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	$ (47,258)	$ (34,693)
Adjustments to reconcile net loss to net cash used in operating activities:
Depreciation	205	226
Stock-based compensation	5,485	4,039
Other non-cash items	194	38
Changes in operating assets and liabilities:
Prepaid expenses and other current assets	(462)	(37)
Other assets	0	(1,366)
Accounts payable	(2,524)	3,415
Accrued expenses	(2,159)	1,251
Operating lease right-of-use assets	889	415
Operating lease liabilities	(579)	(299)
Deferred revenue	38,254	(11)
Net cash used in operating activities	(7,955)	(27,022)
Cash flows from investing activities
Purchase of property and equipment	(329)	(114)
Net cash used in investing activities	(329)	(114)
Cash flows from financing activities
Proceeds from exercise of stock options	96	764
Payment of employee tax obligations related to vesting of restricted stock units	0	(259)
Payments under capital lease obligations	(76)	(33)
Net cash provided by financing activities	60,394	472
Increase (decrease) in cash, cash equivalents and restricted cash	52,110	(26,664)
Cash, cash equivalents and restricted cash, beginning of period	178,425	255,415
Cash, cash equivalents and restricted cash, end of period	230,535	228,751
Supplemental disclosures of non-cash activities:
Purchases of property and equipment in accounts payable and accrued expenses	457	189
Cash paid for interest	531	60
Right-of-use assets obtained in exchange for financing lease liabilities	0	213
At Market Equity Offering Program
Cash flows from financing activities
Net proceeds from the at-the-market facility	$ 60,374	$ 0