Condensed Consolidated Statements of Cash Flows - USD ($) $ in Thousands	6 Months Ended
	Jun. 30, 2022	Jun. 30, 2021
Cash Flows from Operating Activities
Net loss	$ (190,956)	$ (156,800)
Adjustments to reconcile net loss to net cash used in operating activities:
Stock-based compensation expense	44,733	31,355
Amortization of right of use asset	6,184	4,813
Depreciation and amortization	4,042	738
Accretion (amortization) of discounts and premiums on investments	995	3,862
Loss on write-off of fixed assets	314	0
Changes in assets and liabilities:
Prepaid expenses, other assets and long-term assets	(2,661)	(3,038)
Operating lease liabilities, net of tenant improvement allowance received	902	(2,890)
Accounts payable	65	4,950
Accrued expenses and other liabilities	(15,055)	611
Net cash used in operating activities	(151,437)	(116,399)
Cash Flows from Investing Activities
Maturities of investments	284,136	320,151
Purchase of investments	(85,841)	(381,784)
Purchase of property and equipment	(16,016)	(20,321)
Net cash provided by / (used in) investing activities	182,279	(81,954)
Cash Flows from Financing Activities
Tax payments related to shares withheld for vested restricted stock units	(2,649)	0
Proceeds from the issuance of common stock upon purchase of employee stock purchase plan	582	0
Proceeds from the issuance of common stock upon exercise of options	1,417	10,191
Proceeds from the issuance of common stock, net	0	203,155
Proceeds from the issuance of debt	0	1,000
Net cash (used in) / provided by financing activities	(650)	214,346
Net increase in cash, cash equivalents and restricted cash	30,192	15,993
Cash, Cash Equivalents and Restricted Cash Beginning of Period	84,313	72,854
Cash, Cash Equivalents and Restricted Cash End of Period	114,505	88,847
Supplemental disclosure of non-cash investing and financing activities:
Net unrealized (loss) gain on investments	(2,096)	14
Acquisition of property and equipment included in accounts payable and accrued expenses	967	6,472
Conversion of convertible preferred stock to common stock	0	(1)
Lease liabilities arising from obtaining right-of-use asset from new leases	553	0
Lease liabilities arising from obtaining right-of-use asset from lease modifications	$ 7,493	$ 555