Condensed Consolidated Statements of Cash Flows - USD ($) $ in Thousands	9 Months Ended
	Sep. 30, 2022	Sep. 30, 2021
Cash flow from operating activities
Net loss	$ (159,694)	$ (151,066)
Adjustments to reconcile net loss to net cash used in operating activities:
Stock-based compensation expense	23,930	35,742
Depreciation	4,760	3,542
Other non-cash items, net	(226)	1,332
Changes in operating assets and liabilities:
Accounts receivable	147	5,797
Prepaid expenses and other current assets	307	1,414
Right-of-use assets	3,641	7,080
Other non-current assets	(719)	(2,077)
Accounts payable	1,674	(2,978)
Accrued expenses	(485)	(9,439)
Deferred revenue	(3,333)	(11,372)
Operating lease liabilities	(5,078)	(7,196)
Net cash used in operating activities	(135,076)	(129,221)
Cash flow from investing activities
Purchases of property and equipment	(3,494)	(5,132)
Proceeds from the sale of equipment	18
Purchases of marketable securities	(209,782)	(304,570)
Proceeds from maturities of marketable securities	354,854	278,076
Net cash provided by (used in) investing activities	141,596	(31,626)
Cash flow from financing activities
Proceeds from offering of common stock, net of issuance costs		249,458
Proceeds from exercise of stock options	298	31,065
Issuance of common stock under benefit plans	367	526
Net cash provided by financing activities	665	281,049
Net increase in cash, cash equivalents, and restricted cash	7,185	120,202
Cash, cash equivalents, and restricted cash, beginning of period	207,396	143,559
Cash, cash equivalents, and restricted cash, end of period	214,581	263,761
Supplemental disclosure of cash and non-cash activities:
Fixed asset additions included in accounts payable and accrued expenses	413	597
Cash paid in connection with operating lease liabilities	11,894	8,918
Right-of-use assets obtained in exchange of operating lease obligations	$ 4,708	$ 9,753