Consolidated Statements of Cash Flows - USD ($) $ in Thousands	12 Months Ended
	Dec. 31, 2020	Dec. 31, 2019
Cash flows from operating activities:
Net loss	$ (67,254)	$ (35,258)
Adjustment to reconcile net loss to net cash used in operating activities:
Stock-based compensation expense	7,765	3,643
Change in fair value of derivative liabilities	0	6,393
Depreciation expense	52	47
Amortization of premium on investments	1,725	0
Noncash rent expense	548	0
Gain on sale of investments	(24)	0
Loss on disposal of property and equipment	0	38
Changes in current assets and liabilities:
Prepaid expenses and other current assets	(3,439)	(1,024)
Other non-current assets	(47)	(51)
Accounts payable	1,069	1,454
Amounts due to related party	0	(1,707)
Accrued expenses and other current liabilities	8,026	1,791
Non-current operating lease liability	(567)
Net cash used in operating activities	(52,146)	(24,674)
Cash flows from investing activities:
Purchases of equipment	(142)	(21)
Proceeds from sales and maturities of investments	90,928	0
Purchases of investments	(372,477)	0
Net cash used in investing activities	(281,691)	(21)
Cash flows from financing activities:
Proceeds from issuance of convertible preferred stock, net	0	129,499
Proceeds from exercise of common stock options	1,100	0
Proceeds from initial public offering, net of issuance costs of $1,275	213,844	0
Payment of deferred offering costs	0	(1,743)
Net cash provided by financing activities	214,944	127,756
Net increase (decrease) in cash and cash equivalents	(118,893)	103,061
Cash, cash equivalents and restricted cash, beginning of year	154,721	51,660
Cash, cash equivalents and restricted cash, end of year	35,828	154,721
Cash, Cash Equivalents, Restricted Cash and Restricted Cash Equivalents
Cash, cash equivalents and restricted cash, end of year	154,721	154,721
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	656
Conversion of preferred stock	200,573	0
Right-of-Use Asset Obtained in Exchange for Operating Lease Liability	8,474
Series B
Supplemental disclosure of non-cash investing and financing activities:
Conversion of preferred stock	$ 0	$ 6,393