Condensed Statements of Cash Flows (Unaudited) - USD ($) $ in Thousands	6 Months Ended
	Jun. 30, 2022	Jun. 30, 2021
Operating activities
Net loss	$ (197,533)	$ (91,777)
Adjustments to reconcile net loss to net cash used in operating activities:
Stock-based compensation expense	32,400	30,573
Depreciation	803	518
Accretion of discount on marketable securities	1,423	2,771
Amortization of right-of-use operating lease asset	1,767	965
Changes in operating assets and liabilities:
Prepaid expenses and other current assets	(2,501)	(5,589)
Other assets	(18)	0
Accounts payable	2,225	1,612
Accrued expenses and other liabilities	(1,566)	5,719
Accrued compensation	(629)	(2,861)
Net cash used in operating activities	(163,629)	(58,069)
Investing activities
Purchases of marketable securities	(164,537)	(255,763)
Sales and maturities of marketable securities	183,038	169,434
Purchases of property and equipment	(1,974)	(874)
Net cash provided by (used in) investing activities	16,527	(87,203)
Financing activities
Proceeds from issuance of common stock under equity incentive plans	9,370	19,020
Net cash provided by financing activities	9,370	19,020
Net decrease in cash, cash equivalents and restricted cash	(137,732)	(126,252)
Cash, cash equivalents and restricted cash at the beginning of period	429,755	554,174
Cash, cash equivalents and restricted cash at the end of period	292,023	427,922
Supplemental disclosure of cash flow information:
Cash paid for income taxes	0	1
Supplemental disclosure of non-cash investing and financing information:
Purchases of property and equipment in accounts payable	53	250
Operating lease liabilities arising from obtaining right-of-use assets	$ 1,192	$ 3,544