Consolidated Statements of Cash Flows - USD ($) $ in Thousands	3 Months Ended
	Mar. 31, 2022	Mar. 31, 2021
Operating Activities:
Net loss	$ (42,982)	$ (40,179)
Adjustments to reconcile net loss to net cash used in operating activities:
Accretion of discount on convertible notes	0	589
Depreciation and amortization of property and equipment	767	674
Amortization of right of use asset	535	0
Write down of property and equipment, net	40	0
Stock-based compensation	6,270	7,900
Accretion of discount on investments, net	577	620
Changes in operating assets and liabilities:
Prepaid expenses and other assets	(3,936)	(842)
Accounts payable and accrued expenses	(491)	7,047
Operating lease liabilities	(33)	(15)
Finance lease liability	45	(63)
Other long term liabilities	(15)	(14)
Net cash used in operating activities	(39,223)	(24,283)
Investing activities:
Purchases of investments	(143,023)	(103,815)
Proceeds from maturities of investments	81,983	74,969
Purchases of property and equipment	(1,955)	(328)
Net cash used in investing activities	(62,995)	(29,174)
Financing activities:
Issuance of common stock, pursuant to exercise of stock options	76	8,792
Net cash provided by financing activities	76	8,792
Net change in cash, cash equivalents and restricted cash	(102,142)	(44,665)
Cash, cash equivalents and restricted cash at beginning of period	234,037	298,666
Cash, cash equivalents and restricted cash at end of period	131,895	254,001
Supplemental disclosure of non-cash financing and investing activities:
Accrued purchases of property and equipment	1,635	648
Unrealized loss on investments	(468)	(33)
Reclassification of construction in process to finance right of use asset	0	325
Supplemental cash flow information:
Cash paid for interest	$ 0	$ 1,347