Consolidated Statements of Cash Flows (Unaudited) - USD ($) $ in Thousands	3 Months Ended
	Mar. 31, 2022	Mar. 31, 2021
Operating activities
Net loss	$ (25,928)	$ (16,999)
Adjustments to reconcile net loss to net cash used in operating activities:
Depreciation expense	536	603
Stock-based compensation expense	3,847	2,073
Net amortization of premiums and discounts on marketable securities	353	74
Changes in operating assets and liabilities:
Accounts receivable	2,500	2,000
Unbilled accounts receivable	335	(1)
Prepaid expenses and other current assets	96	1,466
Operating lease assets and liabilities	107	(103)
Other assets	(274)	15
Accounts payable	509	920
Accrued expenses and other liabilities	(2,397)	(2,016)
Deferred revenue	(1,790)	(4,258)
Net cash used in operating activities	(22,106)	(16,226)
Investing activities
Purchases of marketable securities	(4,990)	(2,997)
Maturities of marketable securities	24,895	15,674
Purchases of property and equipment	(246)	(262)
Net cash used in investing activities	19,659	12,415
Financing activities
Proceeds from issuance of common stock in connection with follow-on offering, net of issuance costs	0	47,424
Principal payments on capital lease obligations	0	(13)
Proceeds from issuance of common stock under benefit plans, net	348	93
Net cash provided by financing activities	348	47,504
Net increase (decrease) in cash, cash equivalents and restricted cash	(2,099)	43,693
Cash, cash equivalents, and restricted cash, beginning of period	36,504	58,144
Cash, cash equivalents, and restricted cash, end of period	34,405	101,837
Supplemental cash flow information
Cash paid for operating lease liabilities	597	0
Non-cash investing and financing activities:
Property and equipment purchases unpaid at end of period	847	40
Issuance of common stock receivable	47	0
Offering costs unpaid at end of period	0	18
Cash and cash equivalents	33,313	100,745
Restricted cash	$ 1,092	$ 1,092