CONDENSED CONSOLIDATED STATEMENTS OF CASH FLOWS (Unaudited) - USD ($) $ in Thousands	9 Months Ended
	Sep. 30, 2020	Sep. 30, 2019
Operating activities
Net loss	$ (32,908)	$ (29,733)
Adjustments to reconcile net loss to net cash used in operating activities:
Stock-based compensation	3,363	899
Depreciation and amortization	1,266	464
Non-cash research and development expense	332	332
Changes in operating assets and liabilities:
Prepaid expenses and other assets	(1,440)	(384)
Other receivables—due from related parties		148
Contract asset—due from related parties	(577)
Accounts payable	523	(503)
Accrued expenses and other current liabilities	2,268	2,686
Deferred revenue	129,328	54,825
Operating lease right-of-use assets	8,330	493
Operating lease liabilities	(2,287)	(489)
Other non-current assets and liabilities		(32)
Net cash provided by operating activities	108,198	28,706
Investing activities
Purchase of property and equipment, net	(7,659)	(333)
Purchase of marketable securities	(460,939)	(78,112)
Maturities of marketable securities	50,000
Net cash used in investing activities	(418,598)	(78,445)
Financing activities
Proceeds from stock option exercises	138	46
Payments on financing leases	(402)	(253)
Proceeds from initial public offering, net of underwriting discounts and offering costs	182,748
Proceeds from concurrent private placement	13,527
Net cash provided by financing activities	288,992	13,818
Net increase in cash, cash equivalents and restricted cash	(21,408)	(35,921)
Cash, cash equivalents and restricted cash at beginning of period	77,789	41,459
Cash, cash equivalents and restricted cash at end of period	56,381	5,538
Supplemental disclosure of cash flow activities
Cash paid for interest	88
Supplemental disclosure of noncash investing activities
Property and equipment purchases included in accounts payable and accrued expenses	797
Supplemental disclosure of noncash operating activities
Right-of-use assets obtained in exchange for operating lease liabilities		201
Tenant improvement receivable included in other assets	139
Reduction of right-of-use asset and liability due to lease modification	2,161
Cash and cash equivalents	54,593	5,339
Restricted cash	1,788	199
Series B-1 Convertible Preferred
Financing activities
Proceeds from the issuance of Series B-1 Convertible Preferred Stock, net of issuance costs	4,800	$ 14,025
Series C Convertible Preferred Stock
Financing activities
Proceeds from the issuance of Series B-1 Convertible Preferred Stock, net of issuance costs	$ 88,181