STATEMENTS OF CASH FLOWS - USD ($) $ in Thousands	3 Months Ended
	Mar. 31, 2021	Mar. 31, 2020
Cash flows from operating activities:
Net loss	$ (21,554)	$ (18,293)
Adjustments to reconcile net loss to net cash used in operating activities:
Depreciation	540	142
Stock-based compensation	2,197	1,940
(Increase) decrease in:
Receivables	(340)	2,548
Prepaid expenses and other current assets	3,207	2,585
Right of use asset	292	193
Other noncurrent assets	559	(556)
Increase (decrease) in:
Accounts payable	2,654	(510)
Accrued expenses	(2,684)	2,206
Lease liabilities	(184)	(161)
Net cash used in operating activities	(15,313)	(9,906)
Cash flows from investing activities:
Purchases of property and equipment	(717)	(513)
Net cash used in investing activities	(717)	(513)
Cash flows from financing activities:
Proceeds from exercise of stock options	1,017	4
Issuance of common stock in connection with a public offering, net		88,661
Issuance of common stock in connection with at the market offerings, net		13,015
Net cash provided by financing activities	1,017	101,680
Net increase in cash and cash equivalents, and restricted cash	(15,013)	91,261
Cash and cash equivalents, and restricted cash, beginning of period	115,069	79,741
Cash and cash equivalents, and restricted cash, end of period	100,056	171,002
Supplementary disclosure of cash flow information:
Accounts included in accrued expenses and accounts payable related to property and equipment	$ 682	$ 2,303