Condensed Consolidated Balance Sheets (Unaudited) - USD ($) $ in Thousands	Sep. 30, 2021	Dec. 31, 2020
ASSETS
Cash and cash equivalents	$ 256,529	$ 99,871
Short-term investments	4,999
Accounts receivable	21,773	1,157
Prepaid expenses	18,342	10,746
Other current assets	6,758	2,009
Total current assets	308,401	113,783
Property, plant and equipment, net of accumulated amortization and depreciation of $49,433 and $47,201 at September 30, 2021 and December 31, 2020, respectively	50,279	26,790
Operating lease right-of-use assets	31,246	33,480
Goodwill	24,528	25,452
Acquired intangible assets, net of accumulated amortization of $13,335 and $11,841 at September 30, 2021 and December 31, 2020, respectively	8,993	10,886
Other long-term assets	14,192	4,123
Total assets	437,639	214,514
LIABILITIES, CONVERTIBLE PREFERRED STOCK AND STOCKHOLDERS’ EQUITY (DEFICIT)
Current portion, long-term debt	542	833
Current portion, liability related to sale of future royalties and milestones	63,684	57,362
Current portion, deferred revenue	19,682	17,186
Current portion, operating lease liabilities	2,368	1,950
Accounts payable	25,118	17,015
Accrued liabilities	31,955	29,057
Other current liabilities	6,782	6,481
Total current liabilities	150,131	129,884
Long-term debt, net of current portion	12,786	18,879
Liability related to sale of future royalties and milestones, net of current portion	189,229	176,263
Deferred revenue, net of current portion	5,407	28,282
Operating lease liabilities, net of current portion	38,900	34,065
Contingent purchase price considerations	3,739	10,208
Other long-term liabilities	1,894	1,514
Commitments and contingencies
STOCKHOLDERS’ EQUITY (DEFICIT)
Common stock, par value $0.01 per share; 400,000,000 shares authorized; 247,511,769 and 196,090,980 shares issued at September 30, 2021 and December 31, 2020, respectively	2,475	1,961
Additional paid-in capital	1,463,524	1,257,502
Accumulated other comprehensive income	177	2,772
Accumulated deficit	(1,424,322)	(1,465,907)
Total stockholders’ equity (deficit) attributable to Agenus Inc.	41,854	(203,672)
Non-controlling interest	(6,301)	(7,826)
Total stockholders’ equity (deficit)	35,553	(211,498)
Total liabilities, convertible preferred stock and stockholders’ equity (deficit)	437,639	214,514
Series C-1 Convertible Preferred Stock [Member]
CONVERTIBLE PREFERRED STOCK
Series C-1 convertible preferred stock; no and 12,459 shares designated, issued, and outstanding at September 30, 2021 and December 31, 2020, respectively		26,917
Series A-1 convertible preferred stock [Member]
STOCKHOLDERS’ EQUITY (DEFICIT)
Series A-1 convertible preferred stock; 31,620 shares designated, issued, and outstanding at September 30, 2021 and December 31, 2020; liquidation value of $33,408 at September 30, 2021	0	0
Total stockholders’ equity (deficit)	$ 0	$ 0