CONDENSED CONSOLIDATED STATEMENTS OF CASH FLOWS - USD ($) $ in Thousands	3 Months Ended
	Mar. 31, 2022	Mar. 31, 2021
Cash flows from operating activities
Net loss	$ (23,091)	$ (27,200)
Adjustments to reconcile net loss to net cash used in operating activities:
Depreciation and amortization	120	107
Stock-based compensation	1,443	(286)
Net amortization of investments in marketable debt securities	149	92
Non-cash rent expense	893	1,135
Loss on disposal of property and equipment	0	1,611
Changes in operating assets and liabilities:
Accounts receivable from collaboration	(188)	1,027
Prepaid expenses and other current assets	(12)	303
Other assets	(472)	358
Accounts payable	(1,252)	(1,036)
Accrued research and development expenses	196	(102)
Other accrued expenses	(4,365)	(8,312)
Operating lease liabilities	(923)	(1,041)
Net cash used in operating activities	(27,502)	(33,344)
Cash flows from investing activities
Purchases of property and equipment	0	(3,078)
Proceeds from sale of property and equipment	0	857
Purchases of marketable securities	(3,951)	(49,213)
Proceeds from maturities of marketable securities	30,000	66,450
Proceeds from sale of marketable securities	7,000	3,000
Net cash provided by investing activities	33,049	18,016
Cash flows from financing activities
Proceeds from the issuance of common stock under ATM equity offering program, net of issuance costs	0	34,137
Net cash provided by financing activities	0	34,137
Net increase in cash and cash equivalents	5,547	18,809
Cash and cash equivalents at the beginning of the period	45,627	59,444
Cash and cash equivalents at the end of the period	51,174	78,253
Supplemental non-cash investing and financing activities
Operating lease liabilities arising from obtaining ROU assets	0	42
Remeasurement of lease liabilities arising from modification of ROU assets	$ 0	$ (788)