CONDENSED CONSOLIDATED STATEMENTS OF CASH FLOWS (Unaudited) - USD ($) $ in Thousands	6 Months Ended
	Jun. 30, 2021	Jun. 30, 2020
Operating activities
Net loss	$ (37,735)	$ (24,921)
Adjustments to reconcile net loss to net cash used in operating activities:
Stock-based compensation expense	8,898	1,035
Depreciation and amortization	1,037	776
Premiums and discounts on available-for-sale marketable securities	2,511
Non-cash research and development expense		222
Changes in operating assets and liabilities:
Prepaid expenses and other assets	(91)	(2,182)
Receivables—due from related parties	(327)
Contract asset—due from related parties	856
Accounts payable	4,005	(372)
Accrued expenses and other current liabilities	4,092	3,136
Deferred revenue	(35,455)	(6,716)
Operating lease right-of-use assets	197	7,349
Operating lease liabilities	(579)	(1,796)
Other assets and liabilities	(743)
Net cash used in operating activities	(53,334)	(23,469)
Investing activities
Purchase of property and equipment, net	(790)	(5,250)
Purchases of investments	(46,164)	(110,527)
Maturities of investments	152,000	31,500
Net cash provided by (used in) investing activities	105,046	(84,277)
Financing activities
Proceeds from stock option exercises	2,618	29
Proceeds from employee stock purchase plan	307
Payments of offering costs in connection with initial public offering	(397)
Payments on finance leases	(341)	(293)
Net cash provided by financing activities	2,187	92,717
Net increase in cash, cash equivalents and restricted cash	53,899	(15,029)
Cash, cash equivalents and restricted cash at beginning of period	32,593	77,789
Cash, cash equivalents and restricted cash at end of period	86,492	62,760
Supplemental disclosure of cash flow activities
Cash paid for interest	54	65
Supplemental disclosure of noncash investing and financing activities
Property and equipment purchases included in accounts payable and accrued expenses	320	1,076
Purchase of property and equipment through finance lease	1,231
Offering costs included in accrued expenses	154
Supplemental disclosure of noncash operating activities
Tenant improvements included in other assets		833
Reduction of right-of-use asset and liability due to lease modification		2,161
Cash and cash equivalents	84,903	60,971
Restricted cash	$ 1,589	1,789
Series B Convertible Preferred Stock
Financing activities
Proceeds from the issuance of Convertible Preferred Stock, net of issuance costs		4,800
Series C Convertible Preferred Stock
Financing activities
Proceeds from the issuance of Convertible Preferred Stock, net of issuance costs		$ 88,181