Consolidated Statements of Cash Flows - USD ($) $ in Thousands	12 Months Ended
	Dec. 31, 2021	Dec. 31, 2020	Dec. 31, 2019
Cash flows from operating activities
Net loss	$ (170,060)	$ (88,045)	$ (28,208)
Adjustments to reconcile net loss to net cash used in operating activities:
Depreciation	855	1,010	1,245
Net amortization of premiums and discounts on investments	0	(86)	(222)
Stock-based compensation	18,409	7,172	4,872
Other non-cash items	723	148	103
Changes in operating assets and liabilities:
Accounts receivable	0	0	459
Prepaid expenses and other current assets	(2,734)	(1,950)	2,179
Other assets	(718)	(700)	0
Accounts payable	483	942	(3,110)
Accrued expenses	12,570	7,280	(3,569)
Operating lease assets	1,829	1,642	1,771
Operating lease liabilities	(1,827)	(1,281)	(1,883)
Deferred revenue	(43)	(828)	(41,381)
Other liabilities	525	0	0
Net cash used in operating activities	(139,988)	(74,696)	(67,744)
Cash flows from investing activities
Maturities of marketable securities	0	37,500	27,000
Purchase of marketable securities	0	0	(53,688)
Purchase of property and equipment	(648)	(473)	(605)
Net cash (used in) provided by investing activities	(648)	37,027	(27,293)
Cash flows from financing activities
Proceeds from exercise of stock options	1,837	3,138	175
Proceeds from purchases of common stock under ESPP	640	561	489
Payment of employee tax obligations related to vesting of restricted stock units	(259)	0	0
Proceeds from issuance of debt, net of issuance costs	24,042	(197)	4,965
Repayment of debt	(5,486)	0	0
Payments under finance lease obligations	(215)	(116)	(87)
Net cash provided by financing activities	63,646	230,412	97,704
Increase (decrease) in cash, cash equivalents and restricted cash	(76,990)	192,743	2,667
Cash, cash equivalents and restricted cash, beginning of period	255,415	62,672	60,005
Cash, cash equivalents and restricted cash, end of period	178,425	255,415	62,672
Supplemental disclosures of non-cash activities:
Fair value of common stock retired in exchange for issuance of common stock warrant	0	0	8,986
Purchases of property and equipment in accounts payable and accrued expenses	0	102	0
Debt financing costs in accrued expenses	0	0	180
Cash paid for interest	429	234	132
Right-of-use assets obtained in exchange for operating lease liabilities	3,783	9,980	4,369
Right-of-use assets obtained in exchange for financing lease liabilities	609	0	429
Public Stock Offering
Cash flows from financing activities
Net proceeds from issuance of common stock	0	163,990	92,162
At Market Equity Offering Program
Cash flows from financing activities
Net proceeds from issuance of common stock	$ 43,087	$ 63,036	$ 0