Condensed Consolidated Statements of Cash Flows - USD ($) $ in Thousands		3 Months Ended
		Mar. 31, 2022	Mar. 31, 2021
Cash flows from operating activities:
Net loss		$ (56,624)	$ (35,465)
Adjustments to reconcile net loss to net cash used in operating activities:
Stock-based compensation expense		5,079	3,624
Depreciation and amortization expense		1,570	1,476
Non-cash operating lease cost		1,058	655
Accretion (amortization) of discount (premiums) on investments		313	851
Amortization of debt issuance costs		133	118
Collaboration (profit) loss sharing - related party		(976)	0
Changes in operating assets and liabilities:
Prepaid expenses and other current and long-term assets		(3,841)	(1,402)
Accounts receivable		0	6,783
Deferred revenue - related party		(1,493)	(4,648)
Accounts payable		(6,464)	973
Operating lease liabilities		(1,507)	(1,232)
Accrued expenses and other current and long-term liabilities	[1]	(3,693)	(1,229)
Net cash used in operating activities		(66,445)	(29,496)
Cash flows from investing activities:
Purchases of property and equipment		(2,950)	(1,342)
Purchases of investments		(28,156)	(46,944)
Sales and maturities of investments		44,078	27,548
Net cash provided by (used in) investing activities		12,972	(20,738)
Cash flows from financing activities:
Proceeds from exercise of stock options		257	372
Issuance of common stock under ESPP		892	392
Proceeds from issuance of debt		27,606
Repayment of notes payable		(1,907)	0
Net cash provided by financing activities		26,848	764
Net decrease in cash, cash equivalents, and restricted cash		(26,625)	(49,470)
Cash, cash equivalents and restricted cash at beginning of period		188,002	116,049
Cash, cash equivalents and restricted cash at end of period		161,377	66,579
Supplemental disclosure of cash flow information:
Cash paid for interest		558	603
Supplemental disclosure of non-cash investing and financing activities:
Property and equipment purchases included in accounts payable and accrued expenses		622	268
Prepaid rent reclassified to right-of-use assets		4,962
Lease liability arising from obtaining right-of-use assets		$ 4,370	$ 0

[1] Includes related party amounts of $(1,107) and $0 at March 31, 2022 and March 31, 2021, respectively (see Note 11)