Condensed Consolidated Statements of Cash Flows (Unaudited) - USD ($) $ in Thousands	9 Months Ended
	Sep. 30, 2020	Sep. 30, 2019
Cash flows from operating activities:
Net loss	$ (44,628)	$ (25,383)
Adjustment to reconcile net loss to net cash used in operating activities:
Stock-based compensation expense	5,295	1,133
Change in fair value of derivative liabilities	0	6,416
Depreciation expense	37	38
Accretion of discount on investments	(990)	0
Noncash rent expense	287	0
Changes in current assets and liabilities:
Prepaid expenses and other current assets	(2,308)	(270)
Other non-current assets	(33)	(25)
Accounts payable	1,528	496
Amounts due to related party	190	(453)
Accrued expenses and other current liabilities	4,551	860
Non-current operating lease liability	(301)
Net cash used in operating activities	(36,372)	(17,188)
Cash flows from investing activities:
Purchases of equipment	(33)	(19)
Proceeds from sales and maturities of investments	17,765	0
Purchases of investments	(292,775)	0
Net cash used in investing activities	(275,043)	(19)
Cash flows from financing activities:
Proceeds from issuance of convertible preferred stock, net	0	44,669
Proceeds from exercise of common stock options	270	0
Proceeds from initial public offering, net of issuance costs of $1,275	213,844	0
Payment of deferred offering costs	0	(408)
Net cash provided by financing activities	214,114	44,261
Net decrease in cash and cash equivalents	(97,301)	27,054
Cash, cash equivalents and restricted cash, beginning of period	154,721	51,660
Cash, cash equivalents and restricted cash, end of period	57,420	78,714
Cash, Cash Equivalents, Restricted Cash and Restricted Cash Equivalents
Cash, cash equivalents and restricted cash, end of period	57,420	78,714
Supplemental disclosure of non-cash investing and financing activities:
Deferred offering and stock issuance costs included in accounts payable and accrued expenses and other current liabilities	0	1,169
Conversion of preferred stock	200,573	0
Right-of-use assets obtained in exchange for operating lease obligation	8,274
Line of credit for operating lease obligation	1,168	0
Series B preferred stock
Supplemental disclosure of non-cash investing and financing activities:
Conversion of preferred stock	$ 0	$ 6,393