Condensed Consolidated Statements of Cash Flows (Unaudited) - USD ($) $ in Thousands	3 Months Ended
	Mar. 31, 2022	Mar. 31, 2021
CASH FLOWS FROM OPERATING ACTIVITIES
Net loss	$ (24,436)	$ (18,218)
Adjustments to reconcile net loss to net cash used in operating activities:
Depreciation and amortization	403	355
Purchase net premium on marketable securities	(33)	(174)
Net amortization of premium (accretion of discount) on marketable securities	15	181
Stock-based compensation	2,101	1,757
Non-cash operating lease expense	94	108
Other	2	0
Changes in operating assets and liabilities:
License and development receivables	(197)	(21,500)
Prepaid expenses and other assets	150	(340)
Accounts payable	(338)	(376)
Operating lease liabilities	(119)	(123)
Deferred revenue	(767)	21,500
Accrued and other liabilities	(3,138)	(2,700)
Net cash used in operating activities	(26,263)	(19,530)
CASH FLOWS FROM INVESTING ACTIVITIES
Purchases of property and equipment	(37)	(450)
Purchases of marketable securities	(3,500)	(24,250)
Proceeds from maturities of marketable securities	29,296	34,000
Net cash provided by investing activities	25,759	9,300
CASH FLOWS FROM FINANCING ACTIVITIES
Proceeds from employee stock plan purchases and stock option exercises	184	367
Principal payments on finance lease obligation	(172)	(5)
Net cash provided by financing activities	12	362
Effect of exchange rate on cash, cash equivalents, and restricted cash	(23)	7
NET DECREASE IN CASH, CASH EQUIVALENTS, AND RESTRICTED CASH	(515)	(9,861)
CASH, CASH EQUIVALENTS, AND RESTRICTED CASH
Beginning of period	16,980	91,937
End of period	16,465	82,076
Supplemental Disclosure of Non-Cash Investing and Financing Information:
Unrealized loss on investment	$ 120	$ 0