CONSOLIDATED STATEMENTS OF CASH FLOWS - USD ($) $ in Thousands	3 Months Ended		6 Months Ended		9 Months Ended		12 Months Ended
	Mar. 31, 2023	Mar. 31, 2022	Jun. 30, 2023	Jun. 30, 2022	Sep. 30, 2023	Sep. 30, 2022	Dec. 31, 2023	Dec. 31, 2022
Cash flows from operating activities
Net loss	$ (17,326)	$ (19,015)	$ (40,391)	$ (40,497)	$ (52,108)	$ (64,410)	$ (63,078)	$ (86,804)
Adjustments to reconcile net loss to net cash used in operating activities:
Depreciation and amortization expense	174	76	348	166	525	307	704	480
Amortization (accretion) on marketable securities	(143)	0	(182)	0	(182)	0	(182)	(99)
Non-cash interest expense	24	19	54	38	87	58	116	83
Non-cash lease expense	131	179	265	334	401	463	538	593
Non-cash (income) expense from collaborative arrangements, net	1,008	996	1,392	3,007	(1,134)	4,856	(696)	6,603
Stock-based compensation expense	2,689	3,299	5,321	5,378	7,495	7,873	9,217	10,541
Impairment of advance for COVAXIN supply			4,074	0	4,074	0	4,074	0
Loss on disposal of fixed assets related to COVAXIN			363	0	363	0	363	0
Other	352	0	439	0	379	(673)	46	(671)
Changes in assets and liabilities:
Prepaid expenses and other current assets	(60)	(575)	572	132	132	1,888	(296)	91
Accounts payable and accrued expenses	(4,964)	131	(9,049)	2,844	(10,402)	6,734	(12,343)	9,487
Lease obligations	(125)	(176)	(252)	(265)	(382)	(261)	(517)	(383)
Net cash used in operating activities	(18,240)	(15,066)	(37,046)	(28,863)	(50,752)	(43,165)	(62,054)	(60,079)
Cash flows from investing activities
Purchases of marketable securities	(3,947)	0	(3,947)	0	(3,947)	0	(3,947)	(13,271)
Proceeds from maturities of marketable securities	9,000	0	17,500	0	17,500	0	17,500	0
Purchases of property and equipment	(1,612)	(223)	(4,389)	(1,589)	(7,754)	(2,433)	(10,476)	(4,457)
Repayment of note receivable					0	761	0	761
Net cash provided by (used in) investing activities	3,441	(223)	9,164	(1,589)	5,799	(1,672)	3,077	(16,967)
Cash flows from financing activities
Proceeds from issuance of common stock	5,731	50,177	20,690	50,538	20,788	51,141	20,804	59,567
Payment of equity issuance costs	(173)	(75)	(222)	(200)	(355)	(298)	(355)	(549)
Proceeds from issuance of debt			500	0	500	500	500	500
Payments of debt issuance costs	(62)	0	(68)	0	(68)	(43)	(68)	(43)
Net cash provided by financing activities	5,496	50,102	20,900	50,338	20,865	51,300	20,881	59,475
Effect of changes in exchange rate on cash and cash equivalents	(1)	0	(3)	10	2	30	(5)	25
Net (decrease) in cash and cash equivalents	(9,304)	34,813	(6,985)	19,896	(24,086)	6,493	(38,101)	(17,546)
Cash, cash equivalents, and restricted cash at beginning of period	77,563	95,109	77,563	95,109	77,563	95,109	77,563	95,109
Cash and cash equivalents at end of period	68,259	129,922	70,578	115,005	53,477	101,602	39,462	77,563
Supplemental disclosure of non-cash investing and financing transactions:
Purchase of property and equipment	$ 1,119	$ 611	2,637	491	1,969	1,231	2,189	911
Right-of-use assets related to operating leases			$ 0	$ 2,918	0	2,916	572	2,916
Debt issuance costs					$ 0	$ 19	$ 0	$ 37