ADVERUM BIOTECHNOLOGIES, INC., 10-Q filed on 11/12/2025
Quarterly Report
v3.25.3
Cover Page - shares
 9 Months Ended
Sep. 30, 2025
Nov. 07, 2025
Cover [Abstract]    
Document Type 10-Q  
Document Quarterly Report true  
Document Period End Date Sep. 30, 2025  
Document Transition Report false  
Entity File Number 001-36579  
Entity Registrant Name Adverum Biotechnologies, Inc.  
Entity Incorporation, State or Country Code DE  
Entity Tax Identification Number 20-5258327  
Entity Address, Address Line One 100 Cardinal Way  
Entity Address, City or Town Redwood City  
Entity Address, State or Province CA  
Entity Address, Postal Zip Code 94063  
City Area Code 650  
Local Phone Number 656-9323  
Title of 12(b) Security Common Stock, $0.0001 par value  
Trading Symbol ADVM  
Security Exchange Name NASDAQ  
Entity Current Reporting Status Yes  
Entity Interactive Data Current Yes  
Entity Filer Category Non-accelerated Filer  
Entity Small Business true  
Entity Emerging Growth Company false  
Entity Shell Company false  
Entity Common Stock, Shares Outstanding   22,077,467
Amendment Flag false  
Document Fiscal Year Focus 2025  
Document Fiscal Period Focus Q3  
Entity Central Index Key 0001501756  
Current Fiscal Year End Date --12-31  
v3.25.3
Condensed Consolidated Balance Sheets - USD ($)
$ in Thousands
Sep. 30, 2025
Dec. 31, 2024
Current assets:    
Cash and cash equivalents $ 26,060 $ 60,652
Short-term investments 0 65,039
Prepaid expenses and other current assets 2,849 5,609
Total current assets 28,909 131,300
Operating lease right-of-use assets 29,031 33,611
Property and equipment, net 10,462 11,607
Restricted cash 1,976 1,976
Deposit and other long-term assets 2,023 1,347
Total assets 72,401 179,841
Current liabilities:    
Accounts payable 12,459 1,610
Accrued expenses and other current liabilities 26,476 15,620
Lease liability, current portion 5,814 5,668
Total current liabilities 44,749 22,898
Lease liability, net of current portion 83,126 86,037
Other non-current liabilities 179 192
Total liabilities 128,054 109,127
Commitments and contingencies (Note 4)
Stockholders’ (deficit) equity:    
Preferred stock 0 0
Common stock 2 2
Additional paid-in capital 1,155,598 1,138,070
Accumulated other comprehensive loss (440) (407)
Accumulated deficit (1,210,813) (1,066,951)
Total stockholders’ (deficit) equity (55,653) 70,714
Total liabilities and stockholders’ (deficit) equity $ 72,401 $ 179,841
v3.25.3
Condensed Consolidated Statements of Operations and Comprehensive Loss - USD ($)
shares in Thousands, $ in Thousands
 3 Months Ended 9 Months Ended
Sep. 30, 2025
Sep. 30, 2024
Sep. 30, 2025
Sep. 30, 2024
Income Statement [Abstract]        
License revenue $ 0 $ 1,000 $ 0 $ 1,000
Operating expenses:        
Research and development 38,913 20,439 104,785 52,946
General and administrative 9,110 14,999 41,314 44,595
Total operating expenses 48,023 35,438 146,099 97,541
Operating loss (48,023) (34,438) (146,099) (96,541)
Other income, net 371 2,087 2,237 6,545
Net loss (47,652) (32,351) (143,862) (89,996)
Other comprehensive gain (loss):        
Net unrealized gain (loss) on marketable securities 5 241 (59) 198
Foreign currency translation adjustment 6 16 26 7
Comprehensive loss $ (47,641) $ (32,094) $ (143,895) $ (89,791)
Net loss per share — basic (in USD per share) $ (2.03) $ (1.55) $ (6.59) $ (4.64)
Net loss per share — diluted (in USD per share) $ (2.03) $ (1.55) $ (6.59) $ (4.64)
Weighted-average common shares used to compute net loss per share - basic (in shares) 23,487 20,876 21,821 19,408
Weighted-average common shares used to compute net loss per share - diluted (in shares) 23,487 20,876 21,821 19,408
v3.25.3
Condensed Consolidated Statements of Stockholders’ (Deficit) Equity - USD ($)
shares in Thousands, $ in Thousands
Total
Common Stock
Additional Paid-In Capital
Accumulated Other Comprehensive Loss
Accumulated Deficit
Beginning balance (in shares) at Dec. 31, 2023   10,143      
Beginning balance at Dec. 31, 2023 $ 67,222 $ 1 $ 1,003,718 $ (473) $ (936,024)
Increase (Decrease) in Stockholders' Equity [Roll Forward]          
Stock-based compensation expense 4,166   4,166    
Issuance of common stock and pre-funded warrants for cash in private placements, net of issuance costs of $8,449 (in shares)   10,573      
Issuance of common stock and pre-funded warrants for cash in private placements, net of issuance costs of $8,449 119,361 $ 1 119,360    
Common stock issued upon release of restricted stock units (in shares)   25      
Common stock issued upon exercise of stock options (in shares)   14      
Common stock issued upon exercise of stock options 139   139    
Foreign currency translation adjustments (19)     (19)  
Unrealized (loss) gain on marketable securities, net (41)     (41)  
Net loss (27,147)       (27,147)
Ending balance (in shares) at Mar. 31, 2024   20,755      
Ending balance at Mar. 31, 2024 163,681 $ 2 1,127,383 (533) (963,171)
Beginning balance (in shares) at Dec. 31, 2023   10,143      
Beginning balance at Dec. 31, 2023 67,222 $ 1 1,003,718 (473) (936,024)
Increase (Decrease) in Stockholders' Equity [Roll Forward]          
Foreign currency translation adjustments 7        
Net loss (89,996)        
Ending balance (in shares) at Sep. 30, 2024   20,801      
Ending balance at Sep. 30, 2024 108,270 $ 2 1,134,556 (268) (1,026,020)
Beginning balance (in shares) at Mar. 31, 2024   20,755      
Beginning balance at Mar. 31, 2024 163,681 $ 2 1,127,383 (533) (963,171)
Increase (Decrease) in Stockholders' Equity [Roll Forward]          
Stock-based compensation expense 3,945   3,945    
Common stock issued upon release of restricted stock units (in shares)   2      
Common stock issued under employee stock purchase plan (in shares)   44      
Common stock issued under employee stock purchase plan 264   264    
Foreign currency translation adjustments 10     10  
Unrealized (loss) gain on marketable securities, net (2)     (2)  
Net loss (30,498)       (30,498)
Ending balance (in shares) at Jun. 30, 2024   20,801      
Ending balance at Jun. 30, 2024 137,400 $ 2 1,131,592 (525) (993,669)
Increase (Decrease) in Stockholders' Equity [Roll Forward]          
Stock-based compensation expense 2,964   2,964    
Foreign currency translation adjustments 16     16  
Unrealized (loss) gain on marketable securities, net 241     241  
Net loss (32,351)       (32,351)
Ending balance (in shares) at Sep. 30, 2024   20,801      
Ending balance at Sep. 30, 2024 108,270 $ 2 1,134,556 (268) (1,026,020)
Beginning balance (in shares) at Dec. 31, 2024   20,848      
Beginning balance at Dec. 31, 2024 70,714 $ 2 1,138,070 (407) (1,066,951)
Increase (Decrease) in Stockholders' Equity [Roll Forward]          
Stock-based compensation expense 2,778   2,778    
Common stock issued upon release of restricted stock units (in shares)   43      
Foreign currency translation adjustments 2     2  
Unrealized (loss) gain on marketable securities, net (53)     (53)  
Net loss (47,019)       (47,019)
Ending balance (in shares) at Mar. 31, 2025   20,891      
Ending balance at Mar. 31, 2025 26,422 $ 2 1,140,848 (458) (1,113,970)
Beginning balance (in shares) at Dec. 31, 2024   20,848      
Beginning balance at Dec. 31, 2024 70,714 $ 2 1,138,070 (407) (1,066,951)
Increase (Decrease) in Stockholders' Equity [Roll Forward]          
Foreign currency translation adjustments 26        
Net loss (143,862)        
Ending balance (in shares) at Sep. 30, 2025   21,999      
Ending balance at Sep. 30, 2025 (55,653) $ 2 1,155,598 (440) (1,210,813)
Beginning balance (in shares) at Mar. 31, 2025   20,891      
Beginning balance at Mar. 31, 2025 26,422 $ 2 1,140,848 (458) (1,113,970)
Increase (Decrease) in Stockholders' Equity [Roll Forward]          
Stock-based compensation expense 2,423   2,423    
Common stock issued upon release of restricted stock units (in shares)   34      
Common stock issued under employee stock purchase plan (in shares)   57      
Common stock issued under employee stock purchase plan 120   120    
Foreign currency translation adjustments 18     18  
Unrealized (loss) gain on marketable securities, net (11)     (11)  
Net loss (49,191)       (49,191)
Ending balance (in shares) at Jun. 30, 2025   20,982      
Ending balance at Jun. 30, 2025 (20,219) $ 2 1,143,391 (451) (1,163,161)
Increase (Decrease) in Stockholders' Equity [Roll Forward]          
Stock-based compensation expense 2,349   2,349    
Issuance of common stock and pre-funded warrants for cash in private placements, net of issuance costs of $8,449 (in shares)   1,008      
Issuance of common stock and pre-funded warrants for cash in private placements, net of issuance costs of $8,449 9,858   9,858    
Common stock issued upon release of restricted stock units (in shares)   9      
Foreign currency translation adjustments 6     6  
Unrealized (loss) gain on marketable securities, net 5     5  
Net loss (47,652)       (47,652)
Ending balance (in shares) at Sep. 30, 2025   21,999      
Ending balance at Sep. 30, 2025 $ (55,653) $ 2 $ 1,155,598 $ (440) $ (1,210,813)
v3.25.3
Condensed Consolidated Statements of Stockholders’ (Deficit) Equity (Parenthetical) - USD ($)
$ in Thousands
 3 Months Ended
Sep. 30, 2025
Mar. 31, 2024
Statement of Stockholders' Equity [Abstract]    
Stock issuance costs $ 142 $ 8,449
v3.25.3
Condensed Consolidated Statements of Cash Flows - USD ($)
$ in Thousands
 9 Months Ended
Sep. 30, 2025
Sep. 30, 2024
Cash flows from operating activities:    
Net loss $ (143,862) $ (89,996)
Adjustments to reconcile net loss to net cash used in operating activities:    
Depreciation and amortization 1,683 2,843
Stock-based compensation expense 7,550 11,075
Net accretion of discount on marketable securities (544) (1,293)
Non-cash lease expense 165 1,343
Non-cash sublease loss 982 8,477
Loss on disposal of property and equipment 8 2
Other 13 7
Changes in operating assets and liabilities:    
Prepaid expenses and other current assets 2,703 (1,592)
Deposit and other long-term assets (676) (62)
Accounts payable 10,842 187
Accrued expenses and other liabilities 10,815 2,335
Lease liability 668 2,461
Net cash used in operating activities (109,653) (64,213)
Cash flows from investing activities:    
Purchases of marketable securities (1,976) (82,773)
Maturities of marketable securities 67,500 45,400
Purchases of property and equipment (482) (327)
Net cash provided by (used in) investing activities 65,042 (37,700)
Cash flows from financing activities:    
Proceeds from issuance of common stock and pre-funded warrants in private placements, net of issuance costs 9,899 119,361
Proceeds from issuance of common stock pursuant to option exercises 0 139
Proceeds from employee stock purchase plan 120 264
Net cash provided by financing activities 10,019 119,764
Net (decrease) increase in cash and cash equivalents and restricted cash (34,592) 17,851
Cash and cash equivalents and restricted cash at beginning of period 62,628 76,976
Cash and cash equivalents and restricted cash at end of period 28,036 94,827
Cash and cash equivalents 26,060 92,851
Restricted cash 1,976 1,976
Cash and cash equivalents and restricted cash at end of period 28,036 94,827
Supplemental schedule of noncash investing and financing information    
Remeasurement of operating lease right-of-use assets 4,415 0
Issuance costs included in accrued expenses 41 0
Property and equipment in accounts payable, accrued expenses and other current liabilities $ 195 $ 60
v3.25.3
Organization and Basis of Presentation
 9 Months Ended
Sep. 30, 2025
Organization, Consolidation and Presentation of Financial Statements [Abstract]  
Organization and Basis of Presentation Organization and Basis of Presentation
Adverum Biotechnologies, Inc. (the “Company” or “Adverum”) was incorporated in Delaware on July 17, 2006 and is headquartered in Redwood City, California. The Company aims to establish gene therapy as a new standard of care for highly prevalent ocular diseases. The Company develops gene therapy product candidates intended to provide durable efficacy by inducing sustained expression of a therapeutic protein.
For information regarding the Agreement and Plan of Merger ("Merger Agreement") and Secured Promissory Note ("Secured Note") with Eli Lilly and Company, an Indiana corporation (“Lilly”), dated October 24, 2025, see Note 9 “Subsequent Events”.
Going Concern, Liquidity, Risks and Uncertainties—As of September 30, 2025, the Company has devoted substantially all of its efforts to product development and has not realized product sales revenues from its planned principal operations. The Company has a limited operating history, and the sales and income potential of the Company’s business and market are unproven. The Company has experienced net losses since its inception and, as of September 30, 2025, had an accumulated deficit of $1.2 billion. The Company used $109.7 million of cash in operations during the nine months ended September 30, 2025. The Company expects to continue to incur net losses and operating cash outflows for at least the next several years. A successful transition to attaining profitable operations is dependent upon achieving a level of revenue adequate to support the Company’s cost structure.
As of September 30, 2025, the Company had cash, cash equivalents and short-term investments of $26.1 million. The Company has determined that its cash and cash equivalents as of September 30, 2025, would be insufficient to fund its operations for a period of at least twelve months from the date these unaudited condensed consolidated financial statements are issued, which raises substantial doubt regarding the Company’s ability to continue as a going concern.
The Company expects its cash, cash equivalents, and advances under the Secured Note with Lilly to fund operations through the anticipated consummation of the merger. See Note 9 “Subsequent Events” for more information. If the merger is not completed as anticipated, the Company will require additional financing to fund its operations. If the Merger Agreement is terminated, Lilly may accelerate the obligations under the Secured Note. If the Company is unable to obtain additional financing when needed and on acceptable terms, Lilly, as the secured creditor under the Secured Note, may exercise its rights and remedies, including foreclosing on the Company’s assets.
The Company’s financial statements have been prepared using the going concern basis of accounting, which contemplates the continuity of operations, realization of assets and the satisfaction of liabilities and commitments in the ordinary course of business. The financial statements do not include any adjustments relating to the recoverability and classification of recorded asset amounts or the amounts and classification of liabilities that might result from the outcome of the uncertainties described above.
Basis of Presentation — The accompanying unaudited condensed consolidated financial statements have been prepared in accordance with U.S. generally accepted accounting principles (“U.S. GAAP”) and follow the requirements of the Securities and Exchange Commission (“SEC”) for interim reporting. As permitted under those rules, certain footnotes or other financial information that are normally required by U.S. GAAP can be condensed or omitted. These unaudited condensed consolidated financial statements have been prepared on the same basis as the Company’s annual consolidated financial statements and, in the opinion of management, reflect all adjustments, consisting only of normal recurring adjustments, which are necessary for a fair statement of the Company’s consolidated financial information. The condensed consolidated financial statements include the accounts of the Company and its wholly owned subsidiaries. All intercompany balances and transactions have been eliminated in consolidation. The results of operations for the three and nine months ended September 30, 2025 are not necessarily indicative of the results to be expected for the full year or any other future period. The balance sheet as of December 31, 2024 is derived from the audited consolidated financial statements at that date but does not include all of the information required by U.S. GAAP for complete consolidated financial statements.
The accompanying unaudited condensed consolidated financial statements and related financial information should be read in conjunction with the audited consolidated financial statements and the related notes thereto included in the Company’s Annual Report on Form 10-K, filed with the SEC on April 15, 2025 for the year ended December 31, 2024.
v3.25.3
Summary of Significant Accounting Policies
 9 Months Ended
Sep. 30, 2025
Accounting Policies [Abstract]  
Summary of Significant Accounting Policies Summary of Significant Accounting Policies
Use of Estimates
The preparation of condensed consolidated financial statements in conformity with U.S. GAAP requires management to make judgments, estimates and assumptions that affect the reported amounts of assets, liabilities, revenue and expenses, and related disclosures. Management bases its estimates on historical experience and on various other assumptions that it believes to be reasonable under the circumstances. These estimates form the basis for making judgments about the carrying values of assets and liabilities when these values are not readily apparent from other sources. Accounting estimates and judgments are inherently uncertain, and actual results could differ from these estimates.
Significant Accounting Policies and Estimates
No material changes were made to the Company’s significant accounting policies disclosed in Note 3. Summary of significant accounting policies, to its consolidated financial statements included in its Annual Report on Form 10-K, filed with the SEC on April 15, 2025 for the year ended December 31, 2024.
Recent Accounting Pronouncements
The Company has considered all recent accounting pronouncements issued, but not yet effective, and does not expect any to have a material effect on the Company’s condensed consolidated financial statements other than those discussed in its Annual Report on Form 10-K, filed with the SEC on April 15, 2025 for the year ended December 31, 2024. The One Big Beautiful Bill Act (“OBBBA”) was signed into law in July 2025. The OBBBA may be subject to further clarification and interpretative guidance. The provisions do not have a material impact on the Company’s consolidated financial statements.
v3.25.3
Fair Value Measurements and Fair Value of Financial Instruments
 9 Months Ended
Sep. 30, 2025
Fair Value Disclosures [Abstract]  
Fair Value Measurements and Fair Value of Financial Instruments Fair Value Measurements and Fair Value of Financial Instruments
The authoritative guidance on the fair value hierarchy for disclosure of fair value measurements is as follows:
Level 1:    Quoted prices in active markets for identical assets or liabilities.
Level 2:    Observable inputs other than Level 1 prices, such as quoted prices for similar assets or liabilities, quoted prices in markets that are not active, or other inputs that are observable or can be corroborated by observable market data for substantially the full term of the assets or liabilities.
Level 3:    Unobservable inputs that are supported by little or no market activity and that are significant to the fair value of the assets or liabilities.
Level 1 securities consist of highly liquid money market funds. U.S. government and agency securities and commercial paper are valued primarily using market prices of comparable securities, bid/ask quotes, interest rate yields and prepayment spreads and are included in Level 2.
The following is a summary of the Company’s cash equivalents and short-term investments:
September 30, 2025
Amortized
Cost Basis
Unrealized
Gains
Unrealized
Losses
Estimated
Fair Value
(In thousands)
Level 1:
Money market funds
$10,145 $— $— $10,145 
Level 2:
Commercial paper
10,987 — (1)10,986 
Total cash equivalents and short-term investments21,132 — (1)21,131 
Less: Cash equivalents(21,132)— 1 (21,131)
Total short-term investments$— $— $— $— 
December 31, 2024
Amortized
Cost Basis
Unrealized
Gains
Unrealized
Losses
Estimated
Fair Value
(In thousands)
Level 1:
Money market funds$165 $— $— $165 
Level 2:
Commercial paper78,500 10 (9)78,501 
U.S. government and agency securities41,210 56 — 41,266 
Total cash equivalents and short-term investments119,875 66 (9)119,932 
Less: Cash equivalents(54,901)— 8 (54,893)
Total short-term investments$64,974 $66 $(1)$65,039 
The aggregate fair value of debt securities in an unrealized loss position at September 30, 2025 and December 31, 2024 was $11.0 million and $54.2 million, respectively, which are highly liquid funds with high credit ratings that have final maturities of three months or less from date of purchase. The Company has not recorded an allowance for credit losses as of September 30, 2025 and December 31, 2024 related to these securities. The accrued interest receivable on available-for-sale marketable securities was immaterial at September 30, 2025 and December 31, 2024. There were no individual securities that were in a significant unrealized loss position as of September 30, 2025 and December 31, 2024. The Company regularly reviews the securities in an unrealized loss position and evaluates the current expected credit loss by considering factors such as historical experience, market data, issuer-specific factors, and current economic conditions. The Company does not intend to sell the investments and it is not more likely than not that the Company will be required to sell the investments before recovery of their amortized cost bases.
v3.25.3
Commitments and Contingencies
 9 Months Ended
Sep. 30, 2025
Commitments and Contingencies Disclosure [Abstract]  
Commitments and Contingencies Commitments and Contingencies
Leases
Redwood City
The Company has a lease for facilities in Redwood City, California (“Redwood City Premises”), which expires December 31, 2031, with an option to extend for a period of eight years. The lease includes an additional tenant improvement allowance of up to $2.0 million to be used at the Company’s discretion. Any amounts drawn would be amortized over the remaining lease term at 9% per annum, not subject to annual base rent increases. Under this lease, the Company provided the landlord of the Redwood City Premises with a letter of credit in the amount of $2.0 million, which is classified as restricted cash under long-term assets on the Company’s condensed consolidated balance sheets. As of September 30, 2025, the Company had a total future rent obligation of $42.5 million related to this lease.
North Carolina
On January 8, 2021, the Company entered into an operating lease agreement for a building in North Carolina (“NC Premises”). The lease commenced in April 2021, when the Company obtained control of the NC Premises, and the lease term expires in October 2037 with two options to extend the lease term for a period of five years each.
On October 26, 2021, the Company entered into a sublease agreement with Jaguar Gene Therapy, LLC (“Jaguar”) for the NC Premises through October 2037, the remainder of the lease term, and concurrently changed the terms of the head lease. In addition, the remainder of the tenant improvement allowance under the original lease of approximately $22.7 million was transferred to Jaguar.
On April 3, 2023, the Company entered into an amendment of the lease of its NC Premises with the landlord and subtenant. Under this amendment, the parties agreed to substantially reduce the total tenant improvement allowance in exchange for lower monthly rent. The Company accounted for this amendment as a lease modification under ASC 842. The Company remeasured the lease liability, resulting in an increase in the lease liability with a corresponding increase of the right-of-use asset of $0.3 million in the quarter ended June 30, 2023. There was no charge recognized in the consolidated statement of operations.
In April 2023, Jaguar assigned the sublease to Advanced Medicine Partners, LLC (at that time, a wholly-owned subsidiary of Jaguar, “AMP” or the “subtenant”) as the subtenant for the NC Premises for the remainder of the lease term. Pursuant to the sublease and the notice and waiver of assignment (the “assignment agreement”), Jaguar remained obligated for AMP’s proper performance under the sublease.
In the first quarter of 2025, the subtenant made payments totaling $1.4 million for January and February 2025 rent and drew $2.4 million from the available tenant improvement allowance, after which the subtenant failed to remit the March 2025 and subsequent rent payments. As a result, the subtenant and Jaguar defaulted, and failed to cure such defaults under the sublease and the assignment agreement for the NC Premises. The Company assumed responsibility for rent payments beginning in March 2025.
In February 2025, a lien totaling $4.8 million was filed by a third-party contractor against the subtenant’s interest in the NC Premises. The Company discharged the lien in March 2025 by depositing cash in the full amount with the applicable court in order to avoid a default under the head lease. On July 23, 2025, the Company and the third-party contractor resolved the third-party contractor’s and subcontractors’ lien claims against the NC Premises and the $4.8 million deposited by the Company with the court.
The Company remains obligated under the head lease and as of September 30, 2025, had a total future rent obligation of $112.6 million. As a result of the uncured defaults, the Company terminated the sublease and on April 10, 2025 initiated a lawsuit against the subtenant and Jaguar in the Superior Court of Wake County, North Carolina to enforce its rights under the sublease and to seek recovery of losses and damages incurred due to the defaults by the subtenant and Jaguar.
In September 2025, the Company executed a Fourth Amendment to its lease agreement for its NC Premises with ARE-NC-Region No. 21 LLC (the “Landlord”). Under the terms of the amendment, the Company’s rent and related operating expense obligations are contractually abated through February 28, 2026. The amendment also provides for contingent early termination of the lease on or about the earlier to occur of (i) the execution of the Landlord of a replacement lease with a third-party tenant or (ii) the closing of a sale of the NC Premises (either event, an “Early Termination Date”). In connection with this arrangement, the Company agreed to an early termination fee, consisting of (i) a $7.4 million promissory note, delivered in escrow, payable on the maturity date, which is the earlier of January 31, 2031 or an achievement by the Company of at least $150 million in annual net revenues or annual royalties from the Company’s lead candidate, Ixo-vec (the “Maturity Date”) and (ii) $0.1 million in cash payable within 30 days after the Early Termination Date. The lease promissory note will be held in escrow and will not be released to the Landlord unless and until the Early Termination Date occurs. The Maturity Date of the lease promissory note will accelerate upon a change of control of the Company (including a change of control of the Company occurring prior to the Early Termination Date, in which case the Maturity Date will be accelerated upon release of the promissory note from escrow on the Early Termination Date). If early termination does not occur prior to March 1, 2026, the Company’s rent obligations under the lease will resume on March 1, 2026. The Company accounted for this amendment as a lease modification under ASC 842. As a result of the modification, the Company remeasured the lease liability and right-of-use assets, resulting in decrease of the lease liability, current portion of $3.8 million, a decrease in lease liability, net of current portion of $0.6 million, and a decrease in operating lease right-of-use assets of $4.4 million. There was no charge recognized in the consolidated statement of operations.
The following table summarizes the undiscounted future non-cancellable lease payments under the lease agreements as of September 30, 2025 (in thousands):
December 31,Operating Leases
2025 (remaining three months)$1,511 
202613,471 
202715,278 
202815,677 
202916,089 
Thereafter93,087 
Total undiscounted lease payments$155,113 
Less: Imputed interest
(66,173)
Total$88,940 
The Company recorded sublease loss of zero and $1.0 million in the three and nine months ended September 30, 2025, respectively. The Company recorded a sublease loss of $3.7 million and $8.5 million in the three and nine months ended September 30, 2024, respectively. Sublease income or loss was recognized in general and administrative expense.
v3.25.3
Balance Sheet Components
 9 Months Ended
Sep. 30, 2025
Balance Sheet Related Disclosures [Abstract]  
Balance Sheet Components Balance Sheet Components
Property and Equipment, Net
Property and equipment, net consists of the following:
September 30, 2025December 31, 2024
(In thousands)
Laboratory equipment$14,889 $14,963 
Leasehold improvements13,779 13,779 
Computer equipment and software522 901 
Construction in progress23 9 
Total property and equipment29,213 29,652 
Less: Accumulated depreciation and amortization(18,751)(18,045)
Property and equipment, net$10,462 $11,607 
Accrued Expenses and Other Current Liabilities
Accrued expenses and other current liabilities consist of the following:
September 30, 2025December 31, 2024
(In thousands)
Accrued nonclinical, clinical and process development costs$15,057 $4,401 
Employee compensation9,818 9,540 
Accrued professional services701 554 
Other900 1,125 
Total accrued expenses and other current liabilities$26,476 $15,620 
v3.25.3
Stockholders’ (Deficit) Equity
 9 Months Ended
Sep. 30, 2025
Share-Based Payment Arrangement [Abstract]  
Stockholders’ (Deficit) Equity Stockholders’ (Deficit) Equity
August 2025 Private Placement
On August 11, 2025, the Company entered into a securities purchase agreement (the “2025 Securities Purchase Agreement”) with certain institutional and accredited investors, pursuant to which the Company agreed to issue and sell to the Investors in a private placement (the “2025 Private Placement”) an aggregate of 1.0 million shares (the “2025 Private Placement Shares”) of the Company’s common stock, par value $0.0001 per share, and pre-funded warrants (the “2025 Pre-Funded Warrants”) to purchase an aggregate of 3.5 million shares of common stock. The purchase price per 2025 Private Placement Share was $2.24 (or $2.2399 per 2025 Pre-Funded Warrant, which represents the purchase price per 2025 Private Placement Share to be sold in the 2025 Private Placement, minus the $0.0001 per share exercise price of each such 2025 Pre-Funded Warrant). The 2025 Pre-Funded Warrants are exercisable at any time and have no expiration date. The exercise of the outstanding 2025 Pre-Funded Warrants is subject to a beneficial ownership limitation of 9.99%.
At the close of the 2025 Private Placement on August 12, 2025, the Company received the total gross proceeds of $10.0 million, before deducting placement agent fee and offering expenses of $0.1 million.
February 2024 Private Placements
On February 7, 2024, the Company entered into a securities purchase agreement (the “2024 Securities Purchase Agreement”), pursuant to which the Company sold 10.5 million shares of its common stock and, in lieu of common stock, pre-funded warrants (the “2024 Pre-Funded Warrants”) to purchase an aggregate of 75,000 shares of common stock to certain institutional and accredited investors in a private placement. The purchase price per share was $12.00, or $11.999 per 2024 Pre-Funded Warrant, which represents the purchase price per share minus the $0.001 per share exercise price of each 2024 Pre-Funded Warrant. The 2024 Pre-Funded Warrants were exercised in October 2025.
Concurrently, the Company also entered into a securities purchase agreement with two directors of the Company (together with the private placement to certain institutional and accredited investors, the “2024 Private Placements”). The Company issued and sold 23,000 shares at $13.50 per share on otherwise substantially the same terms as those set forth in the 2024 Securities Purchase Agreement.
At the close of the 2024 Private Placements on February 7, 2024, the Company received total gross proceeds of $127.8 million, before deducting placement agent fees and offering expenses.
The 2025 Pre-Funded Warrants and 2024 Pre-Funded Warrants were classified as a component of stockholders’ (deficit) equity. As of September 30, 2025, none of the 2025 Pre-Funded Warrants and 2024 Pre-Funded Warrants had been exercised.
Accumulated Other Comprehensive Loss
Accumulated other comprehensive loss included $0.4 million and $0.5 million of accumulated currency translation adjustments as of September 30, 2025 and December 31, 2024, respectively.
Equity Incentive Awards
Stock Options
The following table summarizes the Company’s option activity and related information:
Number of
Options
(in thousands)		Weighted-
Average
Exercise Price
Balance at December 31, 20243,909 $29.39 
Options granted1,148 3.97 
Options forfeited(88)41.00 
Balance at September 30, 20254,969 23.31 
Exercisable as of September 30, 20252,390 40.39 
Repricing
On June 17, 2025 (“Effective Date” or "Repricing Date”), the Company held its annual meeting of stockholders, at which the Company’s stockholders approved the amendment of certain outstanding stock options to reduce the exercise price per share of such options. The repricing applied to each option to purchase shares of the Company’s common stock that: (a) was granted under the Company’s 2014 Equity Incentive Award Plan, 2017 Inducement Plan or 2024 Equity Incentive Award Plan; (b) was outstanding on the Effective Date; (c) as of the Effective Date, was held by a then-current employee or consultant of the Company (subject to certain exceptions); and (d) had an exercise price that was, as of the Effective Date, higher than the prior 52-week intraday high trading price of the Company’s common stock as of the Effective Date (i.e., higher than $10.14) (“Eligible Options”). The Eligible Options included certain options held by certain of the Company’s executive officers. Options held by non-employee members of the Board were not eligible for the repricing program.
As of the Effective Date, the Eligible Options were immediately repriced such that the exercise price per share for such options was reduced to $10.14, subject to certain retention requirements outlined below.
For a participant to exercise the option at the reduced price, he or she must remain in service to the Company for twenty-four months following the Effective Date (or, if earlier, until a change in control or the participant’s Termination of Service (as defined in the 2024 Equity Incentive Award Plan) by reason of death or disability). If a participant exercises Eligible Options in advance of the end of the retention period, the participant will be required to pay an exercise price equal to the original exercise price per share of the Eligible Options. There were no changes to the number of shares underlying the Eligible Options or to the vesting schedules or expiration dates of the Eligible Options.
As of the Effective Date, the total number of shares underlying all Eligible Options was 1.7 million. The effect of the repricing resulted in total incremental stock-based compensation expense of $0.7 million, which will be recognized on a straight-line basis through the end of the retention period or the original remaining vesting period of the Eligible Options, whichever is longer. The Company used the Hull-White I Lattice model to calculate the incremental stock-based compensation expense. Incremental stock-based compensation expense recognized during the three and nine months ended September 30, 2025 was not material.
Restricted Stock Units (“RSUs”)
The following table summarizes the Company’s RSUs activity and related information:
Number of RSUs
(in thousands)		Weighted-
Average Grant-
Date Fair Value
Outstanding at December 31, 2024259 $16.00 
Granted299 4.09 
Vested and released(86)22.03 
Forfeited(8)5.85 
Outstanding at September 30, 2025464 7.41 
Stock-Based Compensation Expense
The following table presents, by operating expense, the Company’s stock-based compensation expense:
Three Months Ended
September 30,		Nine Months Ended
September 30,
2025202420252024
(In thousands)
Research and development$1,079 $1,086 $3,376 $3,294 
General and administrative1,270 1,878 4,174 7,781 
Total stock-based compensation expense$2,349 $2,964 $7,550 $11,075 
v3.25.3
Segment Reporting
 9 Months Ended
Sep. 30, 2025
Segment Reporting [Abstract]  
Segment Reporting Segment Reporting
Segment Reporting
The chief operating decision maker (“CODM”), who is defined as the Company’s chief executive officer, assesses performance for the Company’s single reportable segment and decides how to allocate resources based on the Company’s total operating expenses as reported on the condensed consolidated statements of operations and comprehensive loss. The CODM’s review of total operating expenses at the consolidated level is used to monitor the Company’s spending as well as budget versus actual results. The Company’s reportable segment primarily generates revenue through its license agreements.
As part of the CODM’s review of the segment’s performance, the CODM reviews the Company’s operating expense information, grouped by certain detailed line items from the internal income statement reporting. This includes research and development costs as well as general and administrative expenses. Based upon the operating expense information, the CODM can reconcile to net loss as reported on the consolidated statements of operations and comprehensive loss, shown in the table below.
The following table presents the segment loss, including significant segment expenses, for the three and nine months ended September 30, 2025 and 2024:
Three Months Ended September 30,
Nine Months Ended September 30,
2025202420252024
(In thousands)
License revenue
$— $1,000 $— $1,000 
Operating expenses
Compensation and benefits$15,801 $13,081 $48,139 $41,010 
Clinical trial and manufacturing
21,559 6,334 51,239 14,172 
Facilities and IT
3,481 9,563 21,274 26,125 
Other research and development2,125 1,572 7,083 3,298 
Other segment(a)
5,057 4,888 18,364 12,936 
Total operating expenses$48,023 $35,438 $146,099 $97,541 
Operating loss(48,023)(34,438)(146,099)(96,541)
Other income, net
371 2,087 2,237 6,545 
Segment and consolidated net loss$(47,652)$(32,351)$(143,862)$(89,996)
(a)
Other segment include professional services, consultants and contractors, travel and entertainment expenses, and general business expenses.
v3.25.3
Net Loss per Share
 9 Months Ended
Sep. 30, 2025
Earnings Per Share [Abstract]  
Net Loss per Share Net Loss per Share
Basic net loss per share is calculated by dividing the net loss by the weighted-average number of shares of common stock outstanding for the period. Diluted net loss per share is computed by giving effect to all potential dilutive common stock equivalents outstanding for the period using the treasury stock method. Outstanding stock options, RSUs and rights under the employee stock purchase plan (“ESPP”) are considered to be common stock equivalents and are only included in the calculation of diluted net loss per share when their effect is dilutive.
For the three and nine months ended September 30, 2025 and 2024, the Pre-Funded Warrants issued in the 2025 Private Placement and the 2024 Private Placements were included in the basic and diluted net loss per share calculation as the exercise price is non-substantive and virtually assured.
The following common stock equivalents outstanding at the end of the periods presented were excluded from the calculation of diluted net loss per share for the periods indicated because including them would have had an anti-dilutive effect:
September 30, 2025September 30, 2024
(In thousands)
Stock options4,9693,729
Restricted stock units464205
ESPP5941
5,4923,975
v3.25.3
Subsequent Events
 9 Months Ended
Sep. 30, 2025
Subsequent Events [Abstract]  
Subsequent Events Subsequent Events
Agreement and Plan of Merger
On October 24, 2025, the Company entered into the Merger Agreement with Lilly, and Flying Tigers Acquisition Corporation, a Delaware corporation and direct wholly owned subsidiary of Lilly (the “Purchaser”). Pursuant to the Merger Agreement, and upon the terms and subject to the conditions thereof, on November 7, 2025, Purchaser commenced a tender offer (the “Offer”) to purchase all of the Company's issued and outstanding shares (the “Shares”) of common stock, par value $0.0001 per share, in exchange for (i) $3.56 per Share, net to the stockholder in cash, without interest (the “Closing Amount”) and less any applicable tax withholding, plus (ii) one non-tradable contingent value right (each, a “CVR”), each of which represents the contractual right of the holder to receive up to an aggregate of $8.91 per CVR, net to the stockholder in cash, without interest and less any applicable tax withholding, upon the achievement of two specified milestones in accordance with the terms and subject to the conditions of a contingent value rights agreement (the “CVR Agreement”) to be entered into with a rights agent selected by Lilly and reasonably acceptable to the Company (the “Rights Agent”) (the Closing Amount plus one CVR, collectively, the “Offer Price”).
The CVR provides payments if and when the following milestones are achieved:
•Up to $1.78 per CVR in cash payable upon U.S. approval of Ixo-vec prior to the seventh anniversary of closing.
•Up to $7.13 per CVR in cash payable upon the first achievement of annual worldwide net sales of Ixo-vec by Lilly, its affiliates or licensees exceeding $1.0 billion dollars prior to the tenth anniversary of closing.
Following the completion of the Offer and subject to satisfaction or waiver of certain conditions set forth in the Merger Agreement, Lilly, Purchaser and the Company will, pursuant to Section 251(h) of the General Corporation Law of the State of Delaware (“DGCL”) without a vote of the Company stockholders, effect a merger of Purchaser with and into the Company (the “Merger” and together with the Offer and the other transactions contemplated by the Merger Agreement, the “Transactions”), with the Company surviving as a wholly owned subsidiary of Lilly, and the Company will cease to be a publicly traded company.
The merger is expected to close in the fourth quarter of 2025. If the Merger Agreement is terminated under specified circumstances, the Company will be required to pay Lilly a termination fee of $4.0 million (including under specified circumstances in connection with the Company's entry into an agreement with respect to a Superior Proposal (as defined in the Merger Agreement) or the Company Board's change of recommendation in favor of the Offer). For more information, please see “Management’s Discussion and Analysis of Financial Condition and Results of Operations—Recent Developments—Agreement and Plan of Merger—Important Information about the Tender Offer and Where to Find It.”
Secured Promissory Note
On October 24, 2025, in connection with the Merger Agreement, the Company entered into a Secured Promissory Note (the “Secured Note”) with Lilly, pursuant to which Lilly agreed to provide up to $65.0 million in secured debt financing to the Company, of which $5.0 million was funded on October 28, 2025 and an additional $15.0 million was funded on November 7, 2025. Pursuant to the terms of the Secured Note, an additional $20.0 million is available at the Company’s election on November 21, 2025 and an additional $25.0 million is available at the Company’s election on December 5, 2025, in each case subject to the prior satisfaction of certain funding conditions specified therein.
Advances under the Secured Note bear interest at a rate equal to SOFR plus 10.0% per annum, compounded bi-weekly. The maturity date of the Secured Note is January 22, 2026. The Secured Note includes a 5.0% prepayment premium applicable to any prepayment or acceleration of the obligations under the Secured Note.
The Secured Note contains customary representations, warranties, covenants, and events of default, including restrictions on incurring additional indebtedness, granting liens, making investments, and transferring assets. Upon the occurrence of certain triggering events, including payment defaults, breaches of covenants, insolvency proceedings, or any termination of the Merger Agreement, Lilly may accelerate the obligations under the Secured Note.
The Company’s obligations under the Secured Note are guaranteed by each of its subsidiaries and are secured by a first-priority lien on substantially all of the Company’s and such guarantors’ assets, including intellectual property, accounts, equipment, and other collateral as defined in the Secured Note.
Jaguar and AMP Settlement Agreement
In October 2025, the Company, Jaguar and the subtenant entered into a settlement agreement related to the NC Premises pursuant to which Jaguar and the subtenant agreed to pay to Company a settlement payment consisting of $9.5 million in cash in consideration for the Company releasing Jaguar and the subtenant from claims associated with losses and damages incurred due to the defaults by the subtenant and Jaguar and the Company. The Company subsequently dismissed the lawsuit against Jaguar and the subtenant on October 9, 2025.
v3.25.3
Insider Trading Arrangements
 3 Months Ended
Sep. 30, 2025
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
v3.25.3
Summary of Significant Accounting Policies (Policies)
 9 Months Ended
Sep. 30, 2025
Accounting Policies [Abstract]  
Basis of Presentation
Basis of Presentation — The accompanying unaudited condensed consolidated financial statements have been prepared in accordance with U.S. generally accepted accounting principles (“U.S. GAAP”) and follow the requirements of the Securities and Exchange Commission (“SEC”) for interim reporting. As permitted under those rules, certain footnotes or other financial information that are normally required by U.S. GAAP can be condensed or omitted. These unaudited condensed consolidated financial statements have been prepared on the same basis as the Company’s annual consolidated financial statements and, in the opinion of management, reflect all adjustments, consisting only of normal recurring adjustments, which are necessary for a fair statement of the Company’s consolidated financial information. The condensed consolidated financial statements include the accounts of the Company and its wholly owned subsidiaries. All intercompany balances and transactions have been eliminated in consolidation. The results of operations for the three and nine months ended September 30, 2025 are not necessarily indicative of the results to be expected for the full year or any other future period. The balance sheet as of December 31, 2024 is derived from the audited consolidated financial statements at that date but does not include all of the information required by U.S. GAAP for complete consolidated financial statements.
The accompanying unaudited condensed consolidated financial statements and related financial information should be read in conjunction with the audited consolidated financial statements and the related notes thereto included in the Company’s Annual Report on Form 10-K, filed with the SEC on April 15, 2025 for the year ended December 31, 2024.
Use of Estimates
Use of Estimates
The preparation of condensed consolidated financial statements in conformity with U.S. GAAP requires management to make judgments, estimates and assumptions that affect the reported amounts of assets, liabilities, revenue and expenses, and related disclosures. Management bases its estimates on historical experience and on various other assumptions that it believes to be reasonable under the circumstances. These estimates form the basis for making judgments about the carrying values of assets and liabilities when these values are not readily apparent from other sources. Accounting estimates and judgments are inherently uncertain, and actual results could differ from these estimates.
Recent Accounting Pronouncements
Recent Accounting Pronouncements
The Company has considered all recent accounting pronouncements issued, but not yet effective, and does not expect any to have a material effect on the Company’s condensed consolidated financial statements other than those discussed in its Annual Report on Form 10-K, filed with the SEC on April 15, 2025 for the year ended December 31, 2024. The One Big Beautiful Bill Act (“OBBBA”) was signed into law in July 2025. The OBBBA may be subject to further clarification and interpretative guidance. The provisions do not have a material impact on the Company’s consolidated financial statements.
v3.25.3
Fair Value Measurements and Fair Value of Financial Instruments (Tables)
 9 Months Ended
Sep. 30, 2025
Fair Value Disclosures [Abstract]  
Schedule of Cash Equivalents and Short-term Investments
The following is a summary of the Company’s cash equivalents and short-term investments:
September 30, 2025
Amortized
Cost Basis
Unrealized
Gains
Unrealized
Losses
Estimated
Fair Value
(In thousands)
Level 1:
Money market funds
$10,145 $— $— $10,145 
Level 2:
Commercial paper
10,987 — (1)10,986 
Total cash equivalents and short-term investments21,132 — (1)21,131 
Less: Cash equivalents(21,132)— 1 (21,131)
Total short-term investments$— $— $— $— 
December 31, 2024
Amortized
Cost Basis
Unrealized
Gains
Unrealized
Losses
Estimated
Fair Value
(In thousands)
Level 1:
Money market funds$165 $— $— $165 
Level 2:
Commercial paper78,500 10 (9)78,501 
U.S. government and agency securities41,210 56 — 41,266 
Total cash equivalents and short-term investments119,875 66 (9)119,932 
Less: Cash equivalents(54,901)— 8 (54,893)
Total short-term investments$64,974 $66 $(1)$65,039 
v3.25.3
Commitment and Contingencies (Tables)
 9 Months Ended
Sep. 30, 2025
Commitments and Contingencies Disclosure [Abstract]  
Schedule of Undiscounted Future Lease Payments under Operating Lease
The following table summarizes the undiscounted future non-cancellable lease payments under the lease agreements as of September 30, 2025 (in thousands):
December 31,Operating Leases
2025 (remaining three months)$1,511 
202613,471 
202715,278 
202815,677 
202916,089 
Thereafter93,087 
Total undiscounted lease payments$155,113 
Less: Imputed interest
(66,173)
Total$88,940 
v3.25.3
Balance Sheet Components (Tables)
 9 Months Ended
Sep. 30, 2025
Balance Sheet Related Disclosures [Abstract]  
Schedule of Property and Equipment, Net
Property and equipment, net consists of the following:
September 30, 2025December 31, 2024
(In thousands)
Laboratory equipment$14,889 $14,963 
Leasehold improvements13,779 13,779 
Computer equipment and software522 901 
Construction in progress23 9 
Total property and equipment29,213 29,652 
Less: Accumulated depreciation and amortization(18,751)(18,045)
Property and equipment, net$10,462 $11,607 
Schedule of Accrued Expenses and Other Current Liabilities
Accrued expenses and other current liabilities consist of the following:
September 30, 2025December 31, 2024
(In thousands)
Accrued nonclinical, clinical and process development costs$15,057 $4,401 
Employee compensation9,818 9,540 
Accrued professional services701 554 
Other900 1,125 
Total accrued expenses and other current liabilities$26,476 $15,620 
v3.25.3
Stockholders’ (Deficit) Equity (Tables)
 9 Months Ended
Sep. 30, 2025
Share-Based Payment Arrangement [Abstract]  
Schedule of Stock Options Activity
The following table summarizes the Company’s option activity and related information:
Number of
Options
(in thousands)		Weighted-
Average
Exercise Price
Balance at December 31, 20243,909 $29.39 
Options granted1,148 3.97 
Options forfeited(88)41.00 
Balance at September 30, 20254,969 23.31 
Exercisable as of September 30, 20252,390 40.39 
Schedule of Restricted Stock Units Activity
The following table summarizes the Company’s RSUs activity and related information:
Number of RSUs
(in thousands)		Weighted-
Average Grant-
Date Fair Value
Outstanding at December 31, 2024259 $16.00 
Granted299 4.09 
Vested and released(86)22.03 
Forfeited(8)5.85 
Outstanding at September 30, 2025464 7.41 
Schedule of Stock-Based Compensation Expense
The following table presents, by operating expense, the Company’s stock-based compensation expense:
Three Months Ended
September 30,		Nine Months Ended
September 30,
2025202420252024
(In thousands)
Research and development$1,079 $1,086 $3,376 $3,294 
General and administrative1,270 1,878 4,174 7,781 
Total stock-based compensation expense$2,349 $2,964 $7,550 $11,075 
v3.25.3
Segment Reporting (Tables)
 9 Months Ended
Sep. 30, 2025
Segment Reporting [Abstract]  
Schedule of Segment Reporting Information, by Segment
The following table presents the segment loss, including significant segment expenses, for the three and nine months ended September 30, 2025 and 2024:
Three Months Ended September 30,
Nine Months Ended September 30,
2025202420252024
(In thousands)
License revenue
$— $1,000 $— $1,000 
Operating expenses
Compensation and benefits$15,801 $13,081 $48,139 $41,010 
Clinical trial and manufacturing
21,559 6,334 51,239 14,172 
Facilities and IT
3,481 9,563 21,274 26,125 
Other research and development2,125 1,572 7,083 3,298 
Other segment(a)
5,057 4,888 18,364 12,936 
Total operating expenses$48,023 $35,438 $146,099 $97,541 
Operating loss(48,023)(34,438)(146,099)(96,541)
Other income, net
371 2,087 2,237 6,545 
Segment and consolidated net loss$(47,652)$(32,351)$(143,862)$(89,996)
(a)
Other segment include professional services, consultants and contractors, travel and entertainment expenses, and general business expenses.
v3.25.3
Net Loss per Share (Tables)
 9 Months Ended
Sep. 30, 2025
Earnings Per Share [Abstract]  
Schedule of Antidilutive Securities Excluded from Computation of Earnings Per Share
The following common stock equivalents outstanding at the end of the periods presented were excluded from the calculation of diluted net loss per share for the periods indicated because including them would have had an anti-dilutive effect:
September 30, 2025September 30, 2024
(In thousands)
Stock options4,9693,729
Restricted stock units464205
ESPP5941
5,4923,975
v3.25.3
Organization and Basis of Presentation (Details) - USD ($)
$ in Thousands
 9 Months Ended
Sep. 30, 2025
Sep. 30, 2024
Dec. 31, 2024
Organization, Consolidation and Presentation of Financial Statements [Abstract]      
Accumulated deficit $ 1,210,813   $ 1,066,951
Net cash used in operations 109,653 $ 64,213  
Cash, cash equivalents, and short-term investments $ 26,100    
v3.25.3
Fair Value Measurements and Fair Value of Financial Instruments - Schedule of Cash Equivalents and Short-term Investments (Details) - USD ($)
$ in Thousands
Sep. 30, 2025
Dec. 31, 2024
Debt Securities, Available-for-sale [Line Items]    
Amortized Cost Basis $ 0 $ 64,974
Unrealized Gains 0 66
Unrealized Losses 0 (1)
Estimated Fair Value 0 65,039
Less: cash equivalents, amortized cost basis (21,132) (54,901)
Less: cash equivalents, unrealized gains 0 0
Less: cash equivalents, unrealized losses 1 8
Less: cash equivalents, estimated fair value (21,131) (54,893)
Money market funds | Level 1    
Debt Securities, Available-for-sale [Line Items]    
Amortized Cost Basis 10,145 165
Unrealized Gains 0 0
Unrealized Losses 0 0
Estimated Fair Value 10,145 165
Commercial paper | Level 2    
Debt Securities, Available-for-sale [Line Items]    
Amortized Cost Basis 10,987 78,500
Unrealized Gains 0 10
Unrealized Losses (1) (9)
Estimated Fair Value 10,986 78,501
U.S. government and agency securities | Level 2    
Debt Securities, Available-for-sale [Line Items]    
Amortized Cost Basis   41,210
Unrealized Gains   56
Unrealized Losses   0
Estimated Fair Value   41,266
Total cash equivalents and short-term investments    
Debt Securities, Available-for-sale [Line Items]    
Amortized Cost Basis 21,132 119,875
Unrealized Gains 0 66
Unrealized Losses (1) (9)
Estimated Fair Value $ 21,131 $ 119,932
v3.25.3
Fair Value Measurements and Fair Value of Financial Instruments - Additional Information (Details) - USD ($)
$ in Millions
Sep. 30, 2025
Dec. 31, 2024
Fair Value Disclosures [Abstract]    
Marketable securities in an unrealized loss $ 11.0 $ 54.2
Allowance for credit losses $ 0.0 $ 0.0
v3.25.3
Commitments and Contingencies - Narrative (Details)
$ in Thousands
 1 Months Ended 2 Months Ended 3 Months Ended 9 Months Ended
Jul. 23, 2025
USD ($)
Jan. 08, 2021
leaseExtensionOption
Sep. 30, 2025
USD ($)
Feb. 28, 2025
USD ($)
Feb. 28, 2025
USD ($)
Sep. 30, 2025
USD ($)
Sep. 30, 2024
USD ($)
Jun. 30, 2023
USD ($)
Sep. 30, 2025
USD ($)
Sep. 30, 2024
USD ($)
Dec. 31, 2024
USD ($)
Oct. 26, 2021
USD ($)
Other Commitments [Line Items]                        
Restricted cash     $ 1,976     $ 1,976 $ 1,976   $ 1,976 $ 1,976 $ 1,976  
Total undiscounted lease payments     155,113     155,113     155,113      
Decrease in lease liability     3,800     3,800     3,800      
Lease liability, net of current portion     600     600     600      
Decrease in operating lease right-of-use assets     4,400     $ 4,400     4,400      
Non-cash sublease loss                 $ 982 8,477    
North Carolina Lease Settlement Agreement, Promissory Note                        
Other Commitments [Line Items]                        
Payments for legal settlements     7,400                  
North Carolina Lease Settlement Agreement, Net Sales                        
Other Commitments [Line Items]                        
Payments for legal settlements     150,000                  
North Carolina Lease Settlement Agreement, Cash Settlement                        
Other Commitments [Line Items]                        
Payments for legal settlements     $ 100                  
Payment period after Early Termination Period     30 days     30 days     30 days      
California | Building                        
Other Commitments [Line Items]                        
Lease renewal term     8 years     8 years     8 years      
Leasehold improvement allowance     $ 2,000     $ 2,000     $ 2,000      
Operating lease, weighted average discount rate, (as percent)     9.00%     9.00%     9.00%      
Restricted cash     $ 2,000     $ 2,000     $ 2,000      
Total undiscounted lease payments     42,500     42,500     42,500      
North Carolina | Manufacturing Facility                        
Other Commitments [Line Items]                        
Lease renewal term   5 years                    
Leasehold improvement allowance                       $ 22,700
Total undiscounted lease payments     $ 112,600     112,600     112,600      
Number of renewal options | leaseExtensionOption   2                    
Re-measurement of operating lease right-of-use assets               $ 300        
Re-measurement of operating lease liabilities               $ 300        
Sublease income from payments for rent made by subtenant         $ 1,400              
Subtenant draw on tenant allowance         $ 2,400              
Amount of lien filed against subtenant       $ 4,800                
Payments for legal settlements $ 4,800                      
Non-cash sublease loss           $ 0 $ 3,700   $ 1,000 $ 8,500    
v3.25.3
Commitments and Contingencies - Schedule of Undiscounted Future Lease Payments under Operating Lease (Details)
$ in Thousands
Sep. 30, 2025
USD ($)
Operating Leases  
2025 (remaining three months) $ 1,511
2026 13,471
2027 15,278
2028 15,677
2029 16,089
Thereafter 93,087
Total undiscounted lease payments 155,113
Less: Imputed interest (66,173)
Total $ 88,940
v3.25.3
Balance Sheet Components - Schedule of Property and Equipment, Net (Details) - USD ($)
$ in Thousands
Sep. 30, 2025
Dec. 31, 2024
Property, Plant and Equipment [Line Items]    
Total property and equipment $ 29,213 $ 29,652
Less: Accumulated depreciation and amortization (18,751) (18,045)
Property and equipment, net 10,462 11,607
Laboratory equipment    
Property, Plant and Equipment [Line Items]    
Total property and equipment 14,889 14,963
Leasehold improvements    
Property, Plant and Equipment [Line Items]    
Total property and equipment 13,779 13,779
Computer equipment and software    
Property, Plant and Equipment [Line Items]    
Total property and equipment 522 901
Construction in progress    
Property, Plant and Equipment [Line Items]    
Total property and equipment $ 23 $ 9
v3.25.3
Balance Sheet Components - Schedule of Accrued Expenses and Other Current Liabilities (Details) - USD ($)
$ in Thousands
Sep. 30, 2025
Dec. 31, 2024
Balance Sheet Related Disclosures [Abstract]    
Accrued nonclinical, clinical and process development costs $ 15,057 $ 4,401
Employee compensation 9,818 9,540
Accrued professional services 701 554
Other 900 1,125
Total accrued expenses and other current liabilities $ 26,476 $ 15,620
v3.25.3
Stockholders’ (Deficit) Equity - Additional Information (Details)
$ / shares in Units, $ in Thousands
 3 Months Ended 9 Months Ended
Aug. 12, 2025
USD ($)
Aug. 11, 2025
$ / shares
shares
Jun. 17, 2025
USD ($)
$ / shares
shares
Feb. 07, 2024
USD ($)
director
$ / shares
shares
Sep. 30, 2025
USD ($)
shares
Sep. 30, 2024
USD ($)
Mar. 31, 2024
USD ($)
Sep. 30, 2025
USD ($)
shares
Sep. 30, 2024
USD ($)
Dec. 31, 2024
USD ($)
Share-based Compensation Arrangement by Share-based Payment Award [Line Items]                    
Stock issuance costs | $         $ 142   $ 8,449      
Accumulated currency translation adjustments | $         400     $ 400   $ 500
Total stock-based compensation expense | $         $ 2,349 $ 2,964   $ 7,550 $ 11,075  
Stock options                    
Share-based Compensation Arrangement by Share-based Payment Award [Line Items]                    
Stock option repricing program, minimum exercise price (in USD per share) | $ / shares     $ 10.14              
Stock option repricing program, minimum exercise price reduced (in USD per share) | $ / shares     $ 10.14              
Share-based payment award, options, eligible and outstanding, number | shares     1,700,000              
Total stock-based compensation expense | $     $ 700              
Private Placement                    
Share-based Compensation Arrangement by Share-based Payment Award [Line Items]                    
Number of shares issued in transaction (in shares) | shares   1,000,000.0   10,500,000            
Common stock, par or stated value (in USD per share) | $ / shares   $ 0.0001                
Share price (in USD per share) | $ / shares   $ 2.24   $ 12.00            
Total gross proceeds | $ $ 10,000                  
Stock issuance costs | $ $ 100                  
Total gross proceeds | $       $ 127,800            
Private Placement | Two Directors                    
Share-based Compensation Arrangement by Share-based Payment Award [Line Items]                    
Number of shares issued in transaction (in shares) | shares       23,000            
Share price (in USD per share) | $ / shares       $ 13.50            
Number of directors | director       2            
Private Placement | Pre-Funded Warrants                    
Share-based Compensation Arrangement by Share-based Payment Award [Line Items]                    
Common stock issued upon exercise of warrants (in shares) | shares   3,500,000   75,000            
Share price (in USD per share) | $ / shares   $ 2.2399   $ 11.999            
Exercise price (in USD per share) | $ / shares   $ 0.0001   $ 0.001            
Beneficial ownership interest limitation (percent)   9.99%                
Warrants exercised (in shares) | shares         0     0    
v3.25.3
Stockholders’ (Deficit) Equity - Schedule of Stock Options Activity (Details)
shares in Thousands
 9 Months Ended
Sep. 30, 2025
$ / shares
shares
Number of Options (in thousands)  
Beginning balance (in shares) | shares 3,909
Options granted (in shares) | shares 1,148
Options forfeited (in shares) | shares (88)
Ending balance (in shares) | shares 4,969
Exercisable (in shares) | shares 2,390
Weighted- Average Exercise Price  
Beginning balance (in USD per share) | $ / shares $ 29.39
Options granted (in USD per share) | $ / shares 3.97
Options forfeited (in USD per share) | $ / shares 41.00
Ending balance (in USD per share) | $ / shares 23.31
Exercisable (in USD per share) | $ / shares $ 40.39
v3.25.3
Stockholders’ (Deficit) Equity - Schedule of Restricted Stock Units Activity (Details) - Restricted stock units
shares in Thousands
 9 Months Ended
Sep. 30, 2025
$ / shares
shares
Number of Units  
Beginning balance (in shares) | shares 259
Granted (in shares) | shares 299
Vested and released (in shares) | shares (86)
Forfeited (in shares) | shares (8)
Ending balance (in shares) | shares 464
Weighted- Average Grant- Date Fair Value  
Beginning balance (in USD per share) | $ / shares $ 16.00
Granted (in USD per share) | $ / shares 4.09
Vested and released (in USD per share) | $ / shares 22.03
Forfeited (in USD per share) | $ / shares 5.85
Ending balance (in USD per share) | $ / shares $ 7.41
v3.25.3
Stockholders’ (Deficit) Equity - Schedule of Stock-Based Compensation Expense (Details) - USD ($)
$ in Thousands
 3 Months Ended 9 Months Ended
Sep. 30, 2025
Sep. 30, 2024
Sep. 30, 2025
Sep. 30, 2024
Share-based Payment Arrangement, Expensed and Capitalized, Amount [Line Items]        
Total stock-based compensation expense $ 2,349 $ 2,964 $ 7,550 $ 11,075
Research and development        
Share-based Payment Arrangement, Expensed and Capitalized, Amount [Line Items]        
Total stock-based compensation expense 1,079 1,086 3,376 3,294
General and administrative        
Share-based Payment Arrangement, Expensed and Capitalized, Amount [Line Items]        
Total stock-based compensation expense $ 1,270 $ 1,878 $ 4,174 $ 7,781
v3.25.3
Segment Reporting (Details)
$ in Thousands
 3 Months Ended 9 Months Ended
Sep. 30, 2025
USD ($)
Jun. 30, 2025
USD ($)
Mar. 31, 2025
USD ($)
Sep. 30, 2024
USD ($)
Jun. 30, 2024
USD ($)
Mar. 31, 2024
USD ($)
Sep. 30, 2025
USD ($)
segment
Sep. 30, 2024
USD ($)
Segment Reporting Information [Line Items]                
Number of reportable segments | segment             1  
License revenue $ 0     $ 1,000     $ 0 $ 1,000
Operating expenses                
Total operating expenses 48,023     35,438     146,099 97,541
Operating loss (48,023)     (34,438)     (146,099) (96,541)
Other income, net 371     2,087     2,237 6,545
Net loss (47,652) $ (49,191) $ (47,019) (32,351) $ (30,498) $ (27,147) (143,862) (89,996)
Reportable Segment                
Segment Reporting Information [Line Items]                
License revenue 0     1,000     0 1,000
Operating expenses                
Compensation and benefits 15,801     13,081     48,139 41,010
Clinical trial and manufacturing 21,559     6,334     51,239 14,172
Facilities and IT 3,481     9,563     21,274 26,125
Other research and development 2,125     1,572     7,083 3,298
Other segment 5,057     4,888     18,364 12,936
Total operating expenses 48,023     35,438     146,099 97,541
Operating loss (48,023)     (34,438)     (146,099) (96,541)
Other income, net 371     2,087     2,237 6,545
Net loss $ (47,652)     $ (32,351)     $ (143,862) $ (89,996)
v3.25.3
Net Loss per Share (Details) - shares
shares in Thousands
 9 Months Ended
Sep. 30, 2025
Sep. 30, 2024
Antidilutive Securities Excluded from Computation of Earnings Per Share [Line Items]    
Antidilutive securities excluded from net loss per share (in shares) 5,492 3,975
Stock options    
Antidilutive Securities Excluded from Computation of Earnings Per Share [Line Items]    
Antidilutive securities excluded from net loss per share (in shares) 4,969 3,729
Restricted stock units    
Antidilutive Securities Excluded from Computation of Earnings Per Share [Line Items]    
Antidilutive securities excluded from net loss per share (in shares) 464 205
ESPP    
Antidilutive Securities Excluded from Computation of Earnings Per Share [Line Items]    
Antidilutive securities excluded from net loss per share (in shares) 59 41
v3.25.3
Subsequent Events (Details)
$ / shares in Units, $ in Millions
 1 Months Ended
Dec. 05, 2025
USD ($)
Nov. 21, 2025
USD ($)
Nov. 07, 2025
USD ($)
milestone
$ / shares
Oct. 28, 2025
USD ($)
Oct. 24, 2025
USD ($)
Oct. 31, 2025
USD ($)
Subsequent Event            
Subsequent Event [Line Items]            
Common stock, par or stated value (in USD per share) | $ / shares     $ 0.0001      
Subsequent Event | Lilly, and Flying Tigers Acquisition Corporation Merger | Forecast            
Subsequent Event [Line Items]            
Common stock, exchange price (in USD per share) | $ / shares     3.56      
Contingent value rights, per share (in USD per share) | $ / shares     $ 8.91      
Milestones to be achieved | milestone     2      
Termination fees     $ 4.0      
North Carolina Lease Settlement Agreement, Cash Settlement | Subsequent Event            
Subsequent Event [Line Items]            
Proceeds from legal settlements           $ 9.5
Secured Promissory Note | Secured Debt | Forecast            
Subsequent Event [Line Items]            
Funding from secured debt financing $ 25.0 $ 20.0        
Secured Promissory Note | Secured Debt | Subsequent Event            
Subsequent Event [Line Items]            
Secured debt financing         $ 65.0  
Funding from secured debt financing     $ 15.0 $ 5.0    
Debt instrument, basis spread (percent)         10.00%  
Debt instrument, prepayment premium (percent)         0.050  
Upon U.S. approval of Ixo-vec prior to seventh anniversary | Subsequent Event | Lilly, and Flying Tigers Acquisition Corporation Merger | Forecast            
Subsequent Event [Line Items]            
Contingent value rights, per share (in USD per share) | $ / shares     $ 1.78      
Upon first achievement of annual worldwide net sales of Ixo-vec | Subsequent Event | Lilly, and Flying Tigers Acquisition Corporation Merger | Forecast            
Subsequent Event [Line Items]            
Contingent value rights, per share (in USD per share) | $ / shares     $ 7.13      
Licensees exceeding amount     $ 1,000.0