Condensed Consolidated Statements of Cash Flows (Unaudited) - USD ($) $ in Thousands	3 Months Ended
	Mar. 31, 2022	Mar. 31, 2021
Operating activities:
Net loss	$ (34,627)	$ (22,901)
Reconciliation of net loss to net cash used in operating activities:
Stock-based compensation	5,755	3,406
Depreciation and amortization	240	224
Noncash lease expense	95	80
Accretion of purchase discounts and amortization of premiums on investment securities, net	322	83
Loss on equity method investment	1,010	0
Increase (decrease) in cash resulting from changes in:
Prepaid expenses and other assets	2,489	(487)
Accounts payable and accrued expenses	1,530	(271)
Contract liabilities	9,869	0
Operating lease liability	(226)	(201)
Net cash used in operating activities	(13,543)	(20,067)
Investing activities:
Purchases of investment securities	(55,017)	(2,535)
Maturities of investment securities	11,720	35,153
Purchases of property and equipment	(87)	(116)
Net cash (used in) provided by investing activities	(43,384)	32,502
Financing activities:
Proceeds from exercise of stock options	1,780	57
Net Cash Provided by (Used in) Financing Activities, Total	1,780	57
Net change in cash, cash equivalents and restricted cash	(55,147)	12,492
Cash, cash equivalents and restricted cash at beginning of period	201,195	93,587
Cash, cash equivalents and restricted cash at end of period	146,048	106,079
Components of cash, cash equivalents and restricted cash:
Cash and cash equivalents	145,548	105,579
Restricted cash	500	500
Cash, cash equivalents and restricted cash at end of period	146,048	106,079
Noncash investing and financing activities:
Change in unvested stock liability	2	5
Amounts accrued for purchases of property and equipment	$ 0	$ 21