Condensed Consolidated Statements of Cash Flows (Unaudited) - USD ($) $ in Thousands	3 Months Ended
	Mar. 31, 2021	Mar. 31, 2020
Cash flows from operating activities:
Net loss	$ (52,171)	$ (40,019)
Adjustments to reconcile net loss to net cash used in operating activities:
Depreciation and amortization	1,541	1,446
Stock-based compensation	8,800	6,642
Amortization of premiums and accretion of discounts on marketable securities	594	(240)
Amortization of right-of-use assets	461	297
Loss from disposal of property and equipment, net		9
Changes in operating assets and liabilities:
Prepaid expenses and other current assets	(3,790)	(3,305)
Other assets	25	(284)
Accounts payable	2,592	3,135
Accrued liabilities and accrued clinical supply costs	(5,500)	7,805
Deferred revenue	(4,110)	(7,171)
Lease liabilities	(821)	(628)
Other long-term liabilities	(314)
Net cash used in operating activities	(52,693)	(32,313)
Cash flows from investing activities:
Purchase of property and equipment	(947)	(3,566)
Purchase of marketable securities		(202,906)
Maturities of marketable securities	110,500	81,600
Net cash provided by (used in) investing activities	109,553	(124,872)
Cash flows from financing activities:
Proceeds from issuance of common stock upon follow-on public offering, net of issuance costs		225,244
Proceeds from the exercise of options to purchase common stock	3,874	3,217
Net cash provided by financing activities	3,874	228,461
Net increase in cash, cash equivalents, and restricted cash	60,734	71,276
Cash, cash equivalents, and restricted cash at beginning of period	51,441	91,113
Cash, cash equivalents, and restricted cash at end of period	112,175	162,389
Non-cash investing and financing activities:
Property and equipment purchases included in accounts payable and accrued liabilities	$ 628	178
Deferred offering costs in accounts payable and accrued liabilities		$ 641