CONDENSED CONSOLIDATED STATEMENTS OF CASH FLOWS (Unaudited) $ in Thousands	3 Months Ended
	Mar. 31, 2021 USD ($)	Mar. 31, 2020 USD ($)
Operating activities
Net loss	$ (13,075)	$ (10,932)
Adjustments to reconcile net loss to net cash used in operating activities:
Stock-based compensation expense	3,172	371
Depreciation and amortization	485	387
Premiums and discounts on available-for-sale marketable securities	1,279
Non-cash research and development expense		111
Changes in operating assets and liabilities:
Prepaid expenses and other assets	(816)	(1,477)
Receivables—due from related parties	(279)
Contract asset—due from related parties	(22)
Accounts payable	4,150	(161)
Accrued expenses and other current liabilities	235	690
Deferred revenue	(17,822)	(3,428)
Operating lease right-of-use assets	95	4,295
Operating lease liabilities	(368)	(1,913)
Other liabilities	143
Net cash used in operating activities	(22,823)	(12,057)
Investing activities
Purchase of property and equipment, net	(164)	(1,395)
Purchases of investments	(16,013)	(36,008)
Maturities of investments	60,500
Net cash provided by (used in) investing activities	44,323	(37,403)
Financing activities
Proceeds from stock option exercises	1,147
Payments of offering costs in connection with initial public offering	(397)
Payments on finance leases	(155)	(142)
Net cash provided by financing activities	595	93,120
Net increase in cash, cash equivalents and restricted cash	22,095	43,660
Cash, cash equivalents and restricted cash at beginning of period	32,593	77,789
Cash, cash equivalents and restricted cash at end of period	54,688	121,449
Supplemental disclosure of cash flow activities
Cash paid for interest	24	34
Supplemental disclosure of noncash investing and financing activities
Offering costs included in accrued liabilities		281
Property and equipment purchases included in accounts payable and accrued expenses	259	1,714
Cash and cash equivalents	53,098	121,250
Restricted cash	$ 1,590	199
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		$ 88,462