023-09 is effective for public entities with annual periods beginning after December 15, 2024, with early adoption permitted. The Company is currently evaluating the impact of this guidance on its consolidated financial statements.
v3.24.0.1
Revenue Recognition and Concentration of Credit Risk
 12 Months Ended
Dec. 31, 2023
Revenue from Contract with Customer [Abstract]  
Revenue Recognition and Concentration of Credit Risk Revenue Recognition and Concentration of Credit Risk
During the years ended December 31, 2023, 2022 and 2021, the Company recognized revenue from various license and other agreements. The following table indicates the percentage of total revenues in excess of 10% with any single customer:
Customer2023 Revenue% of Total
Revenue		2022 Revenue% of Total
Revenue		2021 Revenue% of Total
Revenue
ApolloBio Corporation$245,056 29 %$— — %$— — %
Plumbline Life Sciences, Inc. (affiliated entity)— — 33,596 — 245,310 14 
U.S. Department of Defense— — 9,591,778 94 754,853 43 
All other, including affiliated entities586,954 71 636,894 6 774,595 43 
Total revenue$832,010 100 %$10,262,268 100 %$1,774,758 100 %

No revenue recognized during the year ended December 31, 2023 was in deferred revenue as of December 31, 2022. During the year ended December 31, 2022, the Company recognized revenue of $14,000 that was included in deferred revenue at December 31, 2021. Performance obligations are generally satisfied within 12 months of the initial contract date.
As of December 31, 2023, the Company had no accounts receivable balance. As of December 31, 2022, all of the Company's accounts receivable was attributable to the CEPI MERS grant. There is minimal credit risk with the Company's customers based upon the short-term nature of the accounts receivable, collection history, their size and financial condition. Accordingly, the Company does not record an allowance for potential credit losses against its accounts receivable.
v3.24.0.1
Collaborative Agreements
 12 Months Ended
Dec. 31, 2023
Organization, Consolidation and Presentation of Financial Statements [Abstract]  
Collaborative Agreements Collaborative Agreements
Advaccine Biopharmaceuticals Suzhou Co., Ltd.
On December 31, 2020, the Company entered into a Collaboration and License Agreement with Advaccine Biopharmaceuticals Suzhou Co., Ltd. (“Advaccine”), which was amended and restated on June 7, 2021 (as amended and restated, the “Advaccine Agreement”). Under the terms of the Advaccine Agreement, the Company granted to Advaccine the exclusive right to develop, manufacture and commercialize the Company’s vaccine candidate INO-4800 within the territories of China, Taiwan, Hong Kong and Macau (referred to collectively as “Greater China”) and 33 additional countries in Asia. The June 2021 amendment related to a collaboration between the Company and Advaccine to jointly conduct a global Phase 3 segment of the Company’s clinical trial of INO-4800 that was planned. The parties were jointly participating in the trial and were to equally share the global development costs for the trial, including the Company’s manufacturing costs to supply INO-4800. Advaccine agreed to be fully responsible for conducting the trial in Greater China, including its costs and expenses incurred. In the fourth quarter of 2022, the Company discontinued its internally funded efforts to develop INO-4800 as a COVID-19 heterologous booster vaccine. Advaccine continues to develop INO-4800 with its own resources under the terms of the Advaccine Agreement.
In connection with the June 2021 amendment, the Company determined that the global Phase 3 trial component of the agreement was a collaboration and not a contract with a customer and therefore accounted for the June 2021 amendment under ASC Topic 808. Reimbursements from Advaccine were recognized as contra-research and development expense on the consolidated statement of operations once earned and collectibility was assured. During the years ended December 31, 2023, 2022 and 2021, the Company received funding of $3.6 million, $1.2 million and $4.5 million, respectively, from Advaccine that was recorded as contra-research and development expense.
ApolloBio Corporation
On December 29, 2017, the Company entered into an Amended and Restated License and Collaboration Agreement (the "ApolloBio Agreement"), with ApolloBio Corporation ("ApolloBio"), which was amended on June 14, 2023. Under the terms of the ApolloBio Agreement, the Company granted to ApolloBio the exclusive right to develop and commercialize VGX-3100, its DNA immunotherapy product candidate designed to treat pre-cancers caused by HPV, within the agreed upon territories.
The Company is entitled to receive up to an aggregate of $20.0 million, less required income, withholding or other taxes, upon the achievement of specified milestones related to the regulatory approval of VGX-3100 in accordance with the ApolloBio Agreement. In the event that VGX-3100 is approved for marketing, the Company will be entitled to receive royalty payments based on a tiered percentage of annual net sales, with such percentage being in the low- to mid-teens, subject to reduction in the event of generic competition in a particular territory. ApolloBio’s obligation to pay royalties will continue for 10 years after the first commercial sale in a particular territory or, if later, until the expiration of the last-to-expire patent covering the licensed products in the specified territory.
During the year ended December 31, 2023, the Company received funding of $245,000 from the ApolloBio Agreement that was recorded as revenue. For the years ended December 31, 2022 and 2021, there were no significant reimbursable program costs under the ApolloBio Agreement.
Coalition for Epidemic Preparedness Innovations
The Company previously entered into agreements with CEPI, pursuant to which the Company intended to develop vaccine candidates against Lassa fever and MERS. As part of the arrangement between the parties, CEPI agreed to fund up to an aggregate of $56 million of costs over a five-year period for preclinical studies, as well as planned Phase 1 and Phase 2 clinical trials, to be conducted by the Company and collaborators, with funding from CEPI based on the achievement of identified milestones. In November 2022, the Company announced that it and CEPI would discontinue the development of these product candidates targeting Lassa fever and MERS, following the initial analysis of data from the studies conducted by the Company and funded by CEPI. During the years ended December 31, 2023, 2022 and 2021, the Company received funding of $1.8 million, $6.7 million and $10.0 million, respectively, related to these grants and recorded those payments as contra-research and development expense. As of December 31, 2023 and 2022, the Company had an accounts receivable balance of $0 and $1.7 million, respectively, on the consolidated balance sheet related to these CEPI grants. As of December 31, 2023, the Company had $2.2 million recorded as an accrued liability, and at December 31, 2022, had $0 recorded as deferred grant funding on the consolidated balance sheet related to these CEPI grants.
In January 2020, CEPI awarded the Company a grant of up to $9.0 million to support preclinical and clinical development of INO-4800 through Phase 1 human testing in the United States. In April 2020, CEPI awarded the Company a grant of $6.9 million to work with the International Vaccine Institute ("IVI") and the Korea National Institute of Health ("KNIH") to conduct clinical trials of INO-4800 in South Korea, a grant of $5.0 million to accelerate development of the Company's next-generation intradermal electroporation device, known as CELLECTRA 3PSP, for the intradermal delivery of INO-4800, and a grant of $1.3 million to support large-scale manufacturing of INO-4800. During the years ended December 31, 2023, 2022 and 2021, the Company received funding of $330,000, $1.1 million and $6.9 million, respectively, from CEPI related to these grants for INO-4800 and recorded such amounts as contra-research and development expense. As of December 31, 2023, the Company had $2.1 million recorded as an accrued liability, and at December 31, 2022, had $2.3 million recorded as deferred grant funding on the consolidated balance sheet related to the CEPI grants related to INO-4800.
Bill & Melinda Gates Foundation
In October 2018, Gates awarded and funded the Company a grant of $2.2 million to advance the development of dMAbs to address issues in infectious disease prevention and therapy. This technology has high relevance for the control of influenza and HIV. This next-generation approach to the delivery of monoclonal antibodies would make the technology accessible to low and middle-income countries. In August 2019, Gates funded an additional $1.1 million for the project. During the years ended December 31, 2023, 2022 and 2021, the Company recorded $70,000, $233,000 and $182,000, respectively, as contra-research and development expense related to the Gates dMAb grant. As of December 31, 2023 and 2022, the Company had $87,000 and $153,000, respectively, recorded as deferred grant funding on the consolidated balance sheet related to the grant.
Department of Defense (DoD)
In June 2020, the Company entered into an Other Transaction Authority for Prototype Agreement (the “OTA Agreement”) with the DoD to fund the Company’s efforts in developing the CELLECTRA® 3PSP device and associated arrays to be used for delivery of INO-4800 against COVID-19. The total amount of funding provided to the Company under the OTA Agreement was $54.5 million. The Company determined that the OTA Agreement should be considered under Subtopic 958-605, Not-for-Profit Entities-Revenue Recognition, which is outside the scope of Topic 606, as the government agency granting the Company funds was not receiving reciprocal value for their contributions. The Company recorded contra-research and development expense on the consolidated statement of operations in the same period that the underlying expenses were incurred. During the years ended December 31, 2023, 2022 and 2021, the Company recorded $0, $6.1 million and $27.1 million, respectively, as contra-research and development expense related to the OTA agreement.
Additionally, in June 2020, the Company was awarded a fixed-price contract (the “Procurement Contract”) from the DoD for the purchase of the Company’s intradermal CELLECTRA® 2000 device and accessories. The total purchase price under the Procurement Contract was $16.8 million. The Company determined that the Procurement Contract fell under the scope of ASC Topic 606 as the contract was with a customer and the Company was able to satisfy its obligations under the arrangement. Performance obligations under the Procurement Contract consisted of the delivery of a specified number of CELLECTRA® 2000 devices and accessories. The total transaction price was allocated to the individual performance obligations based on the determined standalone selling price for the devices and accessories. In 2021, the DoD announced that it would discontinue funding for the Phase 3 segment of the Company's clinical trials for INO-4800 and in January 2022, the total purchase price under the Procurement Contract was reduced to $10.7 million. During the year ended December 31, 2022, all performance obligations under the Procurement Contract were satisfied. During the years ended December 31, 2023, 2022 and 2021, the Company recorded revenue of $0, $9.6 million and $755,000, respectively, from the Procurement Contract.
v3.24.0.1
Short-term Investments and Fair Value Measurements
 12 Months Ended
Dec. 31, 2023
Investments, Debt and Equity Securities [Abstract]  
Short-term Investments and Fair Value Measurements Short-term Investments and Fair Value Measurements
The following is a summary of available-for-sale securities as of December 31, 2023 and 2022:
 
 As of December 31, 2023
 Contractual
Maturity (in years)		CostGross Unrealized
Gains		Gross Unrealized
Losses		Fair Market Value
Mutual funds---$55,389,289 $— $(3,522,888)$51,866,401 
U.S. treasury securities
Less than 1
75,164,782 24,938 — 75,189,720 
Certificates of deposit
Less than 1
2,978,917 11,709 (300)2,990,326 
U.S. agency mortgage-backed securities*1,340,439 — (403,973)936,466 
$134,873,427 $36,647 $(3,927,161)$130,982,913 
 As of December 31, 2022
 Contractual
Maturity (in years)		CostGross Unrealized
Gains		Gross Unrealized
Losses		Fair Market Value
Mutual funds---$117,036,232 $— $(9,373,514)$107,662,718 
U.S. treasury securities
Less than 1
95,001,209 7,567 (44,266)94,964,510 
Certificates of deposit
Less than 1
2,977,564 13,664 (320)2,990,908 
U.S. agency mortgage-backed securities*1,435,592 — (384,331)1,051,261 
$216,450,597 $21,231 $(9,802,431)$206,669,397 

*No single maturity date.

During the years ended December 31, 2023 and 2022, the Company recorded gross realized gain on investments of $1,000 and $21,000, respectively, and gross realized loss on investments of $4.8 million and $4.1 million, respectively. During the years ended December 31, 2023 and 2022, the Company recorded net unrealized gain (loss) on available-for-sale equity securities of $5.9 million and $(7.8) million, respectively. No material balances were reclassified out of accumulated other comprehensive loss for the years ended December 31, 2023, 2022 and 2021. Interest and dividends on investments classified as available-for-sale are included in interest income in the consolidated statements of operations. As of December 31, 2023, the Company had 21 available-for-sale securities in a gross unrealized loss position, of which 20 with an aggregate total unrealized loss of $3.9 million were in such position for longer than 12 months.
The Company periodically reviews its portfolio of available-for-sale debt securities to determine if any investment is impaired due to credit loss or other potential valuation concerns. For the debt securities where the fair value of the investment is less than the amortized cost basis, the Company has assessed at the individual security level for various quantitative factors including, but not limited to, the nature of the investments, changes in credit ratings, interest rate fluctuations, industry analyst reports, and the severity of impairment. Unrealized losses on available-for-sale debt securities as of December 31, 2023 were primarily due to changes in interest rates, and not due to increased credit risks associated with specific securities. Based on the credit quality of the available-for-sale debt securities that are in an unrealized loss position, and the Company’s estimates of future cash flows to be collected from those securities, the Company believes the unrealized losses are not credit losses. Accordingly, at December 31, 2023, the Company did not record an allowance for credit losses related to its available-for-sale debt securities.
The following table presents the Company’s assets that were measured at fair value on a recurring basis, determined using the following inputs as of December 31, 2023:
 
Fair Value Measurements at
 December 31, 2023
 TotalQuoted Prices
in Active Markets
(Level 1)		Significant
Other Unobservable
Inputs
(Level 2)		Significant
Unobservable
Inputs
(Level 3)
Short-term investments
    Mutual funds$51,866,401 $51,866,401 $— $— 
    U.S. treasury securities75,189,720 75,189,720 — — 
    Certificates of deposit2,990,326 — 2,990,326 — 
    U.S. agency mortgage-backed securities936,466 — 936,466 — 
Total short-term investments130,982,913 127,056,121 3,926,792 — 
Investment in affiliated entity2,780,287 2,780,287 — — 
Total assets measured at fair value$133,763,200 $129,836,408 $3,926,792 $— 

The following table presents the Company’s assets that were measured at fair value on a recurring basis, determined using the following inputs as of December 31, 2022:
 
Fair Value Measurements at
 December 31, 2022
 TotalQuoted Prices
in Active Markets
(Level 1)		Significant
Other Unobservable
Inputs
(Level 2)		Significant
Unobservable
Inputs
(Level 3)
Short-term investments
     Mutual funds$107,662,718 $107,662,718 $— $— 
     U.S. treasury securities94,964,510 94,964,510 — — 
     Certificates of deposit2,990,908 — 2,990,908 — 
     U.S. agency mortgage-backed securities1,051,261 — 1,051,261 — 
Total short-term investments206,669,397 202,627,228 4,042,169 — 
Investments in affiliated entity2,007,142 2,007,142 — — 
Total assets measured at fair value$208,676,539 $204,634,370 $4,042,169 $— 

Level 1 assets at December 31, 2023 and 2022 consisted of mutual funds and U.S. treasury securities held by the Company that are valued at quoted market prices, as well as the Company’s investment in its affiliated entity, PLS. The Company accounts for its investment in 597,808 common shares of PLS based on the closing price of the shares on the Korea New Exchange Market on the applicable balance sheet date. Unrealized gains and losses on the Company's equity securities are reported in the consolidated statement of operations as unrealized gain or loss on available-for-sale equity securities or as a gain or loss on investment in affiliated entity.
Level 2 assets at December 31, 2023 and 2022 consisted of certificates of deposit and U.S. agency mortgage-backed securities held by the Company that are initially valued at the transaction price and subsequently valued, at the end of each reporting period, typically utilizing market observable data. The Company obtains the fair value of its Level 2 assets from a professional pricing service, which may use quoted market prices for identical or comparable instruments, or inputs other than quoted prices that are observable either directly or indirectly. The professional pricing service gathers quoted market prices and observable inputs from a variety of industry data providers. The valuation techniques used to measure the fair value of the Company's Level 2 financial instruments were derived from non-binding market consensus prices that are corroborated by observable market data, quoted market prices for similar instruments, or pricing models such as discounted cash flow techniques. The Company validates the quoted market prices provided by the primary pricing service by comparing the service's assessment of the fair values of the Company's investment portfolio balance against the fair values of the Company's investment portfolio balance obtained from an independent source.
There were no Level 3 assets held as of December 31, 2023 or 2022.
Short-term Investments and Fair Value Measurements Short-term Investments and Fair Value Measurements
The following is a summary of available-for-sale securities as of December 31, 2023 and 2022:
 
 As of December 31, 2023
 Contractual
Maturity (in years)		CostGross Unrealized
Gains		Gross Unrealized
Losses		Fair Market Value
Mutual funds---$55,389,289 $— $(3,522,888)$51,866,401 
U.S. treasury securities
Less than 1
75,164,782 24,938 — 75,189,720 
Certificates of deposit
Less than 1
2,978,917 11,709 (300)2,990,326 
U.S. agency mortgage-backed securities*1,340,439 — (403,973)936,466 
$134,873,427 $36,647 $(3,927,161)$130,982,913 
 As of December 31, 2022
 Contractual
Maturity (in years)		CostGross Unrealized
Gains		Gross Unrealized
Losses		Fair Market Value
Mutual funds---$117,036,232 $— $(9,373,514)$107,662,718 
U.S. treasury securities
Less than 1
95,001,209 7,567 (44,266)94,964,510 
Certificates of deposit
Less than 1
2,977,564 13,664 (320)2,990,908 
U.S. agency mortgage-backed securities*1,435,592 — (384,331)1,051,261 
$216,450,597 $21,231 $(9,802,431)$206,669,397 

*No single maturity date.

During the years ended December 31, 2023 and 2022, the Company recorded gross realized gain on investments of $1,000 and $21,000, respectively, and gross realized loss on investments of $4.8 million and $4.1 million, respectively. During the years ended December 31, 2023 and 2022, the Company recorded net unrealized gain (loss) on available-for-sale equity securities of $5.9 million and $(7.8) million, respectively. No material balances were reclassified out of accumulated other comprehensive loss for the years ended December 31, 2023, 2022 and 2021. Interest and dividends on investments classified as available-for-sale are included in interest income in the consolidated statements of operations. As of December 31, 2023, the Company had 21 available-for-sale securities in a gross unrealized loss position, of which 20 with an aggregate total unrealized loss of $3.9 million were in such position for longer than 12 months.
The Company periodically reviews its portfolio of available-for-sale debt securities to determine if any investment is impaired due to credit loss or other potential valuation concerns. For the debt securities where the fair value of the investment is less than the amortized cost basis, the Company has assessed at the individual security level for various quantitative factors including, but not limited to, the nature of the investments, changes in credit ratings, interest rate fluctuations, industry analyst reports, and the severity of impairment. Unrealized losses on available-for-sale debt securities as of December 31, 2023 were primarily due to changes in interest rates, and not due to increased credit risks associated with specific securities. Based on the credit quality of the available-for-sale debt securities that are in an unrealized loss position, and the Company’s estimates of future cash flows to be collected from those securities, the Company believes the unrealized losses are not credit losses. Accordingly, at December 31, 2023, the Company did not record an allowance for credit losses related to its available-for-sale debt securities.
The following table presents the Company’s assets that were measured at fair value on a recurring basis, determined using the following inputs as of December 31, 2023:
 
Fair Value Measurements at
 December 31, 2023
 TotalQuoted Prices
in Active Markets
(Level 1)		Significant
Other Unobservable
Inputs
(Level 2)		Significant
Unobservable
Inputs
(Level 3)
Short-term investments
    Mutual funds$51,866,401 $51,866,401 $— $— 
    U.S. treasury securities75,189,720 75,189,720 — — 
    Certificates of deposit2,990,326 — 2,990,326 — 
    U.S. agency mortgage-backed securities936,466 — 936,466 — 
Total short-term investments130,982,913 127,056,121 3,926,792 — 
Investment in affiliated entity2,780,287 2,780,287 — — 
Total assets measured at fair value$133,763,200 $129,836,408 $3,926,792 $— 

The following table presents the Company’s assets that were measured at fair value on a recurring basis, determined using the following inputs as of December 31, 2022:
 
Fair Value Measurements at
 December 31, 2022
 TotalQuoted Prices
in Active Markets
(Level 1)		Significant
Other Unobservable
Inputs
(Level 2)		Significant
Unobservable
Inputs
(Level 3)
Short-term investments
     Mutual funds$107,662,718 $107,662,718 $— $— 
     U.S. treasury securities94,964,510 94,964,510 — — 
     Certificates of deposit2,990,908 — 2,990,908 — 
     U.S. agency mortgage-backed securities1,051,261 — 1,051,261 — 
Total short-term investments206,669,397 202,627,228 4,042,169 — 
Investments in affiliated entity2,007,142 2,007,142 — — 
Total assets measured at fair value$208,676,539 $204,634,370 $4,042,169 $— 

Level 1 assets at December 31, 2023 and 2022 consisted of mutual funds and U.S. treasury securities held by the Company that are valued at quoted market prices, as well as the Company’s investment in its affiliated entity, PLS. The Company accounts for its investment in 597,808 common shares of PLS based on the closing price of the shares on the Korea New Exchange Market on the applicable balance sheet date. Unrealized gains and losses on the Company's equity securities are reported in the consolidated statement of operations as unrealized gain or loss on available-for-sale equity securities or as a gain or loss on investment in affiliated entity.
Level 2 assets at December 31, 2023 and 2022 consisted of certificates of deposit and U.S. agency mortgage-backed securities held by the Company that are initially valued at the transaction price and subsequently valued, at the end of each reporting period, typically utilizing market observable data. The Company obtains the fair value of its Level 2 assets from a professional pricing service, which may use quoted market prices for identical or comparable instruments, or inputs other than quoted prices that are observable either directly or indirectly. The professional pricing service gathers quoted market prices and observable inputs from a variety of industry data providers. The valuation techniques used to measure the fair value of the Company's Level 2 financial instruments were derived from non-binding market consensus prices that are corroborated by observable market data, quoted market prices for similar instruments, or pricing models such as discounted cash flow techniques. The Company validates the quoted market prices provided by the primary pricing service by comparing the service's assessment of the fair values of the Company's investment portfolio balance against the fair values of the Company's investment portfolio balance obtained from an independent source.
There were no Level 3 assets held as of December 31, 2023 or 2022.
v3.24.0.1
Certain Balance Sheet Items
 12 Months Ended
Dec. 31, 2023
Certain Balance Sheet Items [Abstract]  
Certain Balance Sheet Items Certain Balance Sheet Items
Prepaid and other current assets at December 31, 2023 and 2022 consisted of the following:
 
20232022
Insurance recovery (a)$— $30,000,000 
Prepaid manufacturing expenses1,486,638 1,401,028 
Other prepaid expenses3,907,027 18,729,453 
$5,393,665 $50,130,481 
Accounts payable and accrued expenses at December 31, 2023 and 2022 consisted of the following:
20232022
Trade accounts payable$3,577,826 $19,862,487 
Accrued compensation9,837,104 12,574,921 
Accrued litigation settlement (a)— 44,000,000 
Other accrued expenses (b) (c)6,432,814 3,249,477 
$19,847,744 $79,686,885 

(a)In July 2022, the Company entered into a memorandum of understanding for the proposed settlement of class action securities litigation (see Note 11). The final judicial order for the settlement was issued in January 2023. The settlement consisted of $30.0 million in cash and $14.0 million in shares of the Company's common stock to settle all outstanding claims. As of December 31, 2022, the Company's insurance carriers had paid the cash component of the proposed settlement, which amounts were being held in escrow. The Company's insurance carriers paid $252,000 of other expenses on behalf of the Company, which amounts were offset against the insurers' cash commitment as part of the settlement. During the three months ended March 31, 2023, the cash component of the settlement was released from escrow and the Company issued 760,083 shares of common stock pursuant to the securities class action settlement.

(b) In March 2023, the Company entered into a stipulation of settlement for the proposed settlement of shareholder derivative litigation (see Note 11). In June 2023, the court preliminarily approved the proposed settlement. As part of the settlement, in July 2023, the Company paid $1.2 million to plaintiffs’ counsel for their fees and expenses. This amount was accrued within “Other accrued expenses” as of December 31, 2022. On October 12, 2023, the court entered an order and final judgment approving the Settlement, which was effective on November 13, 2023.

(c) December 31, 2023 balance includes $4.3 million liability for unused grant funding.
v3.24.0.1
Fixed Assets
 12 Months Ended
Dec. 31, 2023
Property, Plant and Equipment [Abstract]  
Fixed Assets Fixed Assets
Fixed assets at December 31, 2023 and 2022 consisted of the following:
 
CostAccumulated
Depreciation
and
Amortization		Net Book
Value
As of December 31, 2023
Leasehold improvements$15,917,596 $(11,753,081)$4,164,515 
Research and development equipment3,538,698 (3,078,165)460,533 
Office furniture and fixtures2,827,476 (2,816,577)10,899 
Computer equipment and other 3,529,129 (3,204,090)325,039 
$25,812,899 $(20,851,913)$4,960,986 
As of December 31, 2022
Leasehold improvements$15,803,108 $(10,036,080)$5,767,028 
Research and development equipment5,300,104 (4,295,217)1,004,887 
Office furniture and fixtures2,827,476 (2,803,800)23,676 
Computer equipment and other 5,360,712 (4,428,306)932,406 
$29,291,400 $(21,563,403)$7,727,997 
Depreciation expense for the years ended December 31, 2023, 2022 and 2021 was $2.6 million, $3.7 million and $3.0 million, respectively. The Company determined that the carrying value of its fixed assets was not impaired during the periods presented. During the year ended December 31, 2023, the Company sold fixed assets with no net book value for a gain of $148,000 and disposed of fixed assets with a net book value of $466,000. During the year ended December 31, 2022 the Company sold fixed assets with a net book value of $6.1 million and disposed of fixed assets with a net book value of $1.1 million.
v3.24.0.1
Goodwill and Intangible Assets
 12 Months Ended
Dec. 31, 2023
Goodwill and Intangible Assets Disclosure [Abstract]  
Goodwill and Intangible Assets Goodwill and Intangible Assets
During the three months ended September 30, 2023, as a result of the sustained decline in the Company’s stock price and related market capitalization, and a general decline in equity values in the biotechnology industry, the Company performed an impairment assessment of its goodwill and long-lived assets.
The Company operates as a single reporting unit based on its business and reporting structure. For goodwill, a quantitative impairment assessment was performed using a market approach, whereby the Company’s fair value of equity was compared to its carrying value. The fair value of equity was derived using both the market capitalization of the Company and an estimate of a reasonable range of values of a control premium applied to the Company’s implied business enterprise value. The control premium was estimated based upon control premiums observed in comparable market transactions. This represented a level 2 nonrecurring fair value measurement. Based on this analysis, the Company recognized a non-cash, pre-tax goodwill impairment charge of $10.5 million during the three months ended September 30, 2023. As a result, the goodwill was fully impaired as of September 30, 2023.
Before completing the goodwill impairment assessment, the Company first tested its long-lived assets for impairment. The Company held no indefinite-lived intangible assets as of September 30, 2023. The Company determined that all of its long-lived assets, which included property and equipment, leasehold improvements and right-of-use assets, represented one asset group for purposes of its long-lived asset impairment assessment. The Company concluded that the long-lived assets were not impaired, as their carrying values were not in excess of their fair value.
During the quarter ended June 30, 2023, the Company recorded an impairment charge of $2.0 million to research and development expense for the remaining book value of intangible assets acquired in 2016 from Bioject Medical Technologies, as the Company had no plans to further develop or utilize this technology.
The following sets forth goodwill and intangible assets by major asset class:
 
 December 31, 2023December 31, 2022
 Weighted Average Useful
Life
(Yrs)		GrossAccumulated
Amortization		ImpairmentNet Book
Value		GrossAccumulated
Amortization		Net Book
Value
Indefinite lived:
Goodwill$10,513,371 $— $(10,513,371)$— $10,513,371 $— $10,513,371 
Definite lived:
Licenses10— — — — 1,323,761 (1,323,761)— 
Bioject —5,100,000 (3,115,556)(1,984,444)— 5,100,000 (2,988,889)2,111,111 
Other (a)184,050,000 (4,050,000)— — 4,050,000 (4,031,250)18,750 
Total intangible assets119,150,000 (7,165,556)(1,984,444)— 10,473,761 (8,343,900)2,129,861 
Total goodwill and intangible assets$19,663,371 $(7,165,556)$(12,497,815)$— $20,987,132 $(8,343,900)$12,643,232 

(a)Other intangible assets represent the estimated fair value of acquired intellectual property.
Aggregate amortization expense related to intangible assets was $145,000, $496,000 and $520,000 for the years ended December 31, 2023, 2022 and 2021, respectively.
There were no impairment or impairment indicators present and no losses were recorded during the years ended December 31, 2022 and 2021.
v3.24.0.1
Convertible Debt
 12 Months Ended
Dec. 31, 2023
Debt Disclosure [Abstract]  
Convertible Debt Convertible Debt
Convertible Senior Notes
On February 19, 2019 and March 1, 2019, the Company completed a private placement of $78.5 million aggregate principal amount of its 6.50% convertible senior notes due 2024 (the “Notes”). The Notes were sold in a private offering to qualified institutional buyers pursuant to Rule 144A under the Securities Act of 1933, as amended. Net proceeds from the offering were $75.7 million.
The Notes were senior unsecured obligations of the Company and accrued interest payable in cash semi-annually in arrears on March 1 and September 1 of each year at a rate of 6.50% per annum. The Notes matured on March 1, 2024 and the Company paid the then remaining $16.9 million obligation in full, including accrued interest.
Initially, in accounting for the issuance of the Notes, the Company separated the Notes into liability and equity components. The carrying amount of the liability component was calculated by measuring the fair value of similar debt instruments, which do not have an associated convertible feature. The carrying amount of the equity component representing the conversion option for the Notes was $16.3 million and was recorded as a debt discount, which was being amortized to interest expense at an effective interest rate of 13.1%. In addition, the Company allocated $592,000 of debt issuance costs to the equity component and the remaining debt issuance costs of $2.2 million were allocated to the liability component, which were being amortized to interest expense under the effective interest rate method.
On January 1, 2022, the Company adopted ASU No. 2020-06, Debt—Debt with Conversion and Other Options (Subtopic 470-20) and Derivatives and Hedging—Contracts in Entity’s Own Equity (Subtopic 815-40): Accounting for Convertible Instruments and Contracts in an Entity’s Own Equity (“ASU 2020-06”). The ASU eliminated the cash conversion feature models in ASC 470-20, Debt with Conversion and Other Options, which required an issuer of certain convertible debt to separately account for embedded conversion features as a component of equity. Instead, the Company accounted for these securities as a single unit of account, unless the conversion feature met certain criteria. The Company adopted the new standard using the modified retrospective method and recorded a net reduction to accumulated deficit of $1.8 million, a decrease to additional paid-in capital of $3.3 million, and an increase to convertible senior notes of $1.5 million to reflect the impact of the accounting change. The Notes were subsequently accounted for as a single liability measured at amortized cost, as no other embedded features required bifurcation and recognition as derivatives.
The balance of the Notes at December 31, 2023 was as follows:
Principal amount$78,500,000 
Principal amount converted into common shares(62,085,000)
Unamortized debt issuance cost— 
Accrued interest355,654 
     Net carrying amount $16,770,654 
For the years ended December 31, 2023, 2022 and 2021, the Company recognized $1.2 million, $1.3 million and $1.9 million, respectively, of interest expense related to the Notes, of which $1.1 million related to the contractual interest coupon in each year.
v3.24.0.1
Stockholders' Equity
 12 Months Ended
Dec. 31, 2023
Stockholders' Equity Note [Abstract]  
Stockholders' Equity Stockholders’ Equity
Preferred Stock
   Shares Outstanding as of
December 31,
 Shares AuthorizedShares Issued20232022
Series C Preferred Stock, par $0.001
1,091 1,091 9 9 

The holder of a share or shares of Series C preferred stock has the right at any time, at such holder’s option, to convert all or any lesser portion of such holder’s shares of the preferred stock into fully paid and non-assessable shares of common stock. As of December 31, 2021, the conversion value was $326.40 per share, such that the outstanding shares of Series C preferred stock were convertible into an aggregate of 275 shares of common stock.
Issuances of Common Stock
On November 9, 2021, the Company entered into an ATM Equity OfferingSM Sales Agreement (the “2021 Sales Agreement”) with outside sales agents (collectively, the “Sales Agents”) for the offer and sale of its common stock for an aggregate offering price of up to $300.0 million. The 2021 Sales Agreement provides that the Sales Agents will be entitled to compensation in an amount equal to up to 3.0% of the gross sales proceeds of any common stock sold through the Sales Agents under the 2021 Sales Agreement. During the years ended December 31, 2023 and 2022, the Company sold 875,305 and 2,870,478 shares, respectively, of its common stock under the 2021 Sales Agreement. The sales were made at a weighted average price of $6.33 and $29.34 per share, respectively, resulting in aggregate net proceeds of $5.5 million and $83.0 million, respectively. As of December 31, 2023 there was $161.8 million of remaining capacity under the 2021 Sales Agreement.
During the three months ended March 31, 2023, the Company issued 760,083 shares of common stock pursuant to the securities class action settlement, as described in Note 11.
Stock Options and Restricted Stock Units
The Company's Board of Directors adopted the 2023 Omnibus Incentive Plan (the “2023 Plan”) on March 24, 2023, pursuant to which the Company may grant stock options, restricted stock awards, RSUs and other stock-based awards or short-term cash incentive awards to employees, directors and consultants.
The 2023 Plan was approved by stockholders on May 16, 2023. The aggregate number of shares of the Company’s common stock that may be issued under the 2023 Plan will not exceed the sum of 1,166,666 shares plus any shares that may return from time to time from the 2016 Omnibus Incentive Plan (as amended, the “2016 Plan”) as a result of expirations, terminations or forfeitures of awards outstanding under the 2016 Plan as of May 16, 2023. At December 31, 2023, the Company had 1,334,012 shares of common stock available for future grant under the 2023 Plan, 1,875 shares underlying outstanding but unvested RSUs and 3,150 shares underlying options outstanding to purchase common stock under the 2023 Plan. The awards granted and available for future grant under the 2023 Plan generally vest over three years and have a maximum contractual term of ten years. The 2023 Plan terminates by its terms on March 24, 2033.
At December 31, 2023, the Company had 262,641 shares underlying outstanding but unvested RSU and options outstanding to purchase 961,499 shares of common stock under the 2016 Plan. The outstanding awards granted under the 2016 Plan generally vest over three years and have a maximum contractual term of ten years. Following adoption of the 2023 Plan, no further awards may be made under the 2016 Plan, but outstanding awards continue to be governed by their existing terms.
On June 24, 2022, the Company's board of directors adopted a stock-based incentive plan (the "2022 Inducement Plan"), which provides for the discretionary grant of nonstatutory stock options, stock appreciation rights, restricted stock awards, RSU awards, performance awards, and other awards to individuals as a material inducement to entering into employment with the Company. The aggregate number of shares of the Company’s common stock that may be issued under the 2022 Inducement Plan will not exceed 166,666 shares. At December 31, 2023 the Company had 125,575 shares of common stock available for future grant under the 2022 Inducement Plan, 10,278 shares underlying outstanding but unvested RSUs and options outstanding to purchase 27,759 shares of common stock under the 2022 Inducement Plan. The 2022 Inducement Plan can be terminated by the Company's board of directors at any time.
The Amended and Restated 2007 Omnibus Incentive Plan (the "2007 Incentive Plan") was adopted on March 31, 2007 and terminated by its terms on March 31, 2017. At December 31, 2023, the Company had options outstanding to purchase 136,456 shares of common stock under the 2007 Incentive Plan. The awards granted under the 2007 Incentive Plan generally vest over three years and have a maximum contractual term of ten years.
Total employee and director stock-based compensation expense recognized in the consolidated statements of operations for the years ended December 31, 2023, 2022 and 2021 was $10.4 million, $22.2 million and $25.0 million, respectively, of which $4.5 million, $8.8 million and $13.4 million was included in research and development expenses and $5.9 million, $13.4 million and $11.6 million was included in general and administrative expenses, respectively.
At December 31, 2023 and 2022, there was $4.3 million and $10.5 million, respectively, of total unrecognized compensation expense related to unvested stock options, which is expected to be recognized over a weighted-average period of 1.3 years and 1.6 years, respectively.
At December 31, 2023 and 2022, there was $3.5 million and $7.2 million, respectively, of total unrecognized compensation expense related to unvested RSUs, which is expected to be recognized over a weighted-average period of 1.5 years and 1.7 years, respectively.
The fair value of stock options granted to non-employees was estimated using the Black-Scholes pricing model. Total stock-based compensation expense for stock options and RSUs granted to non-employees for the years ended December 31, 2023, 2022 and 2021 was $669,000, $1.3 million and $1.4 million, respectively. As of December 31, 2023, options to purchase 61,808 shares of common stock granted to non-employees remained outstanding.
The following table summarizes total stock options outstanding at December 31, 2023:
 
 Options OutstandingOptions Exercisable
Exercise PriceShares Underlying Options
Outstanding		Weighted-Average
Remaining
Contractual Life
(in Years)		Weighted
Average
Exercise Price		Shares Underlying Options
Exercisable		Weighted Average
Exercise Price
$4.32-$18.00
283,472 9.2$14.11 66,918 $14.45 
$18.01-$39.00
264,108 7.3$35.69 141,600 $34.99 
$39.01-$52.00
156,505 4.5$44.93 156,271 $44.93 
$52.01-$90.00
129,681 4.2$76.82 121,124 $77.75 
$90.01-$130.00
136,716 4.2$100.15 131,640 $100.00 
$130.01-$233.28
158,382 5.4$140.27 129,250 $141.78 
1,128,864 6.4$58.76 746,803 $72.11 

At December 31, 2023, the aggregate intrinsic value of options outstanding was $2,000, the aggregate intrinsic value of options exercisable was $1,000, and the weighted average remaining contractual term of options exercisable was 5.5 years.
At December 31, 2023, the aggregate intrinsic value of unvested RSUs was $1.7 million and the aggregate intrinsic value of RSUs which vested during the year ended December 31, 2023 was $1.3 million.
At December 31, 2023, options to purchase 1,128,864 shares of common stock and 274,794 RSUs were expected to vest.
Stock option activity under the Company’s equity incentive plans during the year ended December 31, 2023 was as follows:
Number of
Shares		Weighted-Average
Exercise Price
Balance, December 31, 20221,018,095 $75.32 
Granted339,019 14.23 
Exercised— — 
Cancelled(228,250)66.47 
Balance, December 31, 20231,128,864 $58.76 

Restricted stock unit activity under the Company’s equity incentive plans during the year ended December 31, 2023 was as follows:
Number of
Shares
Balance, December 31, 2022212,964 
Granted194,747 
Vested(99,420)
Cancelled(33,497)
Balance, December 31, 2023274,794 

The weighted average exercise price per share was $38.86 for the 9,357 options which expired during the year ended December 31, 2023, $101.64 for the 6,437 options which expired during the year ended December 31, 2022 and $54.72 for the 583 options which expired during the year ended December 31, 2021.
The weighted average grant date fair value per share was $11.19, $28.08 and $91.32 for options granted during the years ended December 31, 2023, 2022 and 2021, respectively.
The weighted average grant date fair value was $10.34, $37.44 and $124.44 per share for RSUs granted during the years ended December 31, 2023, 2022 and 2021, respectively.
No stock options were exercised during the year ended December 31, 2023. The Company received $283,000 and $6.7 million in proceeds from the exercise of stock options during the years ended December 31, 2022 and 2021, respectively. The aggregate intrinsic value of options exercised was $81,000 and $7.0 million during the years ended December 31, 2022 and 2021, respectively.
v3.24.0.1
Commitments and Contingencies
 12 Months Ended
Dec. 31, 2023
Leases [Abstract]  
Commitments and Contingencies Commitments and Contingencies
Leases
The Company leases approximately 56,600 square feet of office, laboratory, and manufacturing space in San Diego, California and 57,360 square feet of office space in Plymouth Meeting, Pennsylvania under various non-cancellable operating lease agreements with remaining lease terms as of December 31, 2023 of 3.4 years to 6.0 years, which represent the non-cancellable periods of the leases. The Company has excluded the extension options from its lease terms in the calculation of future lease payments as they are not reasonably certain to be exercised. The Company's lease payments consist primarily of fixed rental payments for the right to use the underlying leased assets over the lease terms as well as payments for common area maintenance and administrative services. The Company has received customary incentives from its landlords, such as reimbursements for tenant improvements and rent abatement periods, which effectively reduce the total lease payments owed for these leases.
In November 2023, the Company amended one of its leases representing 31,207 square feet of office and laboratory space with a lease term expiring in November 2023, to extend the term to February 29, 2024.
In November 2023, the Company entered into a lease agreement for research and development laboratory space in San Diego, California ("New San Diego Lease"). The total space under the New San Diego Lease is approximately 5,563 square feet. The term of the New San Diego Lease commenced on February 10, 2024 and the initial term is 4.3 years.
The base rent adjusts periodically throughout the term of the New San Diego Lease. Rent payments under the New San Diego Lease will include base rent with an annual increase of approximately three percent, and additional monthly fees to cover the Company's share of certain facility expenses, including utilities, property taxes, insurance and maintenance. In addition, the Company has paid a security deposit of $33,000.
The Company performed an evaluation of its contracts with customers and suppliers in accordance with ASC Topic 842 and determined that, except for the real estate leases described above and various copier leases, none of its other contracts contain a right-of-use asset.
Operating lease right-of-use assets and liabilities on the consolidated balance sheet represents the present value of the remaining lease payments over the remaining lease terms. Payments for additional monthly fees to cover the Company's share of certain facility expenses are not included in operating lease right-of-use assets and liabilities. The Company uses its incremental borrowing rate to calculate the present value of its lease payments, as the implicit rates in the leases are not readily determinable.
As of December 31, 2023, the maturities of the Company's operating lease liabilities were as follows:
Year ending December 31,
2024$3,247,000 
20253,466,000 
20263,555,000 
20272,955,000 
20282,310,000 
Thereafter2,132,000 
   Total remaining lease payments17,665,000 
Less: present value adjustment(4,226,000)
   Total operating lease liabilities13,439,000 
Less: current portion(2,407,000)
Long-term operating lease liabilities$11,032,000 
Weighted-average remaining lease term5.3 years
Weighted-average discount rate8.9 %

Lease costs included in operating expenses in the consolidated statements of operations for the years ended December 31, 2023, 2022 and 2021 were $3.5 million, $3.4 million and $3.4 million, respectively. Operating lease costs consisting of the fixed lease payments included in operating lease liabilities are recorded on a straight-line basis over the lease terms. Variable lease costs are recorded as incurred.
In the third and fourth quarters of 2023, the Company entered into agreements to sublease a total of approximately 4,400 and 7,000 square feet, respectively, in its Plymouth Meeting headquarters, in each case with sublease terms through December 31, 2026.
In the fourth quarter of 2019, the Company entered into two agreements to sublease a total of approximately 13,500 square feet in its Plymouth Meeting headquarters, with one sublease term through March 31, 2025 and the other month-to-month.
In the normal course of business, the Company is a party to a variety of agreements pursuant to which it may be obligated to indemnify the other party. It is not possible to predict the maximum potential amount of future payments under these types of agreements due to the conditional nature of the Company's obligations and the unique facts and circumstances involved in each particular agreement. Historically, payments made by the Company under these types of agreements have not had a material effect on its business, consolidated results of operations or financial condition.
Legal Proceedings
Securities Litigation
In March 2020, a purported shareholder class action complaint, McDermid v. Inovio Pharmaceuticals, Inc. and J. Joseph Kim, was filed in the United States District Court for the Eastern District of Pennsylvania, naming the Company and its former President and Chief Executive Officer as defendants. The lawsuit alleged that the Company made materially false and misleading statements in violation of certain federal securities laws. The plaintiffs sought unspecified monetary damages on behalf of the putative class and an award of costs and expenses, including reasonable attorneys’ fees. The plaintiffs’ complaint was later amended to include certain of the Company’s other officers as defendants. After additional motions were filed in the case, in June 2022 the parties negotiated an agreement in principle to settle the shareholder class action complaint, which was approved by the court in January 2023. Under the settlement, the Company agreed to pay $30.0 million in cash and $14.0 million in shares of its common stock to settle all outstanding claims. The Company's insurance carriers paid the $30.0 million cash component of the settlement. During the three months ended March 31, 2023, the Company issued 760,083 shares of common stock pursuant to the securities class action settlement.
Shareholder Derivative Litigation
In April 2020, a purported shareholder derivative complaint, Behesti v. Kim, et al., was filed in the United States District Court for the Eastern District of Pennsylvania, naming eight current and former directors of the Company as defendants. The lawsuit asserted state and federal claims and was based on the same alleged misstatements as the shareholder class action complaint described above. The lawsuit accused the Company’s board of directors of failing to exercise reasonable and prudent supervision over the Company’s management, policies, practices, and internal controls. The plaintiff sought unspecified
monetary damages on behalf of the Company as well as governance reforms. Between June 2020 and August 2020, additional shareholder derivative complaints were filed and later consolidated by the court.
In March 2022, an additional shareholder derivative complaint was filed in the Delaware Court of Chancery, asserting substantially similar claims as those in the consolidated derivative action. In May 2022, the Delaware Court of Chancery entered a stay of the litigation.
In March 2023, the parties submitted a joint status report to the Court of Chancery reporting that the parties agreed to a settlement in principle, which also provided for the resolution of the consolidated derivative action and certain stockholder demands.
In April 2023, the plaintiffs in the consolidated derivative action filed a motion for preliminary approval of settlement with the United States District Court for the Eastern District of Pennsylvania. The proposed settlement provided for resolution of the consolidated derivative action, the derivative action pending in the Delaware Court of Chancery, and certain stockholder demands.
In June 2023, the court entered an order preliminarily approving the proposed settlement of the derivative claims, in accordance with a Stipulation of Settlement. The Stipulation of Settlement contemplated that, following the settlement hearing and the final approval of the settlement by the court, the Company would implement certain corporate governance reforms described in the Stipulation of Settlement. The preliminary order also approved the form and manner of the notice of the Settlement. As part of the Settlement, in July 2023 the Company paid $1.2 million to plaintiffs’ counsel for their fees and expenses. In October 2023, the court entered an order and final judgment approving the Settlement, which became effective in November 2023. The Company has implemented the corporate governance reforms in response to the provisions of the Stipulation of Settlement.
VGXI Litigation
In June 2020, the Company filed a complaint in the Court of Common Pleas of Montgomery County, Pennsylvania against VGXI, Inc. and GeneOne Life Science, Inc., or GeneOne, and together with VGXI, Inc. collectively referred to as VGXI, alleging that VGXI had materially breached the Company’s supply agreement with them. The complaint seeks declaratory judgments, specific performance of the agreement, injunctive relief, an accounting, damages, attorneys’ fees, interest, costs and other relief from VGXI. In June 2020, the Company filed a petition for preliminary injunction, which was denied.
Following an appeal by the Company, in July 2020, VGXI filed counterclaims against the Company, alleging that the Company had breached the supply agreement, as well as misappropriation of trade secrets and unjust enrichment. The counterclaims seek injunctive relief, damages, attorneys’ fees, interest, costs and other relief from the Company. VGXI also filed a third-party complaint against Ology Bioservices, Inc., a contract manufacturing organization that the Company had engaged to provide services similar to those that were being provided by VGXI. The Company filed an answer to VGXI’s counterclaims, disputing the allegations and the claims raised in VGXI’s filing. In October 2020, the Company filed a notice of discontinuance of appeal with the Pennsylvania Superior Court. A trial date for the litigation has not been set.
The Company intends to aggressively prosecute the claims set forth in its complaint against VGXI and to vigorously defend itself against VGXI’s counterclaims.
GeneOne Litigation
In December 2020, GeneOne filed a complaint in the Court of Common Pleas of Montgomery County, Pennsylvania against the Company, alleging that the Company had breached the CELLECTRA Device License Agreement, or the Agreement, between the Company and GeneOne. The Company terminated the Agreement in October 2020. The complaint asserts claims for breach of contract, declaratory judgment, unfair competition, and unjust enrichment. The complaint seeks injunctive relief, an accounting, damages, disgorgement of profits, attorneys’ fees, interest, and other relief from the Company. The Company filed preliminary objections to the complaint, which were overruled by the court. In September 2021, the Company filed an answer to the complaint, new matter, and counterclaims. The Company’s counterclaims allege that GeneOne breached the Agreement and assert claims for breach of contract and declaratory judgment. The counterclaims seek damages, interest, expenses, attorney’s fees, and costs. A trial date for this litigation has not been set.
The Company intends to aggressively prosecute the claims set forth in its counterclaims against GeneOne and to vigorously defend itself against the claims in GeneOne’s complaint.
Other Matters
From time to time, the Company may be involved in disputes, including litigation, relating to claims arising out of operations in the normal course of its business. Any of these claims could subject the Company to costly legal expenses and, while the Company generally believes that it has adequate insurance to cover many different types of liabilities, its insurance carriers may deny coverage or its policy limits may be inadequate to fully satisfy any damage awards or settlements. If this
were to happen, the payment of any such awards could have a material adverse effect on the Company's consolidated results of operations and financial position. Additionally, any such claims, whether or not successful, could damage the Company's reputation and business. Except as described above, the Company is not a party to any legal proceedings, the adverse outcome of which, in management’s opinion, individually or in the aggregate, would be reasonably expected to have a material adverse effect on the Company’s consolidated results of operations or financial position.
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Income Taxes
 12 Months Ended
Dec. 31, 2023
Income Tax Disclosure [Abstract]  
Income Taxes Income Taxes
In accordance with the guidance pursuant to accounting for income taxes, a deferred tax asset or liability is determined based on the difference between the financial statement and tax basis of assets and liabilities as measured by the enacted tax rates which will be in effect when these differences reverse. The Company provides a valuation allowance against net deferred tax assets unless, based upon the available evidence, it is more likely than not that the deferred tax asset will be realized.
The components of pretax loss from operations are as follows:
Year Ended December 31,
202320222021
     U.S. Domestic$(134,979,579)$(277,440,803)$(302,614,003)
     Foreign(137,772)(211,249)(610,320)
Pretax loss from operations$(135,117,351)$(277,652,052)$(303,224,323)

There was no provision for or benefit from income taxes for the years ended December 31, 2023, 2022 and 2021.
The reconciliation of income taxes attributable to continuing operations computed at the statutory tax rates to income tax benefit, using a 21% statutory tax rate for December 31, 2023, 2022 and 2021, is as follows: 
Year Ended December 31,
202320222021
Benefit from income taxes at statutory rates$(28,375,000)$(58,307,000)$(63,677,000)
State income tax, net of federal benefit(3,922,000)(3,601,000)(3,447,000)
Change in valuation allowance28,394,000 61,065,000 77,424,000 
Research and development tax credits(2,139,000)(7,534,000)(16,523,000)
Stock-based compensation2,099,000 2,913,000 483,000 
Uncertain tax positions861,000 2,291,000 6,509,000 
Goodwill Impairment1,962,000 — — 
Expired NOLs and credits1,352,000 1,459,000 616,000 
Limited NOLs and credits(997,000)(1,337,000)(542,000)
Change in tax rates365,000 (187,000)— 
Foreign tax rate differential(4,000)(8,000)(24,000)
Other404,000 3,246,000 (819,000)
$— $— $— 

Significant components of the Company’s deferred tax assets and liabilities as of December 31, 2023 and 2022 are shown below:
As of December 31,
20232022
Deferred tax assets:
Capitalized research expense$50,143,000 $41,252,000 
NOL carryforwards235,624,000 212,768,000 
Research and development and other tax credits27,734,000 26,442,000 
Deferred revenue22,000 538,000 
Stock-based compensation3,683,000 3,945,000 
Acquired intangibles907,000 559,000 
Investment in affiliated entity1,406,000 1,569,000 
Lease liability2,822,000 3,247,000 
Fixed assets337,000 57,000 
Other6,808,000 11,062,000 
329,486,000 301,439,000 
Valuation allowance(327,493,000)(299,124,000)
Total deferred tax assets1,993,000 2,315,000 
Deferred tax liabilities:
Acquired intangibles— (199,000)
Right of use asset(1,993,000)(2,148,000)
Total deferred tax liabilities(1,993,000)(2,347,000)
Net deferred tax liabilities$— $(32,000)

As of December 31, 2023, the Company had federal, California and other state tax net operating loss (NOL) carryforwards of $1,013.3 million, $251.4 million and $102.6 million, respectively, net of the net operating losses that will expire due to IRC Section 382 limitations. The aggregate federal net operating losses generated in 2018 and after for the amount of $719.3 million will carryforward indefinitely and be available to offset up to 80% of future taxable income each year. The federal NOL carryforward began to expire in 2023, and the California and other state NOL carryforwards will begin and have begun to expire in 2028 and 2023, respectively, unless previously utilized.
The Company also had Korean NOL carryforwards of $1.1 million as of December 31, 2023. The Korean NOLs are available to offset up to 60% of future taxable income and will begin to expire in 2035, unless previously utilized.
In addition, as of December 31, 2023, the Company had federal and state research and development (R&D) tax credit carryforwards of $41.6 million and $6.1 million, respectively. The federal tax credit carryforwards will begin to expire in 2029. The California research tax credits do not expire.
Based upon statute, federal and state losses and credits are expected to expire as follows (in millions):
Expiration Date:Federal NOLsState NOLsForeign NOLsFederal R&DState R&D
2024$18.9 $9.1 $— $— $— 
202513.7 5.2 — — — 
202612.2 7.1 — — — 
2027 and thereafter249.2 332.0 1.1 41.6 — 
Indefinite719.3 0.6 — — 6.1 
$1,013.3 $354.0 $1.1 $41.6 $6.1 

Pursuant to Internal Revenue Code (IRC) Sections 382 and 383, annual use of the Company’s NOL and R&D credit carryforwards may be limited in the event that a cumulative change in ownership of more than 50% occurs within a three-year period. The Company has completed an IRC Section 382/383 analysis regarding the limitation of NOL and R&D credit carryforwards as of December 31, 2023. As a result of the analysis, the Company estimates that approximately $7.3 million of tax benefits related to NOL and R&D carryforwards will expire unused. Accordingly, the related NOL and R&D credit carryforwards have been removed from deferred tax assets accompanied by a corresponding reduction of the valuation
allowance. Due to the existence of the valuation allowance, limitations created by current and future ownership changes, if any, related to the Company's operations in the United States will not impact its effective tax rate. Any additional ownership changes, may further limit the ability to use the NOL and R&D carryforwards.
The Tax Cuts and Jobs Act of 2017 subjects a U.S. stockholder to tax on Global Intangible Low-Taxed Income (GILTI) earned by certain foreign subsidiaries. The FASB Staff Q&A, Topic 740, No. 5, Accounting for Global Intangible Low-Taxed Income, states that an entity can make an accounting policy election to recognize deferred taxes for temporary basis differences expected to reverse as GILTI in future years or to provide for the tax expense related to GILTI in the year the tax is incurred as a period expense only. The Company has elected to provide for the tax expense related to GILTI in the year the tax is incurred as a period expense only. For 2023, 2022 and 2021, the Company did not generate any GILTI due to losses earned by its foreign subsidiary.
The following table summarizes the activity related to the Company's unrecognized tax benefits:
 Year ended December 31,
 202320222021
Balance at beginning of the year$21,139,000 $18,819,000 $12,210,000 
Increases related to current year tax positions1,816,000 2,902,000 6,602,000 
Increases (decreases) related to prior year tax positions(841,000)(582,000)7,000 
Balance at end of the year$22,114,000 $21,139,000 $18,819,000 

The amount of unrecognized tax benefits that, if recognized and realized, would affect the effective tax rate was $20.5 million, $19.7 million and $17.4 million as of December 31, 2023, 2022 and 2021, respectively, subject to valuation allowances. The Company has not recorded any interest and penalties on the unrecognized tax positions as the Company has continued to generate net operating losses after accounting for the unrecognized tax benefits. The Company does not anticipate that the total amount of unrecognized tax benefits will significantly increase or decrease within twelve months of the reporting date.
The Company and its subsidiaries are subject to U.S. federal income tax as well as income tax in multiple state and foreign jurisdictions. With few exceptions, the Company is no longer subject to United States federal income tax examinations for years before 2020 and state and local income tax examinations before 2019. However, to the extent allowed by law, the tax authorities may have the right to examine prior periods where net operating losses were generated and carried forward, and make adjustments up to the amount of the NOL carryforward amount. The Company is not to its knowledge currently under Internal Revenue Service (“IRS”), state, local or foreign tax examination.
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401(k) Plan
 12 Months Ended
Dec. 31, 2023
Retirement Benefits [Abstract]  
401(k) Plan 401(k) Plan
The Company has adopted a 401(k) Profit Sharing Plan covering substantially all of its employees. The defined contribution plan allows the employees to contribute a percentage of their compensation each year. The Company currently matches 50% of its employees’ contributions, up to 6% of their annual compensation. The Company’s contributions are recorded as expense in the accompanying consolidated statements of operations and totaled $1.4 million, $1.8 million and $1.5 million for the years ended December 31, 2023, 2022 and 2021, respectively.
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Related Party Transactions
 12 Months Ended
Dec. 31, 2023
Related Party Transactions [Abstract]  
Related Party Transactions Related Party Transactions
Plumbline Life Sciences, Inc.
The Company owned 597,808 shares of common stock in PLS as of December 31, 2023 and 2022, representing a 17.8% and 18.7% ownership interest, respectively. One of the Company's directors, Dr. David B. Weiner, acts as a consultant to PLS.
Revenue recognized from PLS consists of milestone, license and patent fees. For the years ended December 31, 2023, 2022 and 2021, the Company recognized revenue from PLS of $0, $34,000 and $245,000, respectively. At December 31, 2023 and 2022, the Company had an accounts receivable balance of $0 and $59,000, respectively, related to PLS.

The Wistar Institute
The Company's director Dr. David B. Weiner is a director of the Vaccine Center of The Wistar Institute ("Wistar"). Dr. Weiner is also the Executive Vice President of Wistar.
In March 2016, the Company entered into collaborative research agreements with Wistar for preventive and therapeutic DNA-based immunotherapy applications and products developed by Dr. Weiner and Wistar for the treatment of cancers and infectious diseases. Under the terms of the agreement, the Company reimbursed Wistar for all direct and indirect costs incurred
in the conduct of the collaborative research, not to exceed $3.1 million during the five-year term of the agreement. In March 2021, upon expiration of the March 2016 agreements, the Company entered into new collaborative research agreements with Wistar with the same terms. The Company has the exclusive right to in-license new intellectual property developed under this agreement.
In 2020, the Company received a $10.7 million sub-grant through Wistar, which was amended in 2021 to $13.6 million, for the preclinical development and translational studies of dMAbs as countermeasures for COVID-19, with funding extended through August 2024. The sub-grant also includes an option for an additional $1.6 million in funding through September 2025.
In December 2022, the Company received a $1.2 million sub-grant through Wistar with funding through November 2023, with an option for an additional $5.4 million in funding through November 2027. The Company will support the Wistar lead consortium in the research and development of synthetic DNA-launched nanoparticles (dLNPs) for vaccination against HIV infection.
Deferred grant funding recognized from Wistar and recorded as contra-research and development expense is related to work performed by the Company on the research sub-contract agreements. For the years ended December 31, 2023 and 2022, the Company recorded $1.0 million and $8.7 million, respectively, as contra-research and development expense from Wistar.
Research and development expenses recorded from Wistar relate primarily to the collaborative research agreements and sub-contract agreements related to Gates and CEPI (see Note 4). Research and development expenses recorded from Wistar for the years ended December 31, 2023, 2022 and 2021 were $1.8 million, $1.4 million and $2.9 million, respectively. At December 31, 2023 and 2022, the Company had an accounts receivable balance of $2.4 million and $9.9 million, respectively, and an accounts payable and accrued liability balance of $1.1 million and $1.2 million, respectively, related to Wistar. As of December 31, 2023 and 2022, the Company had a prepaid expense balance of $20,000 and $375,000, respectively, and recorded $22,000 and $88,000, respectively, as deferred grant funding on its consolidated balance sheet related to Wistar.
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Geneos Therapeutics, Inc.
 12 Months Ended
Dec. 31, 2023
Noncontrolling Interest [Abstract]  
Geneos Therapeutics, Inc. Geneos Therapeutics, Inc.
In 2016, the Company formed Geneos to develop and commercialize neoantigen-based personalized cancer therapies. Geneos was considered a variable interest entity (VIE) for which the Company was the primary beneficiary. The Company's Chief Scientific Officer Dr. Laurent Humeau is on the Board of Directors of Geneos. The Company's director Dr. David B. Weiner is the Chairman of the Scientific Advisory Board of Geneos.
Following a series of financing transactions through June 2020, the Company less than a majority of the outstanding equity of Geneos on an as-converted to common stock basis, which triggered a VIE reconsideration, as the Company no longer held a controlling financial interest. Based on the Company’s assessment, Geneos continued to be a VIE as it did not have sufficient equity at risk to finance its activities without additional subordinated financial support. However, the Company was not the primary beneficiary of Geneos, as it did not have the power to direct the activities that most significantly impact Geneos’ economic performance. Accordingly, the Company deconsolidated its investment in Geneos in 2020.
Following the deconsolidation, the Company accounts for its common stock investment in Geneos, in which the Company lacks control but does have the ability to exercise significant influence over operating and financial policies, using the equity method. Generally, the ability to exercise significant influence is presumed when the investor possesses more than 20% of the voting interests of the investee. This presumption may be overcome based on specific facts and circumstances that demonstrate that the ability to exercise significant influence is restricted. The Company's equity method investments are reviewed for indicators of impairment at each reporting period and are written down to fair value if there is evidence of a loss in value that is other-than-temporary. Any difference between the carrying amount of the Company’s investment and the amount of underlying equity in Geneos’ net assets is amortized into income or expense accordingly. There were no basis differences identified as of the deconsolidation date that would need to be amortized.
Upon deconsolidation, the Company recorded its investment at fair value. The Company determined that its investment in Geneos did not have a readily determinable fair value and therefore elected the measurement alternative in ASC 321 to subsequently record the investment at cost, less any impairments, plus or minus changes resulting from observable price changes in orderly transactions for identical or similar investments of the same issuer. When fair value becomes determinable, from observable price changes in orderly transactions, the Company’s investment is marked to fair value. There have been no observable price changes or impairments identified since the deconsolidation date.
The Company’s share of net losses of Geneos for the three months ended March 31, 2021 was $1.5 million; however, only $434,000 was recorded, reducing the Company's total investment in Geneos to $0. Of the total amount, $819,000 was allocated to the equity method investment, reducing the balance to $0 as of March 31, 2021. The remaining $4.2 million loss was allocated to the Company’s Series A and Series A-1 preferred stock investment in Geneos, on a ratable basis, reducing the balance to $0 as of March 31, 2021.
In February 2021, Geneos completed a second closing of its Series A-1 preferred stock financing, in which the Company did not participate. Following this transaction, the Company held approximately 35% of the outstanding equity, on an as-converted to common stock basis.
In March 2022, Geneos completed the closing of a Series A-2 preferred stock financing. The Company invested $2.0 million in the Series A-2 preferred stock financing, which was led by outside investors. The closing date of this transaction was determined to be a VIE reconsideration event; based on the Company’s assessment, Geneos continued to be a VIE as it did not have sufficient equity at risk to finance its activities without additional subordinated financial support. The Company continued to not be the primary beneficiary of Geneos, as it did not have the power to direct the activities that most significantly impact Geneos’s economic performance and should not consolidate Geneos. Following this transaction, the Company held approximately 28% of the outstanding equity, on an as-converted to common stock basis. Accordingly, the Company continued to account for its common stock investment in Geneos as an equity method investment under ASC 323 and its preferred stock investments as equity securities under ASC 321.
The fair value of Geneos’s Series A-2 preferred stock was based on the per share price paid by third-party investors. The Company concluded that its Series A-2 preferred stock investment was a similar financial instrument as its Series A-1 preferred stock, and therefore remeasured the carrying value of the Series A-1 preferred stock investment at the Series A-2 preferred stock price, resulting in a gain on remeasurement of $165,000.
The Company recorded its current and accumulated share of net losses of Geneos of $2.2 million, which was allocated to the Series A-1 and Series A-2 preferred stock investment in Geneos, thereby reducing the balance to $0 as of March 31, 2022.
The Company has not made any further investment in Geneos subsequent to March 31, 2022. The Company will not reduce its investment below $0 and will not record its share of further net losses of Geneos as the Company has no obligation to fund Geneos.
In 2023, Geneos completed the closing of its Series A-3 preferred stock financing, in which the Company did not participate. Following this transaction, the Company held approximately 23% of the outstanding equity of Geneos on an as-converted to common stock basis.
The Company continues to exclusively license its SynCon® immunotherapy and CELLECTRA® technology platform to Geneos to be used in the field of personalized, neoantigen-based therapy for cancer. The license agreement provides for potential royalty payments to the Company in the event that Geneos commercializes any products using the licensed technology. The Company is not obligated to use any of its assets to fund the future operations of Geneos.
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Subsequent Events
 12 Months Ended
Dec. 31, 2023
Subsequent Events [Abstract]  
Subsequent Events Subsequent Events
On January 24, 2024, the Company implemented the 1-for-12 reverse stock split described in Note 2. All share information contained within this report, including the accompanying consolidated financial statements and footnotes, have been retroactively adjusted to reflect the effects of the reverse split.
From January 1, 2024 through the date of these financial statements, the Company sold 543,620 shares of common stock under the 2021 Sales Agreement for net proceeds of $5.2 million. The sales were made at a weighted average price of $9.76 per share.
On March 1, 2024, the Company's Convertible Senior Notes matured and the Company paid the $16.9 million obligation in full.
v3.24.0.1
Pay vs Performance Disclosure - USD ($)
 12 Months Ended
Dec. 31, 2023
Dec. 31, 2022
Dec. 31, 2021
Pay vs Performance Disclosure      
Net loss $ (135,117,352) $ (279,818,065) $ (303,658,710)
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Insider Trading Arrangements
 3 Months Ended
Dec. 31, 2023
Trading Arrangements, by Individual  
Rule 10b5-1 Arrangement Adopted false
Non-Rule 10b5-1 Arrangement Adopted false
Rule 10b5-1 Arrangement Terminated false
Non-Rule 10b5-1 Arrangement Terminated false
v3.24.0.1
Summary of Significant Accounting Policies (Policies)
 12 Months Ended
Dec. 31, 2023
Accounting Policies [Abstract]  
Basis of Presentation and Liquidity
Basis of Presentation and Liquidity
The Company incurred a net loss of $135.1 million for the year ended December 31, 2023. The Company had working capital of $110.5 million and an accumulated deficit of $1.6 billion as of December 31, 2023. The Company has incurred losses in each year since its inception and expects to continue to incur significant expenses and operating losses for the foreseeable future in connection with the research and preclinical and clinical development of its product candidates. The Company’s cash, cash equivalents and short-term investments of $145.3 million as of December 31, 2023 are sufficient to support the Company's operations for a period of at least 12 months from the date it is issuing these financial statements.
In order to continue to fund future research and development activities, the Company will need to seek additional capital. This may occur through strategic alliance and licensing arrangements, grant agreements and/or future public or private debt or equity financings, including under At-the-Market Equity Offering Sales Agreements (“Sales Agreements”). The Company has a history of conducting debt and equity financings, including the receipt of net proceeds of $5.5 million, $83.0 million and $47.7 million from equity offerings under Sales Agreements during the years ending December 31, 2023, 2022 and 2021, respectively, and $162.1 million from a January 2021 underwritten public offering of common stock. However, sufficient funding may not be available in the future, or if available, may be on terms that significantly dilute or otherwise adversely affect the rights of existing stockholders. If adequate funds are not available, the Company may need to delay, reduce the scope of or put on hold one or more of its clinical and/or preclinical programs.
The Company is and, from time to time, may in the future be subject to various legal proceedings and claims arising in the ordinary course of business. The Company assesses contingencies to determine the degree of probability and range of possible loss for potential accrual in its consolidated financial statements. An estimated loss contingency is accrued in the consolidated financial statements if it is probable that a liability has been incurred and the amount of the loss can be reasonably estimated. Legal proceedings, including litigation, government investigations and enforcement actions, could result in material costs,
occupy significant management resources and entail civil and criminal penalties, even if the Company ultimately prevails. Any of the foregoing consequences could result in serious harm to the Company’s business, results of operations and financial condition.
Consolidation
Consolidation
The consolidated financial statements include the accounts of Inovio Pharmaceuticals, Inc. and its wholly-owned subsidiary Inovio Asia LLC.
Segment Reporting
Segment Reporting
Operating segments are identified as components of an enterprise about which separate discrete financial information is available for evaluation by the chief operating decision-maker in making decisions regarding resource allocation and assessing performance. The Company views its operations and manages its business as one segment operating primarily within the United States.
Use of Estimates
Use of Estimates
The preparation of consolidated financial statements in conformity with U.S. GAAP requires management to make estimates and assumptions that affect the reported amounts of assets and liabilities, disclosures of contingent assets and liabilities at the date of the consolidated financial statements and the reported amounts of revenues and expenses during the reporting period. Actual results could differ from those estimates.
Concentration of Credit Risk
Concentration of Credit Risk
Financial instruments that potentially subject the Company to concentrations of credit risk consist primarily of cash and short-term investments. The Company limits its exposure to credit loss by placing its cash and investments with high credit quality financial institutions. Additionally, the Company has established guidelines regarding diversification of its investments and their maturities which are designed to maintain principal and maximize liquidity.
Fair value of Financial Instruments
Fair Value Measurements
The guidance regarding fair value measurements establishes a three-tier fair value hierarchy which prioritizes the inputs used in measuring fair value. These tiers include: Level 1, defined as observable inputs such as quoted prices in active markets that are accessible at the measurement date; Level 2, defined as inputs other than quoted prices in active markets that are either directly or indirectly observable; and Level 3, defined as unobservable inputs in which little or no market data exists, therefore requiring an entity to develop its own assumptions.
The Company’s financial instruments include cash equivalents, short-term investments, investments in affiliated entity, accounts receivable, prepaid expenses and other assets, accounts payable and accrued expenses, and convertible senior notes. The carrying amounts of cash equivalents, accounts receivable, prepaid expenses and other assets, accounts payable and accrued expenses approximate the related fair values due to the short-term maturities of these instruments. Short-term investments are recorded at fair value on a recurring basis, based on current market valuations. The Company carries convertible senior notes at face value less unamortized debt discount and issuance costs on its consolidated balance sheet, and it presents the fair value of such convertible notes for disclosure purposes only.
Cash and Cash Equivalents
Cash and Cash Equivalents
Cash equivalents are considered by the Company to be highly liquid investments purchased with original maturities of three months or less from the date of purchase. Cash and cash equivalents included certain mutual funds and U.S. treasury securities at December 31, 2023 and 2022.
Short Term Investments
Short-term Investments
The Company defines investments as income-yielding securities that can be readily converted into cash or equity investments classified as available-for-sale. Investments included mutual funds, U.S. treasury securities, certificates of deposit, U.S. agency mortgage-backed securities and an equity investment in the Company’s affiliated entity, PLS, at December 31, 2023 and 2022.
Short-term investments are recorded at fair value, based on current market valuations. Unrealized gains and losses on the Company's short-term debt investments are excluded from earnings and reported as a separate component of other comprehensive loss until realized. Realized gains and losses and unrealized gains and losses on available-for-sale equity securities are included in non-operating other income (expense) on the consolidated statements of operations and are derived using the specific identification method for determining the cost of the securities sold.
Accounts Receivable
Accounts Receivable
Accounts receivable are recorded at invoiced amounts and do not bear interest. The Company performs ongoing credit evaluations of its customers’ financial condition. Credit is extended to customers as deemed necessary and generally does not require collateral. Management believes that the risk of loss is significantly reduced due to the quality and financial position of the Company's customers. There was
Fixed Assets
Fixed Assets
Fixed assets include property and equipment and leasehold improvements. Property and equipment are stated at cost and depreciated using the straight-line method over the estimated useful life of the assets, generally three to five years. Leasehold improvements are amortized over the shorter of the remaining term of the related leases or the estimated economic useful lives of the improvements. Repairs and maintenance are expensed as incurred.
The Company evaluates the carrying value of long-lived assets, which includes fixed assets and right-of-use assets, for impairment whenever events or changes in circumstances indicate that the carrying amounts of the asset may not be fully recoverable. No impairment losses have been recognized related to long-lived assets for the year ended December 31, 2023 and 2022.
Goodwill and Intangible Assets
Goodwill and Intangible Assets
Goodwill represents the excess of acquisition cost over the fair value of the net assets of acquired businesses. Goodwill is reviewed for impairment at least annually, or more frequently if an event occurs indicating the potential for impairment. The Company evaluates intangible assets for impairment whenever events or changes in circumstances indicate the carrying amounts of the assets may not be recoverable.
During its goodwill impairment review, the Company may assess qualitative factors to determine whether it is likely that the fair value of its reporting unit is less than its carrying amount, including goodwill. The qualitative factors include, but are not limited to, macroeconomic conditions, industry and market considerations, and the overall financial performance of the Company. If, after assessing the totality of these qualitative factors, the Company determines that it is not likely that the fair value of its reporting unit is less than its carrying amount, then no additional assessment is deemed necessary. Otherwise, the Company will proceed to perform the impairment test in which the fair value of the reporting unit is compared with its carrying amount, and an impairment charge will be recorded for the amount by which the carrying amount exceeds the reporting unit's fair value, if any.
Calculating the fair value of a reporting unit, an asset group and an individual asset involves significant estimates and assumptions. These estimates and assumptions include, among others, projected future cash flows, risk-adjusted discount rates, future economic and market conditions, and the determination of appropriate market comparables. Changes in these factors and assumptions used can materially affect the amount of impairment loss recognized in the period the asset was considered impaired.
During 2023, the Company experienced a decline in its market capitalization as a result of a sustained decrease in the Company’s stock price. This sustained decrease was considered to represent a triggering event requiring management to perform a quantitative goodwill impairment test as of September 30, 2023. The Company first tested its long-lived assets for impairment. The Company determined that all of its long-lived assets, which include property and equipment, leasehold improvements and right-of-use assets, represented one asset group for purposes of its long-lived asset impairment assessment. The Company concluded that the long-lived assets were not impaired, as their carrying values were not in excess of their fair value. Next, the Company determined that the fair value of its reporting unit was less than its carrying value and the Company recorded a loss on impairment of goodwill of $10.5 million.
During 2023, the Company also recorded an impairment charge of $2.0 million to research and development expense for the remaining book value of intangible assets acquired in 2016 from Bioject Medical Technologies, as the Company had no plans to further develop or utilize this technology.
Refer to Note 8 for further information regarding Goodwill and Intangible Assets
Income Taxes
Income Taxes
The Company recognizes deferred tax assets and liabilities for temporary differences between the financial reporting basis and the tax basis of the Company’s assets and liabilities along with net operating loss and tax credit carry forwards. The Company records a valuation allowance against its deferred tax assets to reduce the net carrying value to an amount that it believes is more likely than not to be realized. When the Company establishes or reduces the valuation allowance against its deferred tax assets, its provision for income taxes will increase or decrease, respectively, in the period such determination is made.
Valuation allowances against the Company’s deferred tax assets were $327.5 million and $299.1 million at December 31, 2023 and 2022, respectively. Changes in the valuation allowances, when they are recognized in the provision for income taxes, are included as a component of the estimated annual effective tax rate.
Collaboration Agreements
Collaboration Agreements and Revenue Recognition
The Company assesses whether its collaboration agreements are subject to Accounting Standards Codification ("ASC") Topic 808: Collaborative Arrangements (“Topic 808”) based on whether they involve joint operating activities and whether both parties have active participation in the arrangement and are exposed to significant risks and rewards. To the extent that the arrangement falls within the scope of Topic 808 and the Company concludes that its collaboration partner is not a customer, the Company presents such payments as a reduction of research and development expense. If payments from the collaboration partner to the Company represent consideration from a customer, then the Company accounts for those payments within the scope of Accounting Standards Update (“ASU”) 2014-09, Revenue from Contracts with Customers (“Topic 606”).
Revenue Recognition
Collaboration Agreements and Revenue Recognition
The Company assesses whether its collaboration agreements are subject to Accounting Standards Codification ("ASC") Topic 808: Collaborative Arrangements (“Topic 808”) based on whether they involve joint operating activities and whether both parties have active participation in the arrangement and are exposed to significant risks and rewards. To the extent that the arrangement falls within the scope of Topic 808 and the Company concludes that its collaboration partner is not a customer, the Company presents such payments as a reduction of research and development expense. If payments from the collaboration partner to the Company represent consideration from a customer, then the Company accounts for those payments within the scope of Accounting Standards Update (“ASU”) 2014-09, Revenue from Contracts with Customers (“Topic 606”).
Grants
Grants
The Company accounts for various grant agreements under the contributions guidance under Subtopic 958-605, Not-for-Profit Entities-Revenue Recognition, which is outside the scope of Topic 606, as the government agencies granting the Company funds are not receiving reciprocal value for their contributions. All contributions received from current grant agreements are recorded as a contra-research and development expense as opposed to revenue on the consolidated statement of operations.
Foreign Currency Transactions
Foreign Currency Transactions
The functional and presentation currency of the Company is the U.S. dollar. Transactions denominated in a currency other than the functional currency are recorded on the initial recognition at the exchange rate at the date of the transaction. After initial recognition, monetary assets and liabilities denominated in foreign currency are translated at the end of each reporting period into the functional currency at the exchange rate at that date. The cumulative translation adjustment is included in the accumulated other comprehensive income (loss) within the statement of stockholders' equity. Exchange differences are included in general and administrative expenses in the consolidated statement of operations. Non-monetary assets and liabilities measured at cost are remeasured at the exchange rate at the date of the transaction.
Variable Interest Entities (VIE)
Variable Interest Entities (VIE)
The Company evaluates its ownership, contractual and other interests in entities that are not wholly-owned to determine if these entities are VIEs, and, if so, whether the Company is the primary beneficiary of the VIE. In determining whether the Company is the primary beneficiary of a VIE and therefore required to consolidate the VIE, the Company applies a qualitative approach that determines whether it has both (1) the power to direct the activities of the VIE that most significantly impact the VIE’s economic performance and (2) the obligation to absorb losses of, or the rights to receive benefits from, the VIE that could potentially be significant to that VIE. The Company will continuously perform this assessment, as changes to existing relationships or future transactions may result in the consolidation or deconsolidation of a VIE.
Equity Method Investments
Equity Investments
Under ASC Topic 321, Investments - Equity Securities, the Company must measure equity investments (except those accounted for under the equity method, those that result in consolidation of the investee and certain other investments) at fair value and recognize any changes in fair value in the consolidated statement of operations. The Company can elect a measurement alternative for equity investments that do not have readily determinable fair values and do not qualify for the practical expedient in ASC Topic 820, Fair Value Measurement, to estimate fair value using the net asset value per share (or its equivalent). The Company's equity investments that do not have readily determinable fair values and do not qualify for the net asset value practical expedient for estimating fair value are measured at cost, less any impairments, plus or minus changes resulting from observable price changes in orderly transactions for identifiable or similar investments of the same issuer.
Research and Development Expenses
Research and Development Expenses - Clinical Trial Accruals
The Company's activities have largely consisted of research and development efforts related to developing its proprietary device technology and DNA medicine candidates. For clinical trial expenses, judgements used in estimating accruals rely on estimates of total costs incurred based on participant enrollment, completion of studies and other events. Accrued clinical trial costs are subject to revisions as trials progress. Revisions are charged to expense in the period in which the facts that give rise to the revision become known. Historically, revisions have not resulted in material changes to research and development expense; however, a modification in the protocol of a clinical trial or cancellation of a trial could result in a charge to the Company's results of operations.
Net Loss Per Share
Net Loss Per Share
Basic net loss per share is computed by dividing the net loss for the year by the weighted average number of shares of common stock outstanding during the year. Diluted net loss per share is calculated in accordance with the treasury stock method for the outstanding stock options and restricted stock units ("RSUs") and reflects the potential dilution that would occur if securities or other contracts to issue common stock were exercised or converted to common stock. The dilutive impact of the outstanding Notes issued by the Company (discussed in Note 9) has been considered using the "if-converted" method. The calculation of diluted net loss per share requires that, to the extent the average market price of the underlying shares for the reporting period exceeds the exercise price of the options or other securities and the presumed exercise of such securities are dilutive to net loss per share for the period, an adjustment to net loss used in the calculation is required to remove the change in fair value of such securities from the numerator for the period. Likewise, an adjustment to the denominator is required to reflect the related dilutive shares, if any. For the years ended December 31, 2023, 2022 and 2021, basic and diluted net loss per share are the same, as the assumed exercise or settlement of stock options, RSUs and the potentially dilutive shares issuable upon conversion of the Notes would have been anti-dilutive.
Leases
Leases
For its long-term operating leases, the Company recognized an operating lease right-of-use asset and an operating lease liability on its consolidated balance sheets. The lease liability is determined as the present value of future lease payments using an estimated rate of interest that the Company would pay to borrow equivalent funds on a collateralized basis at the lease commencement date. The right-of-use asset is based on the liability adjusted for any prepaid or deferred rent. The Company determines the lease term at the commencement date by considering whether renewal options and termination options are reasonably assured of exercise.
Fixed rent expense for the Company's operating leases is recognized on a straight-line basis over the term of the lease and is included in operating expenses on the consolidated statements of operations. Variable lease payments including lease operating expenses are recorded as incurred.
Stock-Based Compensation
Stock-Based Compensation
The Company incurs stock-based compensation expense related to RSUs and stock options. The fair value of restricted stock is determined by the closing price of the Company's common stock reported on the Nasdaq Global Select Market on the date of grant. The Company estimates the fair value of stock options granted using the Black-Scholes option pricing model. The Black-Scholes option pricing model was developed for use in estimating the fair value of traded options, which have no vesting restrictions and are fully transferable. In addition, option valuation models require the input of subjective assumptions, including the expected stock price volatility and expected option life. The Company amortizes the fair value of the awards on a straight-line basis over the requisite vesting period of the awards. Expected volatility is based on historical volatility. The expected life of options granted is based on historical expected life. The risk-free interest rate is based on the U.S. Treasury yield in effect at the time of grant. The dividend yield is based on the fact that no dividends have been paid historically and none are currently expected to be paid in the foreseeable future. The Company recognizes forfeitures as they occur.
Recent Accounting Pronouncements - Recently Adopted
Recent Accounting Pronouncements
The recent accounting pronouncements below may have a significant effect on the Company's financial statements. Recent accounting pronouncements that are not anticipated to have an impact on or are unrelated to the Company's financial condition, results of operations, or related disclosures are not discussed.
ASU No. 2023-07. In November 2023, the Financial Accounting Standards Board (FASB) issued Accounting Standards Update (ASU) 2023-07, Segment Reporting (Topic 280): Improvements to Reportable Segment Disclosures. The ASU expands public entities’ segment disclosures by requiring disclosure of significant segment expenses that are regularly reviewed by the Chief Operating Decision Maker (CODM) and included within each reported measure of segment profit or loss, an amount and description of its composition for other segment items, and interim disclosures of a reportable segment’s profit or loss and assets. The ASU also allows, in addition to the measure that is most consistent with U.S. GAAP, the disclosure of additional measures of segment profit or loss that are used by the CODM in assessing segment performance and deciding how to allocate resources. All disclosure requirements under ASU 2023-07 are also required for public entities with a single reportable segment. The ASU is effective for fiscal years beginning after December 15, 2023, and interim periods within fiscal years beginning after December 15, 2024, on a retrospective basis, with early adoption permitted. The Company is currently evaluating the impact of this standard on its consolidated financial statements and disclosures.
ASU No. 2023-09. In December 2023, the FASB issued ASU No. 2023-09, Income Taxes (Topic 740): Improvements to Income Tax Disclosures. ASU 2023-09 requires disaggregated information about a reporting entity’s effective tax rate reconciliation as well as information on income taxes paid. ASU 2023-09 is effective for public entities with annual periods beginning after December 15, 2024, with early adoption permitted. The Company is currently evaluating the impact of this guidance on its consolidated financial statements.
v3.24.0.1
Summary of Significant Accounting Policies (Tables)
 12 Months Ended
Dec. 31, 2023
Accounting Policies [Abstract]  
Schedule of Common Shares That Were Excluded From The Diluted Net Loss Per Share Calculation Because of Their Anti-Dilutive Effect
The following table summarizes potential shares of common stock that were excluded from diluted net loss per share calculation because of their anti-dilutive effect:
Year Ended December 31,
202320222021
Options to purchase common stock1,128,864 1,018,095 874,082 
Service-based restricted stock units274,794 212,964 204,005 
Performance-based restricted stock units— 9,328 55,279 
Convertible preferred stock275 275 275 
Convertible notes254,165 254,165 254,165 
Total1,658,098 1,494,827 1,387,806 
Schedule of Assumptions Used To Estimate The Fair Value Of Stock Options
The weighted average assumptions used in the Black-Scholes model for option grants to employees and directors are presented below:
 Year Ended December 31,
 202320222021
Risk-free interest rate4.05%2.05%0.91%
Expected volatility100%94%93%
Expected life in years5.55.76
Dividend yield———

The weighted average assumptions used in the Black-Scholes model for option grants to non-employees are presented below:
 Year Ended December 31,
 202320222021
Risk-free interest rate3.90%1.96%1.45%
Expected volatility89%87%87%
Expected life in years101010
Dividend yield———
v3.24.0.1
Revenue Recognition and Concentration of Credit Risk (Tables)
 12 Months Ended
Dec. 31, 2023
Revenue from Contract with Customer [Abstract]  
Schedule of Revenue From External Customers The following table indicates the percentage of total revenues in excess of 10% with any single customer:
Customer2023 Revenue% of Total
Revenue		2022 Revenue% of Total
Revenue		2021 Revenue% of Total
Revenue
ApolloBio Corporation$245,056 29 %$— — %$— — %
Plumbline Life Sciences, Inc. (affiliated entity)— — 33,596 — 245,310 14 
U.S. Department of Defense— — 9,591,778 94 754,853 43 
All other, including affiliated entities586,954 71 636,894 6 774,595 43 
Total revenue$832,010 100 %$10,262,268 100 %$1,774,758 100 %
v3.24.0.1
Short-term Investments and Fair Value Measurements (Tables)
 12 Months Ended
Dec. 31, 2023
Investments, Debt and Equity Securities [Abstract]  
Schedule of Available-for-sale Securities
The following is a summary of available-for-sale securities as of December 31, 2023 and 2022:
 
 As of December 31, 2023
 Contractual
Maturity (in years)		CostGross Unrealized
Gains		Gross Unrealized
Losses		Fair Market Value
Mutual funds---$55,389,289 $— $(3,522,888)$51,866,401 
U.S. treasury securities
Less than 1
75,164,782 24,938 — 75,189,720 
Certificates of deposit
Less than 1
2,978,917 11,709 (300)2,990,326 
U.S. agency mortgage-backed securities*1,340,439 — (403,973)936,466 
$134,873,427 $36,647 $(3,927,161)$130,982,913 
 As of December 31, 2022
 Contractual
Maturity (in years)		CostGross Unrealized
Gains		Gross Unrealized
Losses		Fair Market Value
Mutual funds---$117,036,232 $— $(9,373,514)$107,662,718 
U.S. treasury securities
Less than 1
95,001,209 7,567 (44,266)94,964,510 
Certificates of deposit
Less than 1
2,977,564 13,664 (320)2,990,908 
U.S. agency mortgage-backed securities*1,435,592 — (384,331)1,051,261 
$216,450,597 $21,231 $(9,802,431)$206,669,397 

*No single maturity date.
Schedule of Assets and Liabilities Measured at Fair Value on a Recurring Basis
The following table presents the Company’s assets that were measured at fair value on a recurring basis, determined using the following inputs as of December 31, 2023:
 
Fair Value Measurements at
 December 31, 2023
 TotalQuoted Prices
in Active Markets
(Level 1)		Significant
Other Unobservable
Inputs
(Level 2)		Significant
Unobservable
Inputs
(Level 3)
Short-term investments
    Mutual funds$51,866,401 $51,866,401 $— $— 
    U.S. treasury securities75,189,720 75,189,720 — — 
    Certificates of deposit2,990,326 — 2,990,326 — 
    U.S. agency mortgage-backed securities936,466 — 936,466 — 
Total short-term investments130,982,913 127,056,121 3,926,792 — 
Investment in affiliated entity2,780,287 2,780,287 — — 
Total assets measured at fair value$133,763,200 $129,836,408 $3,926,792 $— 

The following table presents the Company’s assets that were measured at fair value on a recurring basis, determined using the following inputs as of December 31, 2022:
 
Fair Value Measurements at
 December 31, 2022
 TotalQuoted Prices
in Active Markets
(Level 1)		Significant
Other Unobservable
Inputs
(Level 2)		Significant
Unobservable
Inputs
(Level 3)
Short-term investments
     Mutual funds$107,662,718 $107,662,718 $— $— 
     U.S. treasury securities94,964,510 94,964,510 — — 
     Certificates of deposit2,990,908 — 2,990,908 — 
     U.S. agency mortgage-backed securities1,051,261 — 1,051,261 — 
Total short-term investments206,669,397 202,627,228 4,042,169 — 
Investments in affiliated entity2,007,142 2,007,142 — — 
Total assets measured at fair value$208,676,539 $204,634,370 $4,042,169 $— 
v3.24.0.1
Certain Balance Sheet Items (Tables)
 12 Months Ended
Dec. 31, 2023
Certain Balance Sheet Items [Abstract]  
Schedule of Prepaid Expenses And Other Current Assets
Prepaid and other current assets at December 31, 2023 and 2022 consisted of the following:
 
20232022
Insurance recovery (a)$— $30,000,000 
Prepaid manufacturing expenses1,486,638 1,401,028 
Other prepaid expenses3,907,027 18,729,453 
$5,393,665 $50,130,481 
Schedule of Accounts Payable And Accrued Expenses
Accounts payable and accrued expenses at December 31, 2023 and 2022 consisted of the following:
20232022
Trade accounts payable$3,577,826 $19,862,487 
Accrued compensation9,837,104 12,574,921 
Accrued litigation settlement (a)— 44,000,000 
Other accrued expenses (b) (c)6,432,814 3,249,477 
$19,847,744 $79,686,885 

(a)In July 2022, the Company entered into a memorandum of understanding for the proposed settlement of class action securities litigation (see Note 11). The final judicial order for the settlement was issued in January 2023. The settlement consisted of $30.0 million in cash and $14.0 million in shares of the Company's common stock to settle all outstanding claims. As of December 31, 2022, the Company's insurance carriers had paid the cash component of the proposed settlement, which amounts were being held in escrow. The Company's insurance carriers paid $252,000 of other expenses on behalf of the Company, which amounts were offset against the insurers' cash commitment as part of the settlement. During the three months ended March 31, 2023, the cash component of the settlement was released from escrow and the Company issued 760,083 shares of common stock pursuant to the securities class action settlement.

(b) In March 2023, the Company entered into a stipulation of settlement for the proposed settlement of shareholder derivative litigation (see Note 11). In June 2023, the court preliminarily approved the proposed settlement. As part of the settlement, in July 2023, the Company paid $1.2 million to plaintiffs’ counsel for their fees and expenses. This amount was accrued within “Other accrued expenses” as of December 31, 2022. On October 12, 2023, the court entered an order and final judgment approving the Settlement, which was effective on November 13, 2023.

(c) December 31, 2023 balance includes $4.3 million liability for unused grant funding.
v3.24.0.1
Fixed Assets (Tables)
 12 Months Ended
Dec. 31, 2023
Property, Plant and Equipment [Abstract]  
Schedule Of Fixed Assets
Fixed assets at December 31, 2023 and 2022 consisted of the following:
 
CostAccumulated
Depreciation
and
Amortization		Net Book
Value
As of December 31, 2023
Leasehold improvements$15,917,596 $(11,753,081)$4,164,515 
Research and development equipment3,538,698 (3,078,165)460,533 
Office furniture and fixtures2,827,476 (2,816,577)10,899 
Computer equipment and other 3,529,129 (3,204,090)325,039 
$25,812,899 $(20,851,913)$4,960,986 
As of December 31, 2022
Leasehold improvements$15,803,108 $(10,036,080)$5,767,028 
Research and development equipment5,300,104 (4,295,217)1,004,887 
Office furniture and fixtures2,827,476 (2,803,800)23,676 
Computer equipment and other 5,360,712 (4,428,306)932,406 
$29,291,400 $(21,563,403)$7,727,997 
v3.24.0.1
Goodwill and Intangible Assets (Tables)
 12 Months Ended
Dec. 31, 2023
Goodwill and Intangible Assets Disclosure [Abstract]  
Schedule of Goodwill and Intangible Assets By Major Asset Class
The following sets forth goodwill and intangible assets by major asset class:
 
 December 31, 2023December 31, 2022
 Weighted Average Useful
Life
(Yrs)		GrossAccumulated
Amortization		ImpairmentNet Book
Value		GrossAccumulated
Amortization		Net Book
Value
Indefinite lived:
Goodwill$10,513,371 $— $(10,513,371)$— $10,513,371 $— $10,513,371 
Definite lived:
Licenses10— — — — 1,323,761 (1,323,761)— 
Bioject —5,100,000 (3,115,556)(1,984,444)— 5,100,000 (2,988,889)2,111,111 
Other (a)184,050,000 (4,050,000)— — 4,050,000 (4,031,250)18,750 
Total intangible assets119,150,000 (7,165,556)(1,984,444)— 10,473,761 (8,343,900)2,129,861 
Total goodwill and intangible assets$19,663,371 $(7,165,556)$(12,497,815)$— $20,987,132 $(8,343,900)$12,643,232 
(a)Other intangible assets represent the estimated fair value of acquired intellectual property.
v3.24.0.1
Convertible Debt (Tables)
 12 Months Ended
Dec. 31, 2023
Debt Disclosure [Abstract]  
Schedule of Convertible Debt
The balance of the Notes at December 31, 2023 was as follows:
Principal amount$78,500,000 
Principal amount converted into common shares(62,085,000)
Unamortized debt issuance cost— 
Accrued interest355,654 
     Net carrying amount $16,770,654 
v3.24.0.1
Stockholders' Equity (Tables)
 12 Months Ended
Dec. 31, 2023
Stockholders' Equity Note [Abstract]  
Schedule of Preferred Stock Authorized, Issued And Outstanding
   Shares Outstanding as of
December 31,
 Shares AuthorizedShares Issued20232022
Series C Preferred Stock, par $0.001
1,091 1,091 9 9 
Schedule Of Shares Authorized Under Stock Option Plans, By Exercise Price Range
The following table summarizes total stock options outstanding at December 31, 2023:
 
 Options OutstandingOptions Exercisable
Exercise PriceShares Underlying Options
Outstanding		Weighted-Average
Remaining
Contractual Life
(in Years)		Weighted
Average
Exercise Price		Shares Underlying Options
Exercisable		Weighted Average
Exercise Price
$4.32-$18.00
283,472 9.2$14.11 66,918 $14.45 
$18.01-$39.00
264,108 7.3$35.69 141,600 $34.99 
$39.01-$52.00
156,505 4.5$44.93 156,271 $44.93 
$52.01-$90.00
129,681 4.2$76.82 121,124 $77.75 
$90.01-$130.00
136,716 4.2$100.15 131,640 $100.00 
$130.01-$233.28
158,382 5.4$140.27 129,250 $141.78 
1,128,864 6.4$58.76 746,803 $72.11 
Schedule Of Stock Options, Activity
Stock option activity under the Company’s equity incentive plans during the year ended December 31, 2023 was as follows:
Number of
Shares		Weighted-Average
Exercise Price
Balance, December 31, 20221,018,095 $75.32 
Granted339,019 14.23 
Exercised— — 
Cancelled(228,250)66.47 
Balance, December 31, 20231,128,864 $58.76 
Schedule Of Restricted Stock Unit Activity
Restricted stock unit activity under the Company’s equity incentive plans during the year ended December 31, 2023 was as follows:
Number of
Shares
Balance, December 31, 2022212,964 
Granted194,747 
Vested(99,420)
Cancelled(33,497)
Balance, December 31, 2023274,794 
v3.24.0.1
Commitments and Contingencies (Tables)
 12 Months Ended
Dec. 31, 2023
Leases [Abstract]  
Schedule Of Maturities Of Operating Lease Liabilities
As of December 31, 2023, the maturities of the Company's operating lease liabilities were as follows:
Year ending December 31,
2024$3,247,000 
20253,466,000 
20263,555,000 
20272,955,000 
20282,310,000 
Thereafter2,132,000 
   Total remaining lease payments17,665,000 
Less: present value adjustment(4,226,000)
   Total operating lease liabilities13,439,000 
Less: current portion(2,407,000)
Long-term operating lease liabilities$11,032,000 
Weighted-average remaining lease term5.3 years
Weighted-average discount rate8.9 %
v3.24.0.1
Income Taxes (Tables)
 12 Months Ended
Dec. 31, 2023
Income Tax Disclosure [Abstract]  
Schedule Of Components Of Pretax Loss From Operations
The components of pretax loss from operations are as follows:
Year Ended December 31,
202320222021
     U.S. Domestic$(134,979,579)$(277,440,803)$(302,614,003)
     Foreign(137,772)(211,249)(610,320)
Pretax loss from operations$(135,117,351)$(277,652,052)$(303,224,323)
Schedule Of Effective Income Tax Rate Reconciliation
The reconciliation of income taxes attributable to continuing operations computed at the statutory tax rates to income tax benefit, using a 21% statutory tax rate for December 31, 2023, 2022 and 2021, is as follows: 
Year Ended December 31,
202320222021
Benefit from income taxes at statutory rates$(28,375,000)$(58,307,000)$(63,677,000)
State income tax, net of federal benefit(3,922,000)(3,601,000)(3,447,000)
Change in valuation allowance28,394,000 61,065,000 77,424,000 
Research and development tax credits(2,139,000)(7,534,000)(16,523,000)
Stock-based compensation2,099,000 2,913,000 483,000 
Uncertain tax positions861,000 2,291,000 6,509,000 
Goodwill Impairment1,962,000 — — 
Expired NOLs and credits1,352,000 1,459,000 616,000 
Limited NOLs and credits(997,000)(1,337,000)(542,000)
Change in tax rates365,000 (187,000)— 
Foreign tax rate differential(4,000)(8,000)(24,000)
Other404,000 3,246,000 (819,000)
$— $— $— 
Schedule Of Deferred Tax Assets And Liabilities
Significant components of the Company’s deferred tax assets and liabilities as of December 31, 2023 and 2022 are shown below:
As of December 31,
20232022
Deferred tax assets:
Capitalized research expense$50,143,000 $41,252,000 
NOL carryforwards235,624,000 212,768,000 
Research and development and other tax credits27,734,000 26,442,000 
Deferred revenue22,000 538,000 
Stock-based compensation3,683,000 3,945,000 
Acquired intangibles907,000 559,000 
Investment in affiliated entity1,406,000 1,569,000 
Lease liability2,822,000 3,247,000 
Fixed assets337,000 57,000 
Other6,808,000 11,062,000 
329,486,000 301,439,000 
Valuation allowance(327,493,000)(299,124,000)
Total deferred tax assets1,993,000 2,315,000 
Deferred tax liabilities:
Acquired intangibles— (199,000)
Right of use asset(1,993,000)(2,148,000)
Total deferred tax liabilities(1,993,000)(2,347,000)
Net deferred tax liabilities$— $(32,000)
Schedule Of Operating Loss And Tax Credit Carryforward Expirations
Based upon statute, federal and state losses and credits are expected to expire as follows (in millions):
Expiration Date:Federal NOLsState NOLsForeign NOLsFederal R&DState R&D
2024$18.9 $9.1 $— $— $— 
202513.7 5.2 — — — 
202612.2 7.1 — — — 
2027 and thereafter249.2 332.0 1.1 41.6 — 
Indefinite719.3 0.6 — — 6.1 
$1,013.3 $354.0 $1.1 $41.6 $6.1 
Schedule Of Unrecognized Tax Benefits Rollforward
The following table summarizes the activity related to the Company's unrecognized tax benefits:
 Year ended December 31,
 202320222021
Balance at beginning of the year$21,139,000 $18,819,000 $12,210,000 
Increases related to current year tax positions1,816,000 2,902,000 6,602,000 
Increases (decreases) related to prior year tax positions(841,000)(582,000)7,000 
Balance at end of the year$22,114,000 $21,139,000 $18,819,000 
v3.24.0.1
Summary of Significant Accounting Policies - Narrative (Details)
 3 Months Ended 12 Months Ended
Jan. 24, 2024
Sep. 30, 2023
USD ($)
Jun. 30, 2023
USD ($)
Dec. 31, 2023
USD ($)
segment
Dec. 31, 2022
USD ($)
Dec. 31, 2021
USD ($)
Property, Plant and Equipment [Line Items]            
Net loss from operations       $ 135,117,352 $ 279,818,065 $ 303,658,710
Working capital       110,500,000    
Accumulated deficit       1,622,965,136 1,487,847,784  
Cash, cash equivalents, and short-term investments       145,300,000    
Proceeds from issuance of common stock       $ 5,461,745 82,955,311 209,441,410
Number of operating segments | segment       1    
Allowance for doubtful accounts       $ 0 0  
Impairment of goodwill   $ 10,500,000   10,513,371 0 0
Valuation allowance       (327,493,000) (299,124,000)  
Impairment of intangible assets       $ 1,984,444 0 0
Bioject            
Property, Plant and Equipment [Line Items]            
Impairment of intangible assets     $ 2,000,000      
Subsequent Event            
Property, Plant and Equipment [Line Items]            
Stock split, conversion ratio 0.083333          
Minimum            
Property, Plant and Equipment [Line Items]            
Property, plant, and equipment, useful life       3 years    
Maximum            
Property, Plant and Equipment [Line Items]            
Property, plant, and equipment, useful life       5 years    
Common stock | Sales Agreement            
Property, Plant and Equipment [Line Items]            
Proceeds from issuance of common stock       $ 5,500,000 $ 83,000,000 47,700,000
Common stock | Underwritten Public Offering            
Property, Plant and Equipment [Line Items]            
Proceeds from issuance of common stock           $ 162,100,000
v3.24.0.1
Summary of Significant Accounting Policies - Antidilutive Securities Table (Details) - shares
 12 Months Ended
Dec. 31, 2023
Dec. 31, 2022
Dec. 31, 2021
Antidilutive Securities Excluded from Computation of Earnings Per Share [Line Items]      
Total antidilutive securities (in shares) 1,658,098 1,494,827 1,387,806
Options to purchase common stock      
Antidilutive Securities Excluded from Computation of Earnings Per Share [Line Items]      
Total antidilutive securities (in shares) 1,128,864 1,018,095 874,082
Service-based restricted stock units      
Antidilutive Securities Excluded from Computation of Earnings Per Share [Line Items]      
Total antidilutive securities (in shares) 274,794 212,964 204,005
Performance-based restricted stock units      
Antidilutive Securities Excluded from Computation of Earnings Per Share [Line Items]      
Total antidilutive securities (in shares) 0 9,328 55,279
Convertible preferred stock      
Antidilutive Securities Excluded from Computation of Earnings Per Share [Line Items]      
Total antidilutive securities (in shares) 275 275 275
Convertible notes | 6.50% Convertible Senior Notes Due 2024      
Antidilutive Securities Excluded from Computation of Earnings Per Share [Line Items]      
Total antidilutive securities (in shares) 254,165 254,165 254,165
v3.24.0.1
Summary of Significant Accounting Policies - Summary of Stock-Based Compensation Assumptions (Details) - Stock Options
 12 Months Ended
Dec. 31, 2023
Dec. 31, 2022
Dec. 31, 2021
Employees and Directors      
Summary of assumptions used to estimate the fair value of stock options      
Risk-free interest rate 4.05% 2.05% 0.91%
Expected volatility 100.00% 94.00% 93.00%
Expected life in years 5 years 6 months 5 years 8 months 12 days 6 years
Dividend yield 0.00% 0.00% 0.00%
Non Employee      
Summary of assumptions used to estimate the fair value of stock options      
Risk-free interest rate 3.90% 1.96% 1.45%
Expected volatility 89.00% 87.00% 87.00%
Expected life in years 10 years 10 years 10 years
Dividend yield 0.00% 0.00% 0.00%
v3.24.0.1
Revenue Recognition and Concentration of Credit Risk- Revenue from External Customers (Details) - USD ($)
 12 Months Ended
Dec. 31, 2023
Dec. 31, 2022
Dec. 31, 2021
Disaggregation of Revenue [Line Items]      
Revenue from collaborative arrangements and other contracts, including affiliated entity $ 832,010 $ 10,262,268 $ 1,774,758
Revenue from Contract with Customer Benchmark | Customer Concentration Risk      
Disaggregation of Revenue [Line Items]      
% of Total Revenue 100.00% 100.00% 100.00%
ApolloBio Corporation      
Disaggregation of Revenue [Line Items]      
Revenue from collaborative arrangements and other contracts, including affiliated entity $ 245,056 $ 0 $ 0
ApolloBio Corporation | Revenue from Contract with Customer Benchmark | Customer Concentration Risk      
Disaggregation of Revenue [Line Items]      
% of Total Revenue 29.00% 0.00% 0.00%
Plumbline Life Sciences, Inc. (affiliated entity)      
Disaggregation of Revenue [Line Items]      
Revenue from collaborative arrangements and other contracts, including affiliated entity $ 0 $ 33,596 $ 245,310
Plumbline Life Sciences, Inc. (affiliated entity) | Revenue from Contract with Customer Benchmark | Customer Concentration Risk      
Disaggregation of Revenue [Line Items]      
% of Total Revenue 0.00% 0.00% 14.00%
U.S. Department of Defense      
Disaggregation of Revenue [Line Items]      
Revenue from collaborative arrangements and other contracts, including affiliated entity $ 0 $ 9,591,778 $ 754,853
U.S. Department of Defense | Revenue from Contract with Customer Benchmark | Customer Concentration Risk      
Disaggregation of Revenue [Line Items]      
% of Total Revenue 0.00% 94.00% 43.00%
All other, including affiliated entities      
Disaggregation of Revenue [Line Items]      
Revenue from collaborative arrangements and other contracts, including affiliated entity $ 586,954 $ 636,894 $ 774,595
All other, including affiliated entities | Revenue from Contract with Customer Benchmark | Customer Concentration Risk      
Disaggregation of Revenue [Line Items]      
% of Total Revenue 71.00% 6.00% 43.00%
v3.24.0.1
Revenue Recognition and Concentration of Credit Risk - Additional Information (Details) - USD ($)
 12 Months Ended
Dec. 31, 2023
Dec. 31, 2022
Revenue from Contract with Customer [Abstract]    
Revenue recognized from deferred revenue $ 0 $ 14,000
v3.24.0.1
Collaborative Agreements (Details) - USD ($)
 1 Months Ended 12 Months Ended
Jan. 31, 2022
Jun. 30, 2020
Apr. 30, 2020
Jan. 31, 2020
Aug. 30, 2019
Oct. 31, 2018
Apr. 30, 2018
Dec. 31, 2023
Dec. 31, 2022
Dec. 31, 2021
Collaborative Arrangement and Arrangement Other than Collaborative [Line Items]                    
Revenue from collaborative arrangements and other contracts, including affiliated entity               $ 832,010 $ 10,262,268 $ 1,774,758
ApolloBio Corporation | Collaborative Arrangement                    
Collaborative Arrangement and Arrangement Other than Collaborative [Line Items]                    
Upfront payment received               3,600,000 1,200,000 4,500,000
ApolloBio | Collaborative Arrangement                    
Collaborative Arrangement and Arrangement Other than Collaborative [Line Items]                    
Additional revenue to be achieved               $ 20,000,000    
Obligation period to pay royalties               10 years    
Funding received               $ 245,000    
Revenue from collaborative arrangements and other contracts, including affiliated entity                 0 0
Coalition for Epidemic Preparedness Innovations | Collaborative Arrangement                    
Collaborative Arrangement and Arrangement Other than Collaborative [Line Items]                    
Upfront payment received               1,800,000 6,700,000 10,000,000
Collaborative agreement, funding to be received     $ 6,900,000              
Coalition for Epidemic Preparedness Innovations | Collaborative Arrangement | Lassa Fever And MERS Vaccine                    
Collaborative Arrangement and Arrangement Other than Collaborative [Line Items]                    
Collaborative agreement, funding to be received             $ 56,000,000      
Collaborative agreement, period to receive funding for research and development             5 years      
Accounts receivable               0 1,700,000  
Accrued Liabilities               2,200,000 0  
Coalition for Epidemic Preparedness Innovations | Collaborative Arrangement | COVID19 Vaccine                    
Collaborative Arrangement and Arrangement Other than Collaborative [Line Items]                    
Collaborative agreement, funding to be received       $ 9,000,000       330,000 1,100,000 6,900,000
Accrued Liabilities               2,100,000    
Grants receivable                 2,300,000  
Coalition for Epidemic Preparedness Innovations | Collaborative Arrangement | CELLECTRA 3PSP Proprietary Smart Device                    
Collaborative Arrangement and Arrangement Other than Collaborative [Line Items]                    
Collaborative agreement, funding to be received     5,000,000              
Coalition for Epidemic Preparedness Innovations | Collaborative Arrangement | IN O4800                    
Collaborative Arrangement and Arrangement Other than Collaborative [Line Items]                    
Collaborative agreement, funding to be received     $ 1,300,000              
Bill And Melinda Gates Foundation | Collaborative Arrangement | D N A Encoded Monoclonal Antibody Technology                    
Collaborative Arrangement and Arrangement Other than Collaborative [Line Items]                    
Collaborative agreement, funding to be received         $ 1,100,000 $ 2,200,000   70,000 233,000 182,000
Grants receivable               87,000 153,000  
Department Of Defence | Collaborative Arrangement                    
Collaborative Arrangement and Arrangement Other than Collaborative [Line Items]                    
Grant proceeds received               0 6,100,000 27,100,000
Procurement contract               $ 0 $ 9,600,000 $ 755,000
Department Of Defence | Collaborative Arrangement | CELLECTRA 3PSP Proprietary Smart Device                    
Collaborative Arrangement and Arrangement Other than Collaborative [Line Items]                    
Funding received   $ 54,500,000                
Purchase price, procurement contract $ 10,700,000 $ 16,800,000                
v3.24.0.1
Short-term Investments and Fair Value Measurements - Schedule of Available-for-sale Securities (Details) - USD ($)
 12 Months Ended
Dec. 31, 2023
Dec. 31, 2022
Debt Securities, Available-for-sale, Sale [Abstract]    
Cost $ 134,873,427 $ 216,450,597
Gross Unrealized Gains 36,647 21,231
Gross Unrealized Losses (3,927,161) (9,802,431)
Fair Market Value 130,982,913 206,669,397
Mutual funds    
Debt Securities, Available-for-sale, Sale [Abstract]    
Cost 55,389,289 117,036,232
Gross Unrealized Gains 0 0
Gross Unrealized Losses (3,522,888) (9,373,514)
Fair Market Value $ 51,866,401 107,662,718
U.S. treasury securities    
Debt Securities, Available-for-sale [Line Items]    
Contractual maturity 1 year  
Debt Securities, Available-for-sale, Sale [Abstract]    
Cost $ 75,164,782 95,001,209
Gross Unrealized Gains 24,938 7,567
Gross Unrealized Losses 0 (44,266)
Fair Market Value 75,189,720 94,964,510
Certificates of deposit    
Debt Securities, Available-for-sale, Sale [Abstract]    
Cost 2,978,917 2,977,564
Gross Unrealized Gains 11,709 13,664
Gross Unrealized Losses (300) (320)
Fair Market Value $ 2,990,326 $ 2,990,908
Certificates of deposit | Maximum    
Debt Securities, Available-for-sale [Line Items]    
Contractual maturity 1 year 1 year
U.S. agency mortgage-backed securities    
Debt Securities, Available-for-sale, Sale [Abstract]    
Cost $ 1,340,439 $ 1,435,592
Gross Unrealized Gains 0 0
Gross Unrealized Losses (403,973) (384,331)
Fair Market Value $ 936,466 $ 1,051,261
v3.24.0.1
Short-term Investments and Fair Value Measurements - Narrative (Details)
 12 Months Ended
Dec. 31, 2023
USD ($)
position
shares
Dec. 31, 2022
USD ($)
shares
Dec. 31, 2021
USD ($)
Debt Securities, Available-for-sale [Line Items]      
Debt securities, available-for-sale, realized gain $ 1,000 $ 21,000  
Debt securities, available-for-sale, realized gain 4,800,000 4,100,000  
Net unrealized gain (loss) on available-for-sale equity securities $ 5,850,626 $ (7,846,172) $ (3,222,838)
Number of securities in a gross unrealized loss position | position 21    
Number of securities in a gross unrealized loss position for more than twelve months | position 20    
Unrealized loss on investments $ 3,900,000    
Fair Value, Inputs, Level 1      
Debt Securities, Available-for-sale [Line Items]      
Number of shares owned (in shares) | shares 597,808 597,808  
v3.24.0.1
Short-term Investments and Fair Value Measurements - Schedule of Assets and Liabilities Measured at Fair Value on a Recurring Basis (Details) - USD ($)
Dec. 31, 2023
Dec. 31, 2022
Financial assets and liabilities that are measured at fair value on recurring basis    
Short-term investments $ 130,982,913 $ 206,669,397
Mutual funds    
Financial assets and liabilities that are measured at fair value on recurring basis    
Short-term investments 51,866,401 107,662,718
Certificates of deposit    
Financial assets and liabilities that are measured at fair value on recurring basis    
Short-term investments 2,990,326 2,990,908
U.S. agency mortgage-backed securities    
Financial assets and liabilities that are measured at fair value on recurring basis    
Short-term investments 936,466 1,051,261
Fair Value, Measurements, Recurring    
Financial assets and liabilities that are measured at fair value on recurring basis    
Short-term investments 130,982,913 206,669,397
Investments in affiliated entity 2,780,287 2,007,142
Total assets measured at fair value 133,763,200 208,676,539
Fair Value, Measurements, Recurring | Quoted Prices in Active Markets (Level 1)    
Financial assets and liabilities that are measured at fair value on recurring basis    
Short-term investments 127,056,121 202,627,228
Investments in affiliated entity 2,780,287 2,007,142
Total assets measured at fair value 129,836,408 204,634,370
Fair Value, Measurements, Recurring | Significant Other Unobservable Inputs (Level 2)    
Financial assets and liabilities that are measured at fair value on recurring basis    
Short-term investments 3,926,792 4,042,169
Investments in affiliated entity 0 0
Total assets measured at fair value 3,926,792 4,042,169
Fair Value, Measurements, Recurring | Significant Unobservable Inputs (Level 3)    
Financial assets and liabilities that are measured at fair value on recurring basis    
Short-term investments 0 0
Investments in affiliated entity 0 0
Total assets measured at fair value 0 0
Fair Value, Measurements, Recurring | Mutual funds    
Financial assets and liabilities that are measured at fair value on recurring basis    
Short-term investments 51,866,401 107,662,718
Fair Value, Measurements, Recurring | Mutual funds | Quoted Prices in Active Markets (Level 1)    
Financial assets and liabilities that are measured at fair value on recurring basis    
Short-term investments 51,866,401 107,662,718
Fair Value, Measurements, Recurring | Mutual funds | Significant Other Unobservable Inputs (Level 2)    
Financial assets and liabilities that are measured at fair value on recurring basis    
Short-term investments 0 0
Fair Value, Measurements, Recurring | Mutual funds | Significant Unobservable Inputs (Level 3)    
Financial assets and liabilities that are measured at fair value on recurring basis    
Short-term investments 0 0
Fair Value, Measurements, Recurring | U.S. treasury securities    
Financial assets and liabilities that are measured at fair value on recurring basis    
Short-term investments 75,189,720 94,964,510
Fair Value, Measurements, Recurring | U.S. treasury securities | Quoted Prices in Active Markets (Level 1)    
Financial assets and liabilities that are measured at fair value on recurring basis    
Short-term investments 75,189,720 94,964,510
Fair Value, Measurements, Recurring | U.S. treasury securities | Significant Other Unobservable Inputs (Level 2)    
Financial assets and liabilities that are measured at fair value on recurring basis    
Short-term investments 0 0
Fair Value, Measurements, Recurring | U.S. treasury securities | Significant Unobservable Inputs (Level 3)    
Financial assets and liabilities that are measured at fair value on recurring basis    
Short-term investments 0 0
Fair Value, Measurements, Recurring | Certificates of deposit    
Financial assets and liabilities that are measured at fair value on recurring basis    
Short-term investments 2,990,326 2,990,908
Fair Value, Measurements, Recurring | Certificates of deposit | Quoted Prices in Active Markets (Level 1)    
Financial assets and liabilities that are measured at fair value on recurring basis    
Short-term investments 0 0
Fair Value, Measurements, Recurring | Certificates of deposit | Significant Other Unobservable Inputs (Level 2)    
Financial assets and liabilities that are measured at fair value on recurring basis    
Short-term investments 2,990,326 2,990,908
Fair Value, Measurements, Recurring | Certificates of deposit | Significant Unobservable Inputs (Level 3)    
Financial assets and liabilities that are measured at fair value on recurring basis    
Short-term investments 0 0
Fair Value, Measurements, Recurring | U.S. agency mortgage-backed securities    
Financial assets and liabilities that are measured at fair value on recurring basis    
Short-term investments 936,466 1,051,261
Fair Value, Measurements, Recurring | U.S. agency mortgage-backed securities | Quoted Prices in Active Markets (Level 1)    
Financial assets and liabilities that are measured at fair value on recurring basis    
Short-term investments 0 0
Fair Value, Measurements, Recurring | U.S. agency mortgage-backed securities | Significant Other Unobservable Inputs (Level 2)    
Financial assets and liabilities that are measured at fair value on recurring basis    
Short-term investments 936,466 1,051,261
Fair Value, Measurements, Recurring | U.S. agency mortgage-backed securities | Significant Unobservable Inputs (Level 3)    
Financial assets and liabilities that are measured at fair value on recurring basis    
Short-term investments $ 0 $ 0
v3.24.0.1
Certain Balance Sheet Items - Schedule of Prepaid and Other Current Assets (Details) - USD ($)
Dec. 31, 2023
Dec. 31, 2022
Certain Balance Sheet Items [Abstract]    
Insurance recovery $ 0 $ 30,000,000
Prepaid manufacturing expenses 1,486,638 1,401,028
Other prepaid expenses 3,907,027 18,729,453
Prepaid expenses and other current assets $ 5,393,665 $ 50,130,481
v3.24.0.1
Certain Balance Sheet Items - Schedule of Accounts Payable and Accrued Expenses (Details) - USD ($)
 1 Months Ended 12 Months Ended
Jul. 31, 2023
Dec. 31, 2023
Dec. 31, 2022
Mar. 31, 2023
Jan. 31, 2023
Jul. 31, 2022
Accounts Payable and Accrued Expenses [Line Items]            
Unused grant funding   $ 4,300,000        
Nonrelated Party            
Accounts Payable and Accrued Expenses [Line Items]            
Trade accounts payable   3,577,826 $ 19,862,487      
Accrued compensation   9,837,104 12,574,921      
Accrued litigation settlement   0 44,000,000      
Other accrued expenses   6,432,814 3,249,477      
Accounts payable and accrued liabilities   $ 19,847,744 79,686,885      
McDermid v. Inovio Pharmaceuticals, Inc. and J. Joseph Kim            
Accounts Payable and Accrued Expenses [Line Items]            
Estimate of cash settlement         $ 30,000,000 $ 30,000,000
Estimate of shares settlement         $ 14,000,000 $ 14,000,000
Amount paid to other party     $ 252,000      
Shares issued in settlement (in shares)       760,083    
Behesti v. Kim, et al.            
Accounts Payable and Accrued Expenses [Line Items]            
Damages paid $ 1,200,000          
v3.24.0.1
Fixed Assets (Details) - USD ($)
 12 Months Ended
Dec. 31, 2023
Dec. 31, 2022
Dec. 31, 2021
Property, Plant and Equipment [Line Items]      
Cost $ 25,812,899 $ 29,291,400  
Accumulated Depreciation and Amortization (20,851,913) (21,563,403)  
Net Book Value 4,960,986 7,727,997  
Depreciation 2,621,649 3,656,713 $ 3,040,096
Property, plant and equipment sold 148,000 6,100,000  
Property, plant and equipment disposed of 466,000 1,100,000  
Leasehold improvements      
Property, Plant and Equipment [Line Items]      
Cost 15,917,596 15,803,108  
Accumulated Depreciation and Amortization (11,753,081) (10,036,080)  
Net Book Value 4,164,515 5,767,028  
Research and development equipment      
Property, Plant and Equipment [Line Items]      
Cost 3,538,698 5,300,104  
Accumulated Depreciation and Amortization (3,078,165) (4,295,217)  
Net Book Value 460,533 1,004,887  
Office furniture and fixtures      
Property, Plant and Equipment [Line Items]      
Cost 2,827,476 2,827,476  
Accumulated Depreciation and Amortization (2,816,577) (2,803,800)  
Net Book Value 10,899 23,676  
Computer equipment and other      
Property, Plant and Equipment [Line Items]      
Cost 3,529,129 5,360,712  
Accumulated Depreciation and Amortization (3,204,090) (4,428,306)  
Net Book Value $ 325,039 $ 932,406  
v3.24.0.1
Goodwill and Intangible Assets - Narrative (Details) - USD ($)
 3 Months Ended 12 Months Ended
Sep. 30, 2023
Jun. 30, 2023
Dec. 31, 2023
Dec. 31, 2022
Dec. 31, 2021
Acquired Finite-Lived Intangible Assets [Line Items]          
Impairment of goodwill $ 10,500,000   $ 10,513,371 $ 0 $ 0
Impairment of intangible assets     1,984,444 0 0
Amortization of intangible assets     $ 145,417 496,494 520,415
Impairment       $ 0 $ 0
Bioject          
Acquired Finite-Lived Intangible Assets [Line Items]          
Impairment of intangible assets   $ 2,000,000      
v3.24.0.1
Goodwill and Intangible Assets - Schedule of Goodwill and Intangible Assets By Major Asset Class (Details) - USD ($)
 3 Months Ended 12 Months Ended
Sep. 30, 2023
Dec. 31, 2023
Dec. 31, 2022
Dec. 31, 2021
Indefinite lived:        
Goodwill, gross   $ 10,513,371 $ 10,513,371  
Impairment loss $ (10,500,000) (10,513,371) 0 $ 0
Goodwill   0 10,513,371  
Definite lived:        
Intangible assets, gross   9,150,000 10,473,761  
Intangible assets, accumulated amortization   (7,165,556) (8,343,900)  
Impairment of intangible assets   (1,984,444) 0 $ 0
Intangible assets, net book value   0 2,129,861  
Goodwill and intangible asset impairment   (12,497,815)    
Total goodwill and intangible assets, gross   19,663,371 20,987,132  
Total goodwill and intangible assets, net book value   $ 0 12,643,232  
Weighted Average Useful Life (Yrs)        
Definite lived:        
Useful life (in years)   11 years    
Licenses        
Definite lived:        
Intangible assets, gross   $ 0 1,323,761  
Intangible assets, accumulated amortization   0 (1,323,761)  
Impairment of intangible assets   0    
Intangible assets, net book value   $ 0 0  
Licenses | Weighted Average Useful Life (Yrs)        
Definite lived:        
Useful life (in years)   10 years    
Bioject        
Definite lived:        
Intangible assets, gross   $ 5,100,000 5,100,000  
Intangible assets, accumulated amortization   (3,115,556) (2,988,889)  
Impairment of intangible assets   (1,984,444)    
Intangible assets, net book value   0 2,111,111  
Other        
Definite lived:        
Intangible assets, gross   4,050,000 4,050,000  
Intangible assets, accumulated amortization   (4,050,000) (4,031,250)  
Impairment of intangible assets   0    
Intangible assets, net book value   $ 0 $ 18,750  
Other | Weighted Average Useful Life (Yrs)        
Definite lived:        
Useful life (in years)   18 years    
v3.24.0.1
Convertible Debt - Narrative (Details) - USD ($)
 12 Months Ended
Mar. 01, 2024
Mar. 01, 2019
Dec. 31, 2023
Dec. 31, 2022
Dec. 31, 2021
Jan. 01, 2022
Feb. 19, 2019
Debt Instrument [Line Items]              
Accumulated deficit     $ (1,622,965,136) $ (1,487,847,784)      
Additional paid-in capital     (1,740,954,074) (1,710,888,191)      
Interest expense     1,222,789 1,253,952 $ 1,936,447    
Accounting Standards Update 2020-06              
Debt Instrument [Line Items]              
Accumulated deficit           $ 1,800,000  
Additional paid-in capital           3,300,000  
Convertible senior notes           $ 1,500,000  
6.50% Convertible Senior Notes Due 2024              
Debt Instrument [Line Items]              
Debt instrument, face amount     78,500,000        
Debt issuance costs, net     0        
Convertible Debt              
Debt Instrument [Line Items]              
Debt issuance costs, net     $ 2,200,000        
Convertible Debt | 6.50% Convertible Senior Notes Due 2024              
Debt Instrument [Line Items]              
Debt instrument, face amount   $ 78,500,000         $ 78,500,000
Debt interest based on the fixed rate   6.50%         6.50%
Proceeds from issuance of debt   $ 75,700,000          
Debt instrument, unamortized discount   $ 16,300,000          
Debt instrument, interest rate, effective percentage     13.10%        
Debt issuance costs, net     $ 592,000        
Interest expense     1,200,000 $ 1,300,000 $ 1,900,000    
Interest expense, debt     $ 1,100,000        
Convertible Debt | 6.50% Convertible Senior Notes Due 2024 | Subsequent Event              
Debt Instrument [Line Items]              
Repayments of convertible debt $ 16,900,000            
v3.24.0.1
Convertible Debt - Schedule of Convertible Debt (Details) - 6.50% Convertible Senior Notes Due 2024
Dec. 31, 2023
USD ($)
Debt Instrument [Line Items]  
Principal amount $ 78,500,000
Principal amount converted into common shares (62,085,000)
Unamortized debt issuance cost 0
Accrued interest 355,654
Net carrying amount $ 16,770,654
v3.24.0.1
Stockholders' Equity - Schedule of Preferred Stock (Details) - $ / shares
Dec. 31, 2023
Dec. 31, 2022
Summary of common and preferred stock authorized, issued and outstanding    
Preferred stock, par value (in dollars per share) $ 0.001 $ 0.001
Preferred stock, shares authorized (in shares) 10,000,000 10,000,000
Preferred stock, shares issued (in shares) 9 9
Preferred stock, shares outstanding (in shares) 9 9
Series C Preferred Stock    
Summary of common and preferred stock authorized, issued and outstanding    
Preferred stock, par value (in dollars per share) $ 0.001 $ 0.001
Preferred stock, shares authorized (in shares) 1,091  
Preferred stock, shares issued (in shares) 1,091  
Preferred stock, shares outstanding (in shares) 9 9
v3.24.0.1
Stockholders' Equity - Narrative (Details) - USD ($)
 12 Months Ended
Nov. 09, 2021
Dec. 31, 2023
Dec. 31, 2022
Dec. 31, 2021
May 16, 2023
Mar. 31, 2023
Jun. 24, 2022
Class of Stock [Line Items]              
Convertible preferred stock, shares issued upon conversion, conversion price (in dollars per share)       $ 326.40      
Common stock, shares issued (in shares) [1]   22,793,075 21,090,938        
Allocated share-based compensation expense   $ 10,400,000 $ 22,200,000 $ 25,000,000      
Employee service share-based compensation, nonvested awards, total compensation cost not yet recognized   $ 4,300,000 $ 10,500,000        
Employee service share-based compensation, nonvested awards, total compensation cost not yet recognized, period for recognition   1 year 3 months 18 days 1 year 7 months 6 days        
Number of options outstanding to purchase common stock (in shares)   1,128,864 1,018,095        
Aggregate intrinsic value of options outstanding   $ 2,000          
Aggregate intrinsic value for options exercisable   $ 1,000          
Options exercisable, remaining contractual term   5 years 6 months          
Number of options expected to vest (in shares)   1,128,864          
Options, expirations in period, weighted average exercise price (in dollars per share)   $ 38.86 $ 101.64 $ 54.72      
Options, expirations in period (in shares)   9,357 6,437 583      
Options, grants in period, weighted average grant date fair value (in dollars per share)   $ 11.19 $ 28.08 $ 91.32      
Proceeds from stock options exercised   $ 0 $ 283,000 $ 6,700,000      
Options, exercises in period, aggregate intrinsic value     81,000 7,000,000      
McDermid v. Inovio Pharmaceuticals, Inc. and J. Joseph Kim              
Class of Stock [Line Items]              
Shares issued in settlement (in shares)           760,083  
Nonemployee              
Class of Stock [Line Items]              
Allocated share-based compensation expense   $ 669,000 1,300,000 1,400,000      
Number of options outstanding to purchase common stock (in shares)   61,808          
Research and Development Expense              
Class of Stock [Line Items]              
Allocated share-based compensation expense   $ 4,500,000 8,800,000 13,400,000      
General and Administrative Expense              
Class of Stock [Line Items]              
Allocated share-based compensation expense   $ 5,900,000 $ 13,400,000 $ 11,600,000      
Restricted Stock Units (RSUs)              
Class of Stock [Line Items]              
Number of shares of unvested restricted stock units and options outstanding (in shares)   274,794 212,964        
Employee service share-based compensation, nonvested awards, total compensation cost not yet recognized   $ 3,500,000 $ 7,200,000        
Employee service share-based compensation, nonvested awards, total compensation cost not yet recognized, period for recognition   1 year 6 months 1 year 8 months 12 days        
Aggregate intrinsic value of unvested   $ 1,700,000          
Aggregate intrinsic value of vested   $ 1,300,000          
RSU's expected to vest (in shares)   274,794          
Weighted average grant date fair value (in dollars per share)   $ 10.34 $ 37.44 $ 124.44      
Restricted Stock Units (RSUs) | Former President and Chief Executive Officer              
Class of Stock [Line Items]              
Awards settled in cash, percentage   50.00%          
2016 Incentive Plan              
Class of Stock [Line Items]              
Number of shares of vested restricted stock outstanding under the plan (in shares)   262,641          
Number of common stock shares outstanding under the Incentive Plan (in shares)   961,499          
Vesting period of incentive plan   3 years          
Contractual year term of incentive plan   10 years          
2022 Inducement Plan              
Class of Stock [Line Items]              
Reserved number of shares under the Incentive Plan (in shares)             166,666
Number of shares available for grants under the Incentive Plan (in shares)   125,575          
Number of common stock shares outstanding under the Incentive Plan (in shares)   27,759          
Number of shares of unvested restricted stock units and options outstanding (in shares)   10,278          
2007 Incentive Plan              
Class of Stock [Line Items]              
Number of common stock shares outstanding under the Incentive Plan (in shares)   136,456          
Vesting period of incentive plan   3 years          
Contractual year term of incentive plan   10 years          
2023 Incentive Plan              
Class of Stock [Line Items]              
Reserved number of shares under the Incentive Plan (in shares)         1,166,666    
Number of shares available for grants under the Incentive Plan (in shares)   1,334,012          
Number of common stock shares outstanding under the Incentive Plan (in shares)   3,150          
Number of shares of unvested restricted stock units and options outstanding (in shares)   1,875          
Vesting period of incentive plan   3 years          
Contractual year term of incentive plan   10 years          
Series C Preferred Stock              
Class of Stock [Line Items]              
Convertible preferred stock, shares issued upon conversion (in shares)       275      
Common stock | 2021 Sales Agreement              
Class of Stock [Line Items]              
Common stock aggregate offering price $ 300,000,000            
Sales Agents will be entitled to compensation 3.00%            
Stock sale agreement, aggregate number of shares issued (in shares)   875,305 2,870,478        
Sales made at a weighted average price (in dollars per share)   $ 6.33 $ 29.34        
Stock sale agreement, aggregate proceeds from issuance of stock   $ 5,500,000 $ 83,000,000        
Remaining authorized amount   $ 161,800,000          
[1]
(1) The Company effected a reverse stock split of its outstanding shares of common stock on January 24, 2024 where every twelve shares of its common stock issued and outstanding was converted into one share of common stock. Any fractional post-split shares as a result of the reverse split were paid in cash. Shareholders of the Company authorized the Board of Directors to approve the reverse stock split at a special meeting of stockholders held on January 12, 2024. Outstanding share amounts have been restated to reflect the reverse stock split on a retroactive basis for all periods presented.
v3.24.0.1
Stockholders' Equity - Schedule of Stock Options Outstanding (Details)
 12 Months Ended
Dec. 31, 2023
$ / shares
shares
Share-based Payment Arrangement, Option, Exercise Price Range [Line Items]  
Options outstanding (in shares) | shares 1,128,864
Weighted-average remaining contractual life (in Years) 6 years 4 months 24 days
Weighted average exercise price (in dollars per share) $ 58.76
Options exercisable (in shares) | shares 746,803
Weighted average exercise price (in dollars per share) $ 72.11
$4.32-$18.00  
Share-based Payment Arrangement, Option, Exercise Price Range [Line Items]  
Exercise price, lower range limit (in dollars per share) 4.32
Exercise price, upper range limit (in dollars per share) $ 18.00
Options outstanding (in shares) | shares 283,472
Weighted-average remaining contractual life (in Years) 9 years 2 months 12 days
Weighted average exercise price (in dollars per share) $ 14.11
Options exercisable (in shares) | shares 66,918
Weighted average exercise price (in dollars per share) $ 14.45
$18.01-$39.00  
Share-based Payment Arrangement, Option, Exercise Price Range [Line Items]  
Exercise price, lower range limit (in dollars per share) 18.01
Exercise price, upper range limit (in dollars per share) $ 39.00
Options outstanding (in shares) | shares 264,108
Weighted-average remaining contractual life (in Years) 7 years 3 months 18 days
Weighted average exercise price (in dollars per share) $ 35.69
Options exercisable (in shares) | shares 141,600
Weighted average exercise price (in dollars per share) $ 34.99
$39.01-$52.00  
Share-based Payment Arrangement, Option, Exercise Price Range [Line Items]  
Exercise price, lower range limit (in dollars per share) 39.01
Exercise price, upper range limit (in dollars per share) $ 52.00
Options outstanding (in shares) | shares 156,505
Weighted-average remaining contractual life (in Years) 4 years 6 months
Weighted average exercise price (in dollars per share) $ 44.93
Options exercisable (in shares) | shares 156,271
Weighted average exercise price (in dollars per share) $ 44.93
$52.01-$90.00  
Share-based Payment Arrangement, Option, Exercise Price Range [Line Items]  
Exercise price, lower range limit (in dollars per share) 52.01
Exercise price, upper range limit (in dollars per share) $ 90.00
Options outstanding (in shares) | shares 129,681
Weighted-average remaining contractual life (in Years) 4 years 2 months 12 days
Weighted average exercise price (in dollars per share) $ 76.82
Options exercisable (in shares) | shares 121,124
Weighted average exercise price (in dollars per share) $ 77.75
$90.01-$130.00  
Share-based Payment Arrangement, Option, Exercise Price Range [Line Items]  
Exercise price, lower range limit (in dollars per share) 90.01
Exercise price, upper range limit (in dollars per share) $ 130.00
Options outstanding (in shares) | shares 136,716
Weighted-average remaining contractual life (in Years) 4 years 2 months 12 days
Weighted average exercise price (in dollars per share) $ 100.15
Options exercisable (in shares) | shares 131,640
Weighted average exercise price (in dollars per share) $ 100.00
$130.01-$233.28  
Share-based Payment Arrangement, Option, Exercise Price Range [Line Items]  
Exercise price, lower range limit (in dollars per share) 130.01
Exercise price, upper range limit (in dollars per share) $ 233.28
Options outstanding (in shares) | shares 158,382
Weighted-average remaining contractual life (in Years) 5 years 4 months 24 days
Weighted average exercise price (in dollars per share) $ 140.27
Options exercisable (in shares) | shares 129,250
Weighted average exercise price (in dollars per share) $ 141.78
v3.24.0.1
Stockholders' Equity - Schedule of Stock Option Activity Under Equity Incentive Plan (Details)
 12 Months Ended
Dec. 31, 2023
$ / shares
shares
Number of Shares  
Beginning balance (in shares) | shares 1,018,095
Granted (in shares) | shares 339,019
Exercised (in shares) | shares 0
Cancelled (in shares) | shares (228,250)
Ending balance (in shares) | shares 1,128,864
Weighted-Average Exercise Price  
Beginning balance (in dollars per share) | $ / shares $ 75.32
Granted (in dollars per share) | $ / shares 14.23
Exercised (in dollars per share) | $ / shares 0
Cancelled (in dollars per share) | $ / shares 66.47
Ending balance (in dollars per share) | $ / shares $ 58.76
v3.24.0.1
Stockholders' Equity - Schedule of RSU Activity Under Equity Incentive Plan (Details) - Performance-based restricted stock units
 12 Months Ended
Dec. 31, 2023
shares
Share-based Compensation Arrangement by Share-based Payment Award, Equity Instruments Other than Options, Nonvested, Number of Shares [Roll Forward]  
Beginning balance (in shares) 212,964
Granted (in shares) 194,747
Vested (in shares) (99,420)
Cancelled (in shares) (33,497)
Ending balance (in shares) 274,794
v3.24.0.1
Commitments and Contingencies - Narrative (Details)
$ in Thousands
 1 Months Ended 3 Months Ended 12 Months Ended
Nov. 30, 2023
USD ($)
ft²
lease
Jul. 31, 2023
USD ($)
Apr. 30, 2020
defendent
Dec. 31, 2023
ft²
Sep. 30, 2023
ft²
Dec. 31, 2019
ft²
agreement
Dec. 31, 2023
USD ($)
ft²
Dec. 31, 2022
USD ($)
Dec. 31, 2021
USD ($)
Mar. 31, 2023
shares
Jan. 31, 2023
USD ($)
Jul. 31, 2022
USD ($)
Operating Leased Assets [Line Items]                        
Number of leases amended | lease 1                      
Area under lease amended | ft² 31,207                      
Lease, cost             $ 3,500 $ 3,400 $ 3,400      
Number of agreements | agreement           2            
McDermid v. Inovio Pharmaceuticals, Inc. and J. Joseph Kim                        
Operating Leased Assets [Line Items]                        
Estimate of cash settlement                     $ 30,000 $ 30,000
Estimate of shares settlement                     $ 14,000 $ 14,000
Shares issued in settlement (in shares) | shares                   760,083    
Behesti v. Kim, et al.                        
Operating Leased Assets [Line Items]                        
Number of defendants | defendent     8                  
Damages paid   $ 1,200                    
Minimum                        
Operating Leased Assets [Line Items]                        
Operating lease, remaining lease term       3 years 4 months 24 days     3 years 4 months 24 days          
Maximum                        
Operating Leased Assets [Line Items]                        
Operating lease, remaining lease term       6 years     6 years          
San Diego, California                        
Operating Leased Assets [Line Items]                        
Lessee, operating lease, area of land under lease | ft² 5,563           56,600          
Initial term of contract 4 years 3 months 18 days                      
Annual increase of base rent percentage 3.00%                      
Deposit payments $ 33                      
Plymouth Meeting, Pennsylvania                        
Operating Leased Assets [Line Items]                        
Lessee, operating lease, area of land under lease | ft²       7,000 4,400 13,500 57,360          
v3.24.0.1
Commitments and Contingencies - Summary of Maturities of Operating Lease Payments (Details) - USD ($)
Dec. 31, 2023
Dec. 31, 2022
Leases [Abstract]    
2024 $ 3,247,000  
2025 3,466,000  
2026 3,555,000  
2027 2,955,000  
2028 2,310,000  
Thereafter 2,132,000  
Total remaining lease payments 17,665,000  
Less: present value adjustment (4,226,000)  
Total operating lease liabilities 13,439,000  
Less: current portion (2,406,522) $ (2,803,973)
Long-term operating lease liabilities $ 11,032,066 $ 12,655,586
Weighted-average remaining lease term 5 years 3 months 18 days  
Weighted-average discount rate 8.90%  
v3.24.0.1
Income Taxes - Components of Pretax Loss from Operations (Details) - USD ($)
 12 Months Ended
Dec. 31, 2023
Dec. 31, 2022
Dec. 31, 2021
Income Tax Disclosure [Abstract]      
U.S. Domestic $ (134,979,579) $ (277,440,803) $ (302,614,003)
Foreign (137,772) (211,249) (610,320)
Net loss before share in net loss of Geneos $ (135,117,351) $ (277,652,052) $ (303,224,323)
v3.24.0.1
Income Taxes - Reconciliation of Income Taxes (Details) - USD ($)
$ in Thousands
 12 Months Ended
Dec. 31, 2023
Dec. 31, 2022
Dec. 31, 2021
Income Tax Expense (Benefit), Continuing Operations, Income Tax Reconciliation [Abstract]      
Benefit from income taxes at statutory rates $ (28,375) $ (58,307) $ (63,677)
State income tax, net of federal benefit (3,922) (3,601) (3,447)
Change in valuation allowance 28,394 61,065 77,424
Research and development tax credits (2,139) (7,534) (16,523)
Stock-based compensation 2,099 2,913 483
Uncertain tax positions 861 2,291 6,509
Goodwill Impairment 1,962 0 0
Expired NOLs and credits 1,352 1,459 616
Limited NOLs and credits (997) (1,337) (542)
Change in tax rates 365 (187) 0
Foreign tax rate differential (4) (8) (24)
Other 404 3,246 (819)
Income tax expense (benefit) $ 0 $ 0 $ 0
v3.24.0.1
Income Taxes - Narrative (Details) - USD ($)
 12 Months Ended
Dec. 31, 2023
Dec. 31, 2022
Dec. 31, 2021
Dec. 31, 2018
Operating Loss Carryforwards [Line Items]        
Income tax expense (benefit) $ 0 $ 0 $ 0  
Tax benefits expired 7,300,000      
Unrecognized tax benefits that would impact effective tax rate 20,500,000 19,700,000 $ 17,400,000  
Federal        
Operating Loss Carryforwards [Line Items]        
Net operating loss carryforwards that will expire due to IRC Section 382 limitations 1,013,300,000      
Net operating loss carryforwards       $ 719,300,000
Federal | Research Tax Credit Carryforward        
Operating Loss Carryforwards [Line Items]        
Tax credit carryforward amount 41,600,000      
California        
Operating Loss Carryforwards [Line Items]        
Net operating loss carryforwards that will expire due to IRC Section 382 limitations 251,400,000      
Pennsylvania        
Operating Loss Carryforwards [Line Items]        
Net operating loss carryforwards that will expire due to IRC Section 382 limitations 102,600,000      
Korean State Income Tax Authority        
Operating Loss Carryforwards [Line Items]        
Net operating loss carryforwards that will expire due to IRC Section 382 limitations   $ 1,100,000    
State        
Operating Loss Carryforwards [Line Items]        
Net operating loss carryforwards 354,000,000.0      
State | Research Tax Credit Carryforward        
Operating Loss Carryforwards [Line Items]        
Tax credit carryforward amount $ 6,100,000      
v3.24.0.1
Income Taxes - Significant Components of Deferred Tax Assets and Liabilities (Details) - USD ($)
$ in Thousands
Dec. 31, 2023
Dec. 31, 2022
Deferred tax assets:    
Capitalized research expense $ 50,143 $ 41,252
NOL carryforwards 235,624 212,768
Research and development and other tax credits 27,734 26,442
Deferred revenue 22 538
Stock-based compensation 3,683 3,945
Acquired intangibles 907 559
Investment in affiliated entity 1,406 1,569
Lease liability 2,822 3,247
Fixed assets 337 57
Other 6,808 11,062
Deferred tax assets, gross 329,486 301,439
Valuation allowance (327,493) (299,124)
Total deferred tax assets 1,993 2,315
Deferred tax liabilities:    
Acquired intangibles 0 (199)
Right of use asset (1,993) (2,148)
Total deferred tax liabilities (1,993) (2,347)
Net deferred tax liabilities $ 0 $ (32)
v3.24.0.1
Income Taxes - Expected Expirations of Federal and State Losses and Credits (Details)
$ in Millions
Dec. 31, 2023
USD ($)
Federal  
Expirations of Operating Loss Carryforwards, Components [Abstract]  
2024 $ 18.9
2025 13.7
2026 12.2
2027 and thereafter 249.2
Indefinite 719.3
Total 1,013.3
State  
Expirations of Operating Loss Carryforwards, Components [Abstract]  
2024 9.1
2025 5.2
2026 7.1
2027 and thereafter 332.0
Indefinite 0.6
Total 354.0
Foreign Tax Authority  
Expirations of Operating Loss Carryforwards, Components [Abstract]  
2024 0.0
2025 0.0
2026 0.0
2027 and thereafter 1.1
Indefinite 0.0
Total 1.1
Research Tax Credit Carryforward | Federal  
Expirations of Tax Credit Carryforwards [Abstract]  
2024 0.0
2025 0.0
2026 0.0
2027 and thereafter 41.6
Indefinite 0.0
Total 41.6
Research Tax Credit Carryforward | State  
Expirations of Tax Credit Carryforwards [Abstract]  
2024 0.0
2025 0.0
2026 0.0
2027 and thereafter 0.0
Indefinite 6.1
Total $ 6.1
v3.24.0.1
Income Taxes - Unrecognized Tax Benefits Activity (Details) - USD ($)
$ in Thousands
 12 Months Ended
Dec. 31, 2023
Dec. 31, 2022
Dec. 31, 2021
Reconciliation of Unrecognized Tax Benefits, Excluding Amounts Pertaining to Examined Tax Returns [Roll Forward]      
Balance at beginning of the year $ 21,139 $ 18,819 $ 12,210
Increases related to current year tax positions 1,816 2,902 6,602
Increases (decreases) related to prior year tax positions (841) (582)  
Increases (decreases) related to prior year tax positions     7
Balance at end of the year $ 22,114 $ 21,139 $ 18,819
v3.24.0.1
401(k) Plan (Details) - USD ($)
$ in Millions
 12 Months Ended
Dec. 31, 2023
Dec. 31, 2022
Dec. 31, 2021
Retirement Benefits [Abstract]      
Employer matching contribution, percent 50.00%    
Maximum annual contribution per employee, percent 6.00%    
Company's contribution to 401(k) plan $ 1.4 $ 1.8 $ 1.5
v3.24.0.1
Related Party Transactions (Details) - USD ($)
 1 Months Ended 3 Months Ended 12 Months Ended
Dec. 31, 2022
Mar. 31, 2016
Mar. 31, 2020
Dec. 31, 2023
Dec. 31, 2022
Dec. 31, 2021
Related Party Transaction [Line Items]            
Revenue from collaborative arrangements and other contracts, including affiliated entity       $ 832,010 $ 10,262,268 $ 1,774,758
Research and development       $ 86,676,563 $ 187,650,503 249,240,324
Plumbline Life Sciences            
Related Party Transaction [Line Items]            
Number of shares owned (in shares) 597,808     597,808 597,808  
Ownership percentage 18.70%     17.80% 18.70%  
Affiliated Entity            
Related Party Transaction [Line Items]            
Expenses to reimburse   $ 3,100,000        
Term   5 years        
Grant proceeds received       $ 1,000,000 $ 8,700,000  
Affiliated Entity | Revenue under collaborative research and development arrangements from affiliated entities            
Related Party Transaction [Line Items]            
Revenue from collaborative arrangements and other contracts, including affiliated entity       0 34,000 245,000
Plumbline Life Sciences | Affiliated Entity            
Related Party Transaction [Line Items]            
Accounts receivable $ 59,000     0 59,000  
The Wistar Institute            
Related Party Transaction [Line Items]            
Agreement amended amount           13,600,000
The Wistar Institute | Affiliated Entity            
Related Party Transaction [Line Items]            
Awarded amount 1,200,000   $ 10,700,000      
Awarded option amount 5,400,000         1,600,000
Research and development       1,800,000 1,400,000 $ 2,900,000
Accounts receivable 9,900,000     2,400,000 9,900,000  
Accounts payable and accrued expenses 1,200,000     1,100,000 1,200,000  
Prepaid expense 375,000     20,000 375,000  
Deferred grant funding from affiliate $ 88,000     $ 22,000 $ 88,000  
v3.24.0.1
Geneos Therapeutics, Inc. - Narrative (Details) - USD ($)
 1 Months Ended 3 Months Ended 12 Months Ended
Mar. 31, 2022
Mar. 31, 2021
Dec. 31, 2023
Dec. 31, 2022
Dec. 31, 2021
Feb. 28, 2021
Noncontrolling Interest [Line Items]            
Share in net loss of Geneos     $ 0 $ 2,165,213 $ 434,387  
Payments to acquire additional interest in subsidiaries     $ 0 $ 1,999,998 $ 0  
Series A-2 One Preferred Stock            
Noncontrolling Interest [Line Items]            
Share in net loss of Geneos $ 2,200,000          
Investment in Geneos 0          
Resulting in again on memeasurement $ 165,000          
Geneos Therapeutics, Inc.            
Noncontrolling Interest [Line Items]            
Noncontrolling interest, ownership percentage by parent 28.00%   23.00%     35.00%
Geneos Therapeutics, Inc.            
Noncontrolling Interest [Line Items]            
Loss from equity method investment, recorded and allocated to investment   $ (1,500,000)        
Share in net loss of Geneos   434,000        
Investment in Geneos   0        
Geneos Therapeutics, Inc. | Common stock            
Noncontrolling Interest [Line Items]            
Investment in Geneos   0        
Geneos Therapeutics, Inc. | Series A-1 Preferred Stock            
Noncontrolling Interest [Line Items]            
Share in net loss of Geneos   819,000        
Geneos Therapeutics, Inc. | Preferred stock            
Noncontrolling Interest [Line Items]            
Share in net loss of Geneos   4,200,000        
Investment in Geneos   $ 0        
Payments to acquire additional interest in subsidiaries $ 2,000,000          
v3.24.0.1
Subsequent Events (Details) - Subsequent Event
$ / shares in Units, $ in Millions
 2 Months Ended
Mar. 01, 2024
USD ($)
Jan. 24, 2024
Mar. 06, 2024
USD ($)
$ / shares
shares
Subsequent Event [Line Items]      
Stock split, conversion ratio   0.083333  
2021 Sales Agreement      
Subsequent Event [Line Items]      
Number of shares issued in transaction (in shares) | shares     543,620
Consideration received     $ 5.2
Sale of stock, price per share (in dollars per share) | $ / shares     $ 9.76
6.50% Convertible Senior Notes Due 2024 | Convertible Debt      
Subsequent Event [Line Items]      
Repayments of convertible debt $ 16.9