Consolidated Statements of Cash Flows - USD ($) $ in Thousands	12 Months Ended
	Dec. 31, 2022	Dec. 31, 2021	Dec. 31, 2020
CASH FLOWS FROM OPERATING ACTIVITIES
Net loss	$ (83,815)	$ (65,801)	$ (80,893)
Adjustments to reconcile net loss to net cash used in operating activities:
Stock-based compensation	7,111	8,038	6,256
Depreciation and amortization	1,567	1,576	996
Purchase net (premium) discount on marketable securities	428	(344)	(286)
Net amortization of premium (accretion of discount) on marketable securities	(327)	548	73
Non-cash operating lease expense	397	425	628
Other	(2)	9	(9)
Changes in operating assets and liabilities:
Development receivable	440	(815)	0
Accounts payable	(2,641)	1,065	(544)
Prepaid expenses and other assets	(1,144)	(1,216)	(1,101)
Deferred revenue	(880)	3,576	0
Operating lease liabilities	(435)	(404)	251
Accrued and other liabilities	(843)	(373)	(1,146)
Net cash used in operating activities	(80,144)	(53,716)	(75,775)
CASH FLOWS FROM INVESTING ACTIVITIES
Purchases of property and equipment	(38)	(573)	(4,280)
Purchases of marketable securities	(39,500)	(133,079)	(129,000)
Proceeds from maturities and sales of marketable securities	96,546	111,033	125,676
Net cash provided by (used in) investing activities	57,008	(22,619)	(7,604)
CASH FLOWS FROM FINANCING ACTIVITIES
Proceeds from issuance of common stock and pre-funded warrants in registered direct offering, net of offering costs	42,874	0	153,716
Proceeds from employee stock plan purchases and stock option exercises	222	1,903	816
Principal payments on finance lease obligation	(418)	(510)	(20)
Net cash provided by financing activities	42,678	1,393	154,512
Effect of exchange rate on cash, cash equivalents, and restricted cash	(106)	(15)	51
NET (DECREASE) INCREASE IN CASH, CASH EQUIVALENTS, AND RESTRICTED CASH	19,436	(74,957)	71,184
CASH, CASH EQUIVALENTS, AND RESTRICTED CASH
Beginning of period	16,980	91,937	20,753
End of period	36,416	16,980	91,937
Supplemental Disclosure of Non-Cash Investing and Financing Information:
Leased assets obtained in exchange for lease obligations	21	872	172
Unpaid amounts related to purchase of property and equipment	$ 0	$ 0	$ 224