Condensed Statements of Cash Flows (Unaudited) - USD ($) $ in Thousands	9 Months Ended
	Sep. 30, 2020	Sep. 30, 2019
Cash flows from operating activities:
Net loss	$ (56,294)	$ (24,601)
Adjustments to reconcile net loss to net cash used in operating activities:
Non-cash rent expense	275	275
Stock based compensation	9,511	1,479
Depreciation and amortization	247	112
Amortization of premium (discount) on available for sale investments	429	(728)
Changes in operating assets and liabilities:
Prepaid expenses and other current assets	1,044	(3,281)
Other assets	8	(253)
Accounts payable	1,234	1,800
Accrued expenses and other current liabilities	6,004	2,870
Net cash used in operating activities	(37,542)	(22,327)
Cash flow from investing activities:
Purchase of investments	(183,356)	(98,475)
Proceeds from maturities of investments	115,141	63,070
Purchase of property and equipment	(42)	(46)
Net cash used in investing activities	(68,257)	(35,451)
Cash flows from financing activities:
Payments of finance leases	(32)
Proceeds from issuance of common stock upon exercise of stock options	1,235	69
Proceeds from initial public offering, net of stock offering costs		77,827
Proceeds from private placement offering, net of issuance costs	117,628
Net cash provided by financing activities	118,831	77,896
Net change in cash and cash equivalents	13,032	20,118
Cash, cash equivalents and restricted cash at beginning of period	51,214	24,872
Cash, cash equivalents and restricted cash at end of period	64,246	44,990
Supplemental disclosures of non-cash information:
Right-of-use assets obtained in exchange for new operating lease liabilities	$ 620	878
Right-of-use assets obtained in exchange for new finance lease liabilities		500
Series A Redeemable Convertible Preferred Stock
Supplemental disclosures of non-cash information:
Conversion of redeemable convertible preferred stock to common stock on initial public offering		17,178
Series B Redeemable Convertible Preferred Stock
Supplemental disclosures of non-cash information:
Conversion of redeemable convertible preferred stock to common stock on initial public offering		87,816
Acceleration of vesting of stock on initial public offering		$ 856