Arcellx (ACLX) 10-Q 8 Aug 24 2024 Q2 Quarterly report Financial data

Document and Entity Information

Document and Entity Information - shares	6 Months Ended
	Jun. 30, 2024	Aug. 02, 2024
Cover [Abstract]
Document Type	10-Q
Amendment Flag	false
Document Quarterly Report	true
Document Transition Report	false
Document Period End Date	Jun. 30, 2024
Document Fiscal Year Focus	2024
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		53,755,679

CONDENSED CONSOLIDATED BALANCE

CONDENSED CONSOLIDATED BALANCE SHEETS (unaudited) - USD ($) $ in Thousands	Jun. 30, 2024	Dec. 31, 2023
Assets, Current [Abstract]
Cash and cash equivalents	$ 100,025	$ 394,583
Marketable securities	416,663	307,434
Restricted cash, current	208	1,903
Prepaid expenses and other current assets	13,307	12,443
Total current assets	530,203	716,363
Restricted cash, non-current	2,418	2,418
Marketable securities non current	130,128	27,168
Property and equipment, net	46,276	42,728
Operating lease right-of-use assets	24,065	27,099
Prepaid research and development expenses and other long-term assets	1,216	9,356
Total assets	734,306	825,132
Current liabilities:
Accounts payable	4,868	2,619
Accrued liabilities	42,033	18,302
Operating lease liabilities, current portion	7,199	7,501
Finance lease liabilities, current portion	19,220	39,283
Contract liability to related party	14,970	50,533
Total current liabilities	88,290	118,238
Operating lease liabilities, net of current portion	47,872	50,841
Contract liability to related party, net of current portion	96,081	170,673
Other non-current liabilities	14,899
Total liabilities	247,142	339,752
Commitments and contingencies (Note 7)
Stockholders' equity
Common stock, par value of $0.001 per share; 1,000,000,000 shares authorized and 53,631,144 shares issued and outstanding as of June 30, 2024; 1,000,000,000 shares authorized and 52,280,077 shares issued and outstanding as of December 31, 2023	53	52
Additional paid-in capital	911,783	874,261
Accumulated other comprehensive income (loss)	(792)	547
Accumulated Deficit	(423,880)	(389,480)
Total stockholders' equity	487,164	485,380
Total liabilities and stockholders' equity	$ 734,306	$ 825,132

CONDENSED CONSOLIDATED BALANC_2

CONDENSED CONSOLIDATED BALANCE SHEETS (unaudited) (Parenthetical) - $ / shares	Jun. 30, 2024	Dec. 31, 2023
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	53,631,144	52,280,077
Common stock, shares, outstanding	53,631,144	52,280,077

CONDENSED CONSOLIDATED STATEMEN

CONDENSED CONSOLIDATED STATEMENTS OF OPERATIONS AND COMPREHENSIVE LOSS (unaudited) - USD ($) $ in Thousands	3 Months Ended		6 Months Ended
	Jun. 30, 2024	Jun. 30, 2023	Jun. 30, 2024	Jun. 30, 2023
Income Statement [Abstract]
Collaboration revenue from related party	$ 27,384	$ 14,302	$ 66,640	$ 32,213
Operating expenses:
Research and development	40,953	28,327	73,271	61,258
General and administrative	21,424	15,535	44,172	30,972
Total operating expenses	62,377	43,862	117,443	92,230
Loss from operations	(34,993)	(29,560)	(50,803)	(60,017)
Other income (expense):
Interest income, net	8,453	6,304	17,653	10,772
Interest expense	(321)	(880)	(909)	(1,906)
Total other income, net	8,132	5,424	16,744	8,866
Loss before income taxes	(26,861)	(24,136)	(34,059)	(51,151)
Income tax benefit (expense)	(341)	282	(341)	(47)
Net loss	(27,202)	(23,854)	(34,400)	(51,198)
Other comprehensive loss:
Unrealized gain (loss) on marketable securities	(280)	(93)	(1,339)	214
Comprehensive loss	$ (27,482)	$ (23,947)	$ (35,739)	$ (50,984)
Net loss per share attributable to common stockholders - basic	$ (0.51)	$ (0.5)	$ (0.65)	$ (1.08)
Net loss per share attributable to common stockholders - diluted	$ (0.51)	$ (0.5)	$ (0.65)	$ (1.08)
Weighted-average common shares outstanding - basic	53,516,907	48,106,528	53,137,440	47,441,647
Weighted-average common shares outstanding - diluted	53,516,907	48,106,528	53,137,440	47,441,647

CONDENSED CONSOLIDATED STATEM_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, 2022	$ 204,954	$ 44	$ 523,921	$ (318,790)	$ (221)
Beginning Balance, Shares at Dec. 31, 2022		44,105,981
Issuance of common stock in accordance with Gilead Stock Purchase Agreement, value	115,270	$ 4	115,266
Issuance of common stock in accordance with Gilead Stock Purchase Agreement, shares		3,478,261
Exercise of stock options, value	374		374
Exercise of stock options, shares		34,713
Issuance of common stock from vesting of restricted stock, shares		222,433
Share-based compensation	10,156		10,156
Unrealized gain (loss) on marketable securities	307				307
Net Income (Loss)	(27,344)			(27,344)
Ending Balance at Mar. 31, 2023	303,717	$ 48	649,717	(346,134)	86
Ending Balance, shares at Mar. 31, 2023		47,841,388
Beginning Balance at Dec. 31, 2022	204,954	$ 44	523,921	(318,790)	(221)
Beginning Balance, Shares at Dec. 31, 2022		44,105,981
Net Income (Loss)	(51,198)
Ending Balance at Jun. 30, 2023	293,667	$ 48	663,614	(369,988)	(7)
Ending Balance, shares at Jun. 30, 2023		48,315,391
Beginning Balance at Mar. 31, 2023	303,717	$ 48	649,717	(346,134)	86
Beginning Balance, Shares at Mar. 31, 2023		47,841,388
Exercise of stock options, value	2,965		2,965
Exercise of stock options, shares		398,861
Issuance of common stock from vesting of restricted stock, shares		46,593
Issuance of common stock pursuant to employee stock purchase plan, value	528		528
Issuance of common stock pursuant to employee stock purchase plan, Shares		28,549
Share-based compensation	10,404		10,404
Unrealized gain (loss) on marketable securities	(93)				(93)
Net Income (Loss)	(23,854)			(23,854)
Ending Balance at Jun. 30, 2023	293,667	$ 48	663,614	(369,988)	(7)
Ending Balance, shares at Jun. 30, 2023		48,315,391
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 gain (loss) on marketable securities	(1,059)				(1,059)
Net Income (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
Net Income (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 gain (loss) on marketable securities	(280)				(280)
Net Income (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

CONDENSED CONSOLIDATED STATEM_3

CONDENSED CONSOLIDATED STATEMENTS OF CASH FLOWS (unaudited) - USD ($) $ in Thousands	6 Months Ended
	Jun. 30, 2024	Jun. 30, 2023
Cash flows from operating activities
Net loss	$ (34,400)	$ (51,198)
Adjustments to reconcile net loss to net cash provided by (used in) operating activities:
Depreciation and amortization	2,065	871
Non-cash operating lease expense	3,034	569
Right-of-use asset expensed	888	1,262
Amortization of premiums and discounts on marketable securities	(8,487)	(4,689)
Share-based compensation	29,984	20,560
Changes in operating assets and liabilities:
Receivable from collaboration partner		(29,431)
Prepaid expenses and other current and non-current assets	7,276	(16,817)
Accounts payable and other current liabilities	2,606	(3,797)
Accrued liabilities	26,679	(1,596)
Operating lease liabilities	(2,546)	10,281
Contract liability to related party	(110,154)	233,412
Other non-current liabilities	14,899
Net cash provided by (used in) operating activities	(68,156)	159,427
Cash flows from investing activities
Purchases of property and equipment	(9,645)	(8,208)
Purchases of marketable securities	(401,040)	(162,144)
Proceeds from maturities of marketable securities	196,000	154,850
Net cash used in investing activities	(214,685)	(15,502)
Cash flows from financing activities
Proceeds from issuance of common stock in accordance with Gilead Stock Purchase Agreement		100,000
Proceeds from exercise of stock options	6,893	3,340
Proceeds from stock issued pursuant to employee stock purchase plan	646	528
Principal payments under finance leases	(20,951)	(8,307)
Net cash provided by (used in) financing activities	(13,412)	95,561
Net increase (decrease) in cash and cash equivalents and restricted cash	(296,253)	239,486
Cash and cash equivalents and restricted cash, beginning of the period	398,904	66,680
Cash and cash equivalents and restricted cash, end of the period	102,651	306,166
Supplemental disclosure of cash flow information:
Cash paid for income taxes	1,066	212
Supplemental disclosures of noncash investing and financing activities:
Purchase of property and equipment included in accounts payable and accrued liabilities	$ 1,070	$ 3,323

Pay vs Performance Disclosure

Pay vs Performance Disclosure - USD ($) $ in Thousands	3 Months Ended				6 Months Ended
	Jun. 30, 2024	Mar. 31, 2024	Jun. 30, 2023	Mar. 31, 2023	Jun. 30, 2024	Jun. 30, 2023
Pay vs Performance Disclosure
Net Income (Loss)	$ (27,202)	$ (7,198)	$ (23,854)	$ (27,344)	$ (34,400)	$ (51,198)

Insider Trading Arrangements

Insider Trading Arrangements	3 Months Ended
	Jun. 30, 2024
Trading Arrangements, by Individual
Material Terms of Trading Arrangement	During our last fiscal quarter, none of our directors or officers, as defined in Rule 16a-1(f), adopted a “Rule 10b5-1 trading arrangement” or a “non-Rule 10b5-1 trading arrangement,” as defined in Regulation S-K Item 408. On June 28, 2024 , Rami Elghandour , our Chief Executive Officer , terminated a trading plan intended to satisfy the affirmative defense of Rule 10b5-1(c), which had been adopted as of December 28, 2023 .
Rule 10b5-1 Arrangement Adopted	false
Non-Rule 10b5-1 Arrangement Adopted	false
Rami Elghandour
Trading Arrangements, by Individual
Name	Rami Elghandour
Title	Chief Executive Officer
Rule 10b5-1 Arrangement Adopted	true
Adoption Date	December 28, 2023
Rule 10b5-1 Arrangement Terminated	true
Termination Date	June 28, 2024

Nature of the Business

Nature of the Business	6 Months Ended
	Jun. 30, 2024
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, 2024, the Company had $ 646.8 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 financial statements.

Summary of Significant Accounti

Summary of Significant Accounting Policies	6 Months Ended
	Jun. 30, 2024
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, 2024 are not necessarily indicative of the results that may be expected for the year ending December 31, 2024 or for any future period. The balance sheet as of December 31, 2023 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, 2023 included in the Company’s Annual Report on Form 10-K filed with the SEC on February 28, 2024. 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 November 2023, the FASB issued ASU No.2023-07 " Improvements to Reportable Segment Disclosures" which requires an enhanced disclosure of significant segment expenses on an annual and interim basis. This guidance will be effective for the annual periods beginning the year ended December 31, 2024, and for interim periods beginning January 1, 2025. Early adoption is permitted. Upon adoption, the guidance should be applied retrospectively to all prior periods presented in the financial statements. The Company does not expect the adoption of this guidance to have a material impact on its consolidated financial statements. 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 report to be filed in early 2026. The Company is currently evaluating the impact of the new guidance on its consolidated financial statements.

Fair Value of Financial Instrum

Fair Value of Financial Instruments	6 Months Ended
	Jun. 30, 2024
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, 2024 Level 1 Level 2 Level 3 Money market fund (cash equivalent) $ 99,769 $ — $ — Money market fund (short-term restricted cash) 208 — — Certificate of deposit (long-term restricted cash) — 2,418 — Marketable securities: Government agency — 546,791 — Total assets measured at fair value $ 99,977 $ 549,209 $ — December 31, 2023 Level 1 Level 2 Level 3 Money market fund (cash equivalent) $ 393,096 $ — $ — Money market fund (short-term restricted cash) 1,903 — — Certificate of deposit (long-term restricted cash) — 2,418 — Marketable securities: Commercial paper — 26,737 — Corporate debt — 5,982 — Government agency — 301,884 — Total assets measured at fair value $ 394,999 $ 337,020 $ — 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, 2024 or the year ended December 31, 2023 .

Cash, Cash Equivalents and Mark

Cash, Cash Equivalents and Marketable Securities	6 Months Ended
	Jun. 30, 2024
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, 2024 Amortized Unrealized Unrealized Fair Value Government agency $ 547,583 $ 66 $ ( 858 ) $ 546,791 Total $ 547,583 $ 66 $ ( 858 ) $ 546,791 December 31, 2023 Amortized Unrealized Unrealized Fair Value Commercial paper $ 26,752 $ — $ ( 15 ) $ 26,737 Corporate debt 5,988 — ( 7 ) 5,982 Government agency 301,315 584 ( 16 ) 301,884 Total $ 334,056 $ 584 $ ( 38 ) $ 334,602 The fair value of available-for-sale marketable securities by contractual maturity as of June 30, 2024 and December 31, 2023 were as follows (in thousands): June 30, 2024 December 31, 2023 Due in 1 year or less $ 416,663 $ 307,434 Due in 1 - 2 years 130,128 27,168 Total $ 546,791 $ 334,602 The Company had 53 and 8 securities in an unrealized loss position as of June 30, 2024 and December 31, 2023, respectively. All securities in an unrealized loss position as of June 30, 2024 and December 31, 2023 had been in a loss position for less than twelve months. Unrealized losses on available-for-sale marketable securities as of June 30, 2024 and December 31, 2023 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, 2024 and for the year ended December 31, 2023. 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, 2024 and December 31, 2023, the Company recognized $ 3.2 million and $ 1.4 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, 2024 2023 Cash and cash equivalents $ 100,025 $ 303,665 Restricted cash 2,626 2,501 Total $ 102,651 $ 306,166

Related Parties

Related Parties	6 Months Ended
	Jun. 30, 2024
Related Party Transactions [Abstract]
Related Parties	5. Related Parties Relationship and transactions with Gilead Sciences, Inc. (Gilead) As of June 30, 2024 , Gilead Sciences, Inc. (Gilead) held approximately 13 % 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 (Gilead SPA) with Gilead; 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, 2024, the Company had $ 111.1 million in contract liability pursuant to the Collaboration and License Agreement with Kite (Kite Collaboration Agreement) and its amendment, of which $ 96.1 million represented the long-term portion of contract liability. For the three and six months ended June 30, 2024, the Company recognized $ 27.4 million and $ 66.6 million in revenue respectively, under the Kite Collaboration Agreement and its amendment. See Note 6 for further discussion of the Kite Collaboration Agreement.

Collaboration Agreement

Collaboration Agreement	6 Months Ended
	Jun. 30, 2024
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 at contract inception and as of June 30, 2024 . 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, to offset prespecified development costs over a limited period of time. 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 clinical, regulatory, and commercial milestone payments of up to $ 598.3 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 July 2024, the Company achieved a clinical milestone of $ 68.3 million for anito-cel from Kite relating to enrollment in the iMMagine-1 trial. 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, 2024, revenue recognized that was included in the contract liability balance at the beginning of the period was $ 27.4 million and $ 66.6 million , respectively. During the three and six months ended June 30, 2024 , no revenue was recognized from performance obligations satisfied in previous periods. As of June 30, 2024, the amount of the transaction price that has not been recognized as revenue was $ 86.4 million , which may be recognized as revenue over the period of time the Company is performing the research and development activities.

Commitments and Contingencies

Commitments and Contingencies	6 Months Ended
	Jun. 30, 2024
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 CROs, 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, 2024 and December 31, 2023, 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, 2024 , 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.

Accrued Liabilities

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, 2024 2023 Research and development accrued expenses $ 9,975 $ 4,559 Accrued bonus 5,158 5,529 Other current liabilities 26,900 8,214 Total accrued liabilities $ 42,033 $ 18,302

Stockholders' Equity

Stockholders' Equity	6 Months Ended
	Jun. 30, 2024
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 (ATM) offering program under which the Company may issue and sell, from time to time and at management’s sole discretion, shares of the Company’s common stock, in an aggregate offering amount of up to $ 350.0 million. No sales of the Company stock have been made under this arrangement as of June 30, 2024. 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.

Income Taxes

Income Taxes	6 Months Ended
	Jun. 30, 2024
Income Tax Disclosure [Abstract]
Income Taxes	10. Income Taxes The Company recorded an income tax expense of $ 0.3 million for the three months ended June 30, 2024 and an income tax benefit of $ 0.3 million for the three months ended June 30, 2023. The Company recorded an income tax expense of $ 0.3 million and $ 47 thousand for the six months ended June 30, 2024 and 2023, respectively. Based on the available evidence, giving more weight to objective factors during the three and six months ended June 30, 2024, 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.

Net Loss Per Share Attributable

Net Loss Per Share Attributable to Common Stockholders	6 Months Ended
	Jun. 30, 2024
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, 2024 2023 Options to purchase common stock 7,863,544 8,491,672 Restricted stock units 1,711,396 1,426,583 Restricted stock units - executive officer 1,447,804 1,447,804 Employee Stock Purchase Plan (ESPP) 16,803 6,688 Total 11,039,547 11,372,747

Summary of Significant Accoun_2

Summary of Significant Accounting Policies (Policies)	6 Months Ended
	Jun. 30, 2024
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, 2024 are not necessarily indicative of the results that may be expected for the year ending December 31, 2024 or for any future period. The balance sheet as of December 31, 2023 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, 2023 included in the Company’s Annual Report on Form 10-K filed with the SEC on February 28, 2024. 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 November 2023, the FASB issued ASU No.2023-07 " Improvements to Reportable Segment Disclosures" which requires an enhanced disclosure of significant segment expenses on an annual and interim basis. This guidance will be effective for the annual periods beginning the year ended December 31, 2024, and for interim periods beginning January 1, 2025. Early adoption is permitted. Upon adoption, the guidance should be applied retrospectively to all prior periods presented in the financial statements. The Company does not expect the adoption of this guidance to have a material impact on its consolidated financial statements. 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 report to be filed in early 2026. The Company is currently evaluating the impact of the new guidance on its consolidated financial statements.

Fair Value of Financial Instr_2

Fair Value of Financial Instruments (Tables)	6 Months Ended
	Jun. 30, 2024
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, 2024 Level 1 Level 2 Level 3 Money market fund (cash equivalent) $ 99,769 $ — $ — Money market fund (short-term restricted cash) 208 — — Certificate of deposit (long-term restricted cash) — 2,418 — Marketable securities: Government agency — 546,791 — Total assets measured at fair value $ 99,977 $ 549,209 $ — December 31, 2023 Level 1 Level 2 Level 3 Money market fund (cash equivalent) $ 393,096 $ — $ — Money market fund (short-term restricted cash) 1,903 — — Certificate of deposit (long-term restricted cash) — 2,418 — Marketable securities: Commercial paper — 26,737 — Corporate debt — 5,982 — Government agency — 301,884 — Total assets measured at fair value $ 394,999 $ 337,020 $ —

Cash, Cash Equivalents and Ma_2

Cash, Cash Equivalents and Marketable Securities (Tables)	6 Months Ended
	Jun. 30, 2024
Marketable Securities [Abstract]
Schedule of Available-for-sale Marketable Securities	Available-for-sale marketable securities were as follows (in thousands): June 30, 2024 Amortized Unrealized Unrealized Fair Value Government agency $ 547,583 $ 66 $ ( 858 ) $ 546,791 Total $ 547,583 $ 66 $ ( 858 ) $ 546,791 December 31, 2023 Amortized Unrealized Unrealized Fair Value Commercial paper $ 26,752 $ — $ ( 15 ) $ 26,737 Corporate debt 5,988 — ( 7 ) 5,982 Government agency 301,315 584 ( 16 ) 301,884 Total $ 334,056 $ 584 $ ( 38 ) $ 334,602
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, 2024 and December 31, 2023 were as follows (in thousands): June 30, 2024 December 31, 2023 Due in 1 year or less $ 416,663 $ 307,434 Due in 1 - 2 years 130,128 27,168 Total $ 546,791 $ 334,602
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, 2024 2023 Cash and cash equivalents $ 100,025 $ 303,665 Restricted cash 2,626 2,501 Total $ 102,651 $ 306,166

Accrued Liabilities (Tables)

Accrued Liabilities (Tables)	6 Months Ended
	Jun. 30, 2024
Accrued Liabilities, Current [Abstract]
Schedule of Accrued Liabilities	Accrued liabilities consist of the following (in thousands): June 30, December 31, 2024 2023 Research and development accrued expenses $ 9,975 $ 4,559 Accrued bonus 5,158 5,529 Other current liabilities 26,900 8,214 Total accrued liabilities $ 42,033 $ 18,302

Net Loss Per Share Attributab_2

Net Loss Per Share Attributable to Common Stockholders (Tables)	6 Months Ended
	Jun. 30, 2024
Earnings Per Share [Abstract]
Schedule of Antidilutive Securities Excluded From Computation of Earnings Per Share	June 30, 2024 2023 Options to purchase common stock 7,863,544 8,491,672 Restricted stock units 1,711,396 1,426,583 Restricted stock units - executive officer 1,447,804 1,447,804 Employee Stock Purchase Plan (ESPP) 16,803 6,688 Total 11,039,547 11,372,747

Nature of the Business - Additi

Nature of the Business - Additional Information (Details) $ in Millions	Jun. 30, 2024 USD ($)
Class of Stock [Line Items]
Cash, cash equivalents and marketable securities	$ 646.8

Fair Value of Financial Instr_3

Fair Value of Financial Instruments - Schedule of Fair Value of Company's Financial Assets (Details) - USD ($) $ in Thousands	Jun. 30, 2024	Dec. 31, 2023
Assets
Money market fund (short-term restricted cash)	$ 208	$ 1,903
Certificate of deposit (long-term restricted cash)	2,418	2,418
Marketable securities	546,791	334,602
Level 1 | Recurring
Assets
Money market fund (cash equivalent)	99,769	393,096
Money market fund (short-term restricted cash)	208	1,903
Total assets measured at fair value	99,977	394,999
Level 2 | Recurring
Assets
Total assets measured at fair value	549,209	337,020
Level 2 | Recurring | Certificates of Deposit
Assets
Certificate of deposit (long-term restricted cash)	2,418	2,418
Level 2 | Recurring | Commercial Paper
Assets
Marketable securities		26,737
Level 2 | Recurring | Corporate Debt
Assets
Marketable securities		5,982
Level 2 | Recurring | Government Agency
Assets
Marketable securities	$ 546,791	$ 301,884

Cash, Cash Equivalents and Ma_3

Cash, Cash Equivalents and Marketable Securities - Schedule of Available-for-sale Marketable Securities (Details) - USD ($) $ in Thousands	Jun. 30, 2024	Dec. 31, 2023
Marketable Securities [Line Items]
Amortized costs	$ 547,583	$ 334,056
Gross Unrealized Gains	66	584
Gross Unrealized Loss	(858)	(38)
Fair Value	546,791	334,602
Commercial Paper
Marketable Securities [Line Items]
Amortized costs		26,752
Gross Unrealized Loss		(15)
Fair Value		26,737
Corporate Debt
Marketable Securities [Line Items]
Amortized costs		5,988
Gross Unrealized Loss		(7)
Fair Value		5,982
Government Agency
Marketable Securities [Line Items]
Amortized costs	547,583	301,315
Gross Unrealized Gains	66	584
Gross Unrealized Loss	(858)	(16)
Fair Value	$ 546,791	$ 301,884

Cash, Cash Equivalents and Ma_4

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, 2024	Dec. 31, 2023
Marketable Securities [Abstract]
Due in 1 year or less	$ 416,663	$ 307,434
Due in 1 - 2 years	130,128	27,168
Total	$ 546,791	$ 334,602

Cash, Cash Equivalents and Ma_5

Cash, Cash Equivalents and Marketable Securities - Additional Information (Details) $ in Millions	Jun. 30, 2024 USD ($) Condition	Dec. 31, 2023 USD ($) Condition
Marketable Securities [Line Items]
Number of securities in an unrealized loss position | Condition	53	8
Allowance for credit losses	$ 0	$ 0
Prepaid Expenses and Other Current Assets
Marketable Securities [Line Items]
Accrued interest receivable	$ 3.2	$ 1.4

Cash, Cash Equivalents and Ma_6

Cash, Cash Equivalents and Marketable Securities - Schedule of Cash, Cash Equivalents and Restricted Cash (Details) - USD ($) $ in Thousands	Jun. 30, 2024	Dec. 31, 2023	Jun. 30, 2023	Dec. 31, 2022
Cash, Cash Equivalents, Restricted Cash, and Restricted Cash Equivalents [Abstract]
Cash and cash equivalents	$ 100,025	$ 394,583	$ 303,665
Restricted cash	2,626		2,501
Total	$ 102,651	$ 398,904	$ 306,166	$ 66,680

Prepaid Expenses and Other Curr

Prepaid Expenses and Other Current Assets - Schedule of Prepaid Expenses and Other Current Assets (Details) - USD ($) $ in Thousands	Jun. 30, 2024	Dec. 31, 2023
Prepaid Expense and Other Assets, Current [Abstract]
Total prepaid expenses and other current assets	$ 13,307	$ 12,443

Related Parties - Additional In

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, 2024	Jun. 30, 2023	Jun. 30, 2024	Jun. 30, 2023
Related Party Transaction [Line Items]
Common stock value	$ 52		$ 53		$ 53
Contract liability, long-term portion	$ 170,673		96,081		96,081
Collaboration revenue from related party			$ 27,384	$ 14,302	$ 66,640	$ 32,213
Gilead
Related Party Transaction [Line Items]
Percentage of ownership held			13%		13%
Contract liability			$ 111,100		$ 111,100
Contract liability, long-term portion			$ 96,100		$ 96,100
Gilead Common Stock Purchase Agreement
Related Party Transaction [Line Items]
Shares purchased			3,478,261		3,478,261
Shares issued, price per share			$ 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			$ 27,400		$ 66,600

Collaboration Agreement - Addit

Collaboration Agreement - Additional Information (Details) - USD ($)	1 Months Ended		3 Months Ended		6 Months Ended
	Dec. 31, 2023	Jan. 31, 2023	Jun. 30, 2024	Jun. 30, 2023	Jun. 30, 2024	Jun. 30, 2023	Jul. 31, 2024	Dec. 28, 2023
Collaborative Arrangement and Arrangement Other than Collaborative [Line Items]
Contract liability revenue recognized			$ 27,384,000	$ 14,302,000	$ 66,640,000	$ 32,213,000
Contract with customer, performance obligation satisfied in previous period			0		0
Unrecognized revenue			86,400,000		86,400,000
Anito-cel | Subsequent Event
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			598,300,000		598,300,000
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%		40%
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%		60%
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
Shares issued, price per share			$ 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

Commitments and Contingencies -

Commitments and Contingencies - Additional Information (Details) $ in Millions	Jun. 30, 2024 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

Accrued Liabilities - Schedule

Accrued Liabilities - Schedule of Accrued Liabilities (Details) - USD ($) $ in Thousands	Jun. 30, 2024	Dec. 31, 2023
Accrued Liabilities, Current [Abstract]
Research and development accrued expenses	$ 9,975	$ 4,559
Accrued bonus	5,158	5,529
Other current liabilities	26,900	8,214
Total accrued liabilities	$ 42,033	$ 18,302

Leases - Supplemental Cash Flow

Leases - Supplemental Cash Flow Information Related to Leases (Details) - USD ($) $ in Thousands	6 Months Ended
	Jun. 30, 2024	Jun. 30, 2023
Lessee Disclosure [Abstract]
Financing cash flows from finance leases	$ 20,951	$ 8,307

Stockholders' Equity - Addition

Stockholders' Equity - Additional Information (Details) - USD ($)			6 Months Ended
	Dec. 28, 2023	Jan. 26, 2023	Jun. 30, 2024	May 31, 2023
Class of Stock [Line Items]
Common stock aggregate offering maximum amount under at the market program				$ 350,000,000
Common stock voting rights			one vote
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]
Dividends declared or paid			$ 0
Private Placement | Gilead SPA and Second Gilead SPA
Class of Stock [Line Items]
Shares purchased	3,242,542	3,478,261
Sale of stock, price per share	$ 61.68	$ 28.75
Proceeds from issuance of private placement	$ 200,000,000	$ 100,000,000
At-the-Market Offering
Class of Stock [Line Items]
Sale of stock, number of shares issued in transaction			0

Income Taxes - Additional Infor

Income Taxes - Additional Information (Details) - USD ($) $ in Thousands	3 Months Ended		6 Months Ended
	Jun. 30, 2024	Jun. 30, 2023	Jun. 30, 2024	Jun. 30, 2023
Income Tax Disclosure [Abstract]
Income tax expense (benefit)	$ 341	$ (282)	$ 341	$ 47

Net Loss Per Share Attributab_3

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, 2024	Jun. 30, 2023
Antidilutive Securities Excluded From Computation Of Earnings Per Share [Line Items]
Antidilutive Securities Excluded From Computation Of Earnings Per Share Amount	11,039,547	11,372,747
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	7,863,544	8,491,672
Restricted Stock Units
Antidilutive Securities Excluded From Computation Of Earnings Per Share [Line Items]
Antidilutive Securities Excluded From Computation Of Earnings Per Share Amount	1,711,396	1,426,583
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	1,447,804	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	16,803	6,688