Condensed Consolidated Statements of Cash Flows - USD ($) $ in Thousands	9 Months Ended
	Sep. 30, 2021	Sep. 30, 2020
Cash flows from operating activities
Net loss	$ (121,077)	$ (59,203)
Adjustments to reconcile net loss to net cash used in operating activities:
Depreciation	644	750
Net amortization of premiums and discounts on investments	0	(86)
Stock-based compensation	13,549	5,183
Other non-cash items	119	110
Changes in operating assets and liabilities:
Prepaid expenses and other current assets	(4,104)	(2,460)
Other assets	(617)	(700)
Accounts payable	(2,429)	(2,766)
Accrued expenses	16,047	2,367
Operating lease assets	1,548	1,235
Operating lease liabilities	(1,236)	(990)
Deferred revenue	(32)	(817)
Net cash used in operating activities	(97,588)	(57,377)
Cash flows from investing activities
Maturities of marketable securities	0	37,500
Purchase of property and equipment	(493)	(285)
Net cash provided by (used in) investing activities	(493)	37,215
Cash flows from financing activities
Proceeds from exercise of stock options	1,545	1,732
Proceeds from purchases of common stock under ESPP	417	333
Payment of employee tax obligations related to vesting of restricted stock units	(259)	0
Proceeds from issuance of debt, net of issuance costs	0	(197)
Payments under capital lease obligations	(139)	(87)
Net cash provided by financing activities	34,851	228,747
Increase (decrease) in cash, cash equivalents and restricted cash	(63,230)	208,585
Cash, cash equivalents and restricted cash, beginning of period	255,415	62,672
Cash, cash equivalents and restricted cash, end of period	192,185	271,257
Supplemental disclosures of non-cash activities:
Purchases of property and equipment in accounts payable and accrued expenses	46	0
Cash paid for interest	187	173
Right-of-use assets obtained in exchange for operating lease liabilities	3,783	9,980
Right-of-use assets obtained in exchange for financing lease liabilities	609	0
Public Stock Offering
Cash flows from financing activities
Net proceeds from public offering of common stock	0	163,990
Net proceeds from the at-the-market (ATM) facility	0	163,990
At Market Equity Offering Program
Cash flows from financing activities
Net proceeds from public offering of common stock	33,287	62,976
Net proceeds from the at-the-market (ATM) facility	$ 33,287	$ 62,976