Consolidated Statements of Cash Flows - USD ($) $ in Thousands	12 Months Ended
	Dec. 31, 2020	Dec. 31, 2019
Operating activities
Net loss	$ (45,593)	$ (41,246)
Adjustments to reconcile net loss to net cash used in operating activities:
Stock-based compensation expense	5,190	1,196
Depreciation and amortization	1,763	825
Non-cash research and development expense	332	443
Net amortization of premiums and discounts on investments	1,571
Changes in operating assets and liabilities:
Prepaid expenses and other assets	(3,816)	(564)
Accounts receivable—due from related party	(577)
Contract asset—due from related parties	(856)
Other receivables—due from related parties		148
Accounts payable	990	904
Accrued expenses and other current liabilities	5,754	2,248
Deferred revenue	117,400	52,991
Other non-current assets	(30)
Operating lease right-of-use assets	8,444	1,350
Operating lease liabilities	(2,647)	(383)
Other non-current liabilities	205	(7)
Net cash provided by operating activities	88,130	17,905
Investing activities
Purchase of property and equipment, net	(9,096)	(532)
Purchase of marketable securities	(529,382)	(15,954)
Maturities of marketable securities	115,890
Net cash used in investing activities	(422,588)	(16,486)
Financing activities
Proceeds from stock option exercises	162	74
Payments on financing leases	(554)	(371)
Proceeds from initial public offering, net of underwriting discounts and offering costs	183,146
Proceeds from concurrent private placement	13,527
Net cash provided by financing activities	289,262	34,911
Net (decrease) increase in cash, cash equivalents and restricted cash	(45,196)	36,330
Cash, cash equivalents and restricted cash at beginning of period	77,789	41,459
Cash, cash equivalents and restricted cash at end of period	32,593	77,789
Supplemental disclosure of cash flow activities
Cash paid for interest	115	46
Supplemental disclosure of noncash investing and financing activities
Purchases of property and equipment through finance and lease liabilities		1,642
Property and equipment purchases included in accounts payable and accrued expenses	27	315
Offering costs included in accounts payable	397
Supplemental disclosure of noncash operating activities
Right-of-use assets obtained in exchange for operating lease liabilities		16,522
Tenant improvement receivable included in other assets		287
Reduction of right-of-use asset and liability due to lease modification	2,161
Cash and cash equivalents	31,004	76,015
Restricted cash	1,589	1,774
Series B Convertible Preferred Stock
Financing activities
Proceeds from the issuance of Convertible Preferred Stock, net of issuance costs		21,183
Series B-1 Convertible Preferred
Financing activities
Proceeds from the issuance of Convertible Preferred Stock, net of issuance costs	4,800	$ 14,025
Series C Convertible Preferred Stock
Financing activities
Proceeds from the issuance of Convertible Preferred Stock, net of issuance costs	$ 88,181