Arcellx (ACLX) 10-K 27 Feb 25 2024 FY Annual report Financial data

Document and Entity Information

Document and Entity Information - USD ($) $ in Billions	12 Months Ended
	Dec. 31, 2024	Dec. 31, 2023	Feb. 21, 2025	Jun. 28, 2024
Cover [Abstract]
Document Type	10-K
Amendment Flag	false
Document Annual Report	true
Document Transition Report	false
Document Period End Date	Dec. 31, 2024
Document Fiscal Year Focus	2024
Document Fiscal Period Focus	FY
Current Fiscal Year End Date	--12-31
Entity Registrant Name	ARCELLX, INC.
Entity Central Index Key	0001786205
Entity Public Float				$ 2.6
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
Auditor Location	San Jose, California	Tysons, Virginia
Entity Well-known Seasoned Issuer	Yes
Entity Voluntary Filers	No
Document Financial Statement Error Correction Flag	false
Auditor Name	PricewaterhouseCoopers LLP	Ernst & Young LLP
Entity Current Reporting Status	Yes
Entity Interactive Data Current	Yes
ICFR Auditor Attestation Flag	true
Auditor Firm ID	238	42
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			54,944,012
Documents Incorporated by Reference [Text Block]	Portions of the Registrant’s definitive Proxy Statement to be filed with the Securities and Exchange Commission in connection with the Registrant’s 2025 Annual Meeting of Stockholders, which will be filed subsequent to the date hereof, are incorporated by reference into Part III of this Form 10-K. Such Proxy Statement will be filed with the Securities and Exchange Commission not later than 120 days following the end of the Registrant’s fiscal year ended December 31, 2024. Except with respect to information specifically incorporated by reference, the Proxy Statement is not deemed to be filed as part of this Annual Report on Form 10-K.
Auditor Opinion [Text Block]	Opinions on the Financial Statements and Internal Control over Financial Reporting We have audited the accompanying consolidated balance sheet of Arcellx, Inc. and its subsidiary (the "Company") as of December 31, 2024, and the related consolidated statements of operations and comprehensive loss, of redeemable convertible preferred stock and stockholders’ equity (deficit) and of cash flows for the year then ended, including the related notes (collectively referred to as the "consolidated financial statements"). We also have audited the Company's internal control over financial reporting as of December 31, 2024, based on criteria established in Internal Control - Integrated Framework (2013) issued by the Committee of Sponsoring Organizations of the Treadway Commission (COSO). In our opinion, the consolidated financial statements referred to above present fairly, in all material respects, the financial position of the Company as of December 31, 2024 and the results of its operations and its cash flows for the year then ended, in conformity with accounting principles generally accepted in the United States of America. Also in our opinion, the Company maintained, in all material respects, effective internal control over financial reporting as of December 31, 2024, based on criteria established in Internal Control - Integrated Framework (2013) issued by the COSO. Opinion on the Financial Statements We have audited the accompanying consolidated balance sheet of Arcellx, Inc. (the Company) as of December 31, 2023, the related consolidated statements of operations and comprehensive loss, redeemable convertible preferred stock and stockholders’ equity (deficit) and cash flows for each of the two years in the period ended December 31, 2023, and the related notes (collectively referred to as the “consolidated financial statements”). In our opinion, the consolidated financial statements present fairly, in all material respects, the financial position of the Company as of December 31, 2023, and the results of its operations and its cash flows for each of the two years in the period ended December 31, 2023, in conformity with U.S. generally accepted accounting principles.

CONSOLIDATED BALANCE SHEETS

CONSOLIDATED BALANCE SHEETS - USD ($) $ in Thousands	Dec. 31, 2024	Dec. 31, 2023
Assets, Current [Abstract]
Cash and cash equivalents	$ 105,679	$ 394,583
Marketable securities	481,696	307,434
Restricted cash, current	208	1,903
Prepaid expenses and other current assets	11,727	12,443
Total current assets	599,310	716,363
Restricted cash, non-current	2,418	2,418
Marketable securities, non-current	38,277	27,168
Property and equipment, net	46,456	42,728
Operating lease right-of-use assets	23,789	27,099
Prepaid research and development expenses and other long-term assets	1,077	9,356
Total assets	711,327	825,132
Current liabilities:
Accounts payable	2,095	2,619
Accrued liabilities	56,716	18,302
Operating lease liabilities, current portion	7,308	7,501
Finance lease liabilities, current portion	230	39,283
Less: current portion	59,056	50,533
Total current liabilities	125,405	118,238
Operating lease liabilities, net of current portion	46,542	50,841
Noncurrent portion	75,995	170,673
Other non-current liabilities	8,593
Total liabilities	256,535	339,752
Commitments and Contingencies (Note 11)
Stockholders' equity
Common stock, par value of $0.001 per share; 1,000,000,000 shares authorized and 54,293,597 shares issued and outstanding as of December 31, 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	950,719	874,261
Accumulated other comprehensive income	848	547
Accumulated Deficit	(496,828)	(389,480)
Total stockholders' equity	454,792	485,380
Total liabilities and stockholders' equity	$ 711,327	$ 825,132

CONSOLIDATED BALANCE SHEETS (Pa

CONSOLIDATED BALANCE SHEETS (Parenthetical) - $ / shares	Dec. 31, 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	54,293,597	52,280,077
Common stock, shares, outstanding	54,293,597	52,280,077

CONSOLIDATED STATEMENTS OF OPER

CONSOLIDATED STATEMENTS OF OPERATIONS AND COMPREHENSIVE LOSS - USD ($) $ in Thousands	12 Months Ended
	Dec. 31, 2024	Dec. 31, 2023	Dec. 31, 2022
Income Statement [Abstract]
Collaboration revenue from related party	$ 107,936	$ 110,319
Operating expenses:
Research and development	157,093	133,849	$ 149,555
General and administrative	88,414	66,350	41,704
Total operating expenses	245,507	200,199	191,259
Loss from operations	(137,571)	(89,880)	(191,259)
Other income (expense):
Interest and other income (expense)	33,322	23,695	4,300
Interest expense	(1,030)	(3,842)	(1,720)
Total other income, net	32,292	19,853	2,580
Loss before income taxes	(105,279)	(70,027)	(188,679)
Income tax expense	(2,069)	(663)
Net loss	(107,348)	(70,690)	(188,679)
Other comprehensive loss:
Unrealized gain (loss) on marketable securities	301	768	(201)
Comprehensive loss	$ (107,047)	$ (69,922)	$ (188,880)
Net loss per share attributable to common stockholders - basic	$ (2)	$ (1.47)	$ (5.19)
Net loss per share attributable to common stockholders - diluted	$ (2)	$ (1.47)	$ (5.19)
Weighted-average common shares outstanding - basic	53,566,153	48,061,450	36,355,758
Weighted-average common shares outstanding - diluted	53,566,153	48,061,450	36,355,758

CONSOLIDATED STATEMENTS OF REDE

CONSOLIDATED STATEMENTS OF REDEEMABLE CONVERTIBLE PREFERRED STOCK AND STOCKHOLDERS' EQUITY (DEFICIT) - USD ($) $ in Thousands	Total	Series A	Series B	Series C	IPO	Private Placement	Follow-on offering	Common Stock	Common Stock IPO	Common Stock Private Placement	Common Stock Follow-on offering	Additional Paid In Capital	Additional Paid In Capital IPO	Additional Paid In Capital Private Placement	Additional Paid In Capital Follow-on offering	Accumulated Deficit	Accumulated Other Comprehensive Income (Loss)
Beginning Balance at Dec. 31, 2021	$ (121,515)							$ 1				$ 8,615				$ (130,111)	$ (20)
Beginning Balance, Shares at Dec. 31, 2021								544,210
Temporary Equity, Beginning Balance at Dec. 31, 2021		$ 28,894	$ 85,367	$ 119,118
Temporary Equity, Beginning balance, shares at Dec. 31, 2021		5,413,272	8,975,585	10,396,707
Issuance of common stock, net of transaction costs, value					$ 127,283	$ 9,958	$ 120,719		$ 9	$ 1	$ 8		$ 127,274	$ 9,957	$ 120,711
Issuance of common stock, net of transaction costs, shares									9,487,500	590,318	8,050,000
Issuance of common stock from vesting / early exercise of restricted stock, value	122											122
Issuance of common stock from vesting / early excercise of restricted stock, shares								42,709
Conversion of preferred stock to common stock, value	233,379							$ 25				233,354
Conversion of preferred stock to common stock, shares								24,785,564
Temporary Equity, Conversion of stock, value		$ (28,894)	$ (85,367)	$ (119,118)
Temporary Equity, Conversion of stock, shares		(5,413,272)	(8,975,585)	(10,396,707)
Exercise of stock options, value	2,344											2,344
Exercise of stock options, shares								605,680
Share-based compensation	21,544											21,544
Unrealized gain (loss) on marketable securities	(201)																(201)
Net Income (Loss)	(188,679)															(188,679)
Ending Balance at Dec. 31, 2022	204,954							$ 44				523,921				(318,790)	(221)
Ending Balance, shares at Dec. 31, 2022								44,105,981
Issuance of common stock, net of transaction costs, value						$ 299,706				$ 7				$ 299,699
Issuance of common stock, net of transaction costs, shares										6,720,803
Issuance of common stock from vesting / early excercise of restricted stock, shares								295,496
Exercise of stock options, value	7,763							$ 1				7,762
Exercise of stock options, shares								1,114,015
Issuance of common stock pursuant to employee stock purchase plan, value	1,090											1,090
Issuance of common stock pursuant to employee stock purchase plan, Shares								43,782
Share-based compensation	41,789											41,789
Unrealized gain (loss) on marketable securities	768																768
Net Income (Loss)	(70,690)															(70,690)
Ending Balance at Dec. 31, 2023	485,380							$ 52				874,261				(389,480)	547
Ending Balance, shares at Dec. 31, 2023								52,280,077
Issuance of common stock from vesting / early excercise of restricted stock, shares								528,711
Exercise of stock options, value	14,209							$ 1				14,208
Exercise of stock options, shares								1,457,826
Issuance of common stock pursuant to employee stock purchase plan, value	1,164											1,164
Issuance of common stock pursuant to employee stock purchase plan, Shares								26,983
Share-based compensation	61,086											61,086
Unrealized gain (loss) on marketable securities	301																301
Net Income (Loss)	(107,348)															(107,348)
Ending Balance at Dec. 31, 2024	$ 454,792							$ 53				$ 950,719				$ (496,828)	$ 848
Ending Balance, shares at Dec. 31, 2024								54,293,597

CONSOLIDATED STATEMENTS OF RE_2

CONSOLIDATED STATEMENTS OF REDEEMABLE CONVERTIBLE PREFERRED STOCK AND STOCKHOLDERS' EQUITY (DEFICIT) (Parenthetical) - Common Stock $ in Thousands	12 Months Ended
	Dec. 31, 2022 USD ($)
IPO [Member]
Transaction costs	$ 15,029
Private Placement [Member]
Transaction costs	42
Follow-on offering [Member]
Transaction costs	$ 8,081

CONSOLIDATED STATEMENTS OF CASH

CONSOLIDATED STATEMENTS OF CASH FLOWS - USD ($) $ in Thousands	12 Months Ended
	Dec. 31, 2024	Dec. 31, 2023	Dec. 31, 2022
Cash flows from operating activities
Net loss	$ (107,348)	$ (70,690)	$ (188,679)
Adjustments to reconcile net loss to net cash used in operating activities:
Depreciation and amortization	5,188	2,040	1,321
Loss on disposal of property and equipment	(260)	174	3
Noncash operating lease expense	3,310	1,010	903
Right of use asset expensed	794	18,871	63,278
Amortization of premiums and discounts on marketable securities	(15,459)	(11,048)	(2,125)
Share-based compensation	61,086	41,789	21,544
Changes in operating assets and liabilities:
Prepaid expenses and other current and non-current assets	8,611	(8,359)	(5,695)
Accounts payable and other current liabilities	(70)	(6,474)	7,419
Accrued liabilities	42,009	5,593	(395)
Operating lease liabilities	(3,767)	13,461	3,123
Contract liability to related party	(86,154)	221,206
Other non-current liabilities	8,593
Net cash provided by (used in) operating activities	(83,467)	207,573	(99,303)
Cash flows from investing activities
Purchases of property and equipment	(13,434)	(21,428)	(2,277)
Purchases of marketable securities	(597,311)	(442,429)	(273,737)
Proceeds from maturities of marketable securities	427,700	309,345	158,340
Net cash used in investing activities	(183,045)	(154,512)	(117,674)
Cash flows from financing activities
Proceeds from issuance of common stock (initial public offering), net of transactions costs			129,156
Proceeds from issuance of common stock in private placement, net of transactions costs		299,706	9,958
Proceeds from issuance of common stock (follow-on offering), net of transactions costs			120,719
Proceeds from exercise of stock options and early exercise of restricted stock	14,595	7,758	2,467
Proceeds from issuance of common stock under the employee stock purchase plan	1,164	1,091
Payments under finance leases	(39,846)	(29,392)	(9,675)
Net cash provided by (used in) financing activities	(24,087)	279,163	252,625
Net increase (decrease) in cash and cash equivalents and restricted cash	(290,599)	332,224	35,648
Cash and cash equivalents and restricted cash, beginning of the year	398,904	66,680	31,032
Cash and cash equivalents and restricted cash, end of the period	108,305	398,904	66,680
Supplemental disclosures of cash flow information:
Cash paid for income taxes	1,635	212
Supplemental disclosures of noncash investing and financing activities:
Purchase of property and equipment included in accounts payable and accrued liabilities	$ 325	$ 1,841	$ 770

CONSOLIDATED STATEMENTS OF CA_2

CONSOLIDATED STATEMENTS OF CASH FLOWS (Parenthetical) - USD ($) $ in Thousands	12 Months Ended
	Dec. 31, 2024	Dec. 31, 2023	Dec. 31, 2022
Proceeds from issuance of common stock to related party	$ 0	$ 299,706	$ 0

Pay vs Performance Disclosure

Pay vs Performance Disclosure - USD ($) $ in Thousands	12 Months Ended
	Dec. 31, 2024	Dec. 31, 2023	Dec. 31, 2022
Pay vs Performance Disclosure
Net Income (Loss)	$ (107,348)	$ (70,690)	$ (188,679)

Insider Trading Arrangements

Insider Trading Arrangements			3 Months Ended
	Jan. 08, 2025	Dec. 18, 2023	Dec. 31, 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 or terminated a “Rule 10b5-1 trading arrangement” or a “non-Rule 10b5-1 trading arrangement,” as defined in Regulation S-K Item 408. On  January 8, 2025 , Michelle Gilson , Chief Financial Officer , terminated a trading plan intended to satisfy the affirmative defense of Rule 10b5-1(c), which was adopted as of December 18, 2023 .
Rule 10b5-1 Arrangement Adopted		true
Non-Rule 10b5-1 Arrangement Adopted			false
Adoption Date		December 18, 2023
Non-Rule 10b5-1 Arrangement Terminated			false
Subsequent Event
Trading Arrangements, by Individual
Name	Michelle Gilson
Title	Chief Financial Officer
Rule 10b5-1 Arrangement Terminated	true
Termination Date	January 8, 2025

Cybersecurity Risk Management,

Cybersecurity Risk Management, Strategy and Governance	12 Months Ended
	Dec. 31, 2024
Cybersecurity Risk Management, Strategy, and Governance [Line Items]
Cybersecurity Risk Management Processes for Assessing, Identifying, and Managing Threats [Text Block]	Item 1C. Cybersecurity. Risk Management and Strategy We have established policies and processes for assessing, identifying, and managing material risk from cybersecurity threats, and have integrated these processes into our overall risk management systems and processes. This program includes: • Robust Firewalls and Intrusion Detection Systems: The company has invested in state-of-the-art firewalls and intrusion detection systems designed to prevent unauthorized access to its networks. • Regular Security Assessments: The company conducts regular security assessments to identify vulnerabilities and address them promptly. This includes penetration testing, vulnerability scanning, and third-party audits. • Employee Training and Awareness: The company provides comprehensive cybersecurity training to all employees to educate them about potential risks, phishing attacks, and best practices for protecting sensitive information. • Incident Response Plan: The company has developed an incident response plan that outlines the steps to be taken in the event of a cybersecurity breach. This includes isolating affected systems, investigating the breach, and notifying relevant stakeholders. • Cyber Insurance: The company has obtained cyber insurance coverage to mitigate the financial impact of a cybersecurity breach. This insurance policy covers expenses related to incident response, legal fees, and potential customer compensation. By implementing these risk management strategies, we aim to minimize the likelihood and impact of a cybersecurity breach, thereby safeguarding our assets and maintaining the trust of our stakeholders. We routinely assess material risks from cybersecurity threats, including any potential unauthorized occurrence on or conducted through our information systems that may result in adverse effects on the confidentiality, integrity, or availability of our information systems or any information residing therein. We conduct periodic risk assessments to identify cybersecurity threats, as well as assessments in the event of a material change in our business practices that may affect information systems that are vulnerable to such cybersecurity threats. These risk assessments include identification of reasonably foreseeable internal and external risks, the likelihood and potential damage that could result from such risks, and the sufficiency of existing policies, procedures, systems, and safeguards in place to manage such risks. Following these risk assessments, we re-design, implement, and maintain reasonable safeguards to minimize identified risks; reasonably address any identified gaps in existing safeguards; and regularly monitor the effectiveness of our safeguards. We devote significant resources and designate high-level personnel, including our Director of Information Technology, who reports to our Chief Financial Officer, to manage the risk assessment and mitigation process. As part of our overall risk management system, we monitor and test our safeguards and train our employees on these safeguards, in collaboration with human resources, IT, and management. Personnel at all levels and departments are made aware of our cybersecurity policies through trainings. We engage assessors, consultants, or other third parties in connection with our risk assessment processes. These service providers assist us to design and implement our cybersecurity policies and procedures, as well as to monitor and test our safeguards. To oversee and identify risks from cybersecurity threats associated with our use of third-party service providers, we require each third-party service provider to certify that it has the ability to implement and maintain appropriate security measures, consistent with all applicable laws, to implement and maintain reasonable security measures in connection with its work with us, and to promptly report any suspected breach of its security measures that may affect our company. For additional information regarding whether any risks from cybersecurity threats, including as a result of any previous cybersecurity incidents, have materially affected or are reasonably likely to materially affect our company, including our business strategy, results of operations, or financial condition, please refer to Item 1A, “Risk Factors,” in this annual report on Form 10-K. Governance One of the key functions of our board of directors is informed oversight of our risk management process, including risks from cybersecurity threats. Our board of directors is responsible for monitoring and assessing strategic risk exposure, and our executive officers are responsible for the day-to-day management of the material risks we face. Our board of directors administers its cybersecurity risk oversight function primarily through the audit committee. Our Director of Information Technology and members of our cybersecurity committee (a management committee), which includes legal and privacy representatives, are primarily responsible to assess and manage our material risks from cybersecurity threats with assistance from third-party service providers. Our Director of Information Technology has expertise in security frameworks and standards (such as the Cybersecurity Framework established by the National Institute of Standards and Technology at the U.S. Department of Commerce), proficiency in security tools such as security information and event management systems, intrusion detection systems and vulnerability scanners, and has experience with threat intelligence, threat modeling, risk assessment, and risk management practices, as well as analyzing logs, investigating security incidents, and performing forensic analysis. Our Director of Information Technology and members of our cybersecurity committee oversee our cybersecurity policies and processes, including those described in “Risk Management and Strategy” above. The processes by which our Director of Information Technology and members of our cybersecurity committee are informed about and monitor the prevention, detection, mitigation, and remediation of cybersecurity incidents includes the following: Security Awareness Training, Patch Management Process, Endpoint Detection and Response, Managed Detection and Response, Incident Response Plan, Data Encryption, Access Control, Network Security, and Vulnerability Management. Our Director of Information Technology, our Controller, and members of our cybersecurity committee provide quarterly briefings to the audit committee regarding our company’s cybersecurity risks and activities, including any recent cybersecurity incidents and related responses, cybersecurity systems testing, activities of third parties, and the like.
Cybersecurity Risk Management Processes Integrated [Flag]	true
Cybersecurity Risk Management Processes Integrated [Text Block]	We have established policies and processes for assessing, identifying, and managing material risk from cybersecurity threats, and have integrated these processes into our overall risk management systems and processes. This program includes: • Robust Firewalls and Intrusion Detection Systems: The company has invested in state-of-the-art firewalls and intrusion detection systems designed to prevent unauthorized access to its networks. • Regular Security Assessments: The company conducts regular security assessments to identify vulnerabilities and address them promptly. This includes penetration testing, vulnerability scanning, and third-party audits. • Employee Training and Awareness: The company provides comprehensive cybersecurity training to all employees to educate them about potential risks, phishing attacks, and best practices for protecting sensitive information. • Incident Response Plan: The company has developed an incident response plan that outlines the steps to be taken in the event of a cybersecurity breach. This includes isolating affected systems, investigating the breach, and notifying relevant stakeholders. Cyber Insurance: The company has obtained cyber insurance coverage to mitigate the financial impact of a cybersecurity breach. This insurance policy covers expenses related to incident response, legal fees, and potential customer compensation.
Cybersecurity Risk Management Third Party Engaged [Flag]	true
Cybersecurity Risk Third Party Oversight and Identification Processes [Flag]	true
Cybersecurity Risk Materially Affected or Reasonably Likely to Materially Affect Registrant [Flag]	true
Cybersecurity Risk Materially Affected or Reasonably Likely to Materially Affect Registrant [Text Block]	For additional information regarding whether any risks from cybersecurity threats, including as a result of any previous cybersecurity incidents, have materially affected or are reasonably likely to materially affect our company, including our business strategy, results of operations, or financial condition, please refer to Item 1A, “Risk Factors,” in this annual report on Form 10-K.
Cybersecurity Risk Board of Directors Oversight [Text Block]	One of the key functions of our board of directors is informed oversight of our risk management process, including risks from cybersecurity threats. Our board of directors is responsible for monitoring and assessing strategic risk exposure, and our executive officers are responsible for the day-to-day management of the material risks we face. Our board of directors administers its cybersecurity risk oversight function primarily through the audit committee. Our Director of Information Technology and members of our cybersecurity committee (a management committee), which includes legal and privacy representatives, are primarily responsible to assess and manage our material risks from cybersecurity threats with assistance from third-party service providers. Our Director of Information Technology has expertise in security frameworks and standards (such as the Cybersecurity Framework established by the National Institute of Standards and Technology at the U.S. Department of Commerce), proficiency in security tools such as security information and event management systems, intrusion detection systems and vulnerability scanners, and has experience with threat intelligence, threat modeling, risk assessment, and risk management practices, as well as analyzing logs, investigating security incidents, and performing forensic analysis. Our Director of Information Technology and members of our cybersecurity committee oversee our cybersecurity policies and processes, including those described in “Risk Management and Strategy” above. The processes by which our Director of Information Technology and members of our cybersecurity committee are informed about and monitor the prevention, detection, mitigation, and remediation of cybersecurity incidents includes the following: Security Awareness Training, Patch Management Process, Endpoint Detection and Response, Managed Detection and Response, Incident Response Plan, Data Encryption, Access Control, Network Security, and Vulnerability Management. Our Director of Information Technology, our Controller, and members of our cybersecurity committee provide quarterly briefings to the audit committee regarding our company’s cybersecurity risks and activities, including any recent cybersecurity incidents and related responses, cybersecurity systems testing, activities of third parties, and the like.
Cybersecurity Risk Board Committee or Subcommittee Responsible for Oversight [Text Block]	One of the key functions of our board of directors is informed oversight of our risk management process, including risks from cybersecurity threats. Our board of directors is responsible for monitoring and assessing strategic risk exposure, and our executive officers are responsible for the day-to-day management of the material risks we face. Our board of directors administers its cybersecurity risk oversight function primarily through the audit committee.
Cybersecurity Risk Process for Informing Board Committee or Subcommittee Responsible for Oversight [Text Block]	One of the key functions of our board of directors is informed oversight of our risk management process, including risks from cybersecurity threats. Our board of directors is responsible for monitoring and assessing strategic risk exposure, and our executive officers are responsible for the day-to-day management of the material risks we face.
Cybersecurity Risk Role of Management [Text Block]	Our Director of Information Technology and members of our cybersecurity committee (a management committee), which includes legal and privacy representatives, are primarily responsible to assess and manage our material risks from cybersecurity threats with assistance from third-party service providers. Our Director of Information Technology has expertise in security frameworks and standards (such as the Cybersecurity Framework established by the National Institute of Standards and Technology at the U.S. Department of Commerce), proficiency in security tools such as security information and event management systems, intrusion detection systems and vulnerability scanners, and has experience with threat intelligence, threat modeling, risk assessment, and risk management practices, as well as analyzing logs, investigating security incidents, and performing forensic analysis. Our Director of Information Technology and members of our cybersecurity committee oversee our cybersecurity policies and processes, including those described in “Risk Management and Strategy” above. The processes by which our Director of Information Technology and members of our cybersecurity committee are informed about and monitor the prevention, detection, mitigation, and remediation of cybersecurity incidents includes the following: Security Awareness Training, Patch Management Process, Endpoint Detection and Response, Managed Detection and Response, Incident Response Plan, Data Encryption, Access Control, Network Security, and Vulnerability Management. Our Director of Information Technology, our Controller, and members of our cybersecurity committee provide quarterly briefings to the audit committee regarding our company’s cybersecurity risks and activities, including any recent cybersecurity incidents and related responses, cybersecurity systems testing, activities of third parties, and the like.
Cybersecurity Risk Management Positions or Committees Responsible [Flag]	true
Cybersecurity Risk Management Positions or Committees Responsible [Text Block]	Our Director of Information Technology and members of our cybersecurity committee (a management committee), which includes legal and privacy representatives, are primarily responsible to assess and manage our material risks from cybersecurity threats with assistance from third-party service providers.
Cybersecurity Risk Management Expertise of Management Responsible [Text Block]	Our Director of Information Technology has expertise in security frameworks and standards (such as the Cybersecurity Framework established by the National Institute of Standards and Technology at the U.S. Department of Commerce), proficiency in security tools such as security information and event management systems, intrusion detection systems and vulnerability scanners, and has experience with threat intelligence, threat modeling, risk assessment, and risk management practices, as well as analyzing logs, investigating security incidents, and performing forensic analysis.
Cybersecurity Risk Process for Informing Management or Committees Responsible [Text Block]	Our Director of Information Technology and members of our cybersecurity committee oversee our cybersecurity policies and processes, including those described in “Risk Management and Strategy” above. The processes by which our Director of Information Technology and members of our cybersecurity committee are informed about and monitor the prevention, detection, mitigation, and remediation of cybersecurity incidents includes the following: Security Awareness Training, Patch Management Process, Endpoint Detection and Response, Managed Detection and Response, Incident Response Plan, Data Encryption, Access Control, Network Security, and Vulnerability Management.
Cybersecurity Risk Management Positions or Committees Responsible Report to Board [Flag]	true

Nature of the Business

Nature of the Business	12 Months Ended
	Dec. 31, 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. Public Offerings On February 8, 2022, the Company closed its initial public offering of 9,487,500 shares of its common stock, including the exercise in full by the underwriters of their option to purchase 1,237,500 additional shares of its common stock, at a public offering price of $ 15.00 per share. The Company received net proceeds of $ 127.3 million, after deducting underwriting discounts and commissions of and other offering expenses paid by the Company of approximately $ 15.0 million. On June 21, 2022, the Company closed a follow-on public offering of 8,050,000 shares of its common stock, including the exercise in full by the underwriters of their option to purchase 1,050,000 additional shares of its common stock, at a public offering price of $ 16.00 per share. The Company received net proceeds of $ 120.7 million after deducting underwriting discounts and commissions and other offering expenses paid by the Company of approximately $ 8.1 million. Liquidity The Company has not commercialized any of its drug candidates and planned commercial operations have not commenced. The Company expects to incur additional operating losses and negative operating cash flows for the foreseeable future as it continues development of drug candidates, including preclinical and clinical testing and regulatory approval prior to commercialization. The Company has not generated any revenue to date from product sales and does not expect to generate any revenues from product sales in the foreseeable future. The Company plans to seek additional funding through public or private equity offerings or debt financings. The Company may not be able to obtain financing on acceptable terms, or at all, and the Company may not be able to enter into other arrangements on favorable terms, or at all. The terms of any financing may adversely affect the holdings or the rights of the Company’s stockholders. If the Company is unable to obtain funding, the Company could be required to delay, reduce or eliminate research and development programs, product portfolio expansion or future commercialization efforts, which could adversely affect its business prospects. The Company has incurred significant operating losses since inception and has an accumulated deficit of $ 496.8 million as of December 31, 2024 . The Company has relied on its ability to fund its operations through private and public equity financings, and its recent collaboration and license agreement with Kite Pharma, Inc. (Kite), a Gilead Sciences, Inc. (Gilead) company. In January 2023, the Company received in the aggregate $ 325.0 million in cash which consisted of $ 100.0 million related to a private placement from the sale of the Company’s common stock to Gilead and a $ 225.0 million non-refundable, upfront payment related to the closing of its Collaboration and License Agreement (Kite Collaboration Agreement) with Kite. In December 2023, the Company received in the aggregate $ 285.0 million in cash which consisted of $ 200.0 million related to a private placement from the sale of the Company’s common stock to Gilead and a $ 85.0 million non-refundable, upfront payment related to the closing of its amendment to the Kite Collaboration Agreement with Kite. See Note 8, Collaboration Agreement. As of December 31, 2024, the Company had $ 625.7 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	12 Months Ended
	Dec. 31, 2024
Accounting Policies [Abstract]
Summary of Significant Accounting Policies	2. Summary of Significant Accounting Policies Basis of Presentation and Consolidation The accompanying consolidated financial statements have been prepared in accordance with U.S. generally accepted accounting principles (U.S. GAAP). Any reference in these notes to applicable guidance is meant to refer to the authoritative GAAP as found in the Accounting Standards Codification (ASC) and Accounting Standards Update (ASU) of the Financial Accounting Standards Board (FASB). The accompanying consolidated financial statements include the accounts of Arcellx, Inc. and its wholly owned subsidiary. All intercompany balances and transactions have been eliminated in consolidation. Use of Accounting Estimates The preparation of consolidated financial statements in conformity with GAAP requires management to make estimates and assumptions that affect the reported amounts of assets and liabilities and disclosure of contingent assets and liabilities at the date of the consolidated financial statements and the reported amounts of revenues and expenses during the reporting period. Significant estimates used in preparing the accompanying consolidated financial statements include, but are not limited to, estimates related to the fair value of assets, collaboration revenue, research and development accruals, and share-based compensation. Although actual results could differ from those estimates, management does not believe that such differences would be material. Cash and Cash Equivalents and Restricted Cash The Company considers all highly liquid investments with an original maturity of three months or less at the date of purchase to be cash equivalents. The Company deposits its cash primarily in checking and sweep accounts with commercial banks and financial institutions in amounts exceeding FDIC insurance limits. Cash equivalents consist of money market funds. The Company is required to maintain cash collateral on deposit in segregated money market bank accounts and certificate of deposit accounts as a condition of its lease agreements on its properties, equal to the required security deposit amounts. These amounts are presented as restricted cash, current and non-current on the accompanying consolidated balance sheets. The following table reconciles cash and cash equivalents and restricted cash per the balance sheets to the statements of cash flows (in thousands): December 31, 2024 2023 Cash and cash equivalents $ 105,679 $ 394,583 Restricted cash, current 208 1,903 Restricted cash, non-current 2,418 2,418 Total $ 108,305 $ 398,904 Marketable Securities The Company carries marketable securities classified as available-for-sale at fair value as determined by prices for identical or similar securities at the balance sheet date. The inputs used to determine the fair value of marketable securities are considered Level 2 within the fair-value hierarchy. The Company records unrealized gains and losses as a component of other comprehensive loss within the statements of operations and comprehensive loss and as accumulated other comprehensive loss in stockholders’ equity. Realized gains or losses on available-for-sale securities are determined using the specific identification method and the Company includes net realized gains and losses in other income, net. Marketable securities are classified as either current or non-current assets based on their contractual maturity dates. For securities available for sale, ASU 2016-13 eliminates the concept of other-than-temporary impairment and instead requires entities to determine if impairment is related to credit loss or non-credit loss. In making the assessment of whether a loss is from credit or other factors, management considers the extent to which fair value is less than amortized cost, any changes to the rating of the security by a rating agency and adverse conditions related to the security, among other factors. If this assessment indicates that a credit loss exists, the present value of cash flows expected to be collected from the security are compared to the amortized cost basis of the security. If the present value of cash flows is less than the amortized cost basis, a credit loss exists and an allowance is created, limited by the amount that the fair value is less than the amortized cost basis. Subsequent activity related to the credit loss component in the form of write-offs or recoveries is recognized as part of the allowance for credit losses on securities available for sale. The Company has made the accounting policy election to exclude accrued interest receivable on securities from the estimate of credit losses. Fair Value of Financial Instruments The Company’s financial instruments consist of cash and cash equivalents, restricted cash, marketable securities, accounts payable, and accrued expenses. The carrying amounts of accounts payable and accrued expenses generally approximate their respective fair value due to their short-term nature. The Company accounts for recurring and non-recurring fair value measurements in accordance with ASC 820, Fair Value Measurements and Disclosures (ASC 820). ASC 820 defines fair value, establishes a fair value hierarchy for assets and liabilities measured at fair value, and requires expanded disclosures about fair value measurements. The ASC 820 hierarchy ranks the quality of reliability of inputs, or assumptions, used in the determination of fair value and requires assets and liabilities carried at fair value to be classified and disclosed in one of the following three categories: Level 1—Fair value is determined by using unadjusted quoted prices that are available in active markets for identical assets and liabilities. Level 2—Fair value 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. Level 3—Fair value is determined by inputs that are unobservable and not corroborated by market data. Use of these inputs involves significant and subjective judgments to be made by a reporting entity—e.g., determining an appropriate adjustment to a discount factor for illiquidity associated with a given security. To the extent the valuation is based on models or inputs that are less observable or unobservable in the market, the determination o f fair values requires more judgment. Accordingly, the degree of judgment exercised by the Company in determining fair value is greatest for instruments categorized as Level 3. A financial instrument’s level within the fair value hierarchy is based on the lowest level of any input that is significant to the fair value measurement. Concentration of Credit Risk Financial instruments that potentially expose the Company to concentrations of credit risk primarily consist of cash and cash equivalents, restricted cash, and marketable securities. The Company maintains its cash and cash equivalents and restricted cash at an accredited financial institution in amounts that exceed federally insured limits. The Company does not believe that it is subject to unusual credit risk beyond the normal credit risk associated with commercial banking relationships. The Company invests in highly rated debt securities consisting entirely of corporate and government bonds, which the Company has the ability to liquidate within one-day should the need for additional cash arise. Accordingly, the Company believes the exposure to credit risk on its marketable securities portfolio is low. Property and Equipment, Net Property and equipment are recorded at cost and depreciated over its estimated useful life using the straight-line method. Upon retirement or disposal, the cost and related accumulated depreciation are removed from the balance sheet and the resulting gain or loss is recognized within operating expenses. Routine expenditures for maintenance and repairs are expensed as incurred. Estim ated useful lives for property and equipment are as follows: Estimated Useful Life Computer equipment 3 years Furniture and fixtures 7 years Lab equipment 7 years Leasehold improvements Lesser of estimated useful life or remaining lease term Equipment under finance lease Lesser of estimated useful life or remaining lease term Impairment of Long-Lived Assets T he Company reviews the recoverability of its long-lived asset group when events or changes in circumstances occur that indicate that the carrying value of the asset group may not be recoverable. Recoverability of the long-lived asset group is measured by a comparison of the carrying amount of the asset to future undiscounted net cash flows expected to be generated by the asset group. If these cash flows are less than the carrying value of such asset group, the Company then determines the fair value of the underlying asset group. Any impairment loss to be recognized is measured by the amount by which the carrying amount of the asset group exceeds the estimated fair value of the asset group. Collaborative Arrangements and Contracts with Customers The Company assesses whether its collaboration agreements are subject to Accounting Standards Codification (ASC) Topic 808, Collaborative Arrangements (ASC 808) based on whether they involve joint operating activities and whether both parties have active participation in the arrangement and are exposed to significant risks and rewards that depend on the commercial success of the joint operating activities. To the extent that the arrangement falls within the scope of ASC 808, the Company applies the unit of account guidance under ASC Topic 606, Revenue from Contracts with Customers (ASC 606), to identify distinct performance obligations, and then determine whether a customer relationship exists for each distinct performance obligation. If the Company determines whether a promised good or service within the arrangement is with a customer, it applies the guidance in ASC 606. If a portion of a distinct bundle of goods or services within an arrangement is not with a customer, then the unit of account is not within the scope of ASC 606, and the recognition and measurement of that unit of account shall be based on analogy to authoritative accounting literature or, if there is no appropriate analogy, a reasonable, rational, and consistently applied accounting policy election. The Company recognizes revenue when its customer obtains control of promised goods or services in a contract for an amount that reflects the consideration the Company expects to receive in exchange for those goods or services. For contracts with customers, the Company performs the following five steps: (i) identify the contract(s) with a customer; (ii) identify the performance obligations in the contract; (iii) determine the transaction price; (iv) allocate the transaction price to the performance obligations in the contract; and (v) recognize revenue when (or as) the Company satisfies each performance obligation. The Company only applies the five-step model to contracts when it is probable that Company will collect the consideration it is entitled to in exchange for the goods or services it transfers to the customer. As part of the accounting for contracts with customers, the Company develop assumptions that require judgment to determine the standalone selling price of each performance obligation identified in the contract. The Company then allocates the total transaction price to each performance obligation based on their estimated standalone selling prices. The Company then recognizes as revenue the amount of the transaction price that is allocated to the respective performance obligation when (or as) the performance obligation is satisfied. For performance obligations satisfied over time, the Company determines the appropriate measure of progress. The effect of any change made to the measure of progress and, therefore a change to revenue, would be recorded as a change in estimate. If the consideration promised in a contract includes a variable amount, the Company estimates the amount of consideration to which it will be entitled in exchange for transferring the promised goods or services to a customer. The Company determines the amount of variable consideration by using the expected value method or the most likely amount method. The Company includes the unconstrained amount of estimated variable consideration in the transaction price. The amount included in the transaction price is the amount for which it is probable that a significant reversal of cumulative revenue recognized will not occur. At the end of each subsequent reporting period, the Company re-evaluates the estimate of variable consideration included in the transaction price and any related constraint, and if necessary, adjusts the estimate of the overall transaction price. Any such adjustments are recorded on a cumulative catch-up basis in the period of adjustment. 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. The Company’s collaborative arrangements can have one or more of the following forms of consideration: (i) license fees; (ii) milestone payments related to the achievement of developmental, regulatory, or commercial goals; (iii) royalties on net sales of licensed products; (iv) fees attributable to options to intellectual property; (v) cost-sharing or research and development (R&D) funding arrangements and (vi) profit and loss sharing. When a portion of non‑refundable upfront fees or other payments received are allocated to continuing performance obligations under the terms of a collaborative arrangement, they are recorded as contract liabilities and recognized as revenue when (or as) the underlying performance obligation is satisfied. The Company classifies contract liabilities as current when it expects to satisfy its performance obligations within one year, and noncurrent when the Company expects to satisfy those performance obligations in greater than one year. Fees attributable to options are deferred until the option expires or is exercised. Changes to collaboration agreements are assessed for whether they represent a modification or should be accounted for as a new contract. Upfront Payments and License Fees If a license to the Company’s intellectual property is determined to be distinct from the other performance obligations identified in the arrangement, the Company recognizes revenues from non-refundable, upfront fees allocated to the license when the license is transferred to the licensee and the licensee is able to use and benefit from the license. For licenses that are bundled with other promises, the Company utilizes judgment to assess the nature of the combined performance obligation to determine whether the combined performance obligation is satisfied over time or at a point in time and, if over time, the appropriate method of measuring progress for purposes of recognizing revenue. The Company evaluates the measure of progress each reporting period and, if necessary, adjusts the measure of performance and related revenue recognition. Cost-sharing Under certain collaborative arrangements, the Company can be reimbursed for a portion of its research and development expenses or reimburse its collaboration partner for its research and development expenses. The Company estimates reimbursements to be received by a collaboration partner and reimbursements to be paid or payable to a collaboration partner as part of variable consideration. When these research and development services are paid to a collaboration partner, the Company reduces its contract liability. Customer Options Customer options, such as options granted to allow a licensee to extend a license or research term, to select additional research targets or to choose to research, develop and commercialize licensed compounds are evaluated at contract inception to determine whether those options provide a material right (i.e., an optional good or service offered for free or at a discount) to the customer. If the customer options represent a material right, the material right is treated as a separate performance obligation at the outset of the arrangement. The Company allocates the transaction price to material rights based on the standalone selling price. As a practical alternative to estimating the standalone selling price of a material right when the underlying goods or services are both (i) similar to the original goods or services in the contract and (ii) provided in accordance with the terms of the original contract, the Company allocates the total amount of consideration expected to be received from the customer to the total goods or services expected to be provided to the customer. Amounts allocated to any material right are recognized as revenue when or as the related future goods or services are transferred or when the option expires. Milestone Payments At the inception of the arrangement, the Company evaluates whether the development or sales-based milestones are considered probable of being reached and estimates the amount to be included in the transaction price using the most likely amount method. If it is probable that a significant revenue reversal would not occur, the associated value is included in the transaction price. Milestone payments that are not within the control of the Company or the Company’s collaboration partner, such as regulatory approvals, are generally not considered probable of being achieved until those approvals are received. At the end of each subsequent reporting period, the Company re-evaluates the probability of achievement of such development or sales-based milestones and any related constraint, and if necessary, adjusts its estimate of the overall transaction price. Any such adjustments are recorded on a cumulative catch-up basis, which would affect revenues in the period of adjustment. For milestone revenues related to sales-based achievements, the Company recognizes the milestone revenues in the corresponding period of the product sale, in accordance with the guidance of ASC 606-10-55-65 for contracts that include a license to intellectual property and the license is the predominant item to which the product sale relates. Royalties For arrangements that include sales-based royalties, the Company recognizes revenue at the later of (i) when the related sales occur, or (ii) when the performance obligation to which some or all of the royalty has been allocated has been satisfied (or partially satisfied). To date, the Company has not recognized any royalty revenue resulting from its collaborative arrangement. Leases The Company leases office and laboratory space and equipment. In addition, the Company enters into manufacturing supply agreements with CMOs and CDMOs to manufacture clinical product candidate materials. Such agreements may include an embedded lease due to the exclusive use of identified manufacturing facilities and equipment that are controlled by the Company and for which the Company obtains substantially all the output. The evaluation of leases that are embedded in the Company’s CMO and CDMO agreements is complex and requires judgment. If a lease arrangement is determined to exist with a lease term of more than 12 months at the lease commencement date, an ROU asset and corresponding lease liability are recorded on the consolidated balance sheet at the lease commencement date based on the present value of fixed lease payments over the lease term. The lease commencement date, defined as the date on which the lessor makes the underlying asset available for use by the lessee and the date from which the Company is required to recognize lease expenses, may be different from the inception date of the contract. An ROU asset represents the right to control the use of an identified asset over the lease term and a lease liability represents the obligation to make lease payments arising from the lease. The Company uses the discount rate implicit in the lease, if available, or its incremental borrowing rate on the lease commencement date to determine the present value of lease payments. The lease terms used to calculate the ROU assets and related lease liabilities include options to extend or terminate the lease when it is reasonably certain that the Company will exercise that option. The Company expenses ROU assets acquired for research and development activities under ASC Topic 730, Research and Development, if they do not have alternative future use, in research and development projects or otherwise. Leases are classified as either operating or finance leases based on the economic substance of the agreement. For operating leases, the Company recognizes lease expense related to fixed payments on a straight-line basis over the lease term. For finance leases, the Company recognizes the amortization of the ROU asset over the shorter of the lease term or useful life of the underlying asset. Interest accretion on the finance lease liabilities is recorded as interest expense. For both operating and finance leases, lease expense related to variable payments is recognized as incurred based on performance or usage in accordance with the contractual agreements. For short-term lease arrangements with a term of one year or less, the Company has elected to recognize the related lease payments on a straight-line basis over the lease term without recording related ROU assets and lease liabilities. The Company evaluates changes to the terms and conditions of a lease contract to determine if they result in a new lease or a modification of an existing lease. For lease modifications, the Company remeasures and reallocates the remaining consideration in the contract and reassesses the lease classification at the effective date of the modification. The Company u ses significant assumptions and judgment in evaluating its lease contracts and other agreements, including the determination of whether an agreement is or contains a lease, whether a change in the terms and conditions of a lease contract represent a new or modified lease, whether a lease represents an operating or finance lease, the discount rate used to determine the present value of lease obligations, and the term of a lease embedded in its manufacturing supply agreements. Research and Development Expenses Research and development costs are expensed as they are incurred. Research and development expenses consist primarily of salaries and benefits of research and development personnel, costs related to research activities, preclinical studies, clinical manufacturing, technical development, and overhead and facility-related costs. The Company makes payments in connection with clinical trials under contracts with contract research organizations that support conducting and managing clinical trials. The financial terms of these agreements are subject to negotiation and vary from contract to contract and may result in uneven payment flows. Generally, these agreements set forth the scope of work to be performed at a fixed fee, unit price, or on a time and materials basis. A portion of the obligation to make payments under these contracts depends on factors such as the successful enrollment or treatment of patients or the completion of other clinical trial milestones. Expenses related to clinical trials are accrued based on estimates and/or representations from service providers regarding work performed, including actual level of patient enrollment, completion of patient trials, and progress of the clinical trials. Other incidental costs related to patient enrollment or treatment are accrued when reasonably certain. Similarly, the Company accrues expenses related to the work performed by contract manufacturing organizations based on the progress of the work performed. If the amounts the Company is obligated to pay under clinical trial agreements and manufacturing agreements are modified (for instance, as a result of changes in the clinical trial protocol or scope of work to be performed), the accruals are adjusted accordingly. Revisions to contractual payment obligations are charged to expense in the period in which the facts that give rise to the revision become reasonably certain. The Company may be obligated to make upfront payments upon execution of certain research and development agreements. Advance payments, including nonrefundable amounts, for goods or services that will be used or rendered for future research and development activities are deferred and included in prepaid expenses and other current assets or other non-current assets in the consolidated balance sheets. Such amounts are recognized as expense as the related goods are delivered or the related services are performed, or at such time when the Company does not expect the goods to be delivered or services to be performed. Share-Based Compensation The Company accounts for its share-based compensation in accordance with ASC 718, Compensation—Stock Compensation (ASC 718). ASC 718 requires all share-based payments to employees and directors, including grants of incentive stock options, nonqualified stock options, restricted stock awards, unrestricted stock awards, or restricted stock units, to be recognized as expense based on their grant date fair values. The determination of grant date fair value may require the Company to make assumptions as further discussed below. Changes in the assumptions can materially affect the fair value and ultimately how much share-based compensation expense is recognized. These assumptions are subjective and generally require significant analysis and judgment to develop. Stock Options The Company’s determination of the fair value of stock options with time-based vesting on the date of grant utilizes the Black-Scholes option-pricing model, and is impacted by the Company’s common stock price as well as other variables including, but not limited to, the expected term that options will remain outstanding, expected common stock price volatility over the expected term of the option awards, risk-free interest rates and expected dividends. The fair value of a stock-based award is recognized over the period during which an optionee is required to provide services in exchange for the option award, known as the requisite service period (usually the vesting period) on a straight-line basis. Stock-based compensation expense is recognized based on the fair value determined on the date of grant and is reduced for forfeitures as they occur. Estimating the fair value of equity-settled awards as of the grant date using valuation models, such as the Black-Scholes option pricing model, is affected by assumptions regarding a number of complex variables as follows: Expected Term — The Company uses the “simplified method” for estimating the expected term of options, whereby the expected term equals the arithmetic average of the vesting term and the original contractual term of the option (generally 10 years). The Company uses the simplified method as the Company does not have sufficient historical exercise data to provide a reasonable basis upon which to estimate the expected term that options will remain outstanding. Expected Volatility — Due to the Company’s limited operating history and a lack of company specific historical and implied volatility data, the Company has based its estimate of expected volatility on the historical volatility of a group of similar companies that are publicly traded. The historical volatility data was computed using the daily closing prices for the selected companies’ shares during the equivalent period of the calculated expected term of the stock-based awards. Risk-Free Interest Rate — The risk-free rate assumption is based on the U.S. treasury yield in effect at the time of grant for instruments with maturities similar to the expected term of the Company’s stock options. Expected Dividend — The Company has not issued any dividends in its history and does not expect to issue dividends over the life of the options and therefore has estimated the dividend yield to be zero . Restricted Stock Awards, Unrestricted Stock Awards, and Restricted Stock Units The fair value of restricted stock awards, unrestricted stock awards, and restricted stock units (collectively, awards), unless a market condition exists, is determined based on the fair value of our common stock on the grant date. Vesting of awards is accelerated for certain employees in the event of a change in control or in the event that we remove the employee with or without cause from their position. The Company estimates the fair value of awards subject to both a market condition and a performance condition on the grant date using a Monte Carlo simulation model. For awards with vesting subject to the fulfillment of both market and performance conditions, share-based compensation expense is recognized using the accelerated attribution method beginning when the achievement of the performance condition becomes probable over the applicable service period. The amount of share-based compensation expense is dependent on our periodic assessment of the probability of the performance condition being satisfied and our estimate, which may vary over time, of the number of shares that will ultimately be issued. If the performance condition is not met, no compensation expense is recognized, and any previously recognized compensation cost is reversed. Income Taxes The Company uses the asset and liability method of accounting for income taxes. Deferred tax assets and liabilities are recognized for the estimated future tax consequences attributable to temporary differences between the financial statement carrying amounts of existing assets and liabilities and their respective tax base. Deferred tax assets and liabilities are measured using enacted tax rates expected to apply to taxable income in the years in which those temporary differences are expected to be recovered or settled. Deferred tax expense or benefit is the result of changes in the deferred tax assets and liabilities. Valuation allowances are established when necessary to reduce deferred tax assets where, based upon the available evidence, the Company concludes that it is not more-likely-than-not that the deferred tax assets will be realized. In evaluating its ability to recover deferred tax assets, the Company considers all available positive and negative evidence, including its operating results, ongoing tax planning, and forecasts of future taxable income on a jurisdiction-by-jurisdiction basis. Because of the uncertainty of the realization of deferred tax assets, the Company has recorded a valuation allowance against its net deferred tax assets. Liabilities are provided for tax benefits for which realization is uncertain. Such benefits are only recognized when the underlying tax position is considered more-likely-than-not to be sustained on examination by a taxing authority, assuming they possess full knowledge of the position and facts. Interest and penalties related to uncertain tax positions are recognized in the provision of income taxes. As of December 31, 2024 and 2023, the Company had no interest or penalties related to uncertain income tax positions. Segment and Geographic Information Operating segments are defined as components of an entity about which separate discrete information is available for evaluation by the chief operating decision maker, or decision-making group, in deciding how to allocate resources and in assessing performance. The Company views its operations as and manages its business in one operating segment operating exclusively in the United States. Recently Adopted Accounting Pronouncements In November 2023, the FASB issued ASU No.2023-07 " Improvements to Reportable

Fair Value of Financial Instrum

Fair Value of Financial Instruments	12 Months Ended
	Dec. 31, 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): 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 $ — 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 Company did not transfer any assets measured at fair value on a recurring basis between levels during the years ended December 31, 2024 or 2023.

Marketable Securities

Marketable Securities	12 Months Ended
	Dec. 31, 2024
Marketable Securities [Abstract]
Marketable Securities	4. Marketable Securities Available-for-sale marketable securities were as follows (in thousands): December 31, 2024 Amortized Unrealized Unrealized Fair Value Government agency 519,125 1,007 ( 159 ) 519,973 Total $ 519,125 $ 1,007 $ ( 159 ) $ 519,973 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 December 31, 2024 and 2023 were as follows (in thousands): December 31, 2024 2023 Due in 1 year or less $ 481,696 $ 307,434 Due in 1 - 2 years 38,277 27,168 Total $ 519,973 $ 334,602 The Company had 9 securities in an unrealized loss position with an aggregate related fair value of $ 108.4 million as of December 31, 2024. The Company had 8 securities in an unrealized loss position with an aggregate related fair value of $ 61.5 million as of December 31, 2023. All securities in an unrealized loss position as of December 31, 2024 and 2023 had been in a loss position for less than twelve months. Unrealized losses on available-for-sale marketable securities as of December 31, 2024 and 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 years ended December 31, 2024 and 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 December 31, 2024 and 2023, the Company recognized $ 2.5 million and $ 1.4 million, respectively, of accrued interest receivable from available-for-sale securities within prepaid expenses and other current assets on the consolidated balance sheets.

Prepaid Expenses and Other Curr

Prepaid Expenses and Other Current Assets	12 Months Ended
	Dec. 31, 2024
Prepaid Expense and Other Assets, Current [Abstract]
Prepaid Expenses and Other Current Assets	5. Prepaid Expenses and Other Current Assets Prepaid expenses and other current assets consist of the following (in thousands): December 31, 2024 2023 Prepaid research and development costs $ 5,882 $ 6,764 Other prepaid expense and current assets 5,845 5,679 Total prepaid expenses and other current assets $ 11,727 $ 12,443

Property and Equipment, Net

Property and Equipment, Net	12 Months Ended
	Dec. 31, 2024
Property, Plant and Equipment [Abstract]
Property and Equipment, Net	6. Property and Equipment, Net Property and equipment consist of the following (in thousands): December 31, 2024 2023 Lab equipment $ 16,033 $ 11,502 Leasehold improvements 38,373 27,153 Lab equipment under finance leases 230 714 Computer equipment 906 661 Furniture and fixtures 158 159 Construction in progress 200 7,792 Property and equipment, gross 55,900 47,981 Less: accumulated depreciation and amortization ( 9,444 ) ( 5,253 ) Property and equipment, net $ 46,456 $ 42,728 Depreciation and amortization expense was $ 5.2 million, $ 2.0 million and $ 1.3 million for the years ended December 31, 2024 , 2023 and 2022, respectively.

Related Parties

Related Parties	12 Months Ended
	Dec. 31, 2024
Related Party Transactions [Abstract]
Related Parties	7. Related Parties Relationship and transactions with Gilead Sciences, Inc. (Gilead) As of December 31, 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 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 8 for further discussion of the agreements with Gilead. The Company partnered anito-cel with Kite Pharma, Inc., a Gilead company (Kite), through its co-development/co-commercialization collaboration agreement, as described in more detail in Note 8 Collaboration Agreement. As of December 31, 2024, the Company had $ 135.1 million in contract liability pursuant to the Collaboration and License Agreement with Kite (Kite Collaboration Agreement) and its amendment, of which $ 76.0 million represented the long-term portion of contract liability. For the year ended December 31, 2024, the Company recognized $ 107.9 million in revenue under the Kite Collaboration Agreement and its amendment. See Note 8, Collaboration Agreement, for further discussion of the Kite Collaboration Agreement.

Collaboration Agreement

Collaboration Agreement	12 Months Ended
	Dec. 31, 2024
Collaboration Agreement [Abstract]
Collaboration Agreement	8. 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 December 31, 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. 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. During the year ended December 31, 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 year ended December 31, 2024 , no revenue was recognized from performance obligations satisfied in previous periods. As of December 31, 2024, the amount of the transaction price that has not been recognized as revenue was $ 50.2 million , which may be recognized as revenue over the period of time the Company is performing the research and development activities. As of December 31, 2024, the balances in contract liability were as follows (in thousands): Contract liability December 31, 2024 Beginning balance at January 1, 2024 $ 221,206 Cash received, net 65,640 Less: Revenue recognized ( 107,936 ) Reclass to other liabilities ( 43,859 ) Ending balance at December 31, 2024 135,051 Less: current portion 59,056 Noncurrent portion $ 75,995

Leases

Leases	12 Months Ended
	Dec. 31, 2024
Leases [Abstract]
Leases	9. Leases Operating Leases In July 2022, the Company entered into an operating lease agreement for 57,902 square feet of office and laboratory space in Rockville, Maryland for a term of approximately 12.9 years. The lease contains annual rent escalation and rent abatement clauses as well as an allowance of approximately $ 12.1 million for tenant improvements. During the year ended December 31, 2023, the landlord and the Company agreed to convert $ 2.8 million of rent abatement to tenant improvement allowance and agreed to an additional tenant improvement allowance of $ 2.9 million. The changes were accounted for as lease modifications. The Rockville lease provides for optional two five-year extensions. The optional period is not included in the lease term used to determine the ROU asset or lease liability associated with this lease as the Company did not consider it reasonably certain it would exercise the option. In May 2022, the Company entered into an operating lease agreement for 51,822 square feet of office and laboratory space in Redwood City, California for a term of approximately 11.7 years. The lease contains annual rent escalation and rent abatement clauses as well as an allowance of approximately $ 9.8 million for tenant improvements. The Redwood City lease provides for an optional five-year extension. The optional period is not included in the lease term used to determine the ROU asset or lease liability associated with this lease as the Company did not consider it reasonably certain it would exercise the option. The Company also leases office and laboratory space in Gaithersburg, Maryland that has a term that expires in 2030 unless renewed. This operating lease agreement contains rent escalation, rent abatement clauses, tenant improvement allowances, and optional renewal clauses. On January 30, 2024, the Company entered into an Assignment of Lease with a third party sublessee, pursuant to which the Company agreed to transfer and assign to a sublessee all of our rights, title, and interest under the Gaithersburg, Maryland Lease. All three operating leases include variable lease payments, which are primarily related to common area maintenance, taxes and utility charges. The Company also has short-term operating leases with a term of one year or less. Finance Leases Pursuant to a manufacturing services agreement with Lonza Houston, Inc. (Lonza) in connection with the development and manufacture of autologous drug product anito-cel (Lonza Agreement), the Company entered into a statement of work with Lonza (Lonza SOW) in February 2022, for the technology transfer and cGMP manufacturing of anito-cel and potentially other pipeline products. The Lonza SOW contains an embedded lease as the Company has exclusive use of, and control over, a portion of manufacturing facilities during the contractual term. The Lonza SOW also contains an agreement to purchase inventory that is accounted for separately. Lease commencement occurred during the three months ended September 30, 2022 when the applicable manufacturing facility and equipment became available for cGMP manufacturing under the Company's exclusive use and control. The arrangement provides the Company the ability to early terminate for any reason upon 12 months prior notification to Lonza. The Company did not consider it reasonably certain it would terminate the arrangement when determining the lease term. The arrangement expired in December 2024 . Variable costs under this arrangement include materials, externa l testing, and other services. The Company elected the practical expedient to combine the lease component and the non-lease components associated with the lease component as a single lease component, except as related to the non-lease component associated with purchase of inventory. The related ROU assets represent assets acquired for research and development activities with no alternative future use and therefore were immediately expensed in the accompanying consolidated statements of operations and comprehensive loss during the year ended December 31, 2022 in the amount of $ 63.3 million. In September 2023, the Company signed Amendment 1 to the Lonza SOW entered into in February 2022. The Amendment 1 increased quantity of manufacturing slots from September 2023 through the end of the lease in December 2024 , providing the Company additional exclusive use of and control over an additional portion of the manufacturing facilities during the term that was previously shared. The Company now has exclusive use of, and control over, the additional facility space and equipment through the remainder of the lease term. This change under Amendment 1 was accounted for as a lease modification, and the Company remeasured the lease liabilities for the modified lease as of the Amendment effective date. The remeasurement of the lease liabilities included fixed consideration with an undiscounted value of approximately $ 51.7 million, or $ 48.5 million discounted using the expected payment timeline and the incremental borrowing rate of 10.8 %, resulting in an increase of $ 15.9 million in lease liabilities. As the Company acquired ROU assets that represented assets acquired for research and development activities that did not have an alternative future use, the Company recorded the ROU assets as research and development expense immediately in the accompanying consolidated statements of operations and comprehensive loss during the year ended December 31, 2023 in the amount of $ 18.9 million. The Company's total lease costs were as follows (in thousands): Year Ended December 31, 2024 2023 2022 Finance lease costs: Right-of-use assets with no alternative future use $ 794 $ 18,871 $ 63,321 Amortization of right-of-use assets — 102 102 Interest on lease liabilities 1,030 3,846 1,720 Operating lease costs 5,437 6,159 3,832 Short-term lease costs 19 32 758 Variable lease costs 7,491 8,043 1,769 Total lease costs $ 14,771 $ 37,053 $ 71,502 Future minimum lease payments were as follows (in thousands) as of December 31, 2024: Operating Leases 2025 $ 7,606 2026 7,835 2027 8,071 2028 8,315 2029 8,567 Thereafter 42,472 Total lease payments 82,866 Less: Imputed interest ( 29,016 ) Present value of total lease liabilities $ 53,850 Supplemental cash flow information related to leases is as follows (in thousands) for the year ended December 31, 2024 and 2023: 2024 2023 2022 Cash paid for amounts included in the measurement of lease liabilities: Operating cash flows from finance leases $ 6,591 $ 8,770 $ 1,708 Operating cash flows from operating leases 7,291 4,603 1,947 Financing cash flows from finance leases 39,846 29,392 9,675 Right-of-use assets obtained in exchange for new finance lease liabilities 794 18,871 63,321 Right-of-use assets obtained in exchange for new operating lease liabilities — ( 550 ) 29,562 Weighted-average remaining lease terms and discount rates were as follows as of December 31, 2024: Weighted-average remaining lease term — operating leases 9.6 years Weighted-average discount rate — operating leases 9.8 %

Accrued Liabilities

Accrued Liabilities	12 Months Ended
	Dec. 31, 2024
Accrued Liabilities, Current [Abstract]
Accrued Liabilities	10. Accrued Liabilities Accrued liabilities consist of the following (in thousands): December 31, 2024 2023 Research and development accrued expenses $ 16,507 $ 4,559 Accrued bonus 10,438 5,529 Other liabilities 8,531 8,214 Liabilities to related party vendor 21,240 — Total accrued liabilities $ 56,716 $ 18,302

Commitments and Contingencies

Commitments and Contingencies	12 Months Ended
	Dec. 31, 2024
Commitments and Contingencies Disclosure [Abstract]
Commitments and Contingencies	1 1. Commitments and Contingencies Commercial and Development Milestones In addition to the arrangement with Lonza, we have entered into other 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 December 31, 2024 and 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 December 31, 2024 and 2023, 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.

Redeemable Convertible Preferre

Redeemable Convertible Preferred Stock and Stockholders' Equity	12 Months Ended
	Dec. 31, 2024
Equity [Abstract]
Redeemable Convertible Preferred Stock and Stockholders' Equity	12. Redeemable Convertible Preferred Stock and 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 the Company’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 December 31, 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 8 - 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 8 - 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 Annual Report on Form 10-K, 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. Redeemable Convertible Preferred Stock In connection with the Company's IPO on February 4, 2022, all outstanding shares of the Company’s redeemable convertible preferred stock automatically converted into shares of common stock at the applicable conversion ratio then in effect. The Company's outstanding shares of preferred stock were converted into 24,785,564 shares of common stock. The Company has authorized 200,000,000 shares of preferred stock, par value $ 0.0001 . There was no preferred stock outstanding as of December 31, 2024 and 2023.

Share-Based Compensation

Share-Based Compensation	12 Months Ended
	Dec. 31, 2024
Share-Based Payment Arrangement [Abstract]
Share-Based Compensation	13. Share-Based Compensation The Company’s 2017 Equity Incentive Plan (the 2017 Plan) provided for the grant of incentive stock options, non-statutory stock options, stock appreciation rights, and restricted stock awards to the Company's employees, directors, and consultants. The 2017 Plan terminated one business day prior to effectiveness of the 2022 Equity Incentive Plan (the 2022 Plan) with respect to the grant of future awards. The 2022 Plan became effective on February 3, 2022 and provides for the grant of incentive stock options to the Company's employees and for the grant of non-statutory stock options, stock appreciation rights, restricted stock, restricted stock units (RSUs), and performance awards to the Company's employees, directors, and consultants. As of December 31, 2024, the aggregate number of shares of common stock that may be issued pursuant to equity awards under the 2022 Plan was 11,667,993 shares. The number of shares of common stock reserved for issuance under the 2022 Plan is cumulatively increased on the first day of each fiscal year, beginning with the Company’s 2023 fiscal year and ending on the ten year anniversary of the date the Company’s board of directors approved the 2022 Plan, by an amount equal to the least of (1) 6,502,174 shares, (ii) 5 % of the total number of shares of common stock outstanding as of the last day of the immediately preceding fiscal year, or (iii) a lesser number of shares determined by the administrator of the 2022 Plan. Share-based compensation cost is measured at fair value and is recognized as expense on a straight-line basis over the requisite service period. Share-based compensation expense by type of award was as follows (in thousands): Year Ended December 31, 2024 2023 2022 Stock options $ 28,057 $ 20,661 $ 14,859 Restricted stock units 27,257 12,254 4,056 Restricted stock units - chief executive officer 5,266 8,336 2,548 ESPP 506 538 81 Total share-based compensation expense $ 61,086 $ 41,789 $ 21,544 Share-based compensation expense as reflected in the consolidated statement of operations and comprehensive loss was as follows (in thousands): Year Ended December 31, 2024 2023 2022 Research and development $ 21,359 $ 11,003 $ 7,007 General and administrative 39,727 30,786 14,537 Total share-based compensation expense $ 61,086 $ 41,789 $ 21,544 Stock Options Stock options granted under the 2017 Plan and the 2022 Plan vest over one to four years and expire after 10 years . The Company uses the Black Scholes option pricing model to determine the grant date fair value of stock options. A summary of stock option activity for awards under the 2017 Plan and the 2022 Plan is presented below: Options Outstanding and Exercisable Shares Subject to Outstanding Options Weighted Weighted Aggregate Outstanding as of January 1, 2024 7,811,231 $ 12.46 7.8 $ 336,174 Options Granted 1,031,954 56.22 Options Forfeited ( 145,261 ) 11.10 Options Exercised ( 1,457,826 ) 9.75 Outstanding as of December 31, 2024 7,240,098 $ 19.28 6.9 $ 415,634 Exercisable as of December 31, 2024 4,712,405 $ 13.30 6.6 $ 298,737 (1) The aggregate intrinsic value is calculated as the difference between the exercise price of the underlying options and the fair value of the common stock for those options for which the exercise price was below the market price as of December 31, 2024 . The weighted-average grant-date fair value per share of stock options granted during the years ended December 31, 2024, 2023 and 2022 was $ 42.38 , $ 21.86 and $ 9.95 , respectively. The aggregate grant-date fair value of stock options vested during the years ended December 31, 2024 2023 and 2022 was approximately $ 27.7 million, $ 21.4 million and $ 14.5 million, respectively. As of December 31, 2024 , there was $ 51.8 million o f unrecognized compensation cost related to unvested stock option based compensation arrangements granted under the 2017 Plan and 2022 Plan. This remaining compensation expense is expected to be recognized over a weighted average period of 1.82 years as of December 31, 2024. The aggregate intrinsic value of the options exercised for the years ended December 31, 2024 , 2023 and 2022 was $ 103.5 million, $ 47.1 million and $ 10.9 million, respectively. The assumptions used in the Black-Scholes option pricing model for stock options granted for the years ending December 31, 2024, 2023 and 2022 were as follows: 2024 2023 2022 Expected term 5.5 - 6.27 years 5.5 - 6.25 years 6.0 - 6.3 years Expected volatility 86 % - 87 % 75 % - 80 % 68 % - 75 % Risk free interest rate 3.82 % - 4.56 % 3.92 % - 4.06 % 1.56 % - 3.88 % Expected dividend yield — % — % — % Restricted Stock Units (RSUs) RSUs granted under the 2022 Plan generally vest annually over three or four years . A summary of RSU activity for awards under the 2022 Plan, excluding the 2023 RSU Award and 2021 RSU Award (each defined below) granted to the chief executive officer, is presented below: Shares Subject to Outstanding Awards Weighted Average Grant Date Fair Value Outstanding as of January 1, 2024 1,416,446 $ 25.47 RSUs Granted 981,531 61.66 RSUs Vested ( 528,711 ) 23.76 RSUs Forfeited ( 57,421 ) 32.55 Outstanding as of December 31, 2024 1,811,845 $ 45.35 For the years ended December 31, 2024, 2023 and 2022, total grant-date fair value of RSUs that vested was $ 13.4 million, $ 5.4 million and zero , respectively. As of December 31, 2024, total unamortized share-based compensation relating to RSUs was $ 56.5 million , which is expected to be recognized over the average period of 1.84 years. The aggregate intrinsic value of RSUs is calculated as the closing price per share of the Company's common stock on the last trading day of the fiscal period, multiplied by the number of RSUs expected to vest as of December 31, 2024. As of December 31, 2024 , the aggregate intrinsic value of RSUs was $ 139.0 million. Restricted Stock Units - Chief Executive Officer 2023 RSU Award In January 2023, the Company granted 495,000 RSUs (the 2023 RSU Award) to its chief executive officer. The 2023 RSU Award has two different scenarios to vesting. The first vesting scenario is subject to service and market conditions. The second vesting scenario adds a performance condition. Each RSU granted in the 2023 RSU Award entitles the chief executive officer to one share of common stock upon vesting subject to the service, performance, and market conditions. All 495,000 RSUs were outstanding and no RSUs were vested as of December 31, 2024. In February 2025, 347,255 shares vested based on performance and market conditions achieved on the measurement date of December 31, 2024. Service Condition The service condition to vesting of the 2023 RSU Award requires the chief executive officer’s continued employment with the Company through the achievement of any of the performance and market conditions. Performance Condition The performance condition to vesting of the 2023 RSU Award requires the consummation of a change in control event. Market Condition The market condition to vesting of the 2023 RSU Award involves evaluating Company market value thresholds depending upon which of the two vesting scenarios is applicable at the time of measurement. The Company market value is measured each June 30 and December 31 subsequent to the grant of the 2023 RSU Award and represents the Company’s Enterprise Value. The Company’s Enterprise Value is determined using the total market capitalization of the Company based on the average closing trading price of one share of the Company’s common stock over the 60-day period ending on the day prior to the applicable semi-annual measurement date, less cash. On the semi-annual measurement date, (i) one-sixth of the award will vest if a minimum Enterprise Value of $2.5 billion is achieved, (ii) all of the award will vest if a $5.0 billion Enterprise Value is achieved, and (iii) a portion of the award will vest based on a straight-line interpolation if an Enterprise Value of between $2.5 billion and $5.0 billion is achieved. The Company's Enterprise Value on a change in control event is measured on the date of the change in control and represents the aggregate amount of deal consideration paid at the closing of the change in control by an acquirer for the Company’s shares of common stock in connection with such change in control. Upon a change in control, (i) one-sixth of the award will vest if a minimum deal consideration of $2.5 billion is achieved, (ii) all of the award will vest if a $5.0 billion deal consideration is achieved, and (iii) a portion of the award will vest based on a straight-line interpolation if a deal consideration of between $2.5 billion and $5.0 billion is achieved. The Company utilized Monte Carlo simulation models to estimate the fair value of the 2023 RSU Award on the date of grant in each of the two vesting scenarios. The application of the Monte Carlo simulation model to each of the two vesting scenarios requires various subjective assumptions, including the following: Expected Time to Award End Date – The expected time to the award end date is based on the Company’s best estimate of the period of employment for the chief executive officer or the achievement of the performance condition, i.e., the change in control event. Expected Equity Volatility – Due to the limited company-specific historical and implied volatility data, the Company based its computation of expected volatility on the historical volatility of a representative group of public companies with similar characteristics to the Company (e.g., public entities of similar size, complexity, stage of development, and industry focus) in addition to the historical volatility of the Company. The historical volatility for the representative group of public companies was calculated based on a period commensurate with the expected time to the award end date. Risk-Free Interest Rate – The risk-free interest rate is based on a U.S. Treasury instrument which term is consistent with the expected time to the measurement dates. The Company determined the fair value of the 2023 RSU Award using third-party valuation reports. The Company considered several objective and subjective factors, including weighted probability of various scenarios, operating and financial performance, and general and industry-specific economic outlook, among other factors. The assumptions used in the Monte Carlos simulation models to determine the grant date fair value of the 2023 RSU Award for the two vesting scenarios were as follows: Semi-Annual Measurement Change in Control Time to award end date 10 years 5 years Equity volatility 75 % 75 % Risk-free interest rate 3.8 % 3.9 % Fair value of the 2023 RSU award (in thousands) $ 13,811 $ 10,999 The Company began recognizing share-based compensation expense using a fair value of $ 13.8 million on an accelerated attribution basis over a 10 -year anticipated service period according to the semi-annual measurement scenario. The performance condition under the change in control scenario was not deemed probable as of December 31, 2024. 2021 RSU Award In June 2021, the Company granted 952,804 RSUs (the 2021 RSU Award) to its chief executive officer. The 2021 RSU Award is subject to service, performance, and market conditions. In December 2021, the Company added alternative performance conditions for vesting of the same RSUs. These additional performance conditions provided alternative paths to vesting from the 2021 RSU Award; its vesting conditions remained the same, i.e., the original award was not modified. Each RSU granted in the 2021 RSU Award entitles the chief executive officer to one share of common stock upon vesting subject to the service, performance, and market conditions . All 952,804 RSUs were outstanding and no RSUs were vested as of December 31, 2024. In February 2025, 668,416 shares were vested based on performance and market conditions achieved on the measurement date of December 31, 2024. Service Condition The service condition to vesting of the 2021 RSU Award requires the chief executive officer’s continued employment with the Company through the achievement of any of the performance and the market conditions. Performance Condition The performance conditions to vesting of the 2021 RSU Award include (i) the consummation of a change in control event, (ii) the consummation of the first firm commitment underwritten public offering covering the offer and sale of Company shares, the consummation of the direct listing or direct placement of Company shares on a publicly traded exchange, or the completion of a merger or consolidation with a special purpose acquisition company in which the shares of the surviving or parent entity are listed on a national securities exchange (IPO), or (iii) a change in control following an IPO. The Company satisfied the IPO performance condition in February 2022 upon completion of the IPO. Market Condition The market condition to vesting of the 2021 RSU Award involves Company value thresholds depending upon which of the vesting scenarios is applicable at the time of measurement. The Company value is measured each June 30 and December 31 following the IPO (subject to applicable lock-up period) and represents the Company’s Enterprise Value. The methodology to determine the Company’s Enterprise Value and the vesting thresholds on the semi-annual measurement dates are the same as those under the 2023 RSU Award. The Company value on a change in control is measured on the date of the change in control. The methodology to determine the Company value and the vesting thresholds on the change in control date are the same as those under the 2023 Award. Upon completion of the IPO in February 2022, the IPO performance condition of the 2021 RSU Award was satisfied and the Company began recognizing share-based compensation expense on an accelerated attribution basis over the 10-year anticipated service period based on a $ 10.3 million aggregate fair value according to the IPO scenario. No other performance condition was deemed probable as of December 31, 2024. The Company utilized Monte Carlo simulation models to estimate the fair value of the 2021 RSU Award on the date of grant in each of the three performance condition scenarios. The application of the Monte Carlo simulation model to each of the three performance condition scenarios requires various subjective assumptions, including the following: Fair Value of Common Stock and Fair Value of Total Equity – Given the lack of an active public market for the common stock (prior to the Company's IPO), the fair value of the Company's common stock and total equity was determined by the board of directors with input from management and consideration of third-party valuation reports. In the absence of a public trading market, and as a clinical-stage company with no significant revenues, the Company believes that it was appropriate to consider a range of factors to determine the fair market value of the common stock at each grant date and resulting total equity value. In determining the fair value of its common stock and total equity value, the Company used methodologies, approaches, and assumptions consistent with the American Institute of Certified Public Accountants' (AICPA) Audit and Accounting Practice Aid Series: Valuation of Privately Held Company Equity Securities Issued as Compensation. In addition, the Company considered various objective and subjective factors, along with input from the independent third-party valuation firm. The factors included (1) the achievement of clinical and operational milestones by the Company; (2) the significant risks associated with the Company's stage of development; (3) capital market conditions for life science companies, particularly similarly situated, privately held, early-stage life science companies; (4) the Company's available cash, financial condition, and results of operations; (5) the most recent sales of the Company's redeemable convertible preferred stock; and (6) the preferential rights of the outstanding redeemable convertible preferred stock. Expected Equity Volatility – Due to the lack of a public market for the Company's common stock (prior to the Company's IPO) and the lack of company-specific historical and implied volatility data, the Company based its computation of expected volatility on the historical volatility of a representative group of public companies with similar characteristics to the Company (e.g., public entities of similar size, complexity, stage of development, and industry focus). The historical volatility was calculated based on a period commensurate with the expected date of achievement of a performance condition. Risk-Free Interest Rate and Discount Period – The risk-free interest rate is based on a treasury instrument which term is consistent with the expected time to achieve of a performance condition. The discount period is the period between the valuation date and the assumed change in control event date, with the assumption that all equity shares in the capital structure are paid out in cash. Expected Dividend Yield – The expected dividend yield is based on the Company's historical and expected dividend payouts. The Company has historically paid no dividends and does not anticipate dividends to be paid in the future. Expected Time to Achievement of a Performance Condition – The time to the achievement of a performance condition is based on the Company's best estimate of the period of time to achievement of a performance condition that attains the established market capitalization thresholds. The Company determined the fair value of the 2021 RSU Award considering third-party valuation reports. The Company considered several objective and subjective factors, including weighted probability of various liquidation event scenarios, operating and financial performance, discount for lack of marketability of the Company's equity, and general and industry-specific economic outlook, among other factors. The discount for lack of marketability was applied to reflect the increased risk arising from the inability to readily sell the RSUs. The assumptions used in the Monte Carlos simulation models to determine the grant date fair value of the 2021 RSU Award for each of the three performance condition scenarios were as follows: Change in Control IPO Change in Control Date of grant June 9, 2021 December 7, 2021 December 7, 2021 Time to liquidity event (years) 1.56 - 3.06 10.00 1.33 Equity volatility 100 % - 110 % 70 % 65 % Risk-free interest rate 0.1 % - 0.3 % 1.5 % 0.4 % Discount for lack of marketability 26 % - 32 % 5 % 5 % Fair value of the 2021 RSU award (in thousands) $ 1,580 $ 10,300 $ 150 As of December 31, 2024, there was $ 8.0 million of unrecognized share-based compensation cost related to the chief executive officer's 2023 RSU Award and 2021 RSU Award.

Employee Stock Purchase Plan (E

Employee Stock Purchase Plan (ESPP)	12 Months Ended
	Dec. 31, 2024
Share-Based Compensation Arrangement by Share-Based Payment Award [Line Items]
Share-Based Compensation	13. Share-Based Compensation The Company’s 2017 Equity Incentive Plan (the 2017 Plan) provided for the grant of incentive stock options, non-statutory stock options, stock appreciation rights, and restricted stock awards to the Company's employees, directors, and consultants. The 2017 Plan terminated one business day prior to effectiveness of the 2022 Equity Incentive Plan (the 2022 Plan) with respect to the grant of future awards. The 2022 Plan became effective on February 3, 2022 and provides for the grant of incentive stock options to the Company's employees and for the grant of non-statutory stock options, stock appreciation rights, restricted stock, restricted stock units (RSUs), and performance awards to the Company's employees, directors, and consultants. As of December 31, 2024, the aggregate number of shares of common stock that may be issued pursuant to equity awards under the 2022 Plan was 11,667,993 shares. The number of shares of common stock reserved for issuance under the 2022 Plan is cumulatively increased on the first day of each fiscal year, beginning with the Company’s 2023 fiscal year and ending on the ten year anniversary of the date the Company’s board of directors approved the 2022 Plan, by an amount equal to the least of (1) 6,502,174 shares, (ii) 5 % of the total number of shares of common stock outstanding as of the last day of the immediately preceding fiscal year, or (iii) a lesser number of shares determined by the administrator of the 2022 Plan. Share-based compensation cost is measured at fair value and is recognized as expense on a straight-line basis over the requisite service period. Share-based compensation expense by type of award was as follows (in thousands): Year Ended December 31, 2024 2023 2022 Stock options $ 28,057 $ 20,661 $ 14,859 Restricted stock units 27,257 12,254 4,056 Restricted stock units - chief executive officer 5,266 8,336 2,548 ESPP 506 538 81 Total share-based compensation expense $ 61,086 $ 41,789 $ 21,544 Share-based compensation expense as reflected in the consolidated statement of operations and comprehensive loss was as follows (in thousands): Year Ended December 31, 2024 2023 2022 Research and development $ 21,359 $ 11,003 $ 7,007 General and administrative 39,727 30,786 14,537 Total share-based compensation expense $ 61,086 $ 41,789 $ 21,544 Stock Options Stock options granted under the 2017 Plan and the 2022 Plan vest over one to four years and expire after 10 years . The Company uses the Black Scholes option pricing model to determine the grant date fair value of stock options. A summary of stock option activity for awards under the 2017 Plan and the 2022 Plan is presented below: Options Outstanding and Exercisable Shares Subject to Outstanding Options Weighted Weighted Aggregate Outstanding as of January 1, 2024 7,811,231 $ 12.46 7.8 $ 336,174 Options Granted 1,031,954 56.22 Options Forfeited ( 145,261 ) 11.10 Options Exercised ( 1,457,826 ) 9.75 Outstanding as of December 31, 2024 7,240,098 $ 19.28 6.9 $ 415,634 Exercisable as of December 31, 2024 4,712,405 $ 13.30 6.6 $ 298,737 (1) The aggregate intrinsic value is calculated as the difference between the exercise price of the underlying options and the fair value of the common stock for those options for which the exercise price was below the market price as of December 31, 2024 . The weighted-average grant-date fair value per share of stock options granted during the years ended December 31, 2024, 2023 and 2022 was $ 42.38 , $ 21.86 and $ 9.95 , respectively. The aggregate grant-date fair value of stock options vested during the years ended December 31, 2024 2023 and 2022 was approximately $ 27.7 million, $ 21.4 million and $ 14.5 million, respectively. As of December 31, 2024 , there was $ 51.8 million o f unrecognized compensation cost related to unvested stock option based compensation arrangements granted under the 2017 Plan and 2022 Plan. This remaining compensation expense is expected to be recognized over a weighted average period of 1.82 years as of December 31, 2024. The aggregate intrinsic value of the options exercised for the years ended December 31, 2024 , 2023 and 2022 was $ 103.5 million, $ 47.1 million and $ 10.9 million, respectively. The assumptions used in the Black-Scholes option pricing model for stock options granted for the years ending December 31, 2024, 2023 and 2022 were as follows: 2024 2023 2022 Expected term 5.5 - 6.27 years 5.5 - 6.25 years 6.0 - 6.3 years Expected volatility 86 % - 87 % 75 % - 80 % 68 % - 75 % Risk free interest rate 3.82 % - 4.56 % 3.92 % - 4.06 % 1.56 % - 3.88 % Expected dividend yield — % — % — % Restricted Stock Units (RSUs) RSUs granted under the 2022 Plan generally vest annually over three or four years . A summary of RSU activity for awards under the 2022 Plan, excluding the 2023 RSU Award and 2021 RSU Award (each defined below) granted to the chief executive officer, is presented below: Shares Subject to Outstanding Awards Weighted Average Grant Date Fair Value Outstanding as of January 1, 2024 1,416,446 $ 25.47 RSUs Granted 981,531 61.66 RSUs Vested ( 528,711 ) 23.76 RSUs Forfeited ( 57,421 ) 32.55 Outstanding as of December 31, 2024 1,811,845 $ 45.35 For the years ended December 31, 2024, 2023 and 2022, total grant-date fair value of RSUs that vested was $ 13.4 million, $ 5.4 million and zero , respectively. As of December 31, 2024, total unamortized share-based compensation relating to RSUs was $ 56.5 million , which is expected to be recognized over the average period of 1.84 years. The aggregate intrinsic value of RSUs is calculated as the closing price per share of the Company's common stock on the last trading day of the fiscal period, multiplied by the number of RSUs expected to vest as of December 31, 2024. As of December 31, 2024 , the aggregate intrinsic value of RSUs was $ 139.0 million. Restricted Stock Units - Chief Executive Officer 2023 RSU Award In January 2023, the Company granted 495,000 RSUs (the 2023 RSU Award) to its chief executive officer. The 2023 RSU Award has two different scenarios to vesting. The first vesting scenario is subject to service and market conditions. The second vesting scenario adds a performance condition. Each RSU granted in the 2023 RSU Award entitles the chief executive officer to one share of common stock upon vesting subject to the service, performance, and market conditions. All 495,000 RSUs were outstanding and no RSUs were vested as of December 31, 2024. In February 2025, 347,255 shares vested based on performance and market conditions achieved on the measurement date of December 31, 2024. Service Condition The service condition to vesting of the 2023 RSU Award requires the chief executive officer’s continued employment with the Company through the achievement of any of the performance and market conditions. Performance Condition The performance condition to vesting of the 2023 RSU Award requires the consummation of a change in control event. Market Condition The market condition to vesting of the 2023 RSU Award involves evaluating Company market value thresholds depending upon which of the two vesting scenarios is applicable at the time of measurement. The Company market value is measured each June 30 and December 31 subsequent to the grant of the 2023 RSU Award and represents the Company’s Enterprise Value. The Company’s Enterprise Value is determined using the total market capitalization of the Company based on the average closing trading price of one share of the Company’s common stock over the 60-day period ending on the day prior to the applicable semi-annual measurement date, less cash. On the semi-annual measurement date, (i) one-sixth of the award will vest if a minimum Enterprise Value of $2.5 billion is achieved, (ii) all of the award will vest if a $5.0 billion Enterprise Value is achieved, and (iii) a portion of the award will vest based on a straight-line interpolation if an Enterprise Value of between $2.5 billion and $5.0 billion is achieved. The Company's Enterprise Value on a change in control event is measured on the date of the change in control and represents the aggregate amount of deal consideration paid at the closing of the change in control by an acquirer for the Company’s shares of common stock in connection with such change in control. Upon a change in control, (i) one-sixth of the award will vest if a minimum deal consideration of $2.5 billion is achieved, (ii) all of the award will vest if a $5.0 billion deal consideration is achieved, and (iii) a portion of the award will vest based on a straight-line interpolation if a deal consideration of between $2.5 billion and $5.0 billion is achieved. The Company utilized Monte Carlo simulation models to estimate the fair value of the 2023 RSU Award on the date of grant in each of the two vesting scenarios. The application of the Monte Carlo simulation model to each of the two vesting scenarios requires various subjective assumptions, including the following: Expected Time to Award End Date – The expected time to the award end date is based on the Company’s best estimate of the period of employment for the chief executive officer or the achievement of the performance condition, i.e., the change in control event. Expected Equity Volatility – Due to the limited company-specific historical and implied volatility data, the Company based its computation of expected volatility on the historical volatility of a representative group of public companies with similar characteristics to the Company (e.g., public entities of similar size, complexity, stage of development, and industry focus) in addition to the historical volatility of the Company. The historical volatility for the representative group of public companies was calculated based on a period commensurate with the expected time to the award end date. Risk-Free Interest Rate – The risk-free interest rate is based on a U.S. Treasury instrument which term is consistent with the expected time to the measurement dates. The Company determined the fair value of the 2023 RSU Award using third-party valuation reports. The Company considered several objective and subjective factors, including weighted probability of various scenarios, operating and financial performance, and general and industry-specific economic outlook, among other factors. The assumptions used in the Monte Carlos simulation models to determine the grant date fair value of the 2023 RSU Award for the two vesting scenarios were as follows: Semi-Annual Measurement Change in Control Time to award end date 10 years 5 years Equity volatility 75 % 75 % Risk-free interest rate 3.8 % 3.9 % Fair value of the 2023 RSU award (in thousands) $ 13,811 $ 10,999 The Company began recognizing share-based compensation expense using a fair value of $ 13.8 million on an accelerated attribution basis over a 10 -year anticipated service period according to the semi-annual measurement scenario. The performance condition under the change in control scenario was not deemed probable as of December 31, 2024. 2021 RSU Award In June 2021, the Company granted 952,804 RSUs (the 2021 RSU Award) to its chief executive officer. The 2021 RSU Award is subject to service, performance, and market conditions. In December 2021, the Company added alternative performance conditions for vesting of the same RSUs. These additional performance conditions provided alternative paths to vesting from the 2021 RSU Award; its vesting conditions remained the same, i.e., the original award was not modified. Each RSU granted in the 2021 RSU Award entitles the chief executive officer to one share of common stock upon vesting subject to the service, performance, and market conditions . All 952,804 RSUs were outstanding and no RSUs were vested as of December 31, 2024. In February 2025, 668,416 shares were vested based on performance and market conditions achieved on the measurement date of December 31, 2024. Service Condition The service condition to vesting of the 2021 RSU Award requires the chief executive officer’s continued employment with the Company through the achievement of any of the performance and the market conditions. Performance Condition The performance conditions to vesting of the 2021 RSU Award include (i) the consummation of a change in control event, (ii) the consummation of the first firm commitment underwritten public offering covering the offer and sale of Company shares, the consummation of the direct listing or direct placement of Company shares on a publicly traded exchange, or the completion of a merger or consolidation with a special purpose acquisition company in which the shares of the surviving or parent entity are listed on a national securities exchange (IPO), or (iii) a change in control following an IPO. The Company satisfied the IPO performance condition in February 2022 upon completion of the IPO. Market Condition The market condition to vesting of the 2021 RSU Award involves Company value thresholds depending upon which of the vesting scenarios is applicable at the time of measurement. The Company value is measured each June 30 and December 31 following the IPO (subject to applicable lock-up period) and represents the Company’s Enterprise Value. The methodology to determine the Company’s Enterprise Value and the vesting thresholds on the semi-annual measurement dates are the same as those under the 2023 RSU Award. The Company value on a change in control is measured on the date of the change in control. The methodology to determine the Company value and the vesting thresholds on the change in control date are the same as those under the 2023 Award. Upon completion of the IPO in February 2022, the IPO performance condition of the 2021 RSU Award was satisfied and the Company began recognizing share-based compensation expense on an accelerated attribution basis over the 10-year anticipated service period based on a $ 10.3 million aggregate fair value according to the IPO scenario. No other performance condition was deemed probable as of December 31, 2024. The Company utilized Monte Carlo simulation models to estimate the fair value of the 2021 RSU Award on the date of grant in each of the three performance condition scenarios. The application of the Monte Carlo simulation model to each of the three performance condition scenarios requires various subjective assumptions, including the following: Fair Value of Common Stock and Fair Value of Total Equity – Given the lack of an active public market for the common stock (prior to the Company's IPO), the fair value of the Company's common stock and total equity was determined by the board of directors with input from management and consideration of third-party valuation reports. In the absence of a public trading market, and as a clinical-stage company with no significant revenues, the Company believes that it was appropriate to consider a range of factors to determine the fair market value of the common stock at each grant date and resulting total equity value. In determining the fair value of its common stock and total equity value, the Company used methodologies, approaches, and assumptions consistent with the American Institute of Certified Public Accountants' (AICPA) Audit and Accounting Practice Aid Series: Valuation of Privately Held Company Equity Securities Issued as Compensation. In addition, the Company considered various objective and subjective factors, along with input from the independent third-party valuation firm. The factors included (1) the achievement of clinical and operational milestones by the Company; (2) the significant risks associated with the Company's stage of development; (3) capital market conditions for life science companies, particularly similarly situated, privately held, early-stage life science companies; (4) the Company's available cash, financial condition, and results of operations; (5) the most recent sales of the Company's redeemable convertible preferred stock; and (6) the preferential rights of the outstanding redeemable convertible preferred stock. Expected Equity Volatility – Due to the lack of a public market for the Company's common stock (prior to the Company's IPO) and the lack of company-specific historical and implied volatility data, the Company based its computation of expected volatility on the historical volatility of a representative group of public companies with similar characteristics to the Company (e.g., public entities of similar size, complexity, stage of development, and industry focus). The historical volatility was calculated based on a period commensurate with the expected date of achievement of a performance condition. Risk-Free Interest Rate and Discount Period – The risk-free interest rate is based on a treasury instrument which term is consistent with the expected time to achieve of a performance condition. The discount period is the period between the valuation date and the assumed change in control event date, with the assumption that all equity shares in the capital structure are paid out in cash. Expected Dividend Yield – The expected dividend yield is based on the Company's historical and expected dividend payouts. The Company has historically paid no dividends and does not anticipate dividends to be paid in the future. Expected Time to Achievement of a Performance Condition – The time to the achievement of a performance condition is based on the Company's best estimate of the period of time to achievement of a performance condition that attains the established market capitalization thresholds. The Company determined the fair value of the 2021 RSU Award considering third-party valuation reports. The Company considered several objective and subjective factors, including weighted probability of various liquidation event scenarios, operating and financial performance, discount for lack of marketability of the Company's equity, and general and industry-specific economic outlook, among other factors. The discount for lack of marketability was applied to reflect the increased risk arising from the inability to readily sell the RSUs. The assumptions used in the Monte Carlos simulation models to determine the grant date fair value of the 2021 RSU Award for each of the three performance condition scenarios were as follows: Change in Control IPO Change in Control Date of grant June 9, 2021 December 7, 2021 December 7, 2021 Time to liquidity event (years) 1.56 - 3.06 10.00 1.33 Equity volatility 100 % - 110 % 70 % 65 % Risk-free interest rate 0.1 % - 0.3 % 1.5 % 0.4 % Discount for lack of marketability 26 % - 32 % 5 % 5 % Fair value of the 2021 RSU award (in thousands) $ 1,580 $ 10,300 $ 150 As of December 31, 2024, there was $ 8.0 million of unrecognized share-based compensation cost related to the chief executive officer's 2023 RSU Award and 2021 RSU Award.
Employee Stock Purchase Plan
Share-Based Compensation Arrangement by Share-Based Payment Award [Line Items]
Share-Based Compensation	14. Employee Stock Purchase Plan (ESPP) In February 2022, the Company adopted the 2022 ESPP, as amended in September 2022. The 2022 ESPP plan was initiated in November 2022 and provides eligible employees with the opportunity to acquire an ownership interest in the Company through periodic payroll deductions, based on a six-month look-back period, at a price equal to the lesser of 85 % of the fair market value of the common stock at either the first business day or last business day of the relevant offering period, provided that no more than $ 25,000 in common stock may be purchased by any one employee during each year. The 2022 ESPP is intended to constitute an “employee stock purchase plan” under Section 423(b) of the Internal Revenue Code of 1986, as amended. The 2022 ESPP may be terminated by the Company’s board of directors at any time. A total of 312,500 shares of common stock were initially re served for issuance under the 2022 ESPP, subject to an annual increase on January 1 of each year, beginning on January 1, 2023, equal to the least of 312,500 shares of the Company's common stock, 1 % or the outstanding shares of the Company's common stock as of the last day of the immediately preceding fiscal year, or such other amount as the administrator under the 2022 ESPP may determine. The assumptions used in the Black-Scholes option pricing model for the ESPP plan for the year ending December 31, 2024, 2023 and 2022 were as follows: 2024 2023 2022 Expected term 0.5 years 0.5 years 0.5 years Expected volatility 45 % - 65 % 65 % - 68 % 132 % Risk free interest rate 4.44 % - 5.46 % 5.26 % - 5.46 % 4.40 % Expected dividend yield — % — % — %

Net Loss Per Share Attributable

Net Loss Per Share Attributable to Common Stockholders	12 Months Ended
	Dec. 31, 2024
Earnings Per Share [Abstract]
Net Loss Per Share Attributable to Common Stockholders	15. 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: December 31, 2024 2023 2022 Options to purchase common stock 7,240,098 7,811,231 8,053,704 Restricted stock units 1,811,845 1,416,446 927,954 Restricted stock units - executive officer 1,447,804 1,447,804 952,804 Employee Stock Purchase Plan (ESPP) 3,959 2,995 5,651 Total 10,503,706 10,678,476 9,940,113

Income Taxes

Income Taxes	12 Months Ended
	Dec. 31, 2024
Income Tax Disclosure [Abstract]
Income Taxes	16. Income Taxes The Company’s provision for income taxes consists of the following (in thousands): Year Ended December 31, 2024 2023 2022 Current income tax provision (expense) benefit: U.S. federal $ ( 1,910 ) $ ( 427 ) $ — State ( 153 ) ( 273 ) — Total $ ( 2,063 ) $ ( 700 ) $ — A reconciliation of the statutory U.S. federal rate and effective rate is as follows: Year Ended December 31, 2024 2023 2022 U.S. federal tax 21.0 % 21.0 % 21.0 % State tax, net of federal benefit 0.3 0.6 6.6 Change in valuation allowance ( 42.9 ) ( 2.8 ) ( 26.9 ) Nondeductible compensation ( 17.0 ) ( 15.2 ) ( 0.2 ) Research and development tax credits 26.3 16.3 0.0 Stock based compensation 16.5 10.2 0.4 Change in state deferred income tax rate ( 0.5 ) ( 27.2 ) 0.0 Changes in unrecognized tax benefits ( 5.7 ) ( 4.8 ) 0.0 Change in tax rates and other 0.1 0.9 ( 0.9 ) Effective income tax rate ( 1.9 )% ( 1.0 )% 0.0 % The significant components of the Company’s deferred income tax assets (liabilities) were as follows (in thousands): December 31, 2024 2023 Deferred income tax assets: U.S. federal net operating loss carryforward $ 10,692 $ 29,929 State net operating loss carryforward 287 1,110 Research and development expenditures 65,346 44,047 Research and development credits 26,838 9,829 Lease liabilities - operating 11,641 12,710 Stock based compensation 8,117 4,600 Accruals and others 2,371 1,323 Deferred Revenue 24,423 — Gross deferred income tax assets 149,715 103,548 Less: Valuation allowance ( 137,302 ) ( 91,841 ) Total deferred income tax assets 12,413 11,707 Deferred income tax liabilities: Depreciation ( 6,692 ) ( 4,930 ) Right-of-use asset - operating ( 5,143 ) ( 5,903 ) Section 481(a) adjustment ( 578 ) ( 874 ) Total deferred income tax liabilities ( 12,413 ) ( 11,707 ) Net deferred income tax assets (liabilities) $ — $ — For tax years beginning on or after January 1, 2022, the Tax Cuts and Jobs Act of 2017 eliminates the option to currently deduct research and development expenses and requires taxpayers to capitalize and amortize them over five years for research activities performed in the United States and 15 years for research activities performed outside the United States pursuant to Internal Revenue Code Section 174. The Company records valuation allowances to reduce deferred tax assets to the amount that is not more likely than not to be realized. In assessing the likelihood of realization, management considers (i) future reversals of existing taxable temporary differences; (ii) future taxable income exclusive of reversing temporary difference and carryforwards; (iii) taxable income in prior carryback years if carryback is permitted under applicable tax law; and (iv) tax planning strategies. The Company’s net deferred income tax assets are not more likely than not to be utilized due to the lack of sufficient sources of future taxable income and cumulative book losses which have resulted over the years. The net increase in the valuation allowance for the year ended December 31, 2024 of approximately $ 45.5 million was primarily due to capitalized research and development expenditures, research and development credits and increase in deferred revenue, partially offset by utilization of net operating loss carryforwards. The change in the valuation allowance for the year ended December 31, 2023 of approximately $ 2.0 million was primarily due to increase in capitalized research and development expenditures and research and development credits, partially offset by utilization of net operating loss carryforwards. The Company had federal and State net operating loss (NOL) carryforwards of approximately $ 51.2 million and $ 74.8 million , respectively, as of December 31, 2024. The Company also had federal and State research and development tax credit carryforwards of approximately $ 8.9 million and $ 3.2 million , respectively, and federal orphan drug credit carryforwards of $ 24.8 million, available to potentially offset future income taxes, as of December 31, 2024. The federal NOL will be carried forward indefinitely, if not utilized, but is limited to eighty percent of taxable income. The St ate NOL will begin expiring in 2038, if not utilized, while a portion is carried forward indefinitely. The federal research and development tax credit carryforwards and orphan drug credit carryforwards, if not utilized, will begin to expire in 2042. The California research and development tax credit carryforwards do not expire while other State research and development tax credit carryforward will begin to expire in 2031 . Under Section 382/383 of the Internal Revenue Code of 1986, as amended, and corresponding provisions of state law, if a corporation undergoes an “ownership change,” which generally occurs if the percentage of the corporation’s stock owned by 5 % stockholders increases by more than 50 % over a three-year period, the corporation’s ability to use its pre-change NOL carryforwards and other pre-change tax attributes to offset its post-change income may be limited. The annual limitation may result in the expiration of net operating losses and credits before utilization. The Company performed a Section 382/383 analysis through December 31, 2024. The Company has experienced ownership changes. Some of the Company’s federal research and development tax credit carryforwards will be permanently limited as a result of the ownership change, which have been excluded from the Company’s deferred income tax assets. Subsequent ownership changes may affect the limitation in future years. Related to unrecognized tax benefits noted below, interest and penalties related to unrecognized tax benefits are recognized in the provision of income taxes. No penalties or interest were recorded during the years ended December 31, 2024 , 2023 and 2022. The Company does not expect its unrecognized tax benefit balance to change materially over the next 12 months. The Company had $ 9.6 million and $ 3.5 million, and no unrecognized tax benefits as of December 31, 2024, 2023 and 2022, respectively. Of the unrecognized tax benefits as of December 31, 2024, 2023 and 2022, none would affect the Company’s effective tax rate if recognized due to the Company's full valuation allowance position. December 31, 2022 $ — Additions based on tax positions related to 2023 809 Additions for tax positions of prior years 2,641 December 31, 2023 3,450 Additions based on tax positions related to 2024 3,177 Additions for tax positions of prior years 2,951 December 31, 2024 $ 9,578 The Company’s federal and State tax returns for all years, 2015 through 2023 , remain subject to examination by taxing authorities due to the tax attribute carryforwards. The Company is not currently under examination by income tax authorities in federal or State jurisdictions.

Segment Reporting

Segment Reporting	12 Months Ended
	Dec. 31, 2024
Segment Reporting [Abstract]
Segment Reporting	17. 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 Company’s CODM is its chief executive officer . 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): Year Ended December 31, 2024 2023 2022 Collaboration revenue $ 107,936 $ 110,319 $ — Operating expenses: Research and development anito-cel in rrMM 50,141 73,530 96,513 ACLX-001 1,975 2,939 8,764 ACLX-002 14,294 5,667 6,458 Other research and development costs 21,364 3,701 5,467 Internal costs [1] 69,319 48,012 32,353 General and administrative 88,414 66,350 41,704 Total operating expenses 245,507 200,199 191,259 Loss from operations ( 137,571 ) ( 89,880 ) ( 191,259 ) Interest and other income (expense), net 33,322 23,695 4,300 Interest expense ( 1,030 ) ( 3,842 ) ( 1,720 ) Total other income, net 32,292 19,853 2,580 Income tax expense ( 2,069 ) ( 663 ) — Net loss $ ( 107,348 ) $ ( 70,690 ) $ ( 188,679 ) [1] Internal costs primarily consist of employee-related costs, including salaries, related benefits, and share-based compensation expense, as well as facility allocation and depreciation expense.

Summary of Significant Accoun_2

Summary of Significant Accounting Policies (Policies)	12 Months Ended
	Dec. 31, 2024
Accounting Policies [Abstract]
Basis of Presentation and Consolidation	Basis of Presentation and Consolidation The accompanying consolidated financial statements have been prepared in accordance with U.S. generally accepted accounting principles (U.S. GAAP). Any reference in these notes to applicable guidance is meant to refer to the authoritative GAAP as found in the Accounting Standards Codification (ASC) and Accounting Standards Update (ASU) of the Financial Accounting Standards Board (FASB). The accompanying consolidated financial statements include the accounts of Arcellx, Inc. and its wholly owned subsidiary. All intercompany balances and transactions have been eliminated in consolidation.
Use of Accounting Estimates	Use of Accounting Estimates The preparation of consolidated financial statements in conformity with GAAP requires management to make estimates and assumptions that affect the reported amounts of assets and liabilities and disclosure of contingent assets and liabilities at the date of the consolidated financial statements and the reported amounts of revenues and expenses during the reporting period. Significant estimates used in preparing the accompanying consolidated financial statements include, but are not limited to, estimates related to the fair value of assets, collaboration revenue, research and development accruals, and share-based compensation. Although actual results could differ from those estimates, management does not believe that such differences would be material.
Cash and Cash Equivalents and Restricted Cash	Cash and Cash Equivalents and Restricted Cash The Company considers all highly liquid investments with an original maturity of three months or less at the date of purchase to be cash equivalents. The Company deposits its cash primarily in checking and sweep accounts with commercial banks and financial institutions in amounts exceeding FDIC insurance limits. Cash equivalents consist of money market funds. The Company is required to maintain cash collateral on deposit in segregated money market bank accounts and certificate of deposit accounts as a condition of its lease agreements on its properties, equal to the required security deposit amounts. These amounts are presented as restricted cash, current and non-current on the accompanying consolidated balance sheets. The following table reconciles cash and cash equivalents and restricted cash per the balance sheets to the statements of cash flows (in thousands): December 31, 2024 2023 Cash and cash equivalents $ 105,679 $ 394,583 Restricted cash, current 208 1,903 Restricted cash, non-current 2,418 2,418 Total $ 108,305 $ 398,904
Marketable Securities	Marketable Securities The Company carries marketable securities classified as available-for-sale at fair value as determined by prices for identical or similar securities at the balance sheet date. The inputs used to determine the fair value of marketable securities are considered Level 2 within the fair-value hierarchy. The Company records unrealized gains and losses as a component of other comprehensive loss within the statements of operations and comprehensive loss and as accumulated other comprehensive loss in stockholders’ equity. Realized gains or losses on available-for-sale securities are determined using the specific identification method and the Company includes net realized gains and losses in other income, net. Marketable securities are classified as either current or non-current assets based on their contractual maturity dates. For securities available for sale, ASU 2016-13 eliminates the concept of other-than-temporary impairment and instead requires entities to determine if impairment is related to credit loss or non-credit loss. In making the assessment of whether a loss is from credit or other factors, management considers the extent to which fair value is less than amortized cost, any changes to the rating of the security by a rating agency and adverse conditions related to the security, among other factors. If this assessment indicates that a credit loss exists, the present value of cash flows expected to be collected from the security are compared to the amortized cost basis of the security. If the present value of cash flows is less than the amortized cost basis, a credit loss exists and an allowance is created, limited by the amount that the fair value is less than the amortized cost basis. Subsequent activity related to the credit loss component in the form of write-offs or recoveries is recognized as part of the allowance for credit losses on securities available for sale. The Company has made the accounting policy election to exclude accrued interest receivable on securities from the estimate of credit losses.
Fair Value of Financial Instruments	Fair Value of Financial Instruments The Company’s financial instruments consist of cash and cash equivalents, restricted cash, marketable securities, accounts payable, and accrued expenses. The carrying amounts of accounts payable and accrued expenses generally approximate their respective fair value due to their short-term nature. The Company accounts for recurring and non-recurring fair value measurements in accordance with ASC 820, Fair Value Measurements and Disclosures (ASC 820). ASC 820 defines fair value, establishes a fair value hierarchy for assets and liabilities measured at fair value, and requires expanded disclosures about fair value measurements. The ASC 820 hierarchy ranks the quality of reliability of inputs, or assumptions, used in the determination of fair value and requires assets and liabilities carried at fair value to be classified and disclosed in one of the following three categories: Level 1—Fair value is determined by using unadjusted quoted prices that are available in active markets for identical assets and liabilities. Level 2—Fair value 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. Level 3—Fair value is determined by inputs that are unobservable and not corroborated by market data. Use of these inputs involves significant and subjective judgments to be made by a reporting entity—e.g., determining an appropriate adjustment to a discount factor for illiquidity associated with a given security. To the extent the valuation is based on models or inputs that are less observable or unobservable in the market, the determination o f fair values requires more judgment. Accordingly, the degree of judgment exercised by the Company in determining fair value is greatest for instruments categorized as Level 3. A financial instrument’s level within the fair value hierarchy is based on the lowest level of any input that is significant to the fair value measurement.
Concentration of Credit Risk	Concentration of Credit Risk Financial instruments that potentially expose the Company to concentrations of credit risk primarily consist of cash and cash equivalents, restricted cash, and marketable securities. The Company maintains its cash and cash equivalents and restricted cash at an accredited financial institution in amounts that exceed federally insured limits. The Company does not believe that it is subject to unusual credit risk beyond the normal credit risk associated with commercial banking relationships. The Company invests in highly rated debt securities consisting entirely of corporate and government bonds, which the Company has the ability to liquidate within one-day should the need for additional cash arise. Accordingly, the Company believes the exposure to credit risk on its marketable securities portfolio is low.
Property and Equipment, Net	Property and Equipment, Net Property and equipment are recorded at cost and depreciated over its estimated useful life using the straight-line method. Upon retirement or disposal, the cost and related accumulated depreciation are removed from the balance sheet and the resulting gain or loss is recognized within operating expenses. Routine expenditures for maintenance and repairs are expensed as incurred. Estim ated useful lives for property and equipment are as follows: Estimated Useful Life Computer equipment 3 years Furniture and fixtures 7 years Lab equipment 7 years Leasehold improvements Lesser of estimated useful life or remaining lease term Equipment under finance lease Lesser of estimated useful life or remaining lease term
Impairment of Long-Lived Assets	Impairment of Long-Lived Assets T he Company reviews the recoverability of its long-lived asset group when events or changes in circumstances occur that indicate that the carrying value of the asset group may not be recoverable. Recoverability of the long-lived asset group is measured by a comparison of the carrying amount of the asset to future undiscounted net cash flows expected to be generated by the asset group. If these cash flows are less than the carrying value of such asset group, the Company then determines the fair value of the underlying asset group. Any impairment loss to be recognized is measured by the amount by which the carrying amount of the asset group exceeds the estimated fair value of the asset group.
Collaborative Arrangements and Contracts with Customers	Collaborative Arrangements and Contracts with Customers The Company assesses whether its collaboration agreements are subject to Accounting Standards Codification (ASC) Topic 808, Collaborative Arrangements (ASC 808) based on whether they involve joint operating activities and whether both parties have active participation in the arrangement and are exposed to significant risks and rewards that depend on the commercial success of the joint operating activities. To the extent that the arrangement falls within the scope of ASC 808, the Company applies the unit of account guidance under ASC Topic 606, Revenue from Contracts with Customers (ASC 606), to identify distinct performance obligations, and then determine whether a customer relationship exists for each distinct performance obligation. If the Company determines whether a promised good or service within the arrangement is with a customer, it applies the guidance in ASC 606. If a portion of a distinct bundle of goods or services within an arrangement is not with a customer, then the unit of account is not within the scope of ASC 606, and the recognition and measurement of that unit of account shall be based on analogy to authoritative accounting literature or, if there is no appropriate analogy, a reasonable, rational, and consistently applied accounting policy election. The Company recognizes revenue when its customer obtains control of promised goods or services in a contract for an amount that reflects the consideration the Company expects to receive in exchange for those goods or services. For contracts with customers, the Company performs the following five steps: (i) identify the contract(s) with a customer; (ii) identify the performance obligations in the contract; (iii) determine the transaction price; (iv) allocate the transaction price to the performance obligations in the contract; and (v) recognize revenue when (or as) the Company satisfies each performance obligation. The Company only applies the five-step model to contracts when it is probable that Company will collect the consideration it is entitled to in exchange for the goods or services it transfers to the customer. As part of the accounting for contracts with customers, the Company develop assumptions that require judgment to determine the standalone selling price of each performance obligation identified in the contract. The Company then allocates the total transaction price to each performance obligation based on their estimated standalone selling prices. The Company then recognizes as revenue the amount of the transaction price that is allocated to the respective performance obligation when (or as) the performance obligation is satisfied. For performance obligations satisfied over time, the Company determines the appropriate measure of progress. The effect of any change made to the measure of progress and, therefore a change to revenue, would be recorded as a change in estimate. If the consideration promised in a contract includes a variable amount, the Company estimates the amount of consideration to which it will be entitled in exchange for transferring the promised goods or services to a customer. The Company determines the amount of variable consideration by using the expected value method or the most likely amount method. The Company includes the unconstrained amount of estimated variable consideration in the transaction price. The amount included in the transaction price is the amount for which it is probable that a significant reversal of cumulative revenue recognized will not occur. At the end of each subsequent reporting period, the Company re-evaluates the estimate of variable consideration included in the transaction price and any related constraint, and if necessary, adjusts the estimate of the overall transaction price. Any such adjustments are recorded on a cumulative catch-up basis in the period of adjustment. 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. The Company’s collaborative arrangements can have one or more of the following forms of consideration: (i) license fees; (ii) milestone payments related to the achievement of developmental, regulatory, or commercial goals; (iii) royalties on net sales of licensed products; (iv) fees attributable to options to intellectual property; (v) cost-sharing or research and development (R&D) funding arrangements and (vi) profit and loss sharing. When a portion of non‑refundable upfront fees or other payments received are allocated to continuing performance obligations under the terms of a collaborative arrangement, they are recorded as contract liabilities and recognized as revenue when (or as) the underlying performance obligation is satisfied. The Company classifies contract liabilities as current when it expects to satisfy its performance obligations within one year, and noncurrent when the Company expects to satisfy those performance obligations in greater than one year. Fees attributable to options are deferred until the option expires or is exercised. Changes to collaboration agreements are assessed for whether they represent a modification or should be accounted for as a new contract. Upfront Payments and License Fees If a license to the Company’s intellectual property is determined to be distinct from the other performance obligations identified in the arrangement, the Company recognizes revenues from non-refundable, upfront fees allocated to the license when the license is transferred to the licensee and the licensee is able to use and benefit from the license. For licenses that are bundled with other promises, the Company utilizes judgment to assess the nature of the combined performance obligation to determine whether the combined performance obligation is satisfied over time or at a point in time and, if over time, the appropriate method of measuring progress for purposes of recognizing revenue. The Company evaluates the measure of progress each reporting period and, if necessary, adjusts the measure of performance and related revenue recognition. Cost-sharing Under certain collaborative arrangements, the Company can be reimbursed for a portion of its research and development expenses or reimburse its collaboration partner for its research and development expenses. The Company estimates reimbursements to be received by a collaboration partner and reimbursements to be paid or payable to a collaboration partner as part of variable consideration. When these research and development services are paid to a collaboration partner, the Company reduces its contract liability. Customer Options Customer options, such as options granted to allow a licensee to extend a license or research term, to select additional research targets or to choose to research, develop and commercialize licensed compounds are evaluated at contract inception to determine whether those options provide a material right (i.e., an optional good or service offered for free or at a discount) to the customer. If the customer options represent a material right, the material right is treated as a separate performance obligation at the outset of the arrangement. The Company allocates the transaction price to material rights based on the standalone selling price. As a practical alternative to estimating the standalone selling price of a material right when the underlying goods or services are both (i) similar to the original goods or services in the contract and (ii) provided in accordance with the terms of the original contract, the Company allocates the total amount of consideration expected to be received from the customer to the total goods or services expected to be provided to the customer. Amounts allocated to any material right are recognized as revenue when or as the related future goods or services are transferred or when the option expires. Milestone Payments At the inception of the arrangement, the Company evaluates whether the development or sales-based milestones are considered probable of being reached and estimates the amount to be included in the transaction price using the most likely amount method. If it is probable that a significant revenue reversal would not occur, the associated value is included in the transaction price. Milestone payments that are not within the control of the Company or the Company’s collaboration partner, such as regulatory approvals, are generally not considered probable of being achieved until those approvals are received. At the end of each subsequent reporting period, the Company re-evaluates the probability of achievement of such development or sales-based milestones and any related constraint, and if necessary, adjusts its estimate of the overall transaction price. Any such adjustments are recorded on a cumulative catch-up basis, which would affect revenues in the period of adjustment. For milestone revenues related to sales-based achievements, the Company recognizes the milestone revenues in the corresponding period of the product sale, in accordance with the guidance of ASC 606-10-55-65 for contracts that include a license to intellectual property and the license is the predominant item to which the product sale relates. Royalties For arrangements that include sales-based royalties, the Company recognizes revenue at the later of (i) when the related sales occur, or (ii) when the performance obligation to which some or all of the royalty has been allocated has been satisfied (or partially satisfied). To date, the Company has not recognized any royalty revenue resulting from its collaborative arrangement.
Leases	Leases The Company leases office and laboratory space and equipment. In addition, the Company enters into manufacturing supply agreements with CMOs and CDMOs to manufacture clinical product candidate materials. Such agreements may include an embedded lease due to the exclusive use of identified manufacturing facilities and equipment that are controlled by the Company and for which the Company obtains substantially all the output. The evaluation of leases that are embedded in the Company’s CMO and CDMO agreements is complex and requires judgment. If a lease arrangement is determined to exist with a lease term of more than 12 months at the lease commencement date, an ROU asset and corresponding lease liability are recorded on the consolidated balance sheet at the lease commencement date based on the present value of fixed lease payments over the lease term. The lease commencement date, defined as the date on which the lessor makes the underlying asset available for use by the lessee and the date from which the Company is required to recognize lease expenses, may be different from the inception date of the contract. An ROU asset represents the right to control the use of an identified asset over the lease term and a lease liability represents the obligation to make lease payments arising from the lease. The Company uses the discount rate implicit in the lease, if available, or its incremental borrowing rate on the lease commencement date to determine the present value of lease payments. The lease terms used to calculate the ROU assets and related lease liabilities include options to extend or terminate the lease when it is reasonably certain that the Company will exercise that option. The Company expenses ROU assets acquired for research and development activities under ASC Topic 730, Research and Development, if they do not have alternative future use, in research and development projects or otherwise. Leases are classified as either operating or finance leases based on the economic substance of the agreement. For operating leases, the Company recognizes lease expense related to fixed payments on a straight-line basis over the lease term. For finance leases, the Company recognizes the amortization of the ROU asset over the shorter of the lease term or useful life of the underlying asset. Interest accretion on the finance lease liabilities is recorded as interest expense. For both operating and finance leases, lease expense related to variable payments is recognized as incurred based on performance or usage in accordance with the contractual agreements. For short-term lease arrangements with a term of one year or less, the Company has elected to recognize the related lease payments on a straight-line basis over the lease term without recording related ROU assets and lease liabilities. The Company evaluates changes to the terms and conditions of a lease contract to determine if they result in a new lease or a modification of an existing lease. For lease modifications, the Company remeasures and reallocates the remaining consideration in the contract and reassesses the lease classification at the effective date of the modification. The Company u ses significant assumptions and judgment in evaluating its lease contracts and other agreements, including the determination of whether an agreement is or contains a lease, whether a change in the terms and conditions of a lease contract represent a new or modified lease, whether a lease represents an operating or finance lease, the discount rate used to determine the present value of lease obligations, and the term of a lease embedded in its manufacturing supply agreements.
Research and Development Expenses	Research and Development Expenses Research and development costs are expensed as they are incurred. Research and development expenses consist primarily of salaries and benefits of research and development personnel, costs related to research activities, preclinical studies, clinical manufacturing, technical development, and overhead and facility-related costs. The Company makes payments in connection with clinical trials under contracts with contract research organizations that support conducting and managing clinical trials. The financial terms of these agreements are subject to negotiation and vary from contract to contract and may result in uneven payment flows. Generally, these agreements set forth the scope of work to be performed at a fixed fee, unit price, or on a time and materials basis. A portion of the obligation to make payments under these contracts depends on factors such as the successful enrollment or treatment of patients or the completion of other clinical trial milestones. Expenses related to clinical trials are accrued based on estimates and/or representations from service providers regarding work performed, including actual level of patient enrollment, completion of patient trials, and progress of the clinical trials. Other incidental costs related to patient enrollment or treatment are accrued when reasonably certain. Similarly, the Company accrues expenses related to the work performed by contract manufacturing organizations based on the progress of the work performed. If the amounts the Company is obligated to pay under clinical trial agreements and manufacturing agreements are modified (for instance, as a result of changes in the clinical trial protocol or scope of work to be performed), the accruals are adjusted accordingly. Revisions to contractual payment obligations are charged to expense in the period in which the facts that give rise to the revision become reasonably certain. The Company may be obligated to make upfront payments upon execution of certain research and development agreements. Advance payments, including nonrefundable amounts, for goods or services that will be used or rendered for future research and development activities are deferred and included in prepaid expenses and other current assets or other non-current assets in the consolidated balance sheets. Such amounts are recognized as expense as the related goods are delivered or the related services are performed, or at such time when the Company does not expect the goods to be delivered or services to be performed.
Share-Based Compensation	Share-Based Compensation The Company accounts for its share-based compensation in accordance with ASC 718, Compensation—Stock Compensation (ASC 718). ASC 718 requires all share-based payments to employees and directors, including grants of incentive stock options, nonqualified stock options, restricted stock awards, unrestricted stock awards, or restricted stock units, to be recognized as expense based on their grant date fair values. The determination of grant date fair value may require the Company to make assumptions as further discussed below. Changes in the assumptions can materially affect the fair value and ultimately how much share-based compensation expense is recognized. These assumptions are subjective and generally require significant analysis and judgment to develop. Stock Options The Company’s determination of the fair value of stock options with time-based vesting on the date of grant utilizes the Black-Scholes option-pricing model, and is impacted by the Company’s common stock price as well as other variables including, but not limited to, the expected term that options will remain outstanding, expected common stock price volatility over the expected term of the option awards, risk-free interest rates and expected dividends. The fair value of a stock-based award is recognized over the period during which an optionee is required to provide services in exchange for the option award, known as the requisite service period (usually the vesting period) on a straight-line basis. Stock-based compensation expense is recognized based on the fair value determined on the date of grant and is reduced for forfeitures as they occur. Estimating the fair value of equity-settled awards as of the grant date using valuation models, such as the Black-Scholes option pricing model, is affected by assumptions regarding a number of complex variables as follows: Expected Term — The Company uses the “simplified method” for estimating the expected term of options, whereby the expected term equals the arithmetic average of the vesting term and the original contractual term of the option (generally 10 years). The Company uses the simplified method as the Company does not have sufficient historical exercise data to provide a reasonable basis upon which to estimate the expected term that options will remain outstanding. Expected Volatility — Due to the Company’s limited operating history and a lack of company specific historical and implied volatility data, the Company has based its estimate of expected volatility on the historical volatility of a group of similar companies that are publicly traded. The historical volatility data was computed using the daily closing prices for the selected companies’ shares during the equivalent period of the calculated expected term of the stock-based awards. Risk-Free Interest Rate — The risk-free rate assumption is based on the U.S. treasury yield in effect at the time of grant for instruments with maturities similar to the expected term of the Company’s stock options. Expected Dividend — The Company has not issued any dividends in its history and does not expect to issue dividends over the life of the options and therefore has estimated the dividend yield to be zero . Restricted Stock Awards, Unrestricted Stock Awards, and Restricted Stock Units The fair value of restricted stock awards, unrestricted stock awards, and restricted stock units (collectively, awards), unless a market condition exists, is determined based on the fair value of our common stock on the grant date. Vesting of awards is accelerated for certain employees in the event of a change in control or in the event that we remove the employee with or without cause from their position. The Company estimates the fair value of awards subject to both a market condition and a performance condition on the grant date using a Monte Carlo simulation model. For awards with vesting subject to the fulfillment of both market and performance conditions, share-based compensation expense is recognized using the accelerated attribution method beginning when the achievement of the performance condition becomes probable over the applicable service period. The amount of share-based compensation expense is dependent on our periodic assessment of the probability of the performance condition being satisfied and our estimate, which may vary over time, of the number of shares that will ultimately be issued. If the performance condition is not met, no compensation expense is recognized, and any previously recognized compensation cost is reversed.
Income Taxes	Income Taxes The Company uses the asset and liability method of accounting for income taxes. Deferred tax assets and liabilities are recognized for the estimated future tax consequences attributable to temporary differences between the financial statement carrying amounts of existing assets and liabilities and their respective tax base. Deferred tax assets and liabilities are measured using enacted tax rates expected to apply to taxable income in the years in which those temporary differences are expected to be recovered or settled. Deferred tax expense or benefit is the result of changes in the deferred tax assets and liabilities. Valuation allowances are established when necessary to reduce deferred tax assets where, based upon the available evidence, the Company concludes that it is not more-likely-than-not that the deferred tax assets will be realized. In evaluating its ability to recover deferred tax assets, the Company considers all available positive and negative evidence, including its operating results, ongoing tax planning, and forecasts of future taxable income on a jurisdiction-by-jurisdiction basis. Because of the uncertainty of the realization of deferred tax assets, the Company has recorded a valuation allowance against its net deferred tax assets. Liabilities are provided for tax benefits for which realization is uncertain. Such benefits are only recognized when the underlying tax position is considered more-likely-than-not to be sustained on examination by a taxing authority, assuming they possess full knowledge of the position and facts. Interest and penalties related to uncertain tax positions are recognized in the provision of income taxes. As of December 31, 2024 and 2023, the Company had no interest or penalties related to uncertain income tax positions.
Segment and Geographic Information	Segment and Geographic Information Operating segments are defined as components of an entity about which separate discrete information is available for evaluation by the chief operating decision maker, or decision-making group, in deciding how to allocate resources and in assessing performance. The Company views its operations as and manages its business in one operating segment operating exclusively in the United States.
Recently Adopted Accounting Pronouncements	Recently Adopted 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. Upon adoption, the guidance should be applied retrospectively to all prior periods presented in the financial statements. The Company adopted ASU No.2023-07 effective December 31, 2024 . Refer to Note 17, Segment Reporting for the inclusion of the new required disclosures.
Recently Issued Accounting Pronouncements	Recently Issued 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 report 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.

Summary of Significant Accoun_3

Summary of Significant Accounting Policies (Tables)	12 Months Ended
	Dec. 31, 2024
Accounting Policies [Abstract]
Schedule of Cash and Cash Equivalents and Restricted Cash	The following table reconciles cash and cash equivalents and restricted cash per the balance sheets to the statements of cash flows (in thousands): December 31, 2024 2023 Cash and cash equivalents $ 105,679 $ 394,583 Restricted cash, current 208 1,903 Restricted cash, non-current 2,418 2,418 Total $ 108,305 $ 398,904
Property and Equipment, Net	Estim ated useful lives for property and equipment are as follows: Estimated Useful Life Computer equipment 3 years Furniture and fixtures 7 years Lab equipment 7 years Leasehold improvements Lesser of estimated useful life or remaining lease term Equipment under finance lease Lesser of estimated useful life or remaining lease term
Schedule of Assumptions used in Black-Scholes Option Pricing Model for Stock Options Granted	The assumptions used in the Black-Scholes option pricing model for stock options granted for the years ending December 31, 2024, 2023 and 2022 were as follows: 2024 2023 2022 Expected term 5.5 - 6.27 years 5.5 - 6.25 years 6.0 - 6.3 years Expected volatility 86 % - 87 % 75 % - 80 % 68 % - 75 % Risk free interest rate 3.82 % - 4.56 % 3.92 % - 4.06 % 1.56 % - 3.88 % Expected dividend yield — % — % — %

Restricted Cash (Tables)

Restricted Cash (Tables)	12 Months Ended
	Dec. 31, 2024
Cash and Cash Equivalents [Abstract]
Schedule of Cash and Cash Equivalents and Restricted Cash	The following table reconciles cash and cash equivalents and restricted cash per the balance sheets to the statements of cash flows (in thousands): December 31, 2024 2023 Cash and cash equivalents $ 105,679 $ 394,583 Restricted cash, current 208 1,903 Restricted cash, non-current 2,418 2,418 Total $ 108,305 $ 398,904

Fair Value of Financial Instr_2

Fair Value of Financial Instruments (Tables)	12 Months Ended
	Dec. 31, 2024
Fair Value Disclosures [Abstract]
Schedule of Fair Value of Company's Financial Assets	fair value of the Company’s financial assets by level within the fair value hierarchy were as follows (in thousands): 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 $ — 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 $ —

Marketable Securities (Tables)

Marketable Securities (Tables)	12 Months Ended
	Dec. 31, 2024
Marketable Securities [Abstract]
Schedule of Available-for-sale Marketable Securities	Available-for-sale marketable securities were as follows (in thousands): December 31, 2024 Amortized Unrealized Unrealized Fair Value Government agency 519,125 1,007 ( 159 ) 519,973 Total $ 519,125 $ 1,007 $ ( 159 ) $ 519,973 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 December 31, 2024 and 2023 were as follows (in thousands): December 31, 2024 2023 Due in 1 year or less $ 481,696 $ 307,434 Due in 1 - 2 years 38,277 27,168 Total $ 519,973 $ 334,602

Prepaid Expenses and Other Cu_2

Prepaid Expenses and Other Current Assets (Tables)	12 Months Ended
	Dec. 31, 2024
Prepaid Expense and Other Assets, Current [Abstract]
Schedule of Prepaid Expenses and Other Current Assets	Prepaid expenses and other current assets consist of the following (in thousands): December 31, 2024 2023 Prepaid research and development costs $ 5,882 $ 6,764 Other prepaid expense and current assets 5,845 5,679 Total prepaid expenses and other current assets $ 11,727 $ 12,443

Property and Equipment, Net (Ta

Property and Equipment, Net (Tables)	12 Months Ended
	Dec. 31, 2024
Property, Plant and Equipment [Abstract]
Schedule of Property and Equipment	Property and equipment consist of the following (in thousands): December 31, 2024 2023 Lab equipment $ 16,033 $ 11,502 Leasehold improvements 38,373 27,153 Lab equipment under finance leases 230 714 Computer equipment 906 661 Furniture and fixtures 158 159 Construction in progress 200 7,792 Property and equipment, gross 55,900 47,981 Less: accumulated depreciation and amortization ( 9,444 ) ( 5,253 ) Property and equipment, net $ 46,456 $ 42,728

Collaboration Agreement (Tables

Collaboration Agreement (Tables)	12 Months Ended
	Dec. 31, 2024
Collaboration Agreement [Abstract]
Schedule of Balances in Contract Liability	As of December 31, 2024, the balances in contract liability were as follows (in thousands): Contract liability December 31, 2024 Beginning balance at January 1, 2024 $ 221,206 Cash received, net 65,640 Less: Revenue recognized ( 107,936 ) Reclass to other liabilities ( 43,859 ) Ending balance at December 31, 2024 135,051 Less: current portion 59,056 Noncurrent portion $ 75,995

Leases (Tables)

Leases (Tables)	12 Months Ended
	Dec. 31, 2024
Leases [Abstract]
Summary of Total Lease Costs	The Company's total lease costs were as follows (in thousands): Year Ended December 31, 2024 2023 2022 Finance lease costs: Right-of-use assets with no alternative future use $ 794 $ 18,871 $ 63,321 Amortization of right-of-use assets — 102 102 Interest on lease liabilities 1,030 3,846 1,720 Operating lease costs 5,437 6,159 3,832 Short-term lease costs 19 32 758 Variable lease costs 7,491 8,043 1,769 Total lease costs $ 14,771 $ 37,053 $ 71,502
Summary of Future Minimum Lease Payments	Future minimum lease payments were as follows (in thousands) as of December 31, 2024: Operating Leases 2025 $ 7,606 2026 7,835 2027 8,071 2028 8,315 2029 8,567 Thereafter 42,472 Total lease payments 82,866 Less: Imputed interest ( 29,016 ) Present value of total lease liabilities $ 53,850
Summary of Supplemental Cash Flow Information Related to Leases	Supplemental cash flow information related to leases is as follows (in thousands) for the year ended December 31, 2024 and 2023: 2024 2023 2022 Cash paid for amounts included in the measurement of lease liabilities: Operating cash flows from finance leases $ 6,591 $ 8,770 $ 1,708 Operating cash flows from operating leases 7,291 4,603 1,947 Financing cash flows from finance leases 39,846 29,392 9,675 Right-of-use assets obtained in exchange for new finance lease liabilities 794 18,871 63,321 Right-of-use assets obtained in exchange for new operating lease liabilities — ( 550 ) 29,562
Summary of Weighted-Average Remaining Lease Terms and Discount Rates	Weighted-average remaining lease terms and discount rates were as follows as of December 31, 2024: Weighted-average remaining lease term — operating leases 9.6 years Weighted-average discount rate — operating leases 9.8 %

Accrued Liabilities (Tables)

Accrued Liabilities (Tables)	12 Months Ended
	Dec. 31, 2024
Accrued Liabilities, Current [Abstract]
Schedule of Accrued Liabilities	Accrued liabilities consist of the following (in thousands): December 31, 2024 2023 Research and development accrued expenses $ 16,507 $ 4,559 Accrued bonus 10,438 5,529 Other liabilities 8,531 8,214 Liabilities to related party vendor 21,240 — Total accrued liabilities $ 56,716 $ 18,302

Share-Based Compensation (Table

Share-Based Compensation (Tables)	12 Months Ended
	Dec. 31, 2024
Share-Based Compensation Arrangement by Share-Based Payment Award [Line Items]
Schedule of Share-based Compensation Expense	Share-based compensation expense by type of award was as follows (in thousands): Year Ended December 31, 2024 2023 2022 Stock options $ 28,057 $ 20,661 $ 14,859 Restricted stock units 27,257 12,254 4,056 Restricted stock units - chief executive officer 5,266 8,336 2,548 ESPP 506 538 81 Total share-based compensation expense $ 61,086 $ 41,789 $ 21,544 Share-based compensation expense as reflected in the consolidated statement of operations and comprehensive loss was as follows (in thousands): Year Ended December 31, 2024 2023 2022 Research and development $ 21,359 $ 11,003 $ 7,007 General and administrative 39,727 30,786 14,537 Total share-based compensation expense $ 61,086 $ 41,789 $ 21,544
Summary of Stock Option Activity	A summary of stock option activity for awards under the 2017 Plan and the 2022 Plan is presented below: Options Outstanding and Exercisable Shares Subject to Outstanding Options Weighted Weighted Aggregate Outstanding as of January 1, 2024 7,811,231 $ 12.46 7.8 $ 336,174 Options Granted 1,031,954 56.22 Options Forfeited ( 145,261 ) 11.10 Options Exercised ( 1,457,826 ) 9.75 Outstanding as of December 31, 2024 7,240,098 $ 19.28 6.9 $ 415,634 Exercisable as of December 31, 2024 4,712,405 $ 13.30 6.6 $ 298,737 (1) The aggregate intrinsic value is calculated as the difference between the exercise price of the underlying options and the fair value of the common stock for those options for which the exercise price was below the market price as of December 31, 2024 .
Schedule of Assumptions used in Black-Scholes Option Pricing Model for Stock Options Granted	The assumptions used in the Black-Scholes option pricing model for stock options granted for the years ending December 31, 2024, 2023 and 2022 were as follows: 2024 2023 2022 Expected term 5.5 - 6.27 years 5.5 - 6.25 years 6.0 - 6.3 years Expected volatility 86 % - 87 % 75 % - 80 % 68 % - 75 % Risk free interest rate 3.82 % - 4.56 % 3.92 % - 4.06 % 1.56 % - 3.88 % Expected dividend yield — % — % — %
Summary of Restricted Stock Units Activity	A summary of RSU activity for awards under the 2022 Plan, excluding the 2023 RSU Award and 2021 RSU Award (each defined below) granted to the chief executive officer, is presented below: Shares Subject to Outstanding Awards Weighted Average Grant Date Fair Value Outstanding as of January 1, 2024 1,416,446 $ 25.47 RSUs Granted 981,531 61.66 RSUs Vested ( 528,711 ) 23.76 RSUs Forfeited ( 57,421 ) 32.55 Outstanding as of December 31, 2024 1,811,845 $ 45.35
January 2023 RSU Grant
Share-Based Compensation Arrangement by Share-Based Payment Award [Line Items]
Schedule of Assumptions used in Determining Fair Value for Stock Options and RSU Awards	Semi-Annual Measurement Change in Control Time to award end date 10 years 5 years Equity volatility 75 % 75 % Risk-free interest rate 3.8 % 3.9 % Fair value of the 2023 RSU award (in thousands) $ 13,811 $ 10,999
June and December 2021 RSU Grant
Share-Based Compensation Arrangement by Share-Based Payment Award [Line Items]
Schedule of Assumptions used in Determining Fair Value for Stock Options and RSU Awards	The assumptions used in the Monte Carlos simulation models to determine the grant date fair value of the 2021 RSU Award for each of the three performance condition scenarios were as follows: Change in Control IPO Change in Control Date of grant June 9, 2021 December 7, 2021 December 7, 2021 Time to liquidity event (years) 1.56 - 3.06 10.00 1.33 Equity volatility 100 % - 110 % 70 % 65 % Risk-free interest rate 0.1 % - 0.3 % 1.5 % 0.4 % Discount for lack of marketability 26 % - 32 % 5 % 5 % Fair value of the 2021 RSU award (in thousands) $ 1,580 $ 10,300 $ 150

Employee Stock Purchase Plan _2

Employee Stock Purchase Plan (ESPP) (Tables)	12 Months Ended
	Dec. 31, 2024
Employee Stock Purchase Plan
Share-Based Compensation Arrangement by Share-Based Payment Award [Line Items]
Schedule of Assumptions used in Black-Scholes Option Pricing Model for ESPP Plan	The assumptions used in the Black-Scholes option pricing model for the ESPP plan for the year ending December 31, 2024, 2023 and 2022 were as follows: 2024 2023 2022 Expected term 0.5 years 0.5 years 0.5 years Expected volatility 45 % - 65 % 65 % - 68 % 132 % Risk free interest rate 4.44 % - 5.46 % 5.26 % - 5.46 % 4.40 % Expected dividend yield — % — % — %

Net Loss Per Share Attributab_2

Net Loss Per Share Attributable to Common Stockholders (Tables)	12 Months Ended
	Dec. 31, 2024
Earnings Per Share [Abstract]
Schedule of Securities Excluded From Computation of Earnings Per Share	December 31, 2024 2023 2022 Options to purchase common stock 7,240,098 7,811,231 8,053,704 Restricted stock units 1,811,845 1,416,446 927,954 Restricted stock units - executive officer 1,447,804 1,447,804 952,804 Employee Stock Purchase Plan (ESPP) 3,959 2,995 5,651 Total 10,503,706 10,678,476 9,940,113

Income Taxes (Tables)

Income Taxes (Tables)	12 Months Ended
	Dec. 31, 2024
Income Tax Disclosure [Abstract]
Summary of Provision for Income Taxes	The Company’s provision for income taxes consists of the following (in thousands): Year Ended December 31, 2024 2023 2022 Current income tax provision (expense) benefit: U.S. federal $ ( 1,910 ) $ ( 427 ) $ — State ( 153 ) ( 273 ) — Total $ ( 2,063 ) $ ( 700 ) $ —
Schedule of Reconciliation of Statutory U.S. Federal Rate and Effective Rate	A reconciliation of the statutory U.S. federal rate and effective rate is as follows: Year Ended December 31, 2024 2023 2022 U.S. federal tax 21.0 % 21.0 % 21.0 % State tax, net of federal benefit 0.3 0.6 6.6 Change in valuation allowance ( 42.9 ) ( 2.8 ) ( 26.9 ) Nondeductible compensation ( 17.0 ) ( 15.2 ) ( 0.2 ) Research and development tax credits 26.3 16.3 0.0 Stock based compensation 16.5 10.2 0.4 Change in state deferred income tax rate ( 0.5 ) ( 27.2 ) 0.0 Changes in unrecognized tax benefits ( 5.7 ) ( 4.8 ) 0.0 Change in tax rates and other 0.1 0.9 ( 0.9 ) Effective income tax rate ( 1.9 )% ( 1.0 )% 0.0 %
Schedule of Deferred Tax Assets and Liabilities	The significant components of the Company’s deferred income tax assets (liabilities) were as follows (in thousands): December 31, 2024 2023 Deferred income tax assets: U.S. federal net operating loss carryforward $ 10,692 $ 29,929 State net operating loss carryforward 287 1,110 Research and development expenditures 65,346 44,047 Research and development credits 26,838 9,829 Lease liabilities - operating 11,641 12,710 Stock based compensation 8,117 4,600 Accruals and others 2,371 1,323 Deferred Revenue 24,423 — Gross deferred income tax assets 149,715 103,548 Less: Valuation allowance ( 137,302 ) ( 91,841 ) Total deferred income tax assets 12,413 11,707 Deferred income tax liabilities: Depreciation ( 6,692 ) ( 4,930 ) Right-of-use asset - operating ( 5,143 ) ( 5,903 ) Section 481(a) adjustment ( 578 ) ( 874 ) Total deferred income tax liabilities ( 12,413 ) ( 11,707 ) Net deferred income tax assets (liabilities) $ — $ —
Schedule of Unrecognized Tax Benefits	The Company had $ 9.6 million and $ 3.5 million, and no unrecognized tax benefits as of December 31, 2024, 2023 and 2022, respectively. Of the unrecognized tax benefits as of December 31, 2024, 2023 and 2022, none would affect the Company’s effective tax rate if recognized due to the Company's full valuation allowance position. December 31, 2022 $ — Additions based on tax positions related to 2023 809 Additions for tax positions of prior years 2,641 December 31, 2023 3,450 Additions based on tax positions related to 2024 3,177 Additions for tax positions of prior years 2,951 December 31, 2024 $ 9,578

Segment Reporting (Tables)

Segment Reporting (Tables)	12 Months Ended
	Dec. 31, 2024
Segment Reporting [Abstract]
Schedule of Segment Reporting	The table below provides information about the Company’s segment (in thousands): Year Ended December 31, 2024 2023 2022 Collaboration revenue $ 107,936 $ 110,319 $ — Operating expenses: Research and development anito-cel in rrMM 50,141 73,530 96,513 ACLX-001 1,975 2,939 8,764 ACLX-002 14,294 5,667 6,458 Other research and development costs 21,364 3,701 5,467 Internal costs [1] 69,319 48,012 32,353 General and administrative 88,414 66,350 41,704 Total operating expenses 245,507 200,199 191,259 Loss from operations ( 137,571 ) ( 89,880 ) ( 191,259 ) Interest and other income (expense), net 33,322 23,695 4,300 Interest expense ( 1,030 ) ( 3,842 ) ( 1,720 ) Total other income, net 32,292 19,853 2,580 Income tax expense ( 2,069 ) ( 663 ) — Net loss $ ( 107,348 ) $ ( 70,690 ) $ ( 188,679 ) [1] Internal costs primarily consist of employee-related costs, including salaries, related benefits, and share-based compensation expense, as well as facility allocation and depreciation expense.

Nature of the Business - Additi

Nature of the Business - Additional Information (Details) - USD ($) $ / shares in Units, $ in Thousands			1 Months Ended		12 Months Ended
	Jun. 21, 2022	Feb. 08, 2022	Dec. 31, 2023	Jan. 31, 2023	Dec. 31, 2023	Dec. 31, 2022	Dec. 31, 2024
Class of Stock [Line Items]
Accumulated Deficit			$ (389,480)		$ (389,480)		$ (496,828)
Proceeds from issuance of private placement and non-refundable upfront payment			285,000	$ 325,000
Cash, cash equivalents and marketable securities							$ 625,700
Kite Collaboration Agreement
Class of Stock [Line Items]
Non-refundable upfront payment received			85,000	225,000
IPO
Class of Stock [Line Items]
Proceeds from issuance of private placement						$ 127,283
IPO | Common Stock
Class of Stock [Line Items]
Number of shares issued		9,487,500				9,487,500
Additional stock issued during period shares exercised by underwriters with option to purchase		1,237,500
Sale of stock, price per share		$ 15
Net proceeds from initial public offering		$ 127,300
Cash paid for underwriting discounts and commissions and other offering expenses		$ 15,000
Proceeds from issuance of private placement						$ 9
Follow-on offering
Class of Stock [Line Items]
Proceeds from issuance of private placement						$ 120,719
Follow-on offering | Common Stock
Class of Stock [Line Items]
Number of shares issued	8,050,000					8,050,000
Additional stock issued during period shares exercised by underwriters with option to purchase	1,050,000
Sale of stock, price per share	$ 16
Net proceeds from initial public offering	$ 120,700
Cash paid for underwriting discounts and commissions and other offering expenses	$ 8,100
Proceeds from issuance of private placement						$ 8
Private Placement
Class of Stock [Line Items]
Proceeds from issuance of private placement					$ 299,706	$ 9,958
Private Placement | Gilead Common Stock Purchase Agreement
Class of Stock [Line Items]
Proceeds from issuance of private placement			$ 200,000	$ 100,000
Private Placement | Common Stock
Class of Stock [Line Items]
Number of shares issued					6,720,803	590,318
Proceeds from issuance of private placement					$ 7	$ 1

Summary of Significant Accoun_4

Summary of Significant Accounting Policies - Additional Information (Details)	12 Months Ended
	Dec. 31, 2024 USD ($) Segment	Dec. 31, 2023 USD ($)
Summary Of Significant Accounting Policies Line Items
Expected dividend yield	0%
Unrecognized tax benefits income tax penalties expense	$ 0	$ 0
Unrecognized tax benefits income tax interest expense	$ 0	$ 0
Number of operating segment | Segment	1
ASU 2023-07
Summary Of Significant Accounting Policies Line Items
Change in accounting principle, accounting standards update, adopted date	Dec. 31, 2024
Change in accounting principle, accounting standards update, adopted [true false]	true

Summary of Significant Accoun_5

Summary of Significant Accounting Policies - Summary of Cash and Cash Equivalents and Restricted Cash (Details) - USD ($) $ in Thousands	Dec. 31, 2024	Dec. 31, 2023	Dec. 31, 2022	Dec. 31, 2021
Cash, Cash Equivalents, Restricted Cash, and Restricted Cash Equivalents [Abstract]
Cash and cash equivalents	$ 105,679	$ 394,583
Restricted cash, current	208	1,903
Restricted cash, non-current	2,418	2,418
Total	$ 108,305	$ 398,904	$ 66,680	$ 31,032

Summary of Significant Accoun_6

Summary of Significant Accounting Policies - Summary of Property and Equipment, Net (Details)	Dec. 31, 2024
Computer Equipment
Property, Plant and Equipment [Line Items]
Estimated Useful Life	3 years
Furniture and Fixtures
Property, Plant and Equipment [Line Items]
Estimated Useful Life	7 years
Lab Equipment
Property, Plant and Equipment [Line Items]
Estimated Useful Life	7 years
Leasehold Improvements
Property, Plant and Equipment [Line Items]
Estimated Useful Lives	Leasehold Improvements
Equipment under finance lease
Property, Plant and Equipment [Line Items]
Estimated Useful Lives	Equipment under finance lease

Summary of Significant Accoun_7

Summary of Significant Accounting Policies - Schedule of Assumptions used in Black-Scholes Option Pricing Model for Stock Options Granted (Details)	12 Months Ended
	Dec. 31, 2024	Dec. 31, 2023	Dec. 31, 2022
Share-Based Compensation Arrangement by Share-Based Payment Award [Line Items]
Expected dividend yield	0%
Stock Options
Share-Based Compensation Arrangement by Share-Based Payment Award [Line Items]
Expected volatility, Minimum	86%	75%	68%
Expected volatility, Maximum	87%	80%	75%
Risk free interest rate, Minimum	3.82%	3.92%	1.56%
Risk free interest rate, Maximum	4.56%	4.06%	3.88%
Expected dividend yield	0%	0%	0%
Minimum | Stock Options
Share-Based Compensation Arrangement by Share-Based Payment Award [Line Items]
Expected term	5 years 6 months	5 years 6 months	6 years
Maximum | Stock Options
Share-Based Compensation Arrangement by Share-Based Payment Award [Line Items]
Expected term	6 years 3 months 7 days	6 years 3 months	6 years 3 months 18 days

Fair Value of Financial Instr_3

Fair Value of Financial Instruments - Schedule of Fair Value of Company's Financial Assets (Details) - USD ($) $ in Thousands	Dec. 31, 2024	Dec. 31, 2023
Assets
Marketable securities	$ 519,973	$ 334,602
Level 1 | Recurring
Assets
Money market fund (cash equivalent)	104,579	393,096
Money market fund (short-term restricted cash)	208	1,903
Total assets measured at fair value	104,787	394,999
Level 2 | Recurring
Assets
Total assets measured at fair value	522,391	337,020
Level 2 | Recurring | Certificates of Deposit
Assets
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	$ 519,973	$ 301,884

Marketable Securities - Schedul

Marketable Securities - Schedule of Available-for-sale Marketable Securities (Details) - USD ($) $ in Thousands	Dec. 31, 2024	Dec. 31, 2023
Marketable Securities [Line Items]
Amortized costs	$ 519,125	$ 334,056
Gross Unrealized Gains	1,007	584
Gross Unrealized Loss	(159)	(38)
Fair Value	519,973	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
U.S. Government Agency
Marketable Securities [Line Items]
Amortized costs	519,125	301,315
Gross Unrealized Gains	1,007	584
Gross Unrealized Loss	(159)	(16)
Fair Value	$ 519,973	$ 301,884

Marketable Securities - Sched_2

Marketable Securities - Schedule of Fair Value of Available-For-Sale Marketable Securities by Contractual Maturity Date (Details) - USD ($) $ in Thousands	Dec. 31, 2024	Dec. 31, 2023
Marketable Securities [Abstract]
Due in 1 year or less	$ 481,696	$ 307,434
Due in 1 - 2 years	38,277	27,168
Total	$ 519,973	$ 334,602

Marketable Securities - Additio

Marketable Securities - Additional Information (Details) $ in Millions	Dec. 31, 2024 USD ($) Condition	Dec. 31, 2023 USD ($) Condition
Marketable Securities [Line Items]
Number of securities in an unrealized loss position | Condition	9	8
Aggregate fair value an unrealized loss position	$ 108.4	$ 61.5
Allowance for credit losses	0	0
Prepaid Expenses and Other Current Assets
Marketable Securities [Line Items]
Accrued interest receivable	$ 2.5	$ 1.4

Prepaid Expenses and Other Cu_3

Prepaid Expenses and Other Current Assets - Schedule of Prepaid Expenses and Other Current Assets (Details) - USD ($) $ in Thousands	Dec. 31, 2024	Dec. 31, 2023
Prepaid Expense and Other Assets, Current [Abstract]
Prepaid research and development costs	$ 5,882	$ 6,764
Other prepaid expense and current assets	5,845	5,679
Total prepaid expenses and other current assets	$ 11,727	$ 12,443

Property and Equipment, Net - S

Property and Equipment, Net - Schedule of Property and Equipment (Details) - USD ($) $ in Thousands	Dec. 31, 2024	Dec. 31, 2023
Property, Plant and Equipment [Line Items]
Property and equipment, gross	$ 55,900	$ 47,981
Less: accumulated depreciation and amortization	(9,444)	(5,253)
Property and equipment, net	46,456	42,728
Lab Equipment
Property, Plant and Equipment [Line Items]
Property and equipment, gross	16,033	11,502
Leasehold Improvements
Property, Plant and Equipment [Line Items]
Property and equipment, gross	38,373	27,153
Lab Equipment under Finance Leases
Property, Plant and Equipment [Line Items]
Property and equipment, gross	230	714
Computer Equipment
Property, Plant and Equipment [Line Items]
Property and equipment, gross	906	661
Furniture and Fixtures
Property, Plant and Equipment [Line Items]
Property and equipment, gross	158	159
Construction in Progress
Property, Plant and Equipment [Line Items]
Property and equipment, gross	$ 200	$ 7,792

Property and Equipment, Net - A

Property and Equipment, Net - Additional Information (Details) - USD ($) $ in Millions	12 Months Ended
	Dec. 31, 2024	Dec. 31, 2023	Dec. 31, 2022
Property, Plant and Equipment [Abstract]
Depreciation and amortization expense	$ 5.2	$ 2	$ 1.3

Related Parties - Additional In

Related Parties - Additional Information (Details) - USD ($) $ / shares in Units, $ in Thousands	1 Months Ended		12 Months Ended
	Dec. 31, 2023	Jan. 31, 2023	Dec. 31, 2024	Dec. 31, 2023	Dec. 31, 2022
Related Party Transaction [Line Items]
Proceeds from issuance of private placement				$ 299,706	$ 9,958
Contract liability	$ 221,206		$ 135,051	221,206
Contract liability, long-term portion	$ 170,673		75,995	170,673
Collaboration revenue from related party			$ 107,936	$ 110,319
Gilead
Related Party Transaction [Line Items]
Percentage of ownership held			13%
Contract liability			$ 135,100
Contract liability, long-term portion			$ 76,000
Gilead Common Stock Purchase Agreement
Related Party Transaction [Line Items]
Shares purchased			3,478,261
Shares issued, price per share			$ 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			$ 107,900

Collaboration Agreement - Addit

Collaboration Agreement - Additional Information (Details) - USD ($)	1 Months Ended		12 Months Ended
	Dec. 31, 2023	Jan. 31, 2023	Dec. 31, 2024	Dec. 31, 2023	Dec. 31, 2022	Dec. 28, 2023	Jan. 26, 2023
Collaborative Arrangement and Arrangement Other than Collaborative [Line Items]
Proceeds from issuance of private placement				$ 299,706,000	$ 9,958,000
Contract with customer, performance obligation satisfied in previous period			$ 0
Unrecognized revenue			50,200,000
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 clinical milestone			530,000,000
Potential payments of regulatory milestone			935,000,000
Potential payments of commercial milestone			$ 507,500,000
Kite Collaboration Agreement
Collaborative Arrangement and Arrangement Other than Collaborative [Line Items]
Non-refundable upfront payment received	$ 85,000,000	$ 225,000,000
Reduction of deemed discount on shares sold							$ 15,300,000
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%
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%
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
Shares issued, price per share			$ 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			$ 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

Collaboration Agreement - Sched

Collaboration Agreement - Schedule of Balances in Contract Liability (Details) - USD ($) $ in Thousands	12 Months Ended
	Dec. 31, 2024	Dec. 31, 2023
Collaborative Arrangement and Arrangement Other than Collaborative [Line Items]
Beginning balance	$ 221,206
Cash received, net	65,640
Less: Revenue recognized	(107,936)	$ (110,319)
Reclass to other liabilities	(43,859)
Ending balance	135,051	221,206
Less: current portion	59,056	50,533
Noncurrent portion	$ 75,995	$ 170,673

Leases - Additional Information

Leases - Additional Information (Details) $ in Thousands	1 Months Ended			12 Months Ended
	Sep. 30, 2023 USD ($)	Jul. 31, 2022 USD ($) ft²	May 31, 2022 USD ($) ft²	Dec. 31, 2024 USD ($)	Dec. 31, 2023 USD ($)	Dec. 31, 2022 USD ($)
Lessee, Lease, Description [Line Items]
Right-of-use assets with no alternative future use				$ 794	$ 18,871	$ 63,321
Lonza
Lessee, Lease, Description [Line Items]
Prior notification period to terminate arrangement				12 months
Finance lease expiration date				2024-12
Undiscounted finance lease value	$ 51,700
Discounted value using the expected payment timeline	$ 48,500
Incremental borrowing rate	10.80%
Increase in lease liability	$ 15,900
Redwood, California
Lessee, Lease, Description [Line Items]
Square feet of space | ft²			51,822
Lease term			11 years 8 months 12 days
Option to extend lease				The Redwood City lease provides for an optional five-year extension.
Option to extend lease term			5 years
Lease includes allowance for tenant improvements			$ 9,800
Rockville, Maryland
Lessee, Lease, Description [Line Items]
Square feet of space | ft²		57,902
Lease term		12 years 10 months 24 days
Option to extend lease				The Rockville lease provides for optional two five-year extensions.
Option to extend lease term		5 years
Lease includes allowance for tenant improvements		$ 12,100			2,800
Tenant Improvement Allowance					$ 2,900
Office and Laboratory Space | Rockville, Maryland
Lessee, Lease, Description [Line Items]
Lease expiration year				2030

Leases - Summary of Lease Costs

Leases - Summary of Lease Costs (Details) - USD ($) $ in Thousands	12 Months Ended
	Dec. 31, 2024	Dec. 31, 2023	Dec. 31, 2022
Leases [Abstract]
Right-of-use assets with no alternative future use	$ 794	$ 18,871	$ 63,321
Amortization of right-of-use assets		102	102
Interest on lease liabilities	1,030	3,846	1,720
Operating lease costs	5,437	6,159	3,832
Short-term lease costs	19	32	758
Variable lease costs	7,491	8,043	1,769
Total lease costs	$ 14,771	$ 37,053	$ 71,502

Leases - Summary of Future Mini

Leases - Summary of Future Minimum Lease Payments (Details) $ in Thousands	Dec. 31, 2024 USD ($)
Leases [Abstract]
Operating Leases, 2025	$ 7,606
Operating Leases, 2026	7,835
Operating Leases, 2027	8,071
Operating Leases, 2028	8,315
Operating Leases, 2029	8,567
Operating Leases, Thereafter	42,472
Total operating lease payments	82,866
Less: Operating Leases, imputed interest	(29,016)
Present value of total operating lease liabilities	$ 53,850

Leases - Supplemental Cash Flow

Leases - Supplemental Cash Flow Information Related to Leases (Details) - USD ($) $ in Thousands	12 Months Ended
	Dec. 31, 2024	Dec. 31, 2023	Dec. 31, 2022
Lessee Disclosure [Abstract]
Operating cash flows from finance leases	$ 6,591	$ 8,770	$ 1,708
Operating cash flows from operating leases	7,291	4,603	1,947
Financing cash flows from finance leases	39,846	29,392	9,675
Right-of-use assets obtained in exchange for new finance lease liabilities	$ 794	18,871	63,321
Right-of-use assets obtained in exchange for new operating lease liabilities		$ (550)
Right-of-use assets obtained in exchange for new operating lease liabilities			$ 29,562

Leases - Summary of Weighted-Av

Leases - Summary of Weighted-Average Remaining Lease Terms and Discount Rates (Details)	Dec. 31, 2024
Leases [Abstract]
Weighted-average remaining lease term - operating leases	9 years 7 months 6 days
Weighted-average discount rate - operating leases	9.80%

Accrued Liabilities - Schedule

Accrued Liabilities - Schedule of Accrued Liabilities (Details) - USD ($) $ in Thousands	Dec. 31, 2024	Dec. 31, 2023
Accrued Liabilities, Current [Abstract]
Research and development accrued expenses	$ 16,507	$ 4,559
Accrued bonus	10,438	5,529
Other liabilities	8,531	8,214
Liabilities to related party vendor	21,240
Total accrued liabilities	$ 56,716	$ 18,302

Commitments and Contingencies -

Commitments and Contingencies - Additional Information (Details) $ in Millions	12 Months Ended
	Dec. 31, 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 commercial milestones to be paid by company	$ 52

Redeemable Convertible Prefer_2

Redeemable Convertible Preferred Stock and Stockholders' Equity - Additional Information (Details) - USD ($)				1 Months Ended		12 Months Ended
	Dec. 28, 2023	Jan. 26, 2023	Feb. 08, 2022	Dec. 31, 2023	Jan. 31, 2023	Dec. 31, 2024	Dec. 31, 2023	Dec. 31, 2022	May 31, 2023
Class of Stock [Line Items]
Common stock voting rights						one vote
Common stock aggregate offering maximum amount under at the market program									$ 350,000,000
Proceeds from issuance of private placement							$ 299,706,000	$ 9,958,000
Gilead Common Stock Purchase Agreement
Class of Stock [Line Items]
Shares issued, price per share						$ 28.75
Kite Collaboration Agreement
Class of Stock [Line Items]
Discount on shares sold price per share		$ 4.39
Premium on shares sold price per share	$ 4.8
Reduction of deemed discount on shares sold		$ 15,300,000
Increase in deemed premium on shares sold	$ 15,600,000
Common Stock
Class of Stock [Line Items]
Dividends declared or paid						$ 0
Redeemable Convertible Preferred Stock
Class of Stock [Line Items]
Preferred stock, shares authorized				200,000,000		200,000,000	200,000,000
Preferred stock par value				$ 0.0001		$ 0.0001	$ 0.0001
Preferred stock, shares outstanding				0		0	0
IPO
Class of Stock [Line Items]
Issuance of common stock, value								$ 127,283,000
IPO | Common Stock
Class of Stock [Line Items]
Number of shares issued			9,487,500					9,487,500
Sale of stock, price per share			$ 15
Issuance of common stock, value								$ 9,000
IPO | Redeemable Convertible Preferred Stock
Class of Stock [Line Items]
Shares issued upon conversion of preferred stock						24,785,564
At-the-Market Offering
Class of Stock [Line Items]
Sale of stock, number of shares issued in transaction						0
Private Placement
Class of Stock [Line Items]
Issuance of common stock, value							$ 299,706,000	$ 9,958,000
Private Placement | Gilead Common Stock Purchase Agreement
Class of Stock [Line Items]
Issuance of common stock, value				$ 200,000,000	$ 100,000,000
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
Private Placement | Common Stock
Class of Stock [Line Items]
Number of shares issued							6,720,803	590,318
Issuance of common stock, value							$ 7,000	$ 1,000

Common Stock - Additional Infor

Common Stock - Additional Information (Details) - USD ($)			12 Months Ended
	Jun. 21, 2022	Feb. 08, 2022	Dec. 31, 2024	Dec. 31, 2023	Dec. 31, 2022
Class of Stock [Line Items]
Proceeds from issuance of private placement				$ 299,706,000	$ 9,958,000
Common stock, shares authorized			1,000,000,000	1,000,000,000
Common stock voting rights			one vote
Common Stock
Class of Stock [Line Items]
Dividends declared or paid			$ 0
Common Stock | Private Placement
Class of Stock [Line Items]
Number of shares issued				6,720,803	590,318
Common Stock | IPO
Class of Stock [Line Items]
Number of shares issued		9,487,500			9,487,500
Additional stock issued during period shares exercised by underwriters with option to purchase		1,237,500
Sale of stock, price per share		$ 15
Net proceeds from initial public offering		$ 127,300,000
Cash paid for underwriting discounts and commissions and other offering expenses		$ 15,000,000
Common Stock | Follow-on offering
Class of Stock [Line Items]
Number of shares issued	8,050,000				8,050,000
Additional stock issued during period shares exercised by underwriters with option to purchase	1,050,000
Sale of stock, price per share	$ 16
Net proceeds from initial public offering	$ 120,700,000
Cash paid for underwriting discounts and commissions and other offering expenses	$ 8,100,000

Share-Based Compensation - Addi

Share-Based Compensation - Additional Information (Details) $ / shares in Units, $ in Thousands		1 Months Ended		12 Months Ended
	Feb. 27, 2025 shares	Jan. 31, 2023 shares	Jun. 30, 2021 shares	Dec. 31, 2024 USD ($) Condition Scenario $ / shares shares	Dec. 31, 2023 USD ($) $ / shares shares	Dec. 31, 2022 USD ($) $ / shares
2022 Equity Incentive Plan
Share-based Compensation Arrangement by Share-based Payment Award [Line Items]
Number of Shares, Granted | shares				11,667,993
Board of Directors
Share-based Compensation Arrangement by Share-based Payment Award [Line Items]
Anniversary period				10 years
Board of Directors | 2022 Equity Incentive Plan
Share-based Compensation Arrangement by Share-based Payment Award [Line Items]
Reserved shares of common stock for issuance | shares				6,502,174
Percentage increase in common stock reserve for future issuance				5%
Stock Options
Share-based Compensation Arrangement by Share-based Payment Award [Line Items]
weighted-average grant-date fair value | $ / shares				$ 42.38	$ 21.86	$ 9.95
Aggregate grant date fair value of stock options vested				$ 27,700	$ 21,400	$ 14,500
Remaining compensation expense, expected to be recognized over a weighted average period				1 year 9 months 25 days
Aggregate intrinsic value, options exercised				$ 103,500	47,100	10,900
Stock Options | 2017 and 2022 Equity Incentive Plan
Share-based Compensation Arrangement by Share-based Payment Award [Line Items]
Expiration period				10 years
Unrecognized compensation cost related to unvested share-based compensation arrangements				$ 51,800
Aggregate intrinsic value, exercisable				$ 298,737
Stock Options | 2017 and 2022 Equity Incentive Plan | Minimum
Share-based Compensation Arrangement by Share-based Payment Award [Line Items]
Vesting period				1 year
Stock Options | 2017 and 2022 Equity Incentive Plan | Maximum
Share-based Compensation Arrangement by Share-based Payment Award [Line Items]
Vesting period				4 years
Restricted Stock Units
Share-based Compensation Arrangement by Share-based Payment Award [Line Items]
Total unamortized share-based compensation				$ 56,500
Compensation expense, expected to be recognized over average remaining vesting period				1 year 10 months 2 days
Aggregate intrinsic value				$ 139,000
Grant-date fair value				$ 13,400	$ 5,400	$ 0
Restricted Stock Units | 2022 Equity Incentive Plan
Share-based Compensation Arrangement by Share-based Payment Award [Line Items]
Restricted stock units, granted | shares				981,531
Restricted stock units, outstanding | shares				1,811,845	1,416,446
Restricted stock units, vested | shares				528,711
Weighted average grant date fair value per share | $ / shares				$ 23.76
Restricted Stock Units | 2022 Equity Incentive Plan | Minimum
Share-based Compensation Arrangement by Share-based Payment Award [Line Items]
Vesting period				3 years
Restricted Stock Units | 2022 Equity Incentive Plan | Maximum
Share-based Compensation Arrangement by Share-based Payment Award [Line Items]
Vesting period				4 years
Restricted Stock Units | January 2023 RSU Grant | Chief Executive Officer
Share-based Compensation Arrangement by Share-based Payment Award [Line Items]
Restricted stock units, granted | shares		495,000
Vesting description				Each RSU granted in the 2023 RSU Award entitles the chief executive officer to one share of common stock upon vesting subject to the service, performance, and market conditions.
Restricted stock units, outstanding | shares				495,000
Restricted stock units, vested | shares	347,255			0
Number of vesting scenarios | Scenario				2
Restricted Stock Units | January 2023 RSU Grant | Semi Annual Measurement
Share-based Compensation Arrangement by Share-based Payment Award [Line Items]
Fair value of the RSU award				$ 13,811
Restricted Stock Units | January 2023 RSU Grant | Semi Annual Measurement | Chief Executive Officer
Share-based Compensation Arrangement by Share-based Payment Award [Line Items]
Anticipated service period				10 years
Fair value of the RSU award				$ 13,800
Restricted Stock Units | January 2023 RSU Grant | IPO | Chief Executive Officer
Share-based Compensation Arrangement by Share-based Payment Award [Line Items]
Vesting description				The Company’s Enterprise Value is determined using the total market capitalization of the Company based on the average closing trading price of one share of the Company’s common stock over the 60-day period ending on the day prior to the applicable semi-annual measurement date, less cash. On the semi-annual measurement date, (i) one-sixth of the award will vest if a minimum Enterprise Value of $2.5 billion is achieved, (ii) all of the award will vest if a $5.0 billion Enterprise Value is achieved, and (iii) a portion of the award will vest based on a straight-line interpolation if an Enterprise Value of between $2.5 billion and $5.0 billion is achieved.
Restricted Stock Units | January 2023 RSU Grant | Change in Control
Share-based Compensation Arrangement by Share-based Payment Award [Line Items]
Fair value of the RSU award				$ 10,999
Restricted Stock Units | January 2023 RSU Grant | Change in Control | Chief Executive Officer
Share-based Compensation Arrangement by Share-based Payment Award [Line Items]
Vesting description				Upon a change in control, (i) one-sixth of the award will vest if a minimum deal consideration of $2.5 billion is achieved, (ii) all of the award will vest if a $5.0 billion deal consideration is achieved, and (iii) a portion of the award will vest based on a straight-line interpolation if a deal consideration of between $2.5 billion and $5.0 billion is achieved.
Restricted Stock Units | June and December 2021 RSU Grant
Share-based Compensation Arrangement by Share-based Payment Award [Line Items]
Number of performance condition scenarios | Condition				3
Restricted Stock Units | June and December 2021 RSU Grant | Chief Executive Officer
Share-based Compensation Arrangement by Share-based Payment Award [Line Items]
Restricted stock units, granted | shares			952,804
Vesting description				Each RSU granted in the 2021 RSU Award entitles the chief executive officer to one share of common stock upon vesting subject to the service, performance, and market conditions
Restricted stock units, outstanding | shares				952,804
Restricted stock units, vested | shares	668,416			0
Restricted Stock Units | June and December 2021 RSU Grant | IPO
Share-based Compensation Arrangement by Share-based Payment Award [Line Items]
Fair value of the RSU award				$ 10,300
Restricted Stock Units | June and December 2021 RSU Grant | IPO | Chief Executive Officer
Share-based Compensation Arrangement by Share-based Payment Award [Line Items]
Anticipated service period				10 years
Fair value of the RSU award				$ 10,300
Restricted Stock Units | June and December 2021 RSU Grant | Change in Control
Share-based Compensation Arrangement by Share-based Payment Award [Line Items]
Fair value of the RSU award				1,580
Restricted Stock Units | 2023 RSU Award and 2021 RSU Award | Chief Executive Officer
Share-based Compensation Arrangement by Share-based Payment Award [Line Items]
Total unamortized share-based compensation				$ 8,000

Share-Based Compensation - Sche

Share-Based Compensation - Schedule of Share-based Compensation Expense (Details) - USD ($) $ in Thousands	12 Months Ended
	Dec. 31, 2024	Dec. 31, 2023	Dec. 31, 2022
Share-based Compensation Arrangement by Share-based Payment Award [Line Items]
Total share-based compensation expense	$ 61,086	$ 41,789	$ 21,544
Stock Options
Share-based Compensation Arrangement by Share-based Payment Award [Line Items]
Total share-based compensation expense	28,057	20,661	14,859
Restricted Stock Units
Share-based Compensation Arrangement by Share-based Payment Award [Line Items]
Total share-based compensation expense	27,257	12,254	4,056
Restricted Stock Units | Chief Executive Officer
Share-based Compensation Arrangement by Share-based Payment Award [Line Items]
Total share-based compensation expense	5,266	8,336	2,548
ESPP
Share-based Compensation Arrangement by Share-based Payment Award [Line Items]
Total share-based compensation expense	$ 506	$ 538	$ 81

Share-Based Compensation - Sc_2

Share-Based Compensation - Schedule of Share-based Compensation Expense reflected in the consolidated statement of operations and comprehensive loss (Details) - USD ($) $ in Thousands	12 Months Ended
	Dec. 31, 2024	Dec. 31, 2023	Dec. 31, 2022
Share-Based Payment Arrangement, Expensed and Capitalized, Amount [Line Items]
Share-Based Payment Arrangement, Expense	$ 61,086	$ 41,789	$ 21,544
Research and Development Expense
Share-Based Payment Arrangement, Expensed and Capitalized, Amount [Line Items]
Share-Based Payment Arrangement, Expense	21,359	11,003	7,007
General and Administrative Expense
Share-Based Payment Arrangement, Expensed and Capitalized, Amount [Line Items]
Share-Based Payment Arrangement, Expense	$ 39,727	$ 30,786	$ 14,537

Share-Based Compensation - Summ

Share-Based Compensation - Summary of Stock Option Activity (Details) - Stock Options - 2017 and 2022 Equity Incentive Plan - USD ($) $ / shares in Units, $ in Thousands	12 Months Ended
	Dec. 31, 2024	Dec. 31, 2023
Share-based Compensation Arrangement by Share-based Payment Award [Line Items]
Number of Shares, Outstanding, Beginning balance	7,811,231
Number of Shares, Granted	1,031,954
Number of Shares, Forfeited	(145,261)
Number of Shares, Exercised	(1,457,826)
Number of Shares, Outstanding, Ending balance	7,240,098	7,811,231
Number of Shares, Exercisable	4,712,405
Weighted Average Exercise Price, Outstanding, Beginning balance	$ 12.46
Weighted Average Exercise Price, Granted	56.22
Weighted Average Exercise Price, Forfeited	11.1
Weighted Average Exercise Price, Exercised	9.75
Weighted Average Exercise Price, Outstanding, Ending balance	19.28	$ 12.46
Weighted Average Exercise Price, Exercisable	$ 13.3
Weighted Average Remaining Contractual Life (Years), Outstanding	6 years 10 months 24 days	7 years 9 months 18 days
Weighted Average Remaining Contractual Life (Years), Exercisable	6 years 7 months 6 days
Aggregate Intrinsic Value, Outstanding	$ 415,634	$ 336,174
Aggregate intrinsic value, exercisable	$ 298,737

Share-Based Compensation - Sc_3

Share-Based Compensation - Schedule of Assumptions used in Black-Scholes Option Pricing Model for Stock Options Granted (Details)	12 Months Ended
	Dec. 31, 2024	Dec. 31, 2023	Dec. 31, 2022
Share-Based Compensation Arrangement by Share-Based Payment Award [Line Items]
Expected dividend yield	0%
Stock Options
Share-Based Compensation Arrangement by Share-Based Payment Award [Line Items]
Expected volatility, Minimum	86%	75%	68%
Expected volatility, Maximum	87%	80%	75%
Risk free interest rate, Minimum	3.82%	3.92%	1.56%
Risk free interest rate, Maximum	4.56%	4.06%	3.88%
Expected dividend yield	0%	0%	0%
Stock Options | Minimum
Share-Based Compensation Arrangement by Share-Based Payment Award [Line Items]
Expected term	5 years 6 months	5 years 6 months	6 years
Stock Options | Maximum
Share-Based Compensation Arrangement by Share-Based Payment Award [Line Items]
Expected term	6 years 3 months 7 days	6 years 3 months	6 years 3 months 18 days

Share-Based Compensation - Su_2

Share-Based Compensation - Summary of Restricted Stock Units Activity (Details) - Restricted Stock Units - 2022 Equity Incentive Plan	12 Months Ended
	Dec. 31, 2024 $ / shares shares
Share-based Compensation Arrangement by Share-based Payment Award [Line Items]
Number of Shares, Outstanding, Beginning balance | shares	1,416,446
Number of Shares, Granted | shares	981,531
Number of Shares, Vested | shares	(528,711)
Number of Shares, Forfeited | shares	(57,421)
Number of Shares, Outstanding, Ending balance | shares	1,811,845
Weighted Average Grant Date Fair Value, Outstanding, Beginning Balance | $ / shares	$ 25.47
Weighted Average Grant Date Fair Value, Granted | $ / shares	61.66
Weighted Average Grant Date Fair Value, Vested | $ / shares	23.76
Weighted Average Grant Date Fair Value, Forfeited | $ / shares	32.55
Weighted Average Grant Date Fair Value, Outstanding, Ending Balance | $ / shares	$ 45.35

Share-Based Compensation - Sc_4

Share-Based Compensation - Schedule of Assumptions used in Determining Fair Value for Stock Options and RSU Awards (Details) - Restricted Stock Units (RSUs) [Member] $ in Thousands	12 Months Ended
	Dec. 31, 2024 USD ($)
Semi Annual Measurement | January 2023 RSU Grant
Share-based Compensation Arrangement by Share-based Payment Award [Line Items]
Time to liquidity event	10 years
Expected volatility	75%
Risk free interest rate	3.80%
Fair value of the RSU award	$ 13,811
Change in Control | January 2023 RSU Grant
Share-based Compensation Arrangement by Share-based Payment Award [Line Items]
Time to liquidity event	5 years
Expected volatility	75%
Risk free interest rate	3.90%
Fair value of the RSU award	$ 10,999
Change in Control | June and December 2021 RSU Grant
Share-based Compensation Arrangement by Share-based Payment Award [Line Items]
Date of grant	Jun. 09, 2021
Expected volatility, Minimum	100%
Expected volatility, Maximum	110%
Risk free interest rate, Minimum	0.10%
Risk free interest rate, Maximum	0.30%
Fair value of the RSU award	$ 1,580
Change in Control | Minimum | June and December 2021 RSU Grant
Share-based Compensation Arrangement by Share-based Payment Award [Line Items]
Time to liquidity event	1 year 6 months 21 days
Discount for lack of marketability	26%
Change in Control | Maximum | June and December 2021 RSU Grant
Share-based Compensation Arrangement by Share-based Payment Award [Line Items]
Time to liquidity event	3 years 21 days
Discount for lack of marketability	32%
IPO | June and December 2021 RSU Grant
Share-based Compensation Arrangement by Share-based Payment Award [Line Items]
Date of grant	Dec. 07, 2021
Time to liquidity event	10 years
Expected volatility	70%
Risk free interest rate	1.50%
Discount for lack of marketability	5%
Fair value of the RSU award	$ 10,300
Change in Control Following IPO | June and December 2021 RSU Grant
Share-based Compensation Arrangement by Share-based Payment Award [Line Items]
Date of grant	Dec. 07, 2021
Time to liquidity event	1 year 3 months 29 days
Expected volatility	65%
Risk free interest rate	0.40%
Discount for lack of marketability	5%
Fair value of the RSU award	$ 150

Employee Stock Purchase Plan _3

Employee Stock Purchase Plan (ESPP) - Additional Information (Details) - USD ($)		1 Months Ended
	Jan. 01, 2023	Feb. 28, 2022	Sep. 30, 2022
Minimum
Share-Based Compensation Arrangement by Share-Based Payment Award [Line Items]
Reserved shares of common stock for issuance	312,500
2022 Employee Stock Purchase Plan
Share-Based Compensation Arrangement by Share-Based Payment Award [Line Items]
Purchase price of common stock expressed as a percentage of its fair market value		85%
Employees Company's common stock shares purchase limit amount		$ 25,000
Reserved shares of common stock for issuance			312,500
Percentage of shares issued from outstanding number of shares	1%

Employee Stock Purchase Plan _4

Employee Stock Purchase Plan (ESPP) - Schedule of Assumptions used in Black-Scholes Option Pricing Model for ESPP Plan (Details)	12 Months Ended
	Dec. 31, 2024	Dec. 31, 2023	Dec. 31, 2022
Share-Based Compensation Arrangement by Share-Based Payment Award [Line Items]
Expected dividend yield	0%
ESPP
Share-Based Compensation Arrangement by Share-Based Payment Award [Line Items]
Expected term	6 months	6 months	6 months
Expected volatility			132%
Expected volatility, Maximum	65%	68%
Expected volatility, Minimum	45%	65%
Risk free interest rate			4.40%
Risk free interest rate, Maximum	5.46%	5.46%
Risk free interest rate, Minimum	4.44%	5.26%
Expected dividend yield	0%	0%	0%

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	12 Months Ended
	Dec. 31, 2024	Dec. 31, 2023	Dec. 31, 2022
Antidilutive Securities Excluded From Computation Of Earnings Per Share [Line Items]
Antidilutive Securities Excluded From Computation Of Earnings Per Share Amount	10,503,706	10,678,476	9,940,113
Employee Stock Option
Antidilutive Securities Excluded From Computation Of Earnings Per Share [Line Items]
Antidilutive Securities Excluded From Computation Of Earnings Per Share Amount	7,240,098	7,811,231	8,053,704
Restricted Stock Units
Antidilutive Securities Excluded From Computation Of Earnings Per Share [Line Items]
Antidilutive Securities Excluded From Computation Of Earnings Per Share Amount	1,811,845	1,416,446	927,954
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	952,804
Employee Stock Ownership Plan (ESPP)
Antidilutive Securities Excluded From Computation Of Earnings Per Share [Line Items]
Antidilutive Securities Excluded From Computation Of Earnings Per Share Amount	3,959	2,995	5,651

Income Taxes - Summary of Provi

Income Taxes - Summary of Provision for Income Taxes (Details) - USD ($) $ in Thousands	12 Months Ended
	Dec. 31, 2024	Dec. 31, 2023
Current income tax provision (expense) benefit:
U.S. federal	$ (1,910)	$ (427)
State	(153)	(273)
Total	$ (2,063)	$ (700)

Income Taxes - Schedule of Reco

Income Taxes - Schedule of Reconciliation of Statutory U.S. Federal Rate and Effective Rate (Details)	12 Months Ended
	Dec. 31, 2024	Dec. 31, 2023	Dec. 31, 2022
Effective Income Tax Rate Reconciliation, Percent [Abstract]
U.S. federal tax	21%	21%	21%
State tax, net of federal benefit	0.30%	0.60%	6.60%
Change in valuation allowance	(42.90%)	(2.80%)	(26.90%)
Nondeductible compensation	(17.00%)	(15.20%)	(0.20%)
Research and development tax credits	26.30%	16.30%	0%
Stock based compensation	16.50%	10.20%	0.40%
Change in state deferred income tax rate	(0.50%)	(27.20%)	0%
Changes in unrecognized tax benefits	(5.70%)	(4.80%)	0%
Change in tax rates and other	0.10%	0.90%	(0.90%)
Effective income tax rate	(1.90%)	(1.00%)	0%

Income Taxes - Schedule of Defe

Income Taxes - Schedule of Deferred Tax Assets and Liabilities (Details) - USD ($) $ in Thousands	Dec. 31, 2024	Dec. 31, 2023
Deferred income tax assets:
U.S. federal net operating loss carryforward	$ 10,692	$ 29,929
State net operating loss carryforward	287	1,110
Research and development expenditures	65,346	44,047
Research and development credits	26,838	9,829
Lease liabilities - operating	11,641	12,710
Stock based compensation	8,117	4,600
Accruals and others	2,371	1,323
Deferred Revenue	24,423
Gross deferred income tax assets	149,715	103,548
Less: Valuation allowance	(137,302)	(91,841)
Total deferred income tax assets	12,413	11,707
Deferred income tax liabilities:
Depreciation	(6,692)	(4,930)
Right-of-use asset - operating	(5,143)	(5,903)
Section 481(a) adjustment	(578)	(874)
Total deferred income tax liabilities	$ (12,413)	$ (11,707)

Income Taxes - Additional Infor

Income Taxes - Additional Information (Details) - USD ($)	12 Months Ended
	Dec. 31, 2024	Dec. 31, 2023	Dec. 31, 2022
Income Tax Disclosure [Line Items]
Capitalized research and development domestic expenses amortization period	5 years
Capitalized research and development foreign expenses amortization period	15 years
Change in valuation allowance	$ 45,500,000	$ 2,000,000
Percentage of corporations stock owned by stockholders to determine ownership change	5%
Maximum threshold percentage increases over a three year period of corporations stock owned by stockholders for ownership change	50%
Income tax penalties or interest	$ 0	0
Unrecognized tax benefits	$ 9,578,000	$ 3,450,000	$ 0
Description of income tax examination	The Company’s federal and State tax returns for all years, 2015 through 2023, remain subject to examination by taxing authorities due to the tax attribute carryforwards.
Domestic Tax Authority
Income Tax Disclosure [Line Items]
Net operating loss carryforwards	$ 51,200,000
State and Local Jurisdiction
Income Tax Disclosure [Line Items]
Net operating loss carryforwards	74,800,000
Federal Orphan Drug Credit
Income Tax Disclosure [Line Items]
Tax credit carryforward amount	24,800
Research Tax Credit Carryforward | Domestic Tax Authority
Income Tax Disclosure [Line Items]
Tax credit carryforward amount	8,900,000
Research Tax Credit Carryforward | State and Local Jurisdiction
Income Tax Disclosure [Line Items]
Tax credit carryforward amount	$ 3,200,000
Tax credit carryforward expiration year	2031
Minimum
Income Tax Disclosure [Line Items]
Income tax examination year under examination	2015
Maximum
Income Tax Disclosure [Line Items]
Income tax examination year under examination	2023

Income Taxes - Schedule of Unre

Income Taxes - Schedule of Unrecognized Tax Benefits (Details) - USD ($)	12 Months Ended
	Dec. 31, 2024	Dec. 31, 2023
Unrecognized Tax Benefits [Roll Forward]
Unrecognized tax benefits, Beginning Balance	$ 3,450,000	$ 0
Additions based on tax positions related to period	3,177,000	809,000
Additions for tax positions of prior years	2,951,000	2,641,000
Unrecognized tax benefits, Ending Balance	$ 9,578,000	$ 3,450,000

Segment Reporting - Additional

Segment Reporting - Additional Information (Details)	12 Months Ended
	Dec. 31, 2024 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 Company’s CODM is its chief executive officer. The CODM uses consolidated net loss for purpose of assessing performance, making operating decisions and allocating resources.
Segment Reporting, CODM, Individual Title and Position or Group Name [Extensible Enumeration]	Chief Executive Officer [Member]

Segment Reporting - Schedule of

Segment Reporting - Schedule of Segment Reporting (Details) - USD ($) $ in Thousands	12 Months Ended
	Dec. 31, 2024	Dec. 31, 2023	Dec. 31, 2022
Segment Reporting Information [Line Items]
Collaboration revenue	$ 107,936	$ 110,319
Operating expenses:
Research and development	157,093	133,849	$ 149,555
General and administrative	88,414	66,350	41,704
Total operating expenses	245,507	200,199	191,259
Loss from operations	(137,571)	(89,880)	(191,259)
Interest and other income (expense), net	33,322	23,695	4,300
Interest expense	(1,030)	(3,842)	(1,720)
Total other income, net	32,292	19,853	2,580
Income tax expense	(2,069)	(663)
Net loss	(107,348)	(70,690)	(188,679)
Anito-cel in rrMM
Operating expenses:
Research and development	50,141	73,530	96,513
ACLX-001
Operating expenses:
Research and development	1,975	2,939	8,764
ACLX-002
Operating expenses:
Research and development	14,294	5,667	6,458
Other Research and Development Costs
Operating expenses:
Research and development	21,364	3,701	5,467
Internal Costs
Operating expenses:
Research and development	$ 69,319	$ 48,012	$ 32,353