Agenus (AGEN) 10-Q 7 May 24 2024 Q1 Quarterly report Financial data

Document and Entity Information

Document and Entity Information - shares	3 Months Ended
	Mar. 31, 2024	May 03, 2024
Cover [Abstract]
Document Type	10-Q
Amendment Flag	false
Document Period End Date	Mar. 31, 2024
Document Fiscal Period Focus	Q1
Document Fiscal Year Focus	2024
Entity Registrant Name	AGENUS INC
Entity Central Index Key	0001098972
Entity Current Reporting Status	Yes
Trading Symbol	AGEN
Security Exchange Name	NASDAQ
Current Fiscal Year End Date	--12-31
Entity Filer Category	Accelerated Filer
Entity Shell Company	false
Entity Small Business	false
Entity Emerging Growth Company	false
Title of 12(b) Security	Common stock, par value $0.01
Entity Interactive Data Current	Yes
Entity Common Stock, Shares Outstanding		20,999,261
Entity File Number	000-29089
Entity Tax Identification Number	06-1562417
Entity Address, Address Line One	3 Forbes Road
Entity Address, City or Town	Lexington
Entity Address, State or Province	MA
Entity Address, Postal Zip Code	02421
City Area Code	781
Local Phone Number	674-4400
Document Quarterly Report	true
Document Transition Report	false
Entity Incorporation, State or Country Code	DE

Condensed Consolidated Balance

Condensed Consolidated Balance Sheets (Unaudited) - USD ($) $ in Thousands	Mar. 31, 2024	Dec. 31, 2023
ASSETS
Cash and cash equivalents	$ 52,856	$ 76,110
Accounts receivable	476	25,836
Prepaid expenses	3,895	8,098
Other current assets	3,125	2,372
Total current assets	60,352	112,416
Property, plant and equipment, net of accumulated amortization and depreciation of $65,080 and $61,943 at March 31, 2024 and December 31, 2023, respectively	130,330	133,421
Operating lease right-of-use assets	29,340	29,606
Goodwill	24,698	24,723
Acquired intangible assets, net of accumulated amortization of $17,799 and $17,688 at March 31, 2024 and December 31, 2023, respectively	4,230	4,411
Other long-term assets	7,609	9,336
Total assets	256,559	313,913
LIABILITIES AND STOCKHOLDERS' DEFICIT
Current portion, long-term debt	13,575	146
Current portion, liability related to sale of future royalties and milestones	133,588	132,502
Current portion, deferred revenue	13	18
Current portion, operating lease liabilities	2,811	2,587
Accounts payable	50,693	61,446
Accrued liabilities	41,291	45,283
Other current liabilities	14,031	13,915
Total current liabilities	256,002	255,897
Long-term debt, net of current portion	0	12,768
Liability related to sale of future royalties and milestones, net of current portion	125,249	124,556
Deferred revenue, net of current portion	1,143	1,143
Operating lease liabilities, net of current portion	61,756	62,511
Other long-term liabilities	2,732	5,420
Commitments and contingencies
STOCKHOLDERS" DEFICIT
Common stock, par value $0.01 per share; 800,000,000 shares authorized; 20,994,143 and 19,718,662 shares issued at March 31, 2024 and December 31, 2023, respectively	210	197
Additional paid-in capital	1,816,985	1,796,095
Accumulated other comprehensive loss	(1,071)	(955)
Accumulated deficit	(2,017,554)	(1,955,668)
Total stockholders' deficit attributable to Agenus Inc.	(201,430)	(160,331)
Non-controlling interest	11,107	11,949
Total stockholders' deficit	(190,323)	(148,382)
Total liabilities and stockholders' deficit	256,559	313,913
Series A-1 convertible preferred stock [Member]
STOCKHOLDERS" DEFICIT
Series A-1 convertible preferred stock; 31,620 shares designated, issued, and outstanding at March 31, 2024 and December 31, 2023; liquidation value of $33,940 at March 31, 2024	$ 0	$ 0

Condensed Consolidated Balanc_2

Condensed Consolidated Balance Sheets (Parenthetical) (Unaudited) - USD ($) $ in Thousands	Mar. 31, 2024	Dec. 31, 2023
Property plant and equipment, accumulated amortization and depreciation	$ 65,080	$ 61,943
Acquired intangible assets, accumulated amortization	$ 17,799	$ 17,688
Common stock, par value	$ 0.01	$ 0.01
Common stock, shares authorized	800,000,000	800,000,000
Common stock, shares issued	20,994,143	19,718,662
Common stock, shares outstanding	20,994,143	19,718,662
Series A-1 convertible preferred stock [Member]
Series A-1 convertible preferred stock, shares designated	31,620	31,620
Series A-1 convertible preferred stock, shares issued	31,620	31,620
Series A-1 convertible preferred stock, shares outstanding	31,620	31,620
Series A-1 convertible preferred stock, liquidation value	$ 33,940

Condensed Consolidated Statemen

Condensed Consolidated Statements of Operations and Comprehensive Loss (Unaudited) - USD ($) shares in Thousands, $ in Thousands	3 Months Ended
	Mar. 31, 2024	Mar. 31, 2023
Revenue:
Total revenues	$ 28,005	$ 22,902
Operating expenses:
Cost of service revenue	(107)	(2,294)
Research and development	(43,925)	(57,118)
General and administrative	(16,855)	(18,237)
Contingent purchase price consideration fair value adjustment	0	406
Operating loss	(32,882)	(54,341)
Other income (expense):
Non-operating income (expense)	(1,106)	40
Interest expense, net	(29,466)	(16,592)
Net loss	(63,454)	(70,893)
Dividends on Series A-1 convertible preferred stock	(54)	(53)
Net loss attributable to non-controlling interest	(1,568)	(2,639)
Net loss attributable to Agenus Inc. common stockholders	$ (61,940)	$ (68,307)
Per common share data:
Basic net loss attributable to Agenus Inc. common stockholders	$ (3.04)	$ (4.31)
Diluted net loss attributable to Agenus Inc. common stockholders	$ (3.04)	$ (4.31)
Weighted average number of Agenus Inc. common shares outstanding:
Basic	20,368	15,855
Diluted	20,368	15,855
Other comprehensive income (loss):
Foreign currency translation income (loss)	$ (116)	$ 2
Other comprehensive income (loss)	(116)	2
Comprehensive loss	(62,056)	(68,305)
Research and Development [Member]
Revenue:
Total revenues	0	2,612
Service Revenue [Member]
Revenue:
Total revenues	238	1,184
Non-Cash Royalty Revenue Related to the Sale of Future Royalties [Member]
Revenue:
Total revenues	$ 27,767	$ 19,106

Condensed Consolidated Statem_2

Condensed Consolidated Statements of Convertible Preferred Stock and Stockholders' Deficit (Unaudited) - USD ($) shares in Thousands, $ in Thousands	Total	Common Stock [Member]	Additional Paid-in Capital [Member]	Treasury Stock [Member]	Accumulated Other Comprehensive Income (Loss) [Member]	Non-controlling Interest [Member]	Accumulated Deficit [Member]	Series A-1 convertible preferred stock [Member] Preferred Stock [Member]
Stockholders' Equity, Beginning Balance at Dec. 31, 2022	$ (54,902)	$ 153	$ 1,647,561		$ 915	$ 6,376	$ (1,709,907)
Balance, shares at Dec. 31, 2022		15,278
Temporary Equity, Beginning Balance at Dec. 31, 2022								$ 0
Temporary Equity, shares at Dec. 31, 2022								32
Net loss	(70,893)					(2,639)	(68,254)
Other comprehensive income (loss)	2				2
Share-based compensation	5,485		4,566			919
Shares sold at the market	60,583	$ 17	60,566
Shares sold at the market, shares		1,689
Issuance of director deferred shares	983	$ 1	982
Issuance of director deferred shares, shares		13
Issuance of shares for services	318		318
Issuance of shares for services, shares		7
Issuance of subsidiary shares to noncontrolling interest	726					726
Exercise of stock options and employee share purchases	374		329			45
Exercise of stock options and employee share purchases, shares		10
Issuance of shares for employee bonus	1,796	$ 1	4,224	$ (2,429)
Issuance of shares for employee bonus, Shares		136		(1)
Retirement of treasury shares	2,419	$ (1)	(9)	$ 2,429
Retirement of treasury shares, share		(50)		1
Stockholders' Equity, Ending Balance at Mar. 31, 2023	(53,109)	$ 171	1,718,537		917	5,427	(1,778,161)
Temporary Equity, Ending Balance at Mar. 31, 2023								$ 0
Balance, shares at Mar. 31, 2023		17,083
Temporary Equity, shares at Mar. 31, 2023								32
Stockholders' Equity, Beginning Balance at Dec. 31, 2022	(54,902)	$ 153	1,647,561		915	6,376	(1,709,907)
Balance, shares at Dec. 31, 2022		15,278
Temporary Equity, Beginning Balance at Dec. 31, 2022								$ 0
Temporary Equity, shares at Dec. 31, 2022								32
Share-based compensation						3,825
Stockholders' Equity, Ending Balance at Dec. 31, 2023	(148,382)	$ 197	1,796,095		(955)	11,949	(1,955,668)
Temporary Equity, Ending Balance at Dec. 31, 2023								$ 0
Balance, shares at Dec. 31, 2023		19,718
Temporary Equity, shares at Dec. 31, 2023								32
Net loss	(63,454)					(1,568)	(61,886)
Other comprehensive income (loss)	(116)				(116)
Share-based compensation	4,196		3,477			719
Shares sold at the market	17,171	$ 13	17,158
Shares sold at the market, shares		1,249
Payment of CEO payroll in shares	89		89
Payment of CEO payroll In shares, shares		7
Vesting of nonvested shares, shares		8
Exercise of stock options and employee share purchases	173		166			7
Exercise of stock options and employee share purchases, shares		12
Stockholders' Equity, Ending Balance at Mar. 31, 2024	$ (190,323)	$ 210	$ 1,816,985		$ (1,071)	$ 11,107	$ (2,017,554)
Temporary Equity, Ending Balance at Mar. 31, 2024								$ 0
Balance, shares at Mar. 31, 2024		20,994
Temporary Equity, shares at Mar. 31, 2024								32

Condensed Consolidated Statem_3

Condensed Consolidated Statements of Cash Flows (Unaudited) - USD ($) $ in Thousands	3 Months Ended
	Mar. 31, 2024	Mar. 31, 2023
Cash flows from operating activities:
Net loss	$ (63,454)	$ (70,893)
Adjustments to reconcile net loss to net cash used in operating activities:
Depreciation and amortization	3,374	2,562
Share-based compensation	4,152	5,485
Non-cash royalty revenue	(27,767)	(19,106)
Non-cash interest expense	29,595	17,273
Loss disposal of assets, net	9	21
Other, net	1,125	(406)
Changes in operating assets and liabilities:
Accounts receivable	25,341	1,291
Prepaid expenses	4,202	2,965
Accounts payable	(10,733)	2,032
Deferred revenue	(4)	(2,382)
Accrued liabilities and other current liabilities	(3,622)	5,158
Other operating assets and liabilities	(409)	(2,526)
Net cash used in operating activities	(38,191)	(58,526)
Cash flows from investing activities:
Purchases of plant and equipment	(35)	(1,842)
Sale of long-term investment	264
Purchases of available-for-sale securities		(14,647)
Proceeds from sale of available-for-sale securities		5,000
Net cash provided by (used in) investing activities	229	(11,489)
Cash flows from financing activities:
Net proceeds from sale of equity	17,171	60,583
Proceeds from employee stock purchases and option exercises	173	374
Purchase of treasury shares to satisfy tax withholdings		(2,819)
Payment of finance lease obligation	(2,514)	(1,888)
Net cash provided by financing activities	14,830	56,250
Effect of exchange rate changes on cash	(122)	(90)
Net decrease in cash, cash equivalents and restricted cash	(23,254)	(13,855)
Cash, cash equivalents and restricted cash, beginning of period	79,779	181,343
Cash, cash equivalents and restricted cash, end of period	56,525	167,488
Supplemental cash flow information:
Cash paid for interest	667	830
Supplemental disclosures - non-cash activities:
Purchases of plant and equipment in accounts payable and accrued liabilities		3,893
Insurance financing agreement	612	707
Issuance of subsidiary shares for employee bonus		726
Lease right-of-use assets obtained in exchange for new operating lease liabilities	105	250
Lease right-of-use assets obtained in exchange for new finance lease liabilities	122	3,630
Payment for Services [Member]
Supplemental disclosures - non-cash activities:
Issuance of common stock		318
Employee Bonus [Member]
Supplemental disclosures - non-cash activities:
Issuance of common stock		$ 4,215
Issuance of subsidiary options	$ 133

Condensed Consolidated Statem_4

Condensed Consolidated Statements of Cash Flows (Unaudited) (Parenthetical)	Mar. 31, 2023 $ / shares
Payment for Services [Member]
Supplemental disclosures - non-cash activities:
Common stock, par value	$ 0.01
Employee Bonus [Member]
Supplemental disclosures - non-cash activities:
Common stock, par value	$ 0.01

Insider Trading Arrangements

Insider Trading Arrangements	3 Months Ended
	Mar. 31, 2024
Trading Arrangements, by Individual
Rule 10b5-1 Arrangement Adopted	false
Non-Rule 10b5-1 Arrangement Adopted	false
Rule 10b5-1 Arrangement Terminated	false
Non-Rule 10b5-1 Arrangement Terminated	false

Business, Liquidity and Basis o

Business, Liquidity and Basis of Presentation	3 Months Ended
	Mar. 31, 2024
Description Of Business [Abstract]
Business, Liquidity and Basis of Presentation	Note A – Business, Liquidity and Basis of Presentation Agenus Inc. (including its subsidiaries, collectively referred to as “Agenus,” the “Company,” “we,” “us,” and “our”) is a leading clinical-stage biotechnology company developing therapies targeting cancer with a robust pipeline of immunological agents. Our mission is to expand patient populations benefiting from cancer immunotherapy through combination approaches, using a broad repertoire of antibody therapeutics, adoptive cell therapies (through our subsidiary MiNK Therapeutics, Inc. (“MiNK”)), and vaccine adjuvants (through our subsidiary SaponiQx, Inc. (“SaponiQx”)). We believe that combination therapies and a deep understanding of each patient’s cancer will significantly expand the patient population benefiting from immuno-oncology (“I-O”) treatments. In addition to our diverse pipeline, we have established fully integrated capabilities encompassing novel target discovery, antibody generation, cell line development, and current good manufacturing practice ("cGMP") manufacturing. We believe these integrated capabilities enable us to develop and, if approved, commercialize novel candidates on accelerated timelines compared to industry standards. Through independent development and strategic partnerships, we leverage our scientific expertise and capabilities to drive innovation in the I-O field. Our I-O portfolio is driven by several platforms and programs, which we plan to utilize individually and in combination: • Multiple antibody discovery platforms, including proprietary display technologies, to identify future antibody candidates. • Antibody candidate programs, including our lead assets, botensilimab (a multifunctional immune cell activator and human Fc-enhanced cytotoxic T-lymphocyte antigen 4 (CTLA-4) blocking antibody, also known as AGEN1811) and balstilimab (a programmed death receptor-1 (PD-1) blocking antibody). • Our saponin-based vaccine adjuvant platform, primarily centered around our STIMULON™ cultured plant cell (“cpc”) QS-21 adjuvant (“STIMULON cpcQS-21”). • A pipeline of novel allogeneic invariant natural killer T cell therapies for treating cancer and other immune-mediated diseases, controlled by MiNK. Our business activities include product research, preclinical and clinical development, intellectual property prosecution, manufacturing, regulatory and clinical affairs, corporate finance and development activities, and support of our collaborations. Our product candidates require successful clinical trials and approvals from regulatory agencies, as well as acceptance in the marketplace. Part of our strategy is to develop and commercialize some of our product candidates by continuing our existing arrangements with academic and corporate collaborators and licensees and by entering into new collaborations. Our cash and cash equivalents at March 31, 2024 were $ 52.9 million, a decrease of $ 23.3 million from December 31, 2023 . Cash and cash equivalents of our subsidiary, MiNK, at December 31, 2023, were $ 3.4 million. MiNK cash can only be accessed by Agenus through a declaration of a dividend by the MiNK Board of Directors or through settlement of intercompany balances. As of March 31, 2024, we had an accumulated deficit of $ 2.0 billion and $ 13.0 million of subordinated notes maturing in February 2025 . Since our founding we have financed our operations principally through income and revenues generated from corporate partnerships, advance royalty sales and proceeds from equity issuances. Based on our current plans and projections, we believe that our cash resources of $ 52.9 million at March 31, 2024, plus the $75.0 million to be received from Ligand Pharmaceuticals and the exercise at their option of an additional $25.0 million under a Purchase and Sale Agreement (see Note P), plus additional funding we may receive from multiple other sources, including out-licensing and/or partnering opportunities, and the repayment of our subordinated notes, will be sufficient to satisfy our liquidity requirements through the end of the year and into 2025. Potential partnership and collaboration transactions along with potential accelerated approval of our lead products, botensilimab and balstilimab, and potential commercial revenues from these products, can extend our runway and allow us to be cash flow positive from our operations. We are also in discussions with several other parties to participate in the Purchase and Sale Agreement for up to an additional $125.0 million under the same structure as the Ligand transaction. In addition, we are also in discussions with several potential corporate collaborators. These transactions could also extend our cash resources. However, because the completion of such transactions is not entirely within our control, in accordance with accounting guidance we are required to disclose that substantial doubt exists about our ability to continue as a going concern for a period of one year after the date of filing of this Quarterly Report on Form 10-Q. The financial statements have been prepared on a basis that assumes Agenus will continue as a going concern and which contemplates the realization of assets and satisfaction of liabilities and commitments in the ordinary course of business. Management continues to address the Company’s liquidity needs and can exercise its flexibility to adjust spending as needed in order to preserve liquidity. In August 2023, we prioritized and focused our resources to accelerate the development, registration, and commercialization of our lead asset postponing all preclinical and other clinical programs and reducing our workforce by approximately 25 %. Our CEO, Dr. Garo Armen has elected to receive his base salary and any potential bonus payments in stock rather than cash. We continuously evaluate the likelihood of success of our programs. As such, our decisions to continue to fund or eliminate funding of each of our programs are predicated on these determinations, on an ongoing basis. We expect our sources of funding to include payments from current collaborations which include milestones and royalty payments from companies, including Bristol-Myers Squibb Company, UroGen Pharma Ltd., Gilead Sciences, Inc., Merck Sharpe & Dohme and Incyte Corporation; out-licensing and/or partnering opportunities for our portfolio programs and product candidates with multiple parties; additional third-party agreements; asset sales; further royalty monetization; project financing, and/or sales of equity securities . The accompanying unaudited interim condensed consolidated financial statements have been prepared in accordance with U.S. generally accepted accounting principles (“U.S. GAAP”) for interim financial information and with the instructions to Article 10 of Regulation S-X. Accordingly, they do not include all of the information and footnotes required by U.S. GAAP for complete annual consolidated financial statements. In the opinion of our management, the condensed consolidated financial statements include all normal and recurring adjustments considered necessary for a fair presentation of our financial position and operating results. All significant intercompany transactions and accounts have been eliminated in consolidation. Operating results for the three months ended March 31, 2024, are not necessarily indicative of the results that may be expected for the year ending December 31, 2024. For further information, refer to our consolidated financial statements and footnotes thereto included in our Annual Report on Form 10-K for the year ended December 31, 2023 filed with the Securities and Exchange Commission (“SEC”). The preparation of consolidated financial statements in conformity with U.S. GAAP requires management to make estimates and assumptions that affect the reported amounts of assets and liabilities and disclosures of contingent assets and liabilities at the date of the financial statements and the reported amounts of revenues and expenses during the reporting period. Management bases its estimates on historical experience and on various assumptions that are believed to be reasonable under the circumstances. Actual results could differ materially from those estimates. For our foreign subsidiaries, the local currency is the functional currency. Assets and liabilities of our foreign subsidiaries are translated into U.S. dollars using rates in effect at the balance sheet date while revenues and expenses are translated into U.S. dollars using average exchange rates during the period. The cumulative translation adjustment resulting from changes in exchange rates are included in the consolidated balance sheets as a component of accumulated other comprehensive income (loss) in total stockholders’ deficit. On April 4, 2024, we executed a reverse stock split of our issued and outstanding common stock, par value $ 0.01 , at a ratio of 1-for-20 with a record date of April 12, 2024 (the “Reverse Stock Split”). All common share, per share and related information included in the accompanying financial statements and footnote disclosures have been adjusted retroactively, where applicable, to reflect the Reverse Stock Split. See Note P for further details.

Net Loss Per Share

Net Loss Per Share	3 Months Ended
	Mar. 31, 2024
Earnings Per Share [Abstract]
Net Loss Per Share	Note B – Net Loss Per Share Basic net loss per common share is calculated by dividing the net loss attributable to common stockholders by the weighted average number of common shares outstanding (including common shares issuable under our Amended and Restated Directors’ Deferred Compensation Plan, or “DDCP”). Diluted loss per common share is calculated by dividing loss attributable to common stockholders by the weighted average number of common shares outstanding (including common shares issuable under our DDCP) plus the dilutive effect of outstanding instruments such as warrants, stock options, non-vested shares and convertible preferred stock. Because we reported a net loss attributable to common stockholders for all periods presented, diluted loss per common share is the same as basic loss per common share, as the effect of utilizing the fully diluted share count would have reduced the net loss per common share. The following securities (listed on an as-if-converted-to-Common-Stock basis) have been excluded from the computation of diluted weighted average shares outstanding as of March 31, 2024 and 2023, as they would be anti-dilutive (in thousands): Three Months Ended March 31, 2024 2023 Warrants 99 99 Stock options 2,205 2,184 Non-vested shares 26 127 Series A-1 convertible preferred stock 17 17

Investments

Investments	3 Months Ended
	Mar. 31, 2024
Cash and Cash Equivalents [Abstract]
Investments	Note C – Investments Cash equivalents and short-term investments consisted of the following as of March 31, 2024 and December 31, 2023 (in thousands): March 31, 2024 December 31, 2023 Cost Estimated Cost Estimated Institutional money market funds $ 49,220 $ 49,220 $ 70,485 $ 70,485 Total $ 49,220 $ 49,220 $ 70,485 $ 70,485 As a result of the short-term nature of these investments, there were minimal unrealized holding gains or losses for the three months ended March 31, 2024 and 2023. As of both March 31, 2024 and December 31, 2023, all of the investments listed above were classified as cash equivalents on our condensed consolidated balance sheets.

Goodwill and Acquired Intangibl

Goodwill and Acquired Intangible Assets	3 Months Ended
	Mar. 31, 2024
Goodwill and Intangible Assets Disclosure [Abstract]
Goodwill and Acquired Intangible Assets	Note D – Goodwill and Acquired Intangible Assets The following table sets forth the changes in the carrying amount of goodwill for the three months ended March 31, 2024 (in thousands): Balance, December 31, 2023 $ 24,723 Effect of foreign currency ( 25 ) Balance, March 31, 2024 $ 24,698 Acquired intangible assets consisted of the following as of March 31, 2024 and December 31, 2023 (in thousands): As of March 31, 2024 Amortization Gross carrying Accumulated Net carrying Intellectual property 7 - 15 years $ 16,841 $ ( 15,268 ) $ 1,573 Trademarks 4 - 4.5 years 1,199 ( 1,193 ) 6 Other 2 - 7 years 1,932 ( 1,338 ) 594 In-process research and development Indefinite 2,057 — 2,057 Total $ 22,029 $ ( 17,799 ) $ 4,230 As of December 31, 2023 Amortization Gross carrying Accumulated Net carrying Intellectual property 7 - 15 years $ 16,841 $ ( 15,184 ) $ 1,657 Trademarks 4 - 4.5 years 1,213 ( 1,185 ) 28 Other 2 - 7 years 1,988 ( 1,319 ) 669 In-process research and development Indefinite 2,057 — 2,057 Total $ 22,099 $ ( 17,688 ) $ 4,411 The weighted average amortization period of our finite-lived intangible assets is 9 years. Amortization expense related to acquired intangibles is estimated at $ 0.4 million for the remainder of 2024, $ 0.5 million for the years ending December 31, 2025 and 2026, $ 0.4 million for the year ending December 31, 2027 and $ 0.3 million for the year ending December 31, 2028.

Debt

Debt	3 Months Ended
	Mar. 31, 2024
Debt Disclosure [Abstract]
Debt	Note E – Debt Debt obligations consisted of the following as of March 31, 2024 and December 31, 2023 (in thousands): Debt instrument Balance at Current Portion: Debentures $ 146 2015 Subordinated Notes 12,817 Other 612 Total $ 13,575 Debt instrument Balance at Current Portion: Debentures $ 146 Long-term Portion: 2015 Subordinated Notes 12,768 Total $ 12,914 As of March 31, 2024 and December 31, 2023, the principal amount of our outstanding debt balance was $ 13.8 million and $ 13.1 million, respectively.

Liability Related to the Sale o

Liability Related to the Sale of Future Royalties and Milestones	3 Months Ended
	Mar. 31, 2024
Liability Related To Sale Of Future Royalties And Milestones [Abstract]
Liability Related to the Sale of Future Royalties and Milestones	Note F – Liability Related to the Sale of Future Royalties and Milestones The following table shows the activity within the liability account in the three months ended March 31, 2024 (in thousands): Period from Liability related to sale of future royalties and milestones - beginning balance $ 257,296 Non-cash royalty revenue ( 27,767 ) Non-cash interest expense recognized 29,531 Liability related to sale of future royalties and milestones - ending balance 259,060 Less: unamortized transaction costs ( 223 ) Liability related to sale of future royalties and milestones, net $ 258,837 Healthcare Royalty Partners In January 2018, we, through our wholly-owned subsidiary Antigenics, LLC (“Antigenics”), entered into a Royalty Purchase Agreement (the “HCR Royalty Purchase Agreement”) with Healthcare Royalty Partners III, L.P. and certain of its affiliates (collectively, “HCR”). Pursuant to the terms of the HCR Royalty Purchase Agreement, we sold to HCR 100 % of Antigenics’ worldwide rights to receive royalties from GlaxoSmithKline (“GSK”) on sales of GSK’s vaccines containing our STIMULON QS-21 adjuvant. At closing, we received gross proceeds of $ 190.0 million from HCR. Although we sold all of our rights to receive royalties on sales of GSK’s vaccines containing QS-21, as a result of our obligation to HCR, we are required to account for the $ 190.0 million in proceeds from this transaction as a liability on our condensed consolidated balance sheet that will be recognized into revenue in proportion to the royalty payments from GSK to HCR over the estimated life of the HCR Royalty Purchase Agreement. The liability is classified between the current and non-current portion of liability related to sale of future royalties and milestones in the condensed consolidated balance sheets based on the estimated royalty payments to be received by HCR in the next 12 months from the financial statement reporting date. During the three months ended March 31, 2024 , we recognized $ 27.8 million of non-cash royalty revenue, and we recorded $ 29.5 million of related non-cash interest expense related to the HCR Royalty Purchase Agreement. As royalties are remitted to HCR from GSK, the balance of the recorded liability will be effectively repaid over the life of the HCR Royalty Purchase Agreement. To determine the amortization of the recorded liability, we are required to estimate the total amount of future royalty payments to be received by HCR. The sum of these amounts less the $ 190.0 million proceeds we received will be recorded as interest expense over the life of the HCR Royalty Purchase Agreement. Periodically, we assess the estimated royalty payments to be paid to HCR from GSK, and to the extent the amount or timing of the payments is materially different from our original estimates, we will prospectively adjust the amortization of the liability, and the related recognition of interest expense. During the three months ended March 31, 2024 , our estimate of the effective annual interest rate over the life of the agreement decreased to 48.0 %, which results in a life of contract interest rate of 26.5 %.

Accrued and Other Current Liabi

Accrued and Other Current Liabilities	3 Months Ended
	Mar. 31, 2024
Other Liabilities Disclosure [Abstract]
Accrued and Other Current Liabilities	Note G – Accrued and Other Current Liabilities Accrued liabilities consisted of the following as of March 31, 2024 and December 31, 2023 (in thousands): March 31, 2024 December 31, 2023 Payroll $ 18,514 $ 14,512 Professional fees 6,195 7,101 Contract manufacturing costs 5,334 7,613 Research services 6,274 10,807 Other 4,974 5,250 Total $ 41,291 $ 45,283 Other current liabilities consisted of the following as of March 31, 2024 and December 31, 2023 (in thousands): March 31, 2024 December 31, 2023 Finance lease liabilities $ 10,738 $ 10,457 Other 3,293 3,458 Total $ 14,031 $ 13,915

Fair Value Measurements

Fair Value Measurements	3 Months Ended
	Mar. 31, 2024
Fair Value Measurements [Abstract]
Fair Value Measurements	Note H – Fair Value Measurements Assets and liabilities measured at fair value are summarized below (in thousands): Description March 31, 2024 Quoted Prices in Significant Significant Assets: Cash equivalents (Note C) $ 49,220 $ 49,220 $ — $ — Long-term investments 1,834 1,834 — — Total $ 51,054 $ 51,054 $ — $ — Liabilities: Contingent purchase price considerations $ 318 $ — $ — $ 318 Total $ 318 $ — $ — $ 318 Description December 31, 2023 Quoted Prices in Significant Significant Assets: Cash equivalents (Note C) $ 70,485 $ 70,485 $ — $ — Long-term investments 3,222 3,222 — — Total $ 73,707 $ 73,707 $ — $ — Liabilities: Contingent purchase price consideration $ 318 $ — $ — $ 318 Total $ 318 $ — $ — $ 318 Long-term investments are included in "Other long-term assets" in our condensed consolidated balance sheets. We measure our contingent purchase price considerations at fair value. The fair values of our contingent purchase price considerations at both March 31, 2024 and December 31, 2023, of $ 0.3 million, included in "Other long-term liabilities" in our condensed consolidated balance sheets, are based on significant inputs not observable in the market, which require them to be reported as Level 3 liabilities within the fair value hierarchy. The valuation of these liabilities use assumptions we believe would be made by a market participant and are mainly based on estimates from a Monte Carlo simulation of our share price, as well as other factors impacting the probability of triggering the milestone payments. Share price was evolved using a geometric Brownian motion, calculated daily for the life of the contingent purchase price considerations. The fair value of our outstanding debt balance at March 31, 2024 and December 31, 2023 was $ 13.6 million and $ 13.0 million, respectively, based on the Level 2 valuation hierarchy of the fair value measurements standard using a present value methodology that was derived by evaluating the nature and terms of each note and considering the prevailing economic and market conditions at the balance sheet date. The principal amount of our outstanding debt balance at March 31, 2024 and December 31, 2023 was $ 13.8 million and $ 13.1 million, respectively.

Revenue from Contracts with Cus

Revenue from Contracts with Customers	3 Months Ended
	Mar. 31, 2024
Collaboration [Abstract]
Revenue from Contracts with Customers	Note I – Revenue from Contracts with Customers Gilead Collaboration Agreement On December 20, 2018, we entered into a series of agreements with Gilead Sciences, Inc. (“Gilead”) focused on the development and commercialization of up to five novel immuno-oncology therapies. Pursuant to the terms of the license agreement, the option and license agreements and the stock purchase agreement we entered into with Gilead (collectively, the “Gilead Collaboration Agreements”), at the closing of the transaction on January 23, 2019, we received an upfront cash payment from Gilead of $ 120.0 million and Gilead made a $ 30.0 million equity investment in Agenus. On November 6, 2020, we received notice from Gilead that it was returning AGEN1423 to us and voluntarily terminating the applicable license agreement. The termination was effective as of February 4, 2021. In the third quarter of 2021 we ceased development of AGEN1223 and in October 2021 the AGEN1223 option and license agreement was formally terminated. The AGEN2373 option and license agreement and the stock purchase agreement remain in full force and effect. We remain eligible to receive a $ 50.0 million exercise fee and, if exercised, up to $ 520.0 million in aggregate potential milestones. Collaboration Revenue No revenue was recognized for the three months ended March 31, 2024. For the three months ended March 31, 2023, we recognized approximately $ 2.3 million of research and development revenue based on the partial satisfaction of the over time performance obligations as of quarter end. Disaggregation of Revenue The following table presents revenue (in thousands) for the three months ended March 31, 2024 and 2023, disaggregated by geographic region and revenue type. Revenue by geographic region is allocated based on the domicile of our respective business operations. Three months ended March 31, 2024 United States Rest of World Total Revenue Type Other services $ — $ 238 $ 238 Non-cash royalties 27,767 — 27,767 $ 27,767 $ 238 $ 28,005 Three months ended March 31, 2023 Revenue Type Research and development services 267 — 267 Other services — 1,184 1,184 Recognition of deferred revenue 2,345 — 2,345 Non-cash royalties 19,106 — 19,106 $ 21,718 $ 1,184 $ 22,902 Contract Balances Contract assets primarily relate to our rights to consideration for work completed in relation to our research and development services performed but not billed at the reporting date. The contract assets are transferred to receivables when the rights become unconditional. Currently, we do not have any contract assets which have not transferred to a receivable. We had no asset impairment charges related to contract assets in the period. Contract liabilities primarily relate to contracts where we received payments but have not yet satisfied the related performance obligations. The advance consideration received from customers for research and development services or licenses bundled with other promises is a contract liability until the underlying performance obligations are transferred to the customer. The following table provides information about contract liabilities from contracts with customers (in thousands): Three months ended March 31, 2024 Balance at beginning of period Additions Deductions Balance at end of period Contract liabilities: Deferred revenue $ 1,161 $ 5 $ ( 10 ) $ 1,156 We also recorded a $ 0.5 million receivable as of March 31, 2024, for research and development and other services provided. During the three months ended March 31, 2024 , we did not recognize any revenue from amounts included in the contract asset or the contract liability balances from performance obligations satisfied in previous periods. No ne of the costs to obtain or fulfill a contract were capitalized.

Share-Based Compensation Plans

Share-Based Compensation Plans	3 Months Ended
	Mar. 31, 2024
Share-Based Payment Arrangement, Noncash Expense [Abstract]
Share-Based Compensation Plans	Note J – Share-based Compensation Plans We primarily use the Black-Scholes option pricing model to value stock options granted to employees and non-employees, including stock options granted to members of our Board of Directors. However, the fair value of stock option market-based awards is calculated based on a Monte Carlo simulation as of the date of issuance. All stock options have 10-year terms and generally vest ratably over a 3 or 4 -year period. A summary of option activity for the three months ended March 31, 2024 is presented below: Options Weighted Weighted Aggregate Outstanding at December 31, 2023 2,141,360 $ 65.00 Granted 164,506 17.44 Exercised — — Forfeited ( 11,982 ) 48.61 Expired ( 88,971 ) 63.66 Outstanding at March 31, 2024 2,204,913 $ 61.55 6.61 $ — Vested or expected to vest at March 31, 2024 2,204,913 $ 61.55 6.61 $ — Exercisable at March 31, 2024 1,558,872 $ 69.34 5.88 $ — The weighted average grant-date fair values of stock options granted during the three months ended March 31, 2024 and 2023 were $ 8.82 and $ 30.60 , respectively. As of March 31, 2024 , there was approximately $ 18.6 million of total unrecognized share-based compensation expense related to these stock options and stock options granted under subsidiary plans which, if all milestones are achieved, will be recognized over a weighted average period of 1.7 years. Certain employees and consultants have been granted non-vested stock. The fair value of non-vested market-based awards is calculated based on a Monte Carlo simulation as of the date of issuance. The fair value of other non-vested stock is calculated based on the closing sale price of our common stock on the date of issuance. A summary of non-vested stock activity for the three months ended March 31, 2024 is presented below: Non-vested Weighted Outstanding at December 31, 2023 27,163 $ 37.20 Granted 10,406 12.16 Vested ( 7,989 ) 31.08 Forfeited ( 4,000 ) 41.72 Outstanding at March 31, 2024 25,580 $ 28.21 As of March 31, 2024 , there was approximately $ 1.3 million of unrecognized share-based compensation expense related to these non-vested shares and non-vested shares granted under subsidiary plans which will be recognized over a period of 3.5 years. During the three months ended March 31, 2024 , 11,816 shares were issued under the 2019 Employee Stock Purchase Plan and 7,989 shares were issued as a result of the vesting of non-vested stock. The impact on our results of operations from share-based compensation for the three months ended March 31, 2024 and 2023, was as follows (in thousands): Three Months Ended March 31, 2024 2023 Research and development $ 1,314 $ 1,733 General and administrative 2,882 3,752 Total share-based compensation expense $ 4,196 $ 5,485

Restricted Cash

Restricted Cash	3 Months Ended
	Mar. 31, 2024
Cash and Cash Equivalents [Abstract]
Restricted Cash	Note K – Restricted Cash As of both March 31, 2024, and December 31, 2023 , we maintained non-current restricted cash of $ 3.7 million. This amount is included within “Other long-term assets” in our condensed consolidated balance sheets and is comprised of deposits under letters of credit required under our facility leases. The following table provides a reconciliation of cash, cash equivalents and restricted cash that sums to the total of the same such amounts shown in the condensed consolidated statements of cash flows (in thousands): Three Months Ended March 31, 2024 Three Months Ended March 31, 2023 Beginning of Period End of Period Beginning of Period End of Period Cash and cash equivalents $ 76,110 $ 52,856 $ 178,674 $ 164,819 Restricted cash 3,669 3,669 2,669 2,669 Cash, cash equivalents and restricted cash $ 79,779 $ 56,525 $ 181,343 $ 167,488

Equity

Equity	3 Months Ended
	Mar. 31, 2024
Equity [Abstract]
Equity	Note L – Equity On March 14, 2024, we filed a Post-effective Amendment to an Automatic Shelf Registration Statement on Form POSASR (file no. 333-272911) and a Post-Effective Amendments for Registration Statement on Form POS AM (file no. 333-272911) (together, the “Registration Statement”). The Registration Statement included both a base prospectus that covered the potential offering, issuance and sale from time to time of up to $ 300.0 million of common stock, preferred stock, warrants, debt securities and units of Agenus and a prospectus supplement for the potential offer and sale of up to 6,725,642 shares of common stock (the “Placement Shares”) in “at the market” offerings pursuant to an At Market Issuance Sales Agreement by and between Agenus and B. Riley Securities, Inc. (the “Sales Agent”), dated as of July 22, 2020 (the “Sales Agreement”). Sales pursuant to the Sales Agreement will be made only upon our instruction to the Sales Agent, and we cannot provide assurances that we will issue any additional Placement Shares pursuant to the Sales Agreement. During the three months ended March 31, 2024 , we received net proceeds of approximately $ 17.2 million from the sale of approximately 1.2 million shares of our common stock in at-the-market offerings under the Sales Agreement.

Non-controlling Interest

Non-controlling Interest	3 Months Ended
	Mar. 31, 2024
Noncontrolling Interest [Abstract]
Non-controlling Interest	Note M – Non-controlling Interest Non-controlling interest recorded in our condensed consolidated financial statements as of March 31, 2024 and December 31, 2023, relates to the following approximate interests in certain consolidated subsidiaries, which we do not own. March 31, 2024 December 31, 2023 MiNK Therapeutics, Inc. 37 % 37 % SaponiQx, Inc. 30 % 30 % Changes in non-controlling interest for the periods ended March 31, 2024 and December 31, 2023, were as follows (in thousands): March 31, 2024 December 31, 2023 Beginning balance $ 11,949 $ 6,376 Net loss attributable to non-controlling interest ( 1,568 ) ( 11,676 ) Other items: Distribution of subsidiary shares to Agenus stockholders — 14,888 Purchase of subsidiary shares — ( 2,546 ) Issuance of subsidiary shares for employee bonus — 1,011 Issuance of subsidiary shares for employee stock purchase plan and exercise of options 7 71 Subsidiary share-based compensation 719 3,825 Total other items 726 17,249 Ending balance $ 11,107 $ 11,949 Distribution of subsidiary shares to Agenus stockholders On March 29, 2023 , our Board of Directors declared a stock dividend (the "Dividend") consisting of an aggregate of 5.0 million shares (the "Dividend Stock") of common stock, par value $ 0.00001 per share, of MiNK held by Agenus to record holders of Agenus' common stock, par value $ 0.01 per share as of the close of business on April 17, 2023 (the "Record Date"). On May 1, 2023 , we paid the Dividend and distributed 0.292 of a share of the Dividend Stock for each share of Agenus common stock outstanding as of the close of business on the Record Date. No fractional shares were issued in connection with the Dividend and the shareholders of Agenus who were entitled to receive fractional shares of the Dividend Stock received cash (without interest) in lieu of such fractional shares. Subsequent to the distribution of the Dividend Stock, we maintained a controlling voting interest in MiNK. Purchase of subsidiary shares During the year ended December 31, 2023, we purchased 446,494 shares of MiNK common stock in multiple open market transactions.

Related Party Transactions

Related Party Transactions	3 Months Ended
	Mar. 31, 2024
Related Party Transactions [Abstract]
Related Party Transactions	Note N – Related Party Transactions In 2023, our Audit and Finance Committee approved a contract between Avillion Life Sciences LTD ("Avillion") and Agenus for the performance of up to $ 450,000 of clinical consulting services. Allison Jeynes, a member of our Board of Directors, is chief executive officer of Avillion. No expenses were incurred in the three months ended March 31, 2024. For the three months ended March 31, 2023, approximately $ 228,000 related to these services is included in “Research and development” expense in our condensed consolidated statements of operations.

Recent Accounting Pronouncement

Recent Accounting Pronouncements	3 Months Ended
	Mar. 31, 2024
Accounting Standards Update and Change in Accounting Principle [Abstract]
Recent Accounting Pronouncements	Note O – Recent Accounting Pronouncements Recently Issued, Not Yet Adopted In November 2023, the Financial Accounting Standards Board (“FASB”) issued ASU 2023-07, Segment Reporting (Topic 280): Improvements to Reportable Segment Disclosures. ASU 2023-07 requires incremental annual and quarterly disclosures about segment measures of profit or loss as well as significant segment expenditures. It also requires public entities with a single reportable segment to provide all segment disclosures required by the amendments and all existing segment disclosures in Topic 280. ASU 2023-07 is effective for fiscal years beginning after December 15, 2023 and interim periods within fiscal years beginning after December 15, 2024. As we have a single reportable segment, we expect the adoption of this standard to result in increased disclosures in the notes to our consolidated financial statements. In December 2023, the FASB issued ASU 2023-09, Income Taxes (Topic 740): Improvements to Income Tax Disclosures. ASU 2023-09 requires incremental annual disclosures around income tax rate reconciliations, income taxes paid and other related disclosures. For public business entities, ASU 2023-09 is effective for fiscal years beginning after December 15, 2024. Early adoption is permitted for any annual periods for which financial statements have not been issued or made available for issuance. We are currently evaluating the impact that ASU 2023-09 will have on the notes to our consolidated financial statements. No other new accounting pronouncement issued or effective during the three months ended March 31, 2024 had or is expected to have a material impact on our consolidated financial statements or disclosures.

Subsequent Events

Subsequent Events	3 Months Ended
	Mar. 31, 2024
Subsequent Events [Abstract]
Subsequent Events	Note P – Subsequent Events Reverse Stock Split On April 3, 2024, our stockholders approved a proposal to amend our Amended and Restated Certificate of Incorporation, as amended (the “Certificate of Incorporation”), to effect a reverse stock split of our issued and outstanding common stock at a ratio of 1-for-20 (the “Reverse Stock Split”). On April 4, 2024, we filed a Certificate of Eighth Amendment (the “Certificate of Amendment”) to our Certificate of Incorporation with the Secretary of State of the State of Delaware to effect the Reverse Stock Split. Pursuant to the Certificate of Amendment, the Reverse Stock Split became effective at 12:01 a.m., Eastern Time, on April 12, 2024. As of the opening of trading on April 12, 2024, our common stock began trading on a post-split basis under CUSIP number 00847G 804. All common share, per share and related information included in the accompanying financial statements and footnote disclosures have been adjusted retroactively, where applicable, to reflect the Reverse Stock Split. Purchase Agreement On May 6, 2024, we, and certain wholly-owned subsidiaries, entered into a Purchase and Sale Agreement (the “Purchase Agreement”) with Ligand Pharmaceuticals Incorporated (“Ligand”) for the sale to Ligand of (i) 31.875 % of the development, regulatory and commercial milestone payments we are eligible to receive under our agreements with Bristol-Myers Squibb Company, UroGen Pharma Ltd., Gilead Sciences, Inc., Merck Sharpe & Dohme and Incyte Corporation, (the “Covered License Agreements”) (ii) 18.75 % of the royalties the Company receives under the Covered License Agreements; and (iii) a 2.625 % synthetic royalty on worldwide net sales of botensilimab and balstilimab (collectively the “Purchased Assets”). The total amounts payable to Ligand are subject to a 50 % reduction in the event total payments to Ligand exceed a specified return hurdle. The synthetic royalty is subject to a reduction if annual worldwide net sales exceed a specified level, and a cap on annual worldwide net sales if annual worldwide net sales exceed a higher specified level. The synthetic royalty can increase by 1 % based on the occurrence of certain future events. In consideration for the sale of the Purchased Assets, we will receive $ 75.0 million, less certain reimbursable expenses, on the closing date. The Purchase Agreement permits additional sales of the Purchased Assets to third parties on substantially similar terms on a pro rata basis, up to a maximum of $ 200.0 million. In addition, Ligand has a time-based option to invest an additional $ 25.0 million on a pro rata basis. The Purchase Agreement contains customary representations, warranties and agreements by us and Ligand, indemnification obligations of the parties and certain other obligations of the parties. As part of the transaction, we will grant Ligand security over certain assets related to the Purchased Assets pursuant to security agreements, subject to certain customary exceptions. Closing of the transaction is subject to customary conditions, including execution of customary ancillary documents for a transaction of this type. The transaction is expected to close in May 2024. In connection with the sale of the Purchased Assets, we issued to Ligand a warrant (“Warrant”) to purchase 867,052 shares of our common stock, at an exercise price equal to $ 17.30 . The exercise price of the Warrant and the number of shares issuable upon exercise of the Warrant are subject to adjustments for stock splits, combinations, stock dividends or similar events. The Warrant is exercisable until May 6, 2029 .

Net Loss Per Share (Tables)

Net Loss Per Share (Tables)	3 Months Ended
	Mar. 31, 2024
Earnings Per Share [Abstract]
Schedule of Anti-dilutive Securities Excluded from Computation of Diluted Weighted Average Shares Outstanding	The following securities (listed on an as-if-converted-to-Common-Stock basis) have been excluded from the computation of diluted weighted average shares outstanding as of March 31, 2024 and 2023, as they would be anti-dilutive (in thousands): Three Months Ended March 31, 2024 2023 Warrants 99 99 Stock options 2,205 2,184 Non-vested shares 26 127 Series A-1 convertible preferred stock 17 17

Investments (Tables)

Investments (Tables)	3 Months Ended
	Mar. 31, 2024
Cash and Cash Equivalents [Abstract]
Schedule of Cash Equivalents	Cash equivalents and short-term investments consisted of the following as of March 31, 2024 and December 31, 2023 (in thousands): March 31, 2024 December 31, 2023 Cost Estimated Cost Estimated Institutional money market funds $ 49,220 $ 49,220 $ 70,485 $ 70,485 Total $ 49,220 $ 49,220 $ 70,485 $ 70,485

Goodwill and Acquired Intangi_2

Goodwill and Acquired Intangible Assets (Tables)	3 Months Ended
	Mar. 31, 2024
Goodwill and Intangible Assets Disclosure [Abstract]
Schedule of Changes in Goodwill	The following table sets forth the changes in the carrying amount of goodwill for the three months ended March 31, 2024 (in thousands): Balance, December 31, 2023 $ 24,723 Effect of foreign currency ( 25 ) Balance, March 31, 2024 $ 24,698
Schedule of Acquired Intangible Assets	Acquired intangible assets consisted of the following as of March 31, 2024 and December 31, 2023 (in thousands): As of March 31, 2024 Amortization Gross carrying Accumulated Net carrying Intellectual property 7 - 15 years $ 16,841 $ ( 15,268 ) $ 1,573 Trademarks 4 - 4.5 years 1,199 ( 1,193 ) 6 Other 2 - 7 years 1,932 ( 1,338 ) 594 In-process research and development Indefinite 2,057 — 2,057 Total $ 22,029 $ ( 17,799 ) $ 4,230 As of December 31, 2023 Amortization Gross carrying Accumulated Net carrying Intellectual property 7 - 15 years $ 16,841 $ ( 15,184 ) $ 1,657 Trademarks 4 - 4.5 years 1,213 ( 1,185 ) 28 Other 2 - 7 years 1,988 ( 1,319 ) 669 In-process research and development Indefinite 2,057 — 2,057 Total $ 22,099 $ ( 17,688 ) $ 4,411

Debt (Tables)

Debt (Tables)	3 Months Ended
	Mar. 31, 2024
Debt Disclosure [Abstract]
Schedule of Debt Obligations	Debt obligations consisted of the following as of March 31, 2024 and December 31, 2023 (in thousands): Debt instrument Balance at Current Portion: Debentures $ 146 2015 Subordinated Notes 12,817 Other 612 Total $ 13,575 Debt instrument Balance at Current Portion: Debentures $ 146 Long-term Portion: 2015 Subordinated Notes 12,768 Total $ 12,914

Liability Related to the Sale_2

Liability Related to the Sale of Future Royalties and Milestones (Tables)	3 Months Ended
	Mar. 31, 2024
Liability Related To Sale Of Future Royalties And Milestones [Abstract]
Schedule of Liability Account	The following table shows the activity within the liability account in the three months ended March 31, 2024 (in thousands): Period from Liability related to sale of future royalties and milestones - beginning balance $ 257,296 Non-cash royalty revenue ( 27,767 ) Non-cash interest expense recognized 29,531 Liability related to sale of future royalties and milestones - ending balance 259,060 Less: unamortized transaction costs ( 223 ) Liability related to sale of future royalties and milestones, net $ 258,837

Accrued and Other Current Lia_2

Accrued and Other Current Liabilities (Tables)	3 Months Ended
	Mar. 31, 2024
Other Liabilities Disclosure [Abstract]
Schedule of Accrued Liabilities	Accrued liabilities consisted of the following as of March 31, 2024 and December 31, 2023 (in thousands): March 31, 2024 December 31, 2023 Payroll $ 18,514 $ 14,512 Professional fees 6,195 7,101 Contract manufacturing costs 5,334 7,613 Research services 6,274 10,807 Other 4,974 5,250 Total $ 41,291 $ 45,283
Schedule of Other Current Liabilities	Other current liabilities consisted of the following as of March 31, 2024 and December 31, 2023 (in thousands): March 31, 2024 December 31, 2023 Finance lease liabilities $ 10,738 $ 10,457 Other 3,293 3,458 Total $ 14,031 $ 13,915

Fair Value Measurements (Tables

Fair Value Measurements (Tables)	3 Months Ended
	Mar. 31, 2024
Fair Value Disclosures [Abstract]
Schedule of Assets and Liabilities measured at Fair Value	Assets and liabilities measured at fair value are summarized below (in thousands): Description March 31, 2024 Quoted Prices in Significant Significant Assets: Cash equivalents (Note C) $ 49,220 $ 49,220 $ — $ — Long-term investments 1,834 1,834 — — Total $ 51,054 $ 51,054 $ — $ — Liabilities: Contingent purchase price considerations $ 318 $ — $ — $ 318 Total $ 318 $ — $ — $ 318 Description December 31, 2023 Quoted Prices in Significant Significant Assets: Cash equivalents (Note C) $ 70,485 $ 70,485 $ — $ — Long-term investments 3,222 3,222 — — Total $ 73,707 $ 73,707 $ — $ — Liabilities: Contingent purchase price consideration $ 318 $ — $ — $ 318 Total $ 318 $ — $ — $ 318

Revenue from Contracts with C_2

Revenue from Contracts with Customers (Tables)	3 Months Ended
	Mar. 31, 2024
Collaboration [Abstract]
Summary of Disaggregation of Revenue	The following table presents revenue (in thousands) for the three months ended March 31, 2024 and 2023, disaggregated by geographic region and revenue type. Revenue by geographic region is allocated based on the domicile of our respective business operations. Three months ended March 31, 2024 United States Rest of World Total Revenue Type Other services $ — $ 238 $ 238 Non-cash royalties 27,767 — 27,767 $ 27,767 $ 238 $ 28,005 Three months ended March 31, 2023 Revenue Type Research and development services 267 — 267 Other services — 1,184 1,184 Recognition of deferred revenue 2,345 — 2,345 Non-cash royalties 19,106 — 19,106 $ 21,718 $ 1,184 $ 22,902
Schedule of Information about Contract Assets and Contract Liabilities from Contracts with Customers	The following table provides information about contract liabilities from contracts with customers (in thousands): Three months ended March 31, 2024 Balance at beginning of period Additions Deductions Balance at end of period Contract liabilities: Deferred revenue $ 1,161 $ 5 $ ( 10 ) $ 1,156

Share-Based Compensation Plans

Share-Based Compensation Plans (Tables)	3 Months Ended
	Mar. 31, 2024
Share-Based Payment Arrangement, Noncash Expense [Abstract]
Schedule of Stock Option Activity	A summary of option activity for the three months ended March 31, 2024 is presented below: Options Weighted Weighted Aggregate Outstanding at December 31, 2023 2,141,360 $ 65.00 Granted 164,506 17.44 Exercised — — Forfeited ( 11,982 ) 48.61 Expired ( 88,971 ) 63.66 Outstanding at March 31, 2024 2,204,913 $ 61.55 6.61 $ — Vested or expected to vest at March 31, 2024 2,204,913 $ 61.55 6.61 $ — Exercisable at March 31, 2024 1,558,872 $ 69.34 5.88 $ —
Summary of Non-vested Stock Activity	A summary of non-vested stock activity for the three months ended March 31, 2024 is presented below: Non-vested Weighted Outstanding at December 31, 2023 27,163 $ 37.20 Granted 10,406 12.16 Vested ( 7,989 ) 31.08 Forfeited ( 4,000 ) 41.72 Outstanding at March 31, 2024 25,580 $ 28.21
Schedule of Share-Based Compensation Expense	The impact on our results of operations from share-based compensation for the three months ended March 31, 2024 and 2023, was as follows (in thousands): Three Months Ended March 31, 2024 2023 Research and development $ 1,314 $ 1,733 General and administrative 2,882 3,752 Total share-based compensation expense $ 4,196 $ 5,485

Restricted Cash (Tables)

Restricted Cash (Tables)	3 Months Ended
	Mar. 31, 2024
Cash and Cash Equivalents [Abstract]
Schedule of Reconciliation of Cash, Cash Equivalents and Restricted Cash	The following table provides a reconciliation of cash, cash equivalents and restricted cash that sums to the total of the same such amounts shown in the condensed consolidated statements of cash flows (in thousands): Three Months Ended March 31, 2024 Three Months Ended March 31, 2023 Beginning of Period End of Period Beginning of Period End of Period Cash and cash equivalents $ 76,110 $ 52,856 $ 178,674 $ 164,819 Restricted cash 3,669 3,669 2,669 2,669 Cash, cash equivalents and restricted cash $ 79,779 $ 56,525 $ 181,343 $ 167,488

Non-controlling Interest (Table

Non-controlling Interest (Tables)	3 Months Ended
	Mar. 31, 2024
Noncontrolling Interest [Abstract]
Schedule Of Approximate Interests In Certain Consolidated Subsidiaries	Non-controlling interest recorded in our condensed consolidated financial statements as of March 31, 2024 and December 31, 2023, relates to the following approximate interests in certain consolidated subsidiaries, which we do not own. March 31, 2024 December 31, 2023 MiNK Therapeutics, Inc. 37 % 37 % SaponiQx, Inc. 30 % 30 %
Schedule Of Changes In Non-controlling Interest	Changes in non-controlling interest for the periods ended March 31, 2024 and December 31, 2023, were as follows (in thousands): March 31, 2024 December 31, 2023 Beginning balance $ 11,949 $ 6,376 Net loss attributable to non-controlling interest ( 1,568 ) ( 11,676 ) Other items: Distribution of subsidiary shares to Agenus stockholders — 14,888 Purchase of subsidiary shares — ( 2,546 ) Issuance of subsidiary shares for employee bonus — 1,011 Issuance of subsidiary shares for employee stock purchase plan and exercise of options 7 71 Subsidiary share-based compensation 719 3,825 Total other items 726 17,249 Ending balance $ 11,107 $ 11,949

Business, Liquidity and Basis_2

Business, Liquidity and Basis of Presentation (Narrative) (Details) $ / shares in Units, $ in Thousands		1 Months Ended	3 Months Ended
	Apr. 03, 2024 $ / shares	Aug. 31, 2023	Mar. 31, 2024 USD ($) $ / shares	Dec. 31, 2023 USD ($) $ / shares	Mar. 31, 2023 USD ($)	Mar. 29, 2023 $ / shares	Dec. 31, 2022 USD ($)
Product Information [Line Items]
Cash, cash equivalents and short term investment			$ 52,900
Decrease cash, cash equivalents and short term investment			23,300
Accumulated deficit			2,017,554	$ 1,955,668
Cash and cash equivalents			$ 52,856	$ 76,110	$ 164,819		$ 178,674
Percentage of reduced workforce		25%
Common stock, par value | $ / shares			$ 0.01	$ 0.01		$ 0.01
Subsequent Event [Member]
Product Information [Line Items]
Common stock, par value | $ / shares	$ 0.01
Subsequent Event [Member] | Common Stock [Member]
Product Information [Line Items]
Reverse stock split, ratio	0.05
Reverse stock split ratio, description	1-for-20
Subordinated Notes [Member]
Product Information [Line Items]
Debt instrument, face amount			$ 13,000
Debt instrument maturity month and year			2025-02
MiNK Therapeutics, Inc.
Product Information [Line Items]
Cash and cash equivalents				$ 3,400

Net Loss Per Share (Schedule of

Net Loss Per Share (Schedule of Anti-dilutive Securities Excluded from Computation of Diluted Weighted Average Shares Outstanding) (Details) - shares	3 Months Ended
	Mar. 31, 2024	Mar. 31, 2023
Warrants [Member]
Antidilutive Securities Excluded from Computation of Earnings Per Share [Line Items]
Antidilutive Securities Excluded from Computation of Earnings Per Share, Amount	99,000	99,000
Employee Stock Option [Member]
Antidilutive Securities Excluded from Computation of Earnings Per Share [Line Items]
Antidilutive Securities Excluded from Computation of Earnings Per Share, Amount	2,205,000	2,184,000
Non-vested Shares [Member]
Antidilutive Securities Excluded from Computation of Earnings Per Share [Line Items]
Antidilutive Securities Excluded from Computation of Earnings Per Share, Amount	26,000	127,000
Series A-1 convertible preferred stock [Member]
Antidilutive Securities Excluded from Computation of Earnings Per Share [Line Items]
Antidilutive Securities Excluded from Computation of Earnings Per Share, Amount	17,000	17,000

Investments (Schedule of Cash E

Investments (Schedule of Cash Equivalents and Short Term Investments) (Details) - USD ($) $ in Thousands	Mar. 31, 2024	Dec. 31, 2023
Cash And Cash Equivalents [Line Items]
Cash equivalents and short term investments	$ 52,900
Cost [Member]
Cash And Cash Equivalents [Line Items]
Cash equivalents and short term investments	49,220	$ 70,485
Estimated Fair Value [Member]
Cash And Cash Equivalents [Line Items]
Cash equivalents and short term investments	49,220	70,485
Institutional Money Market Funds [Member] | Cost [Member]
Cash And Cash Equivalents [Line Items]
Cash equivalents and short term investments	49,220	70,485
Institutional Money Market Funds [Member] | Estimated Fair Value [Member]
Cash And Cash Equivalents [Line Items]
Cash equivalents and short term investments	$ 49,220	$ 70,485

Goodwill and Acquired Intangi_3

Goodwill and Acquired Intangible Assets (Schedule of Changes in Goodwill) (Details) $ in Thousands	3 Months Ended
	Mar. 31, 2024 USD ($)
Goodwill [Roll Forward]
Beginning balance	$ 24,723
Effect of foreign currency	(25)
Ending balance	$ 24,698

Goodwill and Acquired Intangi_4

Goodwill and Acquired Intangible Assets (Acquired Intangible Assets) (Details) - USD ($) $ in Thousands	3 Months Ended	12 Months Ended
	Mar. 31, 2024	Dec. 31, 2023
Finite-Lived Intangible Assets [Line Items]
Intangible Assets, Gross (Excluding Goodwill)	$ 22,029	$ 22,099
Accumulated amortization	(17,799)	(17,688)
Net carrying amount	4,230	4,411
Indefinite-lived Intangible Assets Acquired	2,057	2,057
Intellectual Property [Member]
Finite-Lived Intangible Assets [Line Items]
Gross carrying amount	16,841	16,841
Accumulated amortization	(15,268)	(15,184)
Net carrying amount	$ 1,573	$ 1,657
Intellectual Property [Member] | Minimum [Member]
Finite-Lived Intangible Assets [Line Items]
Amortization period (years)	7 years	7 years
Intellectual Property [Member] | Maximum [Member]
Finite-Lived Intangible Assets [Line Items]
Amortization period (years)	15 years	15 years
Trademarks [Member]
Finite-Lived Intangible Assets [Line Items]
Gross carrying amount	$ 1,199	$ 1,213
Accumulated amortization	(1,193)	(1,185)
Net carrying amount	$ 6	$ 28
Trademarks [Member] | Minimum [Member]
Finite-Lived Intangible Assets [Line Items]
Amortization period (years)	4 years	4 years
Trademarks [Member] | Maximum [Member]
Finite-Lived Intangible Assets [Line Items]
Amortization period (years)	4 years 6 months	4 years 6 months
Other [Member]
Finite-Lived Intangible Assets [Line Items]
Gross carrying amount	$ 1,932	$ 1,988
Accumulated amortization	(1,338)	(1,319)
Net carrying amount	$ 594	$ 669
Other [Member] | Minimum [Member]
Finite-Lived Intangible Assets [Line Items]
Amortization period (years)	2 years	2 years
Other [Member] | Maximum [Member]
Finite-Lived Intangible Assets [Line Items]
Amortization period (years)	7 years	7 years

Goodwill and Acquired Intangi_5

Goodwill and Acquired Intangible Assets (Narrative) (Details) $ in Millions	3 Months Ended
	Mar. 31, 2024 USD ($)
Goodwill and Intangible Assets Disclosure [Abstract]
Acquired Finite-lived Intangible Assets, Weighted Average Useful Life	9 years
Finite-Lived Intangible Assets, Estimated Amortization Expense, Remainder of 2024	$ 0.4
Finite-Lived Intangible Assets, Estimated Amortization Expense, December 31, 2025	0.5
Finite-Lived Intangible Assets, Estimated Amortization Expense, December 31, 2026	0.5
Finite-Lived Intangible Assets, Estimated Amortization Expense, December 31, 2027	0.4
Finite-Lived Intangible Assets, Estimated Amortization Expense, December 31, 2028	$ 0.3

Debt - Schedule of Debt Obligat

Debt - Schedule of Debt Obligations (Details) - USD ($) $ in Thousands	Mar. 31, 2024	Dec. 31, 2023
Debt Instrument [Line Items]
Other	$ 612
Total	13,575	$ 12,914
2015 Subordinated Notes [Member]
Debt Instrument [Line Items]
2015 Subordinated Notes	12,817	12,768
Debentures [Member]
Debt Instrument [Line Items]
Debentures	$ 146	$ 146

Debt (Narrative) (Details)

Debt (Narrative) (Details) - USD ($) $ in Millions	Mar. 31, 2024	Dec. 31, 2023
Debt Disclosure [Abstract]
Principal amount of outstanding debt	$ 13.8	$ 13.1

Liability Related to the Sale_3

Liability Related to the Sale of Future Royalties and Milestones (Schedule of Liability Account) (Details) $ in Thousands	3 Months Ended
	Mar. 31, 2024 USD ($)
Liability Related To Sale Of Future Royalties And Milestones [Abstract]
Liability related to sale of future royalties and milestones - beginning balance	$ 257,296
Non-cash royalty revenue	(27,767)
Non-cash interest expense recognized	29,531
Liability related to sale of future royalties and milestones - ending balance	259,060
Less: unamortized transaction costs	(223)
Liability related to sale of future royalties and milestones, net	$ 258,837

Liability Related to the Sale_4

Liability Related to the Sale of Future Royalties and Milestones (Narrative) (Details) - USD ($) $ in Thousands		3 Months Ended
	Jan. 19, 2018	Mar. 31, 2024
Liability Related To Sale Of Future Royalties And Milestones [Line Items]
Non-cash royalty revenue recognized		$ 27,767
Non-cash interest expense		29,531
HCR [Member] | GSK Agreements [Member] | Royalty Purchase Agreement [Member]
Liability Related To Sale Of Future Royalties And Milestones [Line Items]
Percentage of purchase of worldwide rights to receive royalties	100%
Gross proceeds received for royalty rights	$ 190,000
Non-cash royalty revenue recognized		27,800
Non-cash interest expense		$ 29,500
Effective annual interest rate		48%
Prospective effective annual interest rate		26.50%

Accrued and Other Current Lia_3

Accrued and Other Current Liabilities (Schedule of Accrued Liabilities) (Details) - USD ($) $ in Thousands	Mar. 31, 2024	Dec. 31, 2023
Accrued Liabilities, Current [Abstract]
Payroll	$ 18,514	$ 14,512
Professional fees	6,195	7,101
Contract manufacturing costs	5,334	7,613
Research services	6,274	10,807
Other	4,974	5,250
Total	$ 41,291	$ 45,283

Accrued and Other Current Lia_4

Accrued and Other Current Liabilities (Schedule of Other Current Liabilities) (Details) - USD ($) $ in Thousands	Mar. 31, 2024	Dec. 31, 2023
Other Liabilities, Current [Abstract]
Finance lease liabilities	$ 10,738	$ 10,457
Other	3,293	3,458
Total	$ 14,031	$ 13,915

Fair Value Measurements (Narrat

Fair Value Measurements (Narrative) (Details) - USD ($) $ in Thousands	Mar. 31, 2024	Dec. 31, 2023
Fair Value Assets And Liabilities Measured On Recurring And Nonrecurring Basis [Line Items]
Contingent purchase price considerations	$ 318	$ 318
Long-term Debt, Gross	13,800	13,100
Level 2 [Member]
Fair Value Assets And Liabilities Measured On Recurring And Nonrecurring Basis [Line Items]
Contingent purchase price considerations	0	0
Debt Instrument, Fair Value Disclosure	$ 13,600	$ 13,000

Fair Value Measurements (Schedu

Fair Value Measurements (Schedule of Assets and Liabilities Measured at Fair Value) (Details) - USD ($) $ in Thousands	Mar. 31, 2024	Dec. 31, 2023
Fair Value Balance Sheet Grouping Financial Statement Captions [Line Items]
Cash equivalents	$ 49,220	$ 70,485
Long-term investments	1,834	3,222
Total	51,054	73,707
Contingent purchase price considerations	318	318
Total	318	318
Quoted Prices in Active Markets for Identical Assets (Level 1) [Member]
Fair Value Balance Sheet Grouping Financial Statement Captions [Line Items]
Cash equivalents	49,220	70,485
Long-term investments	1,834	3,222
Total	51,054	73,707
Contingent purchase price considerations	0	0
Total	0	0
Significant Other Observable Inputs (Level 2) [Member]
Fair Value Balance Sheet Grouping Financial Statement Captions [Line Items]
Cash equivalents	0	0
Long-term investments	0	0
Total	0	0
Contingent purchase price considerations	0	0
Total	0	0
Significant Unobservable Inputs (Level 3) [Member]
Fair Value Balance Sheet Grouping Financial Statement Captions [Line Items]
Cash equivalents	0	0
Long-term investments	0	0
Total	0	0
Contingent purchase price considerations	318	318
Total	$ 318	$ 318

Revenue from Contracts with C_3

Revenue from Contracts with Customers (Narrative) (Details) - USD ($)		3 Months Ended
	Jan. 23, 2019	Mar. 31, 2024	Mar. 31, 2023	Dec. 20, 2018
Revenue From Contract With Customer [Line Items]
Shares sold at the market		$ 17,171,000	$ 60,583,000
Revenue		28,005,000	22,902,000
Asset impairment charges		0
Contract with customer, liability, revenue recognized		10,000
Receivables for R & D services		500,000
Capitalized contract , cost		0
Research and Development Revenue [Member]
Revenue From Contract With Customer [Line Items]
Revenue		0	2,612,000
Gilead Sciences, Inc. [Member] | Collaborative Arrangement [Member]
Revenue From Contract With Customer [Line Items]
Fee received	$ 120,000,000
Shares sold at the market	30,000,000
Upfront license exercise fee	$ 50,000,000
Milestone Payments Receivable				$ 520,000,000
Revenue		$ 0
Gilead Sciences, Inc. [Member] | Collaborative Arrangement [Member] | Research and Development Revenue [Member]
Revenue From Contract With Customer [Line Items]
Revenue			$ 2,300,000

Revenue from Contracts with C_4

Revenue from Contracts with Customers (Summary of Disaggregation of Revenue) (Details) - USD ($) $ in Thousands	3 Months Ended
	Mar. 31, 2024	Mar. 31, 2023
Disaggregation Of Revenue [Line Items]
Revenue	$ 28,005	$ 22,902
Research and development services [Member]
Disaggregation Of Revenue [Line Items]
Revenue		267
Other services [Member]
Disaggregation Of Revenue [Line Items]
Revenue	238	1,184
Recognition of deferred revenue [Member]
Disaggregation Of Revenue [Line Items]
Revenue		2,345
Non-cash royalty revenue [Member]
Disaggregation Of Revenue [Line Items]
Revenue	27,767	19,106
Non-Cash Royalty Revenue Related to the Sale of Future Royalties [Member]
Disaggregation Of Revenue [Line Items]
Revenue	27,767	19,106
United States [Member]
Disaggregation Of Revenue [Line Items]
Revenue	27,767	21,718
United States [Member] | Research and development services [Member]
Disaggregation Of Revenue [Line Items]
Revenue		267
United States [Member] | Recognition of deferred revenue [Member]
Disaggregation Of Revenue [Line Items]
Revenue		2,345
United States [Member] | Non-cash royalty revenue [Member]
Disaggregation Of Revenue [Line Items]
Revenue	27,767	19,106
Rest of World [Member]
Disaggregation Of Revenue [Line Items]
Revenue	238	1,184
Rest of World [Member] | Other services [Member]
Disaggregation Of Revenue [Line Items]
Revenue	$ 238	$ 1,184

Revenue from Contracts with C_5

Revenue from Contracts with Customers (Schedule of Information about Contract Assets and Contract Liabilities from Contracts with Customers) (Details) $ in Thousands	3 Months Ended
	Mar. 31, 2024 USD ($)
Contract with Customer, Contract Asset, Contract Liability, and Receivable [Abstract]
Deferred revenue, Beginning Balance	$ 1,161
Additions	5
Deferred revenue, Deductions	(10)
Deferred revenue, Ending Balance	$ 1,156

Share-Based Compensation Plan_2

Share-Based Compensation Plans (Narrative) (Details) - USD ($) $ / shares in Units, $ in Millions	3 Months Ended
	Mar. 31, 2024	Mar. 31, 2023
Deferred Compensation Arrangement with Individual, Share-based Payments [Line Items]
Weighted average grant-date fair value of options granted	$ 8.82	$ 30.6
Shares issued from vesting of non vested stock	$ 31.08
Employee Stock Option [Member]
Deferred Compensation Arrangement with Individual, Share-based Payments [Line Items]
Unrecognized share-based compensation expense	$ 18.6
Unrecognized share-based compensation expense, weighted average period	1 year 8 months 12 days
Restricted Stock [Member]
Deferred Compensation Arrangement with Individual, Share-based Payments [Line Items]
Unrecognized share-based compensation expense, Other than option	$ 1.3
Unrecognized share-based compensation expense, weighted average period, Other than option	3 years 6 months
2009 EIP [Member]
Deferred Compensation Arrangement with Individual, Share-based Payments [Line Items]
Deferred Compensation Arrangement with Individual, Maximum Contractual Term	10 years
2009 EIP [Member] | Minimum [Member]
Deferred Compensation Arrangement with Individual, Share-based Payments [Line Items]
Vesting period	3 years
2009 EIP [Member] | Maximum [Member]
Deferred Compensation Arrangement with Individual, Share-based Payments [Line Items]
Vesting period	4 years
2019 ESPP [Member]
Deferred Compensation Arrangement with Individual, Share-based Payments [Line Items]
Shares issued under ESPP	11,816
Shares issued from vesting of non vested stock	7,989

Share-Based Compensation Plan_3

Share-Based Compensation Plans (Schedule of Stock Option Activity) (Details)	3 Months Ended
	Mar. 31, 2024 $ / shares shares
Share-Based Payment Arrangement, Noncash Expense [Abstract]
Options Outstanding, Beginning Balance | shares	2,141,360
Options Granted | shares	164,506
Options Forfeited | shares	(11,982)
Options Expired | shares	(88,971)
Options Outstanding, Ending Balance | shares	2,204,913
Options Vested or expected to vest | shares	2,204,913
Options Exercisable | shares	1,558,872
Options Outstanding, Weighted Average Exercise Price, Beginning Balance | $ / shares	$ 65
Options Granted, Weighted Average Exercise Price | $ / shares	17.44
Options Forfeited, Weighted Average Exercise Price | $ / shares	48.61
Options Expired, Weighted Average Exercise Price | $ / shares	63.66
Options Outstanding, Weighted Average Exercise Price, Ending Balance | $ / shares	61.55
Options Vested or expected to vest, Weighted Average Exercise Price | $ / shares	61.55
Options Exercisable, Weighted Average Exercise Price | $ / shares	$ 69.34
Options Outstanding, Weighted Average Remaining Contractual Term	6 years 7 months 9 days
Options Vested or expected to vest, Weighted Average Remaining Contractual Term	6 years 7 months 9 days
Options Exercisable, Weighted Average Remaining Contractual Term	5 years 10 months 17 days

Share-Based Compensation Plan_4

Share-Based Compensation Plans (Summary of Non-vested Stock Activity) (Details)	3 Months Ended
	Mar. 31, 2024 $ / shares shares
Share-Based Payment Arrangement, Noncash Expense [Abstract]
Non-vested Shares Outstanding, Beginning Balance | shares	27,163
Non-vested Shares Granted | shares	10,406
Non-vested Shares Vested | shares	(7,989)
Non-vested Shares Forfeited | shares	(4,000)
Non-vested Shares Outstanding, Ending Balance | shares	25,580
Non-vested Shares Outstanding, Weighted Average Grant Date Fair Value, Beginning Balance | $ / shares	$ 37.20
Non-vested Shares Granted, Weighted Average Grant Date Fair Value | $ / shares	12.16
Non-vested Shares Vested, Weighted Average Grant Date Fair Value | $ / shares	31.08
Non-vested Shares Forfeited, Weighted Average Grant Date Fair Value | $ / shares	41.72
Non-vested Shares Outstanding, Weighted Average Grant Date Fair Value, Ending Balance | $ / shares	$ 28.21

Share-Based Compensation Plan_5

Share-Based Compensation Plans (Schedule of Share-Based Compensation Expense) (Details) - USD ($) $ in Thousands	3 Months Ended
	Mar. 31, 2024	Mar. 31, 2023
Employee Service Share-based Compensation, Allocation of Recognized Period Costs [Line Items]
Share-based compensation expense	$ 4,196	$ 5,485
Research and Development [Member]
Employee Service Share-based Compensation, Allocation of Recognized Period Costs [Line Items]
Share-based compensation expense	1,314	1,733
General and Administrative [Member]
Employee Service Share-based Compensation, Allocation of Recognized Period Costs [Line Items]
Share-based compensation expense	$ 2,882	$ 3,752

Restricted Cash (Narrative) (De

Restricted Cash (Narrative) (Details) - USD ($) $ in Millions	Mar. 31, 2024	Dec. 31, 2023
Cash and Cash Equivalents [Abstract]
Restricted cash	$ 3.7	$ 3.7

Restricted Cash (Schedule of Re

Restricted Cash (Schedule of Reconciliation of Cash, Cash Equivalents and Restricted Cash) (Details) - USD ($) $ in Thousands	Mar. 31, 2024	Dec. 31, 2023	Mar. 31, 2023	Dec. 31, 2022
Cash and Cash Equivalents [Abstract]
Cash and cash equivalents	$ 52,856	$ 76,110	$ 164,819	$ 178,674
Restricted cash	3,669	3,669	2,669	2,669
Cash, cash equivalents and restricted cash	$ 56,525	$ 79,779	$ 167,488	$ 181,343

Equity (Narrative) (Details)

Equity (Narrative) (Details) - At Market Issuance Sales Agreement [Member] - B. Riley FBR, Inc. [Member] - New Sales Agreement [Member] $ in Millions	3 Months Ended
	Mar. 31, 2024 USD ($) shares
Class Of Stock [Line Items]
Shares sold at the market, shares | shares	6,725,642
Common stock, preferred stock, warrants, debt securities and units | $	$ 300
Net proceeds from issuance of common stock | $	$ 17.2
Shares sold at the market, shares | shares	1,200,000

Non-controlling Interest - Sche

Non-controlling Interest - Schedule Of Approximate Interests In Certain Consolidated Subsidiaries (Details)	Mar. 31, 2024	Dec. 31, 2023
MiNK Therapeutics, Inc.
Minority Interest [Line Items]
Percentage of Non-controlling interest	37%	37%
SaponiQx, Inc.
Minority Interest [Line Items]
Percentage of Non-controlling interest	30%	30%

Non-controlling Interest - Sc_2

Non-controlling Interest - Schedule Of Changes In Non-controlling Interest (Details) - USD ($) $ in Thousands	3 Months Ended		12 Months Ended
	Mar. 31, 2024	Mar. 31, 2023	Dec. 31, 2023
Minority Interest [Line Items]
Beginning balance	$ 11,949
Net loss attributable to non-controlling interest	(1,568)	$ (2,639)
Issuance of subsidiary shares for employee bonus		726
Share-based compensation	4,196	5,485
Ending balance	11,107		$ 11,949
Non-controlling Interest [Member]
Minority Interest [Line Items]
Beginning balance	11,949	6,376	6,376
Net loss attributable to non-controlling interest	(1,568)		(11,676)
Distribution of subsidiary shares to Agenus stockholders			14,888
Purchase of subsidiary shares			(2,546)
Issuance of subsidiary shares for employee bonus			1,011
Issuance of subsidiary shares for employee stock purchase plan and exercise of options	7		71
Share-based compensation	719	$ 919	3,825
Total other items	726		17,249
Ending balance	$ 11,107		$ 11,949

Non-controlling Interest - Addi

Non-controlling Interest - Additional Information (Details) - USD ($) $ / shares in Units, $ in Thousands			3 Months Ended	12 Months Ended
	May 01, 2023	Mar. 29, 2023	Mar. 31, 2023	Dec. 31, 2023	Mar. 31, 2024
Minority Interest [Line Items]
Issuance of subsidiary shares to noncontrolling interest			$ 726
Date of declared stock dividend		Mar. 29, 2023
Dividends common stock, shares		5,000,000
Common stock, par value		$ 0.01		$ 0.01	$ 0.01
Close of business, date of record		Apr. 17, 2023
Dividend Paid [Member]
Minority Interest [Line Items]
Dividends, date to be paid	May 01, 2023
Dividend distribution price per share	$ 0.292
Number of fractional shares issued	0
MiNK Therapeutics, Inc.
Minority Interest [Line Items]
Common stock, par value		$ 0.00001
Purchase of subsidiary shares				446,494

Related Party Transactions (Nar

Related Party Transactions (Narrative) (Details) - USD ($)	3 Months Ended
	Mar. 31, 2024	Mar. 31, 2023
Related Party Transaction [Line Items]
Related party expenses incurred	$ 0
Research and Development Manufacturing Services [Member]
Related Party Transaction [Line Items]
Total expenses		$ 228,000
Clinical Research Services [Member]
Related Party Transaction [Line Items]
Total expenses	$ 450,000

Subsequent Events (Narrative) (

Subsequent Events (Narrative) (Details) - Subsequent Event [Member] $ / shares in Units, $ in Millions	May 06, 2024 USD ($) $ / shares shares	Apr. 03, 2024
Purchase Agreement [Member] | Ligand Pharmaceuticals Incorporated [Member]
Subsequent Event [Line Items]
Percentage of synthetic royalty on worldwide net sales of purchased assets	2.625%
Percentage reduction in amounts payable upon overall payments due exceeding specified return hurdle	50%
Percentage increase in synthetic royalty based on certain future events	1%
Consideration on sale of purchased assets less reimbursable expenses	$ 75
Time-based option to invest, additional amount	25
Purchase Agreement [Member] | Ligand Pharmaceuticals Incorporated [Member] | Maximum [Member]
Subsequent Event [Line Items]
Additional sales of purchased sssets to third parties on pro rata basis	$ 200
Purchase Agreement [Member] | Ligand Pharmaceuticals Incorporated [Member] | Covered License Agreements [Member]
Subsequent Event [Line Items]
Percentage of sale of development, regulatory and commercial milestone payments eligible to receive	31.875%
Percentage of royalties receipts	18.75%
Common Stock [Member]
Subsequent Event [Line Items]
Reverse stock split, ratio		0.05
Reverse stock split ratio, description		1-for-20
Common Stock [Member] | Ligand Pharmaceuticals Incorporated [Member]
Subsequent Event [Line Items]
Warrants issued to purchase shars of common stock | shares	867,052
Warrants, exercise price | $ / shares	$ 17.3
Warrants, expiration date	May 06, 2029