Consolidated Statements of Cash Flows - USD ($) $ in Thousands		12 Months Ended
		Dec. 31, 2022	Dec. 31, 2021	Dec. 31, 2020
Cash flows from operating activities:
Net loss		$ (250,157)	$ (65,578)	$ (89,127)
Adjustments to reconcile net loss to net cash provided by (used in) operating activities:
Stock-based compensation expense		25,482	20,222	8,824
Depreciation and amortization expense		6,629	5,947	6,578
Non-cash operating lease cost		5,224	3,275	2,315
Accretion (amortization) of discount (premium) on issued debt securities		688	498	446
Amortization of debt issuance costs		705	2,526	551
Collaboration (profit) loss sharing - related party		1,004	(1,732)	0
Changes in operating assets and liabilities:
Prepaid expenses and other current and non-current assets		(12,599)	(12,337)	(2,186)
Accounts receivable		0	9,387	(7,602)
Deferred revenue - related party		(7,128)	(4,357)	(11,565)
Accounts payable		2,203	9,362	(1,159)
Operating lease liabilities		(4,203)	(3,550)	(4,456)
Accrued expenses and other current and long-term liabilities	[1]	3,336	43,025	3,771
Net cash (used in) provided by operating activities		(228,816)	6,688	(93,610)
Cash flows from investing activities:
Purchases of property and equipment		(9,821)	(9,566)	(591)
Purchases of investments		(48,221)	(95,971)	(218,284)
Sales and maturities of investments		140,470	169,625	59,984
Net cash provided by (used in) investing activities		82,428	64,088	(158,891)
Cash flows from financing activities:
Proceeds from issuance of common stock		96,721	0	243,748
Proceeds from Securities Purchase Agreement, net of issuance costs - related party		0	0	19,900
Proceeds from issuance of note payable		27,606	0	0
Proceeds from at the market equity offering, net of commissions		4,447	0	24,773
Proceeds from exercise of stock options		966	1,299	14,421
Proceeds from issuance of common stock and restricted common stock		0	0	120
Issuance of common stock under ESPP		1,769	827	462
Repayment of notes payable		(1,907)	(948)	0
Net cash provided by financing activities		129,602	1,178	303,424
Net increase (decrease) in cash, cash equivalents and restricted cash		(16,786)	71,954	50,923
Effect of exchange rate changes on cash, cash equivalents and restricted cash		(1)	(1)	0
Cash, cash equivalents and restricted cash at beginning of year		188,002	116,049	65,126
Cash, cash equivalents and restricted cash at end of year		171,215	188,002	116,049
Supplemental disclosure of cash flow information:
Cash paid for interest		4,926	2,446	2,453
Supplemental disclosure of non-cash investing and financing activities:
Property and equipment purchases included in accounts payable and accrued expenses		2,276	874	451
Lease liability arising from obtaining right-of-use assets		91,412	12,442	0
Prepaid rent reclassified to right-of-use assets		$ 6,822	$ 0	$ 0

[1] Includes related party amounts of $3,087 and $31,683 at December 31, 2022 and 2021 respectively (see Note 11)