CONDENSED CONSOLIDATED STATEMENTS OF CASH FLOWS - USD ($) $ in Thousands	3 Months Ended
	Mar. 31, 2022	Mar. 31, 2021
Operating activities
Net loss	$ (32,450)	$ (27,544)
Adjustments to reconcile net loss to net cash used in operating activities:
Stock-based compensation expense	7,820	6,582
Depreciation	1,427	1,554
Amortization of premium on marketable securities	518	570
Non-cash lease expense	475	441
Other non-cash expenses	460	(315)
Changes in operating assets and liabilities:
Related party receivable from collaboration	4,842	8
Related party contract asset	0	1,500
Prepaid expenses and other assets	241	(1,299)
Accounts payable	(431)	(2,128)
Accrued and other liabilities	(4,747)	(427)
Operating lease liability	(1,236)	(1,167)
Contract liabilities	(12,657)	0
Net cash used in operating activities	(35,738)	(22,225)
Investing activities
Purchase of marketable securities	(86,904)	(144,996)
Proceeds from maturities of marketable securities	80,336	28,000
Purchases of property and equipment	(285)	(160)
Net cash used in investing activities	(6,853)	(117,156)
Financing activities
Proceeds from follow on offering, net	0	134,570
Proceeds from exercise of stock options	668	5,907
Net cash provided by financing activities	668	140,477
Net (decrease) increase in cash and cash equivalents	(41,923)	1,096
Cash, cash equivalents and restricted cash, at beginning of period	153,294	148,516
Cash, cash equivalents and restricted cash, at end of period	111,371	149,612
Supplemental disclosures of non-cash investing and financing activities:
Property and equipment purchases accrued and not yet paid	436	637
Right of use asset acquired under operating lease on the adoption of ASC 842	0	5,855
Vesting of common stock from early exercises	$ 0	$ 41