ARCELLX, INC., 10-Q filed on 8/7/2025
Quarterly Report
v3.25.2
Document and Entity Information - shares
 6 Months Ended
Jun. 30, 2025
Aug. 01, 2025
Cover [Abstract]    
Document Type 10-Q  
Amendment Flag false  
Document Quarterly Report true  
Document Transition Report false  
Document Period End Date Jun. 30, 2025  
Document Fiscal Year Focus 2025  
Document Fiscal Period Focus Q2  
Current Fiscal Year End Date --12-31  
Entity Registrant Name ARCELLX, INC.  
Entity Central Index Key 0001786205  
Entity File Number 001-41259  
Entity Tax Identification Number 47-2855917  
Title of 12(b) Security Common Stock, $0.001 par value per share  
Trading Symbol ACLX  
Security Exchange Name NASDAQ  
Entity Current Reporting Status Yes  
Entity Interactive Data Current Yes  
Entity Shell Company false  
Entity Filer Category Large Accelerated Filer  
Entity Small Business false  
Entity Emerging Growth Company false  
Entity Incorporation, State or Country Code DE  
Entity Address, Address Line One 800 Bridge Parkway  
Entity Address, City or Town Redwood City  
Entity Address, State or Province CA  
Entity Address, Postal Zip Code 94065  
City Area Code 240  
Local Phone Number 327-0630  
Entity Common Stock, Shares Outstanding   55,458,912
v3.25.2
CONDENSED CONSOLIDATED BALANCE SHEETS (unaudited) - USD ($)
$ in Thousands
Jun. 30, 2025
Dec. 31, 2024
Assets, Current [Abstract]    
Cash and cash equivalents $ 62,336 $ 105,679
Marketable securities 390,767 481,696
Restricted cash, current 0 208
Prepaid expenses and other current assets 10,792 11,727
Total current assets 463,895 599,310
Restricted cash, non-current 2,418 2,418
Marketable securities non current 84,502 38,277
Property and equipment, net 44,472 46,456
Operating lease right-of-use assets 23,416 23,789
Prepaid research and development expenses and other long-term assets 383 1,077
Total assets 619,086 711,327
Current liabilities:    
Accounts payable 2,079 2,095
Accrued liabilities 53,034 56,716
Operating lease liabilities, current portion 7,416 7,308
Finance lease liabilities, current portion 0 230
Contract liability to related party 59,321 59,056
Total current liabilities 121,850 125,405
Operating lease liabilities, net of current portion 45,097 46,542
Contract liability to related party, net of current portion 59,916 75,995
Other non-current liabilities 0 8,593
Total liabilities 226,863 256,535
Commitments and contingencies (Note 7)
Stockholders' equity    
Common stock, par value of $0.001 per share; 1,000,000,000 shares authorized and 55,066,903 shares issued and outstanding as of March 31, 2025; 1,000,000,000 shares authorized and 54,293,597 shares issued and outstanding as of December 31, 2024 54 53
Additional paid-in capital 1,003,635 950,719
Accumulated other comprehensive income 403 848
Accumulated Deficit (611,869) (496,828)
Total stockholders' equity 392,223 454,792
Total liabilities and stockholders' equity $ 619,086 $ 711,327
v3.25.2
CONDENSED CONSOLIDATED BALANCE SHEETS (unaudited) (Parenthetical) - $ / shares
Jun. 30, 2025
Dec. 31, 2024
Common stock, par or stated value per share $ 0.001 $ 0.001
Common stock, shares authorized 1,000,000,000 1,000,000,000
Common stock, shares, issued 55,371,173 54,293,597
Common stock, shares, outstanding 55,371,173 54,293,597
v3.25.2
CONDENSED CONSOLIDATED STATEMENTS OF OPERATIONS AND COMPREHENSIVE LOSS (unaudited) - USD ($)
$ in Thousands
 3 Months Ended 6 Months Ended
Jun. 30, 2025
Jun. 30, 2024
Jun. 30, 2025
Jun. 30, 2024
Income Statement [Abstract]        
Collaboration revenue from related party $ 7,554 $ 27,384 $ 15,683 $ 66,640
Operating expenses:        
Research and development 37,627 40,953 88,428 73,271
General and administrative 28,653 21,424 54,879 44,172
Total operating expenses 66,280 62,377 143,307 117,443
Loss from operations (58,726) (34,993) (127,624) (50,803)
Other income (expense):        
Interest income, net 5,984 8,453 12,624 17,653
Interest expense 0 (321) (12) (909)
Total other income, net 5,984 8,132 12,612 16,744
Loss before income taxes (52,742) (26,861) (115,012) (34,059)
Income tax expense (29) (341) (29) (341)
Net loss (52,771) (27,202) (115,041) (34,400)
Other comprehensive loss:        
Unrealized loss on marketable securities (246) (280) (445) (1,339)
Comprehensive loss $ (53,017) $ (27,482) $ (115,486) $ (35,739)
Net loss per share attributable to common stockholders - basic $ (0.94) $ (0.51) $ (2.06) $ (0.65)
Net loss per share attributable to common stockholders - diluted $ (0.94) $ (0.51) $ (2.06) $ (0.65)
Weighted-average common shares outstanding - basic 56,221,331 53,516,907 55,741,563 53,137,440
Weighted-average common shares outstanding - diluted 56,221,331 53,516,907 55,741,563 53,137,440
v3.25.2
CONDENSED CONSOLIDATED STATEMENTS OF STOCKHOLDERS' EQUITY (unaudited) - USD ($)
$ in Thousands
Total
Common Stock
Additional Paid In Capital
Accumulated Deficit
Accumulated Other Comprehensive Gain (Loss)
Beginning Balance at Dec. 31, 2023 $ 485,380 $ 52 $ 874,261 $ (389,480) $ 547
Beginning Balance, Shares at Dec. 31, 2023   52,280,077      
Exercise of stock options, value 4,605 $ 1 4,604    
Exercise of stock options, shares   567,097      
Issuance of common stock from vesting of restricted stock, shares   440,816      
Share-based compensation 14,845   14,845    
Unrealized loss on marketable securities (1,059)       (1,059)
Net loss (7,198)     (7,198)  
Ending Balance at Mar. 31, 2024 496,573 $ 53 893,710 (396,678) (512)
Ending Balance, shares at Mar. 31, 2024   53,287,990      
Beginning Balance at Dec. 31, 2023 485,380 $ 52 874,261 (389,480) 547
Beginning Balance, Shares at Dec. 31, 2023   52,280,077      
Unrealized loss on marketable securities (1,339)        
Net loss (34,400)        
Ending Balance at Jun. 30, 2024 487,164 $ 53 911,783 (423,880) (792)
Ending Balance, shares at Jun. 30, 2024   53,631,144      
Beginning Balance at Mar. 31, 2024 496,573 $ 53 893,710 (396,678) (512)
Beginning Balance, Shares at Mar. 31, 2024   53,287,990      
Exercise of stock options, value 2,288   2,288    
Exercise of stock options, shares   274,334      
Issuance of common stock from vesting of restricted stock, shares   53,606      
Issuance of common stock pursuant to employee stock purchase plan, value 646   646    
Issuance of common stock pursuant to employee stock purchase plan, Shares   15,214      
Share-based compensation 15,139   15,139    
Unrealized loss on marketable securities (280)       (280)
Net loss (27,202)     (27,202)  
Ending Balance at Jun. 30, 2024 487,164 $ 53 911,783 (423,880) (792)
Ending Balance, shares at Jun. 30, 2024   53,631,144      
Beginning Balance at Dec. 31, 2024 454,792 $ 53 950,719 (496,828) 848
Beginning Balance, Shares at Dec. 31, 2024   54,293,597      
Exercise of stock options, value 766 $ 1 765    
Exercise of stock options, shares   93,568      
Issuance of common stock from vesting of restricted stock, shares   679,738      
Share-based compensation 23,817   23,817    
Unrealized loss on marketable securities (199)       (199)
Net loss (62,270)     (62,270)  
Ending Balance at Mar. 31, 2025 416,906 $ 54 975,301 (559,098) 649
Ending Balance, shares at Mar. 31, 2025   55,066,903      
Beginning Balance at Dec. 31, 2024 454,792 $ 53 950,719 (496,828) 848
Beginning Balance, Shares at Dec. 31, 2024   54,293,597      
Unrealized loss on marketable securities (445)        
Net loss (115,041)        
Ending Balance at Jun. 30, 2025 392,223 $ 54 1,003,635 (611,869) (403)
Ending Balance, shares at Jun. 30, 2025   55,371,173      
Beginning Balance at Mar. 31, 2025 416,906 $ 54 975,301 (559,098) 649
Beginning Balance, Shares at Mar. 31, 2025   55,066,903      
Issuance of common stock in offerings, net of issuance costs, value 7,812   7,812    
Issuance of common stock in offerings, net of issuance costs, shares   120,000      
Exercise of stock options, value 1,675   1,675    
Exercise of stock options, shares   108,620      
Issuance of common stock from vesting of restricted stock, shares   60,272      
Issuance of common stock pursuant to employee stock purchase plan, value 771   771    
Issuance of common stock pursuant to employee stock purchase plan, Shares   15,378      
Share-based compensation 18,076   18,076    
Unrealized loss on marketable securities (246)       (246)
Net loss (52,771)     (52,771)  
Ending Balance at Jun. 30, 2025 $ 392,223 $ 54 $ 1,003,635 $ (611,869) $ (403)
Ending Balance, shares at Jun. 30, 2025   55,371,173      
v3.25.2
CONDENSED CONSOLIDATED STATEMENTS OF CASH FLOWS (unaudited) - USD ($)
$ in Thousands
 6 Months Ended
Jun. 30, 2025
Jun. 30, 2024
Cash flows from operating activities    
Net loss $ (115,041) $ (34,400)
Adjustments to reconcile net loss to net cash used in operating activities:    
Depreciation and amortization 3,194 2,065
Non-cash operating lease expense 374 3,034
Right-of-use asset expensed 0 888
Amortization of premiums and discounts on marketable securities (5,533) (8,487)
Share-based compensation 41,893 29,984
Changes in operating assets and liabilities:    
Prepaid expenses and other current and non-current assets 1,621 7,276
Accounts payable and other current liabilities (47) 2,606
Accrued liabilities (3,592) 26,679
Operating lease liabilities (1,337) (2,546)
Contract liability to related party (15,815) (110,154)
Other non-current liabilities (8,593) 14,899
Net cash used in operating activities (102,876) (68,156)
Cash flows from investing activities    
Purchases of property and equipment (1,267) (9,645)
Purchases of marketable securities (235,208) (401,040)
Proceeds from maturities of marketable securities 285,000 196,000
Net cash provided by (used in) investing activities 48,525 (214,685)
Cash flows from financing activities    
Proceeds from issuance of common stock in offerings, net of transactions costs 7,812 0
Proceeds from exercise of stock options 2,447 6,893
Proceeds from stock issued pursuant to employee stock purchase plan 771 646
Principal payments under finance leases (230) (20,951)
Net cash provided by (used in) financing activities 10,800 (13,412)
Net decrease in cash and cash equivalents and restricted cash (43,551) (296,253)
Cash and cash equivalents and restricted cash, beginning of the period 108,305 398,904
Cash and cash equivalents and restricted cash, end of the period 64,754 102,651
Supplemental disclosure of cash flow information:    
Cash paid for income taxes 1,274 1,066
Supplemental disclosures of noncash investing and financing activities:    
Purchase of property and equipment included in accounts payable and accrued liabilities $ 262 $ 1,070
v3.25.2
Pay vs Performance Disclosure - USD ($)
$ in Thousands
 3 Months Ended 6 Months Ended
Jun. 30, 2025
Mar. 31, 2025
Jun. 30, 2024
Mar. 31, 2024
Jun. 30, 2025
Jun. 30, 2024
Pay vs Performance Disclosure            
Net Income (Loss) $ (52,771) $ (62,270) $ (27,202) $ (7,198) $ (115,041) $ (34,400)
v3.25.2
Insider Trading Arrangements
 3 Months Ended
Jun. 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
v3.25.2
Nature of the Business
 6 Months Ended
Jun. 30, 2025
Organization, Consolidation and Presentation of Financial Statements [Abstract]  
Nature of The Business

1. Nature of the Business

 

Organization

 

Arcellx, Inc. (Arcellx or the Company) was incorporated in Delaware in December 2014 and is headquartered in Redwood City, California. The Company is a clinical-stage biopharmaceutical company reimagining cell therapy through the development of innovative therapies for patients with cancer and other incurable diseases.

 

Liquidity

 

As of June 30, 2025, the Company had $537.6 million of cash, cash equivalents and marketable securities, which management believes will be sufficient to meet the Company’s anticipated operating and capital expenditure requirements for at least twelve months following the date of issuance of these condensed consolidated financial statements.
v3.25.2
Summary of Significant Accounting Policies
 6 Months Ended
Jun. 30, 2025
Accounting Policies [Abstract]  
Summary of Significant Accounting Policies

2. Summary of Significant Accounting Policies

 

Basis of Presentation and Consolidation

 

The accompanying unaudited condensed consolidated financial statements have been prepared in accordance with U.S. generally accepted accounting principles (U.S. GAAP) for interim financial information and the related rules and regulations of the Securities and Exchange Commission (SEC). Accordingly, they do not include all of the information and footnotes required by U.S. GAAP for complete financial statements. In the Company’s opinion, all adjustments (consisting only of normal recurring adjustments) considered necessary for a fair statement of the results of operations and cash flows for the periods presented have been included.

 

Operating results for the three and six months ended June 30, 2025 are not necessarily indicative of the results that may be expected for the year ending December 31, 2025 or for any future period. The balance sheet as of December 31, 2024 has been derived from audited consolidated financial statements at that date but does not include all of the information required by U.S. GAAP for complete 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 as of and for the year ended December 31, 2024 included in the Company’s Annual Report on Form 10-K filed with the SEC on February 27, 2025. There have been no significant changes to our accounting policies as described in Note 2, Summary of significant accounting policies, in the notes to the audited consolidated financial statements in Item 8 of Part II of the Form 10-K.

 

The accompanying condensed consolidated financial statements include the accounts of Arcellx, Inc. and its wholly-owned subsidiary. All intercompany balances and transactions have been eliminated in consolidation.

 

Recent Accounting Pronouncements

 

In December 2023, the FASB issued ASU No.2023-09 "Improvements to Income Tax Disclosures" which requires incremental annual disclosures around income tax rate reconciliation, income taxes paid and other related disclosures. This guidance requires prospective application and permits retrospective application to prior periods presented. The Company plans to adopt it beginning with its 2025 annual consolidated financial statements, to be filed in early 2026. The Company is currently evaluating the impact of the new guidance on its consolidated financial statements.

 

In November 2024, the FASB issued ASU No. 2024-03 "Disaggregation of Income Statement Expenses (DISE)" which requires disaggregated information about certain income statement expense line items on an annual and interim basis. This guidance will be effective for annual periods beginning the year ended December 31, 2027 and for interim periods thereafter. The new standard permits early adoption and can be applied prospective or retrospectively. The Company is currently evaluating the impact of the new guidance on its consolidated financial statements.
v3.25.2
Fair Value of Financial Instruments
 6 Months Ended
Jun. 30, 2025
Fair Value Disclosures [Abstract]  
Fair Value of Financial Instruments

3. Fair Value of Financial Instruments

 

The fair value of the Company’s financial assets by level within the fair value hierarchy were as follows (in thousands):

 

June 30, 2025

 

 

Level 1

 

Level 2

 

Level 3

 

Money market fund (cash equivalent)

$

60,934

 

$

—

 

$

—

 

Certificate of deposit (long-term restricted cash)

 

—

 

 

2,418

 

 

—

 

Marketable securities:

 

 

 

 

 

 

   Government agency

 

—

 

 

475,269

 

 

—

 

Total assets measured at fair value

$

60,934

 

$

477,687

 

$

—

 

 

 

December 31, 2024

 

 

Level 1

 

Level 2

 

Level 3

 

Money market fund (cash equivalent)

$

104,579

 

$

—

 

$

—

 

Money market fund (short-term restricted cash)

 

208

 

 

—

 

 

—

 

Certificate of deposit (long-term restricted cash)

 

—

 

 

2,418

 

 

—

 

Marketable securities:

 

 

 

 

 

 

   Government agency

 

—

 

 

519,973

 

 

—

 

Total assets measured at fair value

$

104,787

 

$

522,391

 

$

—

 

 

The fair value of financial assets categorized within Level 1 of the fair value hierarchy is determined by using unadjusted quoted prices that are available in active markets for identical assets and liabilities. The fair value of financial assets categorized within Level 2 of the fair value hierarchy is determined by using inputs other than Level 1 quoted prices that are directly or indirectly observable. Inputs can include quoted prices for similar assets and liabilities in active markets or quoted prices for identical assets and liabilities in inactive markets. Related inputs can also include those used in valuation or other pricing models, such as interest rates and yield curves that can be corroborated by observable market data.

 

The Company did not transfer any assets measured at fair value on a recurring basis between levels during the six months ended June 30, 2025 or the year ended December 31, 2024.
v3.25.2
Cash, Cash Equivalents and Marketable Securities
 6 Months Ended
Jun. 30, 2025
Marketable Securities [Abstract]  
Cash, Cash Equivalents, and Marketable Securities

4. Cash, Cash Equivalents and Marketable Securities

 

Available-for-sale marketable securities were as follows (in thousands):

 

 

June 30, 2025

 

 

Amortized
Cost

 

 

Unrealized
Gains

 

 

Unrealized
Losses

 

 

Fair Value

 

Government agency

$

474,866

 

 

$

501

 

 

$

(98

)

 

$

475,269

 

Total

$

474,866

 

 

$

501

 

 

$

(98

)

 

$

475,269

 

 

 

 

 

 

 

 

 

 

 

 

 

 

December 31, 2024

 

 

Amortized
Cost

 

 

Unrealized
Gains

 

 

Unrealized
Losses

 

 

Fair Value

 

Government agency

$

519,125

 

 

$

1,007

 

 

$

(159

)

 

$

519,973

 

Total

$

519,125

 

 

$

1,007

 

 

$

(159

)

 

$

519,973

 

 

The fair value of available-for-sale marketable securities by contractual maturity as of June 30, 2025 and December 31, 2024 were as follows (in thousands):

 

 

June 30, 2025

 

 

December 31, 2024

 

Due in 1 year or less

$

390,767

 

 

$

481,696

 

Due in 1 - 2 years

 

84,502

 

 

 

38,277

 

Total

$

475,269

 

 

$

519,973

 

 

The Company had 13 and 9 securities in an unrealized loss position as of June 30, 2025 and December 31, 2024, respectively. All securities in an unrealized loss position as of June 30, 2025 and December 31, 2024 had been in a loss position for less than twelve

months. Unrealized losses on available-for-sale marketable securities as of June 30, 2025 and December 31, 2024 were not significant and were primarily due to changes in interest rates, including market credit spreads, and not due to increased credit risks associated with specific securities. Accordingly, no allowance for credit losses related to the Company’s available-for-sale marketable securities was recorded for the six months ended June 30, 2025 and for the year ended December 31, 2024. The Company does not intend to sell these securities and it is unlikely that the Company will be required to sell the investments before recovery of their amortized cost bases, which may be at maturity.

 

As of June 30, 2025 and December 31, 2024, the Company recognized $3.3 million and $2.5 million, respectively, of accrued interest receivable from available-for-sale securities within prepaid expenses and other current assets on the condensed consolidated balance sheets.

 

The following table reconciles cash, cash equivalents and restricted cash per the condensed consolidated balance sheets to the condensed consolidated statements of cash flows (in thousands):

 

 

 

 

 

 

 

 

June 30,

 

 

2025

 

 

2024

 

Cash and cash equivalents

$

62,336

 

 

$

100,025

 

Restricted cash

 

2,418

 

 

 

2,626

 

Total

$

64,754

 

 

$

102,651

 
v3.25.2
Related Parties
 6 Months Ended
Jun. 30, 2025
Related Party Transactions [Abstract]  
Related Parties

5. Related Parties

Relationship and transactions with Gilead Sciences, Inc. (Gilead)

 

As of June 30, 2025, Gilead Sciences, Inc. (Gilead) held approximately 12% of the Company's outstanding common stock. These holdings resulted from Gilead's investment in the Company of: (i) $100.0 million, by purchasing 3,478,261 shares of common stock at a per share price of $28.75 pursuant to a Common Stock Purchase Agreement with Gilead (Gilead SPA); and (ii) $200.0 million, by purchasing 3,242,542 shares of common stock at a per share price of $61.68 pursuant to a second Common Stock Purchase Agreement with Gilead (Second Gilead SPA). See Note 6 for further discussion of the agreements with Gilead.

 

The Company partnered anito-cel with Kite, through its co-development/co-commercialization collaboration agreement, as described in more detail in Note 6 Collaboration Agreement.

 

As of June 30, 2025, the Company had $119.2 million in contract liability pursuant to the Collaboration and License Agreement with Kite (Kite Collaboration Agreement) and its amendment, of which $59.9 million represented the long-term portion of contract liability. For the three and six months ended June 30, 2025, the Company recognized $7.6 million and $15.7 million in revenue, respectively, under the Kite Collaboration Agreement and its amendment. See Note 6 for further discussion of the Kite Collaboration Agreement.
v3.25.2
Collaboration Agreement
 6 Months Ended
Jun. 30, 2025
Collaboration Agreement [Abstract]  
Collaboration Agreement

6. Collaboration Agreement

 

In December 2022, the Company entered into the Kite Collaboration Agreement, the Gilead SPA and a standstill and stock restriction agreement with Gilead (the Standstill Agreement). Upon closing in January 2023, Kite made an upfront payment of $225.0 million and obtained a license to co-develop and co-commercialize anito-cel, and next-generation autologous and non-autologous CAR-T cell therapy products that use the same D-domain BCMA binder used in anito-cel, in each case for the treatment of multiple myeloma. The Company also granted Kite the ability to negotiate a development and commercialization license for the inclusion of a limited number of pre-specified additional autologous CAR-T-cell therapy products for the treatment of multiple myeloma, which can be exercised by Kite after the Company provides to Kite a phase 1 clinical study report. Gilead made an equity investment of $100.0 million by purchasing 3,478,261 shares of Arcellx common stock at a fixed per share price of $28.75 pursuant to the Gilead SPA, which represented a $15.3 million discount on the sale of the Company’s common stock based on the share price on the date of closing.

 

In November 2023, the Company entered into an amendment to its Kite Collaboration Agreement, the Second Gilead SPA and an amended and restated standstill and stock restriction agreement with Gilead (the Amended Standstill Agreement). Upon closing in December 2023, Kite commenced negotiation of a license for the Company’s ARC-SparX program, ACLX-001, in multiple myeloma. The Company and Kite have also expanded the scope of the collaboration for the Company’s anito-cel to include lymphomas, which is subject to further negotiation by both parties in order to be developed and is therefore not a performance obligation either at contract inception or at June 30, 2025. In connection with the amendment to the Kite Collaboration Agreement, the Company received a $85.0 million upfront cash payment and are eligible for additional potential milestone payments. Gilead made an equity investment of $200.0 million by purchasing 3,242,542 shares of Arcellx common stock at a fixed per share price of $61.68 pursuant to the Second Gilead SPA, which represented a $15.6 million premium on the sale of the Company’s common stock based on the share price on the date of closing.

 

Under the Kite Collaboration Agreement and its amendment, the Company will be eligible to receive additional clinical, regulatory, and commercial milestone payments of up to $530.0 million, $935.0 million and $507.5 million, for anito-cel, each next-generation autologous CAR-T cell therapy product, and each non-autologous CAR-T cell therapy product, respectively. In 2024, the Company achieved a clinical milestone for anito-cel relating to enrollment in the iMMagine-1 trial and received $68.3 million from Kite.

 

In the United States, the Company and Kite will equally share profits and losses from the commercialization of anito-cel and any next-generation autologous CAR-T cell therapy product for which the Company has exercised its option to co-promote with Kite (collectively, the Co-Promote Products). The Company has the option to designate next-generation autologous CAR-T therapy product as a Co-Promote Product after Kite provides the first phase 1 clinical study report for such product with the proposed core development plan and budget. For Co-Promote Products outside of the United States and for any other products worldwide that are not a Co-Promote Product (Non-Co-Promote Products), including any next-generation autologous CAR-T cell therapy product for which the company has opted out of designating as a Co-Promote Product, the Company will be eligible for tiered royalties in the low to mid teen percentages. The Company and Kite will jointly develop the Co-Promote Products in accordance with mutually agreed development plans and development budgets. On a Co-Promote Product-by-Co-Promote Product basis, the Company may, upon advance written notice to Kite, opt out of sharing development costs and profits and losses from the commercialization of such Co-Promote Product (for example, anito-cel), in which case, it will become a Non-Co-Promote Product and eligible for tiered royalties in the low to mid teen percentages.

 

Other than certain items expressly set forth in the Kite Collaboration Agreement and its amendment, the out-of-pocket development costs for activities conducted in the United States for Co-Promote Products will be shared equally by the Company and Kite. The out-of-pocket development costs for activities conducted outside the United States as part of a global clinical trial for Co-Promote Products will be borne 60% by Kite and 40% by the Company, however Kite will be solely responsible for its costs for country-specific clinical trials and chemistry, manufacturing and control (CMC) commercial readiness. Kite will be solely responsible for the conduct of development and commercialization of the Non-Co-Promote Products at its sole cost. In the United States, the Company and Kite will be jointly responsible for commercialization of the Co-Promote Products. Kite will manufacture the licensed products and bear the CMC commercial readiness costs and capital expenses, except that the Company is responsible for manufacturing anito-cel prior to transferring the manufacturing process to Kite and the parties share associated out-of-pocket costs. Reimbursement costs expected to be received from Kite or paid to Kite represent variable consideration and are included in the estimated transaction price.

 

The Company’s promises under the Kite Collaboration Agreement include development, manufacture, and commercialization licenses, research and development activities, manufacturing activities, and the transfer of manufacturing know-how to Kite (collectively, the research and development services). These promises represent a single combined performance obligation as the promises are not distinct from each other. The Company determined that the license and research and development services are combined based on the specialized nature of the Company’s know-how and manufacturing process.

 

The Company evaluated the amendment to the Kite Collaboration Agreement and determined that the contract modifications should be accounted for as changes to the original contract, as the services to be provided after the contract modification are not distinct from those services already provided.

The Company uses a cost-based input method to measure proportional performance and to calculate the corresponding amount of revenue to recognize. In applying the cost-based input method of revenue recognition, the Company measures actual costs incurred relative to budgeted costs to fulfill the combined performance obligation. These costs consist primarily of third-party contract costs. Revenue is recognized based on actual costs incurred as a percentage of total budgeted costs as the Company completes its performance obligations. The Company uses the expected value method and most-likely-amount method to estimate variable consideration and will re-evaluate the transaction price in each reporting period, as uncertain events are resolved or other changes in circumstances occur.

 

During the three and six months ended June 30, 2025, revenue recognized that was included in the contract liability balance at the beginning of the period was $7.6 million and $15.7 million, respectively. During the three and six months ended June 30, 2025, no revenue was recognized from performance obligations satisfied in previous periods. As of June 30, 2025, the amount of the transaction price that has not been recognized as revenue was $34.4 million, which may be recognized as revenue over the period of time the Company is performing the research and development activities.
v3.25.2
Commitments and Contingencies
 6 Months Ended
Jun. 30, 2025
Commitments and Contingencies [Abstract]  
Commitments and Contingencies

7. Commitments and Contingencies

Commercial and Development Milestones

We have entered into contracts in the normal course of business with contract research organizations (CROs), contract manufacturing organizations (CMOs), and other third parties for preclinical research studies and testing, clinical trials, and manufacturing services. These contracts do not contain any minimum purchase commitments and are cancelable by us upon prior notice. For such contracts, payments due upon cancellation consist only of payments for services provided and expenses incurred, including non-cancelable obligations of our service providers, up to the date of cancellation.

 

We have also entered into agreements with certain vendors for the provision of goods and services, which include manufacturing services with CMOs and development services with CROs. These agreements may include certain provisions for purchase obligations and termination obligations that could require payments for the cancellation of committed purchase obligations or for early termination of the agreements. The amount of the cancellation or termination payments vary and are based on the timing of the cancellation or termination and the specific terms of the agreement. In addition, certain agreements with our CMOs and third-party vendors contain (a) development and commercial milestone payments and low single-digit royalties on worldwide net sales for certain products we sell that incorporate certain goods provided by our manufacturers and suppliers, (b) development milestones of up to $25.3 million in the aggregate and (c) commercial milestones of up to $52.0 million in the aggregate, along with royalty buyout provisions.

 

Purchase Commitments

The Company conducts product research and development programs through a combination of internal and collaborative programs that include, among others, arrangements with universities, contract research organizations and clinical research sites. The Company has contractual arrangements with these organizations; however, these contracts are generally cancelable on 30 days’ notice and the obligations under these contracts are largely based on services performed.

 

Contingencies

 

From time to time, the Company may be subject to various litigation and related matters arising in the ordinary course of business. The Company records a provision for a liability when it believes that it is both probable that a liability has been incurred and the amount can be reasonably estimated. Significant judgment is required to determine both probability and the estimated amount. As of June 30, 2025 and December 31, 2024, the Company was not involved in any material legal proceedings.

Indemnification Agreements

 

As permitted under Delaware law, the Company indemnifies its executive officers and directors for certain events or occurrences while the executive officer or director is, or was, serving at our request in such capacity. The term of this indemnification is for the officer’s or director’s lifetime. Additionally, the Company has entered into and expects to continue to enter into indemnification agreements with certain executive officers and directors. Further, in the ordinary course of business, the Company may provide indemnification of varying scope and terms to vendors, lessors, business partners, and other parties with respect to certain matters including, but not limited to, losses arising out of breach of such agreements or from intellectual property infringement claims made by third parties. The maximum potential amount of future payments the Company could be required to make under these indemnification agreements is, in many cases, unlimited. To date however, the Company has not incurred any material costs as a result of such indemnifications nor experienced any losses related to them. As of June 30, 2025, the Company was not aware of any claims under indemnification arrangements and does not expect significant claims related to these indemnification obligations. Therefore, no related reserves were established.
v3.25.2
Accrued Liabilities
 6 Months Ended
Jun. 30, 2024
Accrued Liabilities, Current [Abstract]  
Accrued Liabilities

8. Accrued Liabilities

Accrued liabilities consist of the following (in thousands):

 

 

June 30,

 

December 31,

 

 

2025

 

2024

 

Research and development accrued expenses

$

16,383

 

$

16,507

 

Accrued bonus

 

6,696

 

 

10,438

 

Other current liabilities

 

8,505

 

 

8,531

 

Liabilities to related party vendor

 

21,450

 

 

21,240

 

Total accrued liabilities

$

53,034

 

$

56,716

 

 

 

 

 

 
v3.25.2
Stockholders' Equity
 6 Months Ended
Jun. 30, 2025
Equity [Abstract]  
Stockholders' Equity

9. Stockholders' Equity

 

"At-the-Market" Offering Program

 

In May 2023, the Company entered into a sales agreement (Sales Agreement) with Stifel, Nicolaus & Company (Stifel) with respect to an at-the-market offering program under which the Company may issue and sell, from time to time and at the Company’s sole discretion, shares of the Company’s common stock, in an aggregate offering amount of up to $350.0 million. During the three months ended June 30, 2025, the Company sold a total of 120,000 shares of its common stock in at-the-market offerings for total net proceeds of $7.8 million.

 

Gilead SPA and Second Gilead SPA

 

On January 26, 2023, the Company issued and sold an aggregate of 3,478,261 shares of common stock in a private placement to Gilead at a price of $28.75 per share for an aggregate purchase price of $100.0 million. The shares were sold pursuant to the Gilead SPA in connection with the Kite Collaboration Agreement and the transaction is considered part of the arrangement. The shares were sold at a discount of $4.39 per share as compared to the closing price of the stock on the date of the expiration of anti-trust provisions and accordingly, the $15.3 million discount is reflected as an increase to additional paid-in capital and decrease to the total fixed transaction price in the arrangement. See Note 6 - Collaboration Agreement.

 

On December 28, 2023, the Company issued and sold an aggregate of 3,242,542 shares of common stock in a private placement to Gilead at a price of $61.68 per share for an aggregate purchase price of $200.0 million. The shares were sold pursuant to the Second Gilead SPA in connection with the amendment to the Kite Collaboration Agreement and the transaction is considered part of the arrangement. The shares were sold at a premium of $4.80 per share as compared to the closing price of the stock on the date of the expiration of anti-trust provisions and accordingly, the $15.6 million premium is reflected as an increase to additional paid-in capital and decrease to the total fixed transaction price in the arrangement. See Note 6 - Collaboration Agreement.

 

Common Stock

 

Each share of common stock entitles the holder to one vote on all matters submitted to a vote of the Company’s stockholders. Common stockholders are entitled to receive dividends, as may be declared by the board of directors, if any. As of the date of the filing of this Quarterly Report on Form 10-Q, no dividends have been declared or paid by the Company.

 

In the event of any liquidation or dissolution of the Company, the holders of common stock are entitled to the assets of the Company legally available for distribution.

 

Restricted Stock Units - Chief Executive Officer

In February 2025, the compensation committee of the board of directors determined that the performance criteria under each of the June 9, 2021 RSU award and January 3, 2023 RSU award held by the Company's Chief Executive Officer were partially satisfied (measured as of December 31, 2024), such that the awards vested as to 668,416 and 347,255, respectively. The number of restricted stock units vested are included in net loss per share calculation and are excluded from Condensed Consolidated Statements of Stockholders' Equity until issuance.

Preferred Stock

The Company has authorized 200,000,000 shares of preferred stock, par value $0.0001. There was no preferred stock outstanding as of June 30, 2025 and December 31, 2024.
v3.25.2
Income Taxes
 6 Months Ended
Jun. 30, 2025
Income Tax Disclosure [Abstract]  
Income Taxes

10. Income Taxes

The Company recorded an income tax provision of $29 thousand for the three and six months ended June 30, 2025, respectively. The Company recorded an income tax provision of $0.3 million for the three and six months ended June 30, 2024, respectively.

Based on the available objective evidence during the three and six months ended June 30, 2025, the Company maintains a full valuation allowance against its net deferred tax assets as the Company believes it is not more likely than not that the benefit will be realized. The primary difference between the effective tax rate and the statutory tax rate relates to the change in valuation allowance.
v3.25.2
Net Loss Per Share Attributable to Common Stockholders
 6 Months Ended
Jun. 30, 2025
Earnings Per Share [Abstract]  
Net Loss Per Share Attributable to Common Stockholders

11. Net Loss Per Share Attributable to Common Stockholders

The Company excluded the following potential common shares, presented based on amounts outstanding at period end, from the computation of diluted net loss per share attributable to common stockholders for the periods indicated because including them would have had an anti-dilutive effect:

 

 

June 30,

 

 

2025

 

2024

 

Options to purchase common stock

 

6,994,636

 

 

7,863,544

 

Restricted stock units

 

2,096,728

 

 

1,711,396

 

Restricted stock units - executive officer

 

432,133

 

 

1,447,804

 

Employee Stock Purchase Plan (ESPP)

 

4,580

 

 

16,803

 

Total

 

9,528,077

 

 

11,039,547

 
v3.25.2
Segment Reporting
 6 Months Ended
Jun. 30, 2025
Segment Reporting [Abstract]  
Segment Reporting

12. Segment Reporting

The Company operates in a single operating segment and has one reportable segment, which includes all activities related to the discovery, development, and manufacturing of its product candidates. The determination of a single segment is consistent with the consolidated financial information regularly provided to the Company's chief operating decision maker ("CODM"). The CODM uses consolidated net loss for purpose of assessing performance, making operating decisions and allocating resources. The measurement of segment assets is reported on the balance sheet as total consolidated assets.

The table below provides information about the Company’s segment (in thousands):

 

Three Months Ended June 30,

Six Months Ended June 30,

 

 

2025

 

 

2024

 

 

2025

 

 

2024

 

Collaboration revenue

$

7,554

 

 

$

27,384

 

 

$

15,683

 

 

$

66,640

 

Operating expenses:

 

 

 

 

 

 

 

Research and development

 

 

 

 

 

 

 

 

 

 

 

anito-cel in rrMM

 

8,304

 

 

 

13,317

 

 

 

21,575

 

 

 

25,108

 

ACLX-002

 

2,891

 

 

 

3,234

 

 

 

6,732

 

 

 

6,472

 

Other research and development costs

 

5,899

 

 

 

7,428

 

 

 

13,130

 

 

 

10,597

 

Internal costs [1]

 

20,533

 

 

 

16,974

 

 

 

46,991

 

 

 

31,094

 

General and administrative

 

28,653

 

 

 

21,424

 

 

 

54,879

 

 

 

44,172

 

Total operating expenses

 

66,280

 

 

 

62,377

 

 

 

143,307

 

 

 

117,443

 

Loss from operations

 

(58,726

)

 

 

(34,993

)

 

 

(127,624

)

 

 

(50,803

)

       Interest income, net

 

5,984

 

 

 

8,453

 

 

 

12,624

 

 

 

17,653

 

       Interest expense

 

—

 

 

 

(321

)

 

 

(12

)

 

 

(909

)

Total other income, net

 

5,984

 

 

 

8,132

 

 

 

12,612

 

 

 

16,744

 

       Income tax expense

 

(29

)

 

 

(341

)

 

 

(29

)

 

 

(341

)

Net loss

$

(52,771

)

 

$

(27,202

)

 

$

(115,041

)

 

$

(34,400

)

 

[1]Internal costs primarily consist of employee-related costs, including salaries, related benefits, and share-based compensation expense, as well as facility and depreciation expense.
v3.25.2
Summary of Significant Accounting Policies (Policies)
 6 Months Ended
Jun. 30, 2025
Accounting Policies [Abstract]  
Basis of Presentation and Consolidation

Basis of Presentation and Consolidation

 

The accompanying unaudited condensed consolidated financial statements have been prepared in accordance with U.S. generally accepted accounting principles (U.S. GAAP) for interim financial information and the related rules and regulations of the Securities and Exchange Commission (SEC). Accordingly, they do not include all of the information and footnotes required by U.S. GAAP for complete financial statements. In the Company’s opinion, all adjustments (consisting only of normal recurring adjustments) considered necessary for a fair statement of the results of operations and cash flows for the periods presented have been included.

 

Operating results for the three and six months ended June 30, 2025 are not necessarily indicative of the results that may be expected for the year ending December 31, 2025 or for any future period. The balance sheet as of December 31, 2024 has been derived from audited consolidated financial statements at that date but does not include all of the information required by U.S. GAAP for complete 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 as of and for the year ended December 31, 2024 included in the Company’s Annual Report on Form 10-K filed with the SEC on February 27, 2025. There have been no significant changes to our accounting policies as described in Note 2, Summary of significant accounting policies, in the notes to the audited consolidated financial statements in Item 8 of Part II of the Form 10-K.

 

The accompanying condensed consolidated financial statements include the accounts of Arcellx, Inc. and its wholly-owned subsidiary. All intercompany balances and transactions have been eliminated in consolidation.
Recent Accounting Pronouncements

Recent Accounting Pronouncements

 

In December 2023, the FASB issued ASU No.2023-09 "Improvements to Income Tax Disclosures" which requires incremental annual disclosures around income tax rate reconciliation, income taxes paid and other related disclosures. This guidance requires prospective application and permits retrospective application to prior periods presented. The Company plans to adopt it beginning with its 2025 annual consolidated financial statements, to be filed in early 2026. The Company is currently evaluating the impact of the new guidance on its consolidated financial statements.

 

In November 2024, the FASB issued ASU No. 2024-03 "Disaggregation of Income Statement Expenses (DISE)" which requires disaggregated information about certain income statement expense line items on an annual and interim basis. This guidance will be effective for annual periods beginning the year ended December 31, 2027 and for interim periods thereafter. The new standard permits early adoption and can be applied prospective or retrospectively. The Company is currently evaluating the impact of the new guidance on its consolidated financial statements.
v3.25.2
Fair Value of Financial Instruments (Tables)
 6 Months Ended
Jun. 30, 2025
Fair Value Disclosures [Abstract]  
Schedule of Fair Value of Company's Financial Assets

The fair value of the Company’s financial assets by level within the fair value hierarchy were as follows (in thousands):

 

June 30, 2025

 

 

Level 1

 

Level 2

 

Level 3

 

Money market fund (cash equivalent)

$

60,934

 

$

—

 

$

—

 

Certificate of deposit (long-term restricted cash)

 

—

 

 

2,418

 

 

—

 

Marketable securities:

 

 

 

 

 

 

   Government agency

 

—

 

 

475,269

 

 

—

 

Total assets measured at fair value

$

60,934

 

$

477,687

 

$

—

 

 

 

December 31, 2024

 

 

Level 1

 

Level 2

 

Level 3

 

Money market fund (cash equivalent)

$

104,579

 

$

—

 

$

—

 

Money market fund (short-term restricted cash)

 

208

 

 

—

 

 

—

 

Certificate of deposit (long-term restricted cash)

 

—

 

 

2,418

 

 

—

 

Marketable securities:

 

 

 

 

 

 

   Government agency

 

—

 

 

519,973

 

 

—

 

Total assets measured at fair value

$

104,787

 

$

522,391

 

$

—

 

 
v3.25.2
Cash, Cash Equivalents and Marketable Securities (Tables)
 6 Months Ended
Jun. 30, 2025
Marketable Securities [Abstract]  
Schedule of Available-for-sale Marketable Securities

Available-for-sale marketable securities were as follows (in thousands):

 

 

June 30, 2025

 

 

Amortized
Cost

 

 

Unrealized
Gains

 

 

Unrealized
Losses

 

 

Fair Value

 

Government agency

$

474,866

 

 

$

501

 

 

$

(98

)

 

$

475,269

 

Total

$

474,866

 

 

$

501

 

 

$

(98

)

 

$

475,269

 

 

 

 

 

 

 

 

 

 

 

 

 

 

December 31, 2024

 

 

Amortized
Cost

 

 

Unrealized
Gains

 

 

Unrealized
Losses

 

 

Fair Value

 

Government agency

$

519,125

 

 

$

1,007

 

 

$

(159

)

 

$

519,973

 

Total

$

519,125

 

 

$

1,007

 

 

$

(159

)

 

$

519,973

 
Schedule of Fair Value of Available-For-Sale Marketable Securities by Contractual Maturity Date

The fair value of available-for-sale marketable securities by contractual maturity as of June 30, 2025 and December 31, 2024 were as follows (in thousands):

 

 

June 30, 2025

 

 

December 31, 2024

 

Due in 1 year or less

$

390,767

 

 

$

481,696

 

Due in 1 - 2 years

 

84,502

 

 

 

38,277

 

Total

$

475,269

 

 

$

519,973

 
Schedule of Cash, Cash Equivalents and Restricted Cash

The following table reconciles cash, cash equivalents and restricted cash per the condensed consolidated balance sheets to the condensed consolidated statements of cash flows (in thousands):

 

 

 

 

 

 

 

 

June 30,

 

 

2025

 

 

2024

 

Cash and cash equivalents

$

62,336

 

 

$

100,025

 

Restricted cash

 

2,418

 

 

 

2,626

 

Total

$

64,754

 

 

$

102,651

 
v3.25.2
Accrued Liabilities (Tables)
 6 Months Ended
Jun. 30, 2025
Accrued Liabilities, Current [Abstract]  
Schedule of Accrued Liabilities

Accrued liabilities consist of the following (in thousands):

 

 

June 30,

 

December 31,

 

 

2025

 

2024

 

Research and development accrued expenses

$

16,383

 

$

16,507

 

Accrued bonus

 

6,696

 

 

10,438

 

Other current liabilities

 

8,505

 

 

8,531

 

Liabilities to related party vendor

 

21,450

 

 

21,240

 

Total accrued liabilities

$

53,034

 

$

56,716

 

 

 

 

 

 
v3.25.2
Net Loss Per Share Attributable to Common Stockholders (Tables)
 6 Months Ended
Jun. 30, 2025
Earnings Per Share [Abstract]  
Schedule of Antidilutive Securities Excluded From Computation of Earnings Per Share

 

June 30,

 

 

2025

 

2024

 

Options to purchase common stock

 

6,994,636

 

 

7,863,544

 

Restricted stock units

 

2,096,728

 

 

1,711,396

 

Restricted stock units - executive officer

 

432,133

 

 

1,447,804

 

Employee Stock Purchase Plan (ESPP)

 

4,580

 

 

16,803

 

Total

 

9,528,077

 

 

11,039,547

 
v3.25.2
Segment Reporting (Tables)
 6 Months Ended
Jun. 30, 2025
Segment Reporting [Abstract]  
Schedule of Segment Reporting

The table below provides information about the Company’s segment (in thousands):

 

Three Months Ended June 30,

Six Months Ended June 30,

 

 

2025

 

 

2024

 

 

2025

 

 

2024

 

Collaboration revenue

$

7,554

 

 

$

27,384

 

 

$

15,683

 

 

$

66,640

 

Operating expenses:

 

 

 

 

 

 

 

Research and development

 

 

 

 

 

 

 

 

 

 

 

anito-cel in rrMM

 

8,304

 

 

 

13,317

 

 

 

21,575

 

 

 

25,108

 

ACLX-002

 

2,891

 

 

 

3,234

 

 

 

6,732

 

 

 

6,472

 

Other research and development costs

 

5,899

 

 

 

7,428

 

 

 

13,130

 

 

 

10,597

 

Internal costs [1]

 

20,533

 

 

 

16,974

 

 

 

46,991

 

 

 

31,094

 

General and administrative

 

28,653

 

 

 

21,424

 

 

 

54,879

 

 

 

44,172

 

Total operating expenses

 

66,280

 

 

 

62,377

 

 

 

143,307

 

 

 

117,443

 

Loss from operations

 

(58,726

)

 

 

(34,993

)

 

 

(127,624

)

 

 

(50,803

)

       Interest income, net

 

5,984

 

 

 

8,453

 

 

 

12,624

 

 

 

17,653

 

       Interest expense

 

—

 

 

 

(321

)

 

 

(12

)

 

 

(909

)

Total other income, net

 

5,984

 

 

 

8,132

 

 

 

12,612

 

 

 

16,744

 

       Income tax expense

 

(29

)

 

 

(341

)

 

 

(29

)

 

 

(341

)

Net loss

$

(52,771

)

 

$

(27,202

)

 

$

(115,041

)

 

$

(34,400

)

 

[1]Internal costs primarily consist of employee-related costs, including salaries, related benefits, and share-based compensation expense, as well as facility and depreciation expense.
v3.25.2
Nature of the Business - Additional Information (Details)
$ in Millions
Jun. 30, 2025
USD ($)
Class of Stock [Line Items]  
Cash, cash equivalents and marketable securities $ 537.6
v3.25.2
Fair Value of Financial Instruments - Schedule of Fair Value of Company's Financial Assets (Details) - USD ($)
$ in Thousands
Jun. 30, 2025
Dec. 31, 2024
Assets    
Money market fund (short-term restricted cash) $ 0 $ 208
Certificate of deposit (long-term restricted cash) 2,418 2,418
Marketable securities 475,269 519,973
Level 1 | Recurring    
Assets    
Money market fund (cash equivalent) 60,934 104,579
Money market fund (short-term restricted cash)   208
Total assets measured at fair value 60,934 104,787
Level 2 | Recurring    
Assets    
Total assets measured at fair value 477,687 522,391
Level 2 | Recurring | Certificates of Deposit    
Assets    
Certificate of deposit (long-term restricted cash) 2,418 2,418
Level 2 | Recurring | Government Agency    
Assets    
Marketable securities $ 475,269 $ 519,973
v3.25.2
Cash, Cash Equivalents and Marketable Securities - Schedule of Available-for-sale Marketable Securities (Details) - USD ($)
$ in Thousands
Jun. 30, 2025
Dec. 31, 2024
Marketable Securities [Line Items]    
Amortized costs $ 474,866 $ 519,125
Gross Unrealized Gains 501 1,007
Gross Unrealized Loss (98) (159)
Fair Value 475,269 519,973
Government Agency    
Marketable Securities [Line Items]    
Amortized costs 474,866 519,125
Gross Unrealized Gains 501 1,007
Gross Unrealized Loss (98) (159)
Fair Value $ 475,269 $ 519,973
v3.25.2
Cash, Cash Equivalents and Marketable Securities - Schedule of Fair Value of Available-For-Sale Marketable Securities by Contractual Maturity Date (Details) - USD ($)
$ in Thousands
Jun. 30, 2025
Dec. 31, 2024
Marketable Securities [Abstract]    
Due in 1 year or less $ 390,767 $ 481,696
Due in 1 - 2 years 84,502 38,277
Total $ 475,269 $ 519,973
v3.25.2
Cash, Cash Equivalents and Marketable Securities - Additional Information (Details)
$ in Millions
Jun. 30, 2025
USD ($)
Condition
Dec. 31, 2024
USD ($)
Condition
Marketable Securities [Line Items]    
Number of securities in an unrealized loss position | Condition 13 9
Allowance for credit losses $ 0.0 $ 0.0
Prepaid Expenses and Other Current Assets    
Marketable Securities [Line Items]    
Accrued interest receivable $ 3.3 $ 2.5
v3.25.2
Cash, Cash Equivalents and Marketable Securities - Schedule of Cash, Cash Equivalents and Restricted Cash (Details) - USD ($)
$ in Thousands
Jun. 30, 2025
Dec. 31, 2024
Jun. 30, 2024
Dec. 31, 2023
Cash, Cash Equivalent, Restricted Cash, and Restricted Cash Equivalent, Continuing Operation [Abstract]        
Cash and cash equivalents $ 62,336 $ 105,679 $ 100,025  
Restricted cash 2,418   2,626  
Total $ 64,754 $ 108,305 $ 102,651 $ 398,904
v3.25.2
Related Parties - Additional Information (Details) - USD ($)
$ / shares in Units, $ in Thousands
 1 Months Ended 3 Months Ended 6 Months Ended
Dec. 31, 2023
Jan. 31, 2023
Jun. 30, 2025
Jun. 30, 2024
Jun. 30, 2025
Jun. 30, 2024
Dec. 31, 2024
Related Party Transaction [Line Items]              
Contract liability, long-term portion     $ 59,916   $ 59,916   $ 75,995
Collaboration revenue from related party     $ 7,554 $ 27,384 $ 15,683 $ 66,640  
Gilead              
Related Party Transaction [Line Items]              
Percentage of ownership held     12.00%   12.00%    
Contract liability     $ 119,200   $ 119,200    
Contract liability, long-term portion     $ 59,900   $ 59,900    
Gilead Common Stock Purchase Agreement              
Related Party Transaction [Line Items]              
Shares purchased   3,478,261 3,478,261   3,478,261    
Shares issued, price per share   $ 28.75 $ 28.75   $ 28.75    
Gilead Common Stock Purchase Agreement | Gilead              
Related Party Transaction [Line Items]              
Proceeds from issuance of private placement   $ 100,000          
Second Gilead Common Stock Purchase Agreement              
Related Party Transaction [Line Items]              
Shares purchased 3,242,542   3,242,542   3,242,542    
Shares issued, price per share $ 61.68   $ 61.68   $ 61.68    
Second Gilead Common Stock Purchase Agreement | Gilead              
Related Party Transaction [Line Items]              
Proceeds from issuance of private placement $ 200,000            
Gilead Collaboration Agreement              
Related Party Transaction [Line Items]              
Collaboration revenue from related party     $ 7,600   $ 15,700    
v3.25.2
Collaboration Agreement - Additional Information (Details) - USD ($)
 1 Months Ended 3 Months Ended 6 Months Ended
Dec. 31, 2023
Jan. 31, 2023
Jun. 30, 2025
Jun. 30, 2024
Jun. 30, 2025
Jun. 30, 2024
Dec. 31, 2024
Dec. 28, 2023
Collaborative Arrangement and Arrangement Other than Collaborative [Line Items]                
Contract liability revenue recognized     $ 7,554,000 $ 27,384,000 $ 15,683,000 $ 66,640,000    
Contract with customer, performance obligation satisfied in previous period     0   0      
Unrecognized revenue     34,400,000   34,400,000      
Anito-cel in rrMM                
Collaborative Arrangement and Arrangement Other than Collaborative [Line Items]                
Clinical milestone achieved             $ 68,300,000  
Anito-cel Next Gen Non-autologous | Maximum                
Collaborative Arrangement and Arrangement Other than Collaborative [Line Items]                
Potential payments of commercial milestone     507,500,000   507,500,000      
Potential payments of clinical milestone     530,000,000   530,000,000      
Potential payments of regulatory milestone     $ 935,000,000   $ 935,000,000      
Kite Collaboration Agreement                
Collaborative Arrangement and Arrangement Other than Collaborative [Line Items]                
Non-refundable upfront payment received   $ 225,000,000            
Increase in deemed premium on shares sold               $ 15,600,000
Kite Collaboration Agreement and Amendment | United States                
Collaborative Arrangement and Arrangement Other than Collaborative [Line Items]                
Percentage of out-of-pocket development costs for co-promote products         40.00%      
Kite Collaboration Agreement and Amendment | Kite Pharma, Inc. | Outside United States                
Collaborative Arrangement and Arrangement Other than Collaborative [Line Items]                
Percentage of out-of-pocket development costs for co-promote products         60.00%      
Amended Kite Collaboration Agreement                
Collaborative Arrangement and Arrangement Other than Collaborative [Line Items]                
Non-refundable upfront payment received $ 85,000,000              
Gilead Common Stock Purchase Agreement                
Collaborative Arrangement and Arrangement Other than Collaborative [Line Items]                
Shares purchased   3,478,261 3,478,261   3,478,261      
Shares issued, price per share   $ 28.75 $ 28.75   $ 28.75      
Reduction of deemed discount on shares sold   $ 15,300,000            
Gilead Common Stock Purchase Agreement | Gilead                
Collaborative Arrangement and Arrangement Other than Collaborative [Line Items]                
Proceeds from issuance of private placement   $ 100,000,000            
Second Gilead Common Stock Purchase Agreement                
Collaborative Arrangement and Arrangement Other than Collaborative [Line Items]                
Shares purchased 3,242,542   3,242,542   3,242,542      
Shares issued, price per share $ 61.68   $ 61.68   $ 61.68      
Increase in deemed premium on shares sold $ 15,600,000              
Second Gilead Common Stock Purchase Agreement | Gilead                
Collaborative Arrangement and Arrangement Other than Collaborative [Line Items]                
Proceeds from issuance of private placement $ 200,000,000              
v3.25.2
Commitments and Contingencies - Additional Information (Details)
$ in Millions
Jun. 30, 2025
USD ($)
Related Party Transaction [Line Items]  
Contracts cancelable period 30 days
Maximum amount of development milestones to be paid by company $ 25.3
Maximum amount of development milestones to be paid by company $ 52.0
v3.25.2
Accrued Liabilities - Schedule of Accrued Liabilities (Details) - USD ($)
$ in Thousands
Jun. 30, 2025
Dec. 31, 2024
Accrued Liabilities, Current [Abstract]    
Research and development accrued expenses $ 16,383 $ 16,507
Accrued bonus 6,696 10,438
Other current liabilities 8,505 8,531
Liabilities to related party vendor 21,450 21,240
Total accrued liabilities $ 53,034 $ 56,716
v3.25.2
Stockholders' Equity - Additional Information (Details) - USD ($)
 3 Months Ended 6 Months Ended
Dec. 28, 2023
Jan. 26, 2023
Jun. 30, 2025
Jun. 30, 2025
Jun. 30, 2024
Dec. 31, 2024
May 31, 2023
Class of Stock [Line Items]              
Common stock aggregate offering maximum amount under at the market program             $ 350,000,000
Total net proceeds from common stock       $ 7,812,000 $ 0    
Issuance of common stock, value     $ 7,812,000        
Common stock voting rights       one vote      
Preferred stock, shares authorized     200,000,000 200,000,000      
Preferred stock par value     $ 0.0001 $ 0.0001      
Preferred stock, shares outstanding     0 0   0  
2021 CEO | Restricted Stock Units              
Class of Stock [Line Items]              
Restricted stock units, vested       668,416      
2023 CEO | Restricted Stock Units              
Class of Stock [Line Items]              
Restricted stock units, vested       347,255      
Kite Collaboration Agreement              
Class of Stock [Line Items]              
Discount on shares sold price per share   $ 4.39          
Reduction of deemed discount on shares sold   $ 15,300,000          
Premium on shares sold price per share $ 4.8            
Increase in deemed premium on shares sold $ 15,600,000            
Common Stock              
Class of Stock [Line Items]              
Number of shares issued     120,000        
Dividends declared or paid       $ 0      
Private Placement | Gilead SPA and Second Gilead SPA              
Class of Stock [Line Items]              
Number of shares issued 3,242,542 3,478,261          
Sale of stock, price per share $ 61.68 $ 28.75          
Issuance of common stock, value $ 200,000,000 $ 100,000,000          
At-the-Market Offering              
Class of Stock [Line Items]              
Sale of stock, number of shares issued in transaction     120,000        
Total net proceeds from common stock     $ 7,800,000        
v3.25.2
Income Taxes - Additional Information (Details) - USD ($)
$ in Thousands
 3 Months Ended 6 Months Ended
Jun. 30, 2025
Jun. 30, 2024
Jun. 30, 2025
Jun. 30, 2024
Income Tax Disclosure [Abstract]        
Income tax expense (benefit) $ 29 $ 341 $ 29 $ 341
v3.25.2
Net Loss Per Share Attributable to Common Stockholders - Summary of Dilutive Securities Excluded from Computation of Diluted Net Loss Per Share (Details) - shares
 6 Months Ended
Jun. 30, 2025
Jun. 30, 2024
Antidilutive Securities Excluded From Computation Of Earnings Per Share [Line Items]    
Antidilutive Securities Excluded From Computation Of Earnings Per Share Amount 9,528,077 11,039,547
Options to Purchase Common Stock    
Antidilutive Securities Excluded From Computation Of Earnings Per Share [Line Items]    
Antidilutive Securities Excluded From Computation Of Earnings Per Share Amount 6,994,636 7,863,544
Restricted Stock Units    
Antidilutive Securities Excluded From Computation Of Earnings Per Share [Line Items]    
Antidilutive Securities Excluded From Computation Of Earnings Per Share Amount 2,096,728 1,711,396
Restricted stock units - executive officer    
Antidilutive Securities Excluded From Computation Of Earnings Per Share [Line Items]    
Antidilutive Securities Excluded From Computation Of Earnings Per Share Amount 432,133 1,447,804
Employee Stock Purchase Plan (ESPP)    
Antidilutive Securities Excluded From Computation Of Earnings Per Share [Line Items]    
Antidilutive Securities Excluded From Computation Of Earnings Per Share Amount 4,580 16,803
v3.25.2
Segment Reporting - Additional Information (Details)
 6 Months Ended
Jun. 30, 2025
Segment
Segment Reporting [Abstract]  
Number of reportable segments 1
Segment Reporting, CODM, Profit (Loss) Measure, How Used, Description The determination of a single segment is consistent with the consolidated financial information regularly provided to the Company's chief operating decision maker ("CODM"). The CODM uses consolidated net loss for purpose of assessing performance, making operating decisions and allocating resources.
v3.25.2
Segment Reporting - Schedule of Segment Reporting (Details) - USD ($)
$ in Thousands
 3 Months Ended 6 Months Ended
Jun. 30, 2025
Mar. 31, 2025
Jun. 30, 2024
Mar. 31, 2024
Jun. 30, 2025
Jun. 30, 2024
Segment Reporting Information [Line Items]            
Collaboration revenue $ 7,554   $ 27,384   $ 15,683 $ 66,640
Operating expenses:            
Research and development 37,627   40,953   88,428 73,271
General and administrative 28,653   21,424   54,879 44,172
Total operating expenses 66,280   62,377   143,307 117,443
Loss from operations (58,726)   (34,993)   (127,624) (50,803)
Interest income, net 5,984   8,453   12,624 17,653
Interest expense 0   (321)   (12) (909)
Total other income, net 5,984   8,132   12,612 16,744
Income tax expense (29)   (341)   (29) (341)
Net loss (52,771) $ (62,270) (27,202) $ (7,198) (115,041) (34,400)
Anito-cel in rrMM            
Operating expenses:            
Research and development 8,304   13,317   21,575 25,108
ACLX-002            
Operating expenses:            
Research and development 2,891   3,234   6,732 6,472
Other Research and Development Costs            
Operating expenses:            
Research and development 5,899   7,428   13,130 10,597
Internal Costs            
Operating expenses:            
Research and development $ 20,533   $ 16,974   $ 46,991 $ 31,094