Condensed Consolidated Statements of Cash Flows - USD ($) $ in Thousands	3 Months Ended
	Mar. 31, 2021	Mar. 31, 2020
Cash flow from operating activities
Net loss	$ (72,593)	$ (27,753)
Adjustments to reconcile net loss to net cash used in operating activities:
Stock-based compensation expense	12,761	3,462
Depreciation and amortization	800	842
Amortization of right-of-use assets	538	144
Amortization of premiums on investments	506	(248)
Changes in operating assets and liabilities:
Receivable from collaboration partners (($3,981) and $0 from a related party)	(4,186)	(212)
Prepaid expenses and other current assets	(4,568)	(3,704)
Other long-term assets	63	(91)
Accounts payable	7,722	(2,342)
Accrued research and development expenses	4,716	2,226
Other accrued liabilities	(2,007)	(1,578)
Deferred revenue (($7,711) and $0 to a related party)	(9,461)	(1,750)
Operating lease liabilities	(605)	(273)
Other long-term liabilities	(2)
Net cash used in operating activities	(66,316)	(31,277)
Cash flow from investing activities
Purchases of short-term and long-term investments	(192,398)	(8,885)
Proceeds from maturities of short-term and long-term investments	251,365	49,150
Sales of short-term and long-term investments	7,500
Purchases of property and equipment	(3,641)	(209)
Net cash provided by investing activities	62,826	40,056
Cash flow from financing activities
Proceeds from issuance of common stock to related party	220,235
Proceeds from issuance of common stock pursuant to equity award plans	1,885	643
Repurchase of unvested shares of stock		(33)
Net cash provided by financing activities	222,120	610
Net increase in cash and cash equivalents	218,630	9,389
Cash, cash equivalents and restricted cash at beginning of period	173,618	58,140
Cash, cash equivalents and restricted cash at end of period	392,248	67,529
Supplemental disclosures:
Cash paid for amounts included in measurement of lease liabilities	927	519
Non-cash investing and financing activities:
Unpaid portion of property and equipment purchases included in accounts payable and accrued liabilities	2,784	76
Vesting of early exercised stock options	$ 183	$ 220