STATEMENTS OF CASH FLOWS - USD ($) $ in Thousands	9 Months Ended
	Sep. 30, 2021	Sep. 30, 2020
Cash flows from operating activities:
Net loss	$ (66,957)	$ (57,204)
Adjustments to reconcile net loss to net cash used in operating activities:
Depreciation	1,892	708
Amortization of financing costs	148
Stock-based compensation	9,857	5,393
(Increase) decrease in:
Receivables	3,155	(2,098)
Prepaid expenses and other current assets	7,646	8,249
Right of use asset	(529)	(98)
Other noncurrent assets	508	(636)
Increase (decrease) in:
Accounts payable	503	1,713
Accrued expenses	(3,169)	3,828
Lease liabilities	604	168
Net cash used in operating activities	(46,342)	(39,977)
Cash flows from investing activities:
Purchases of property and equipment	(2,964)	(6,012)
Net cash used in investing activities	(2,964)	(6,012)
Cash flows from financing activities:
Proceeds from long-term debt borrowing	25,000
Debt issuance costs	(75)
Proceeds from exercise of stock options	1,037	43
Issuance of common stock in connection with a public offering, net	0	88,661
Issuance of common stock in connection with at the market offerings, net	0	13,015
Net cash provided by financing activities	25,962	101,719
Net increase (decrease) in cash and cash equivalents	(23,344)	55,730
Cash and cash equivalents, and restricted cash, beginning of period	115,069	79,741
Cash and cash equivalents, and restricted cash, end of period	91,725	135,471
Supplementary disclosure of cash flow information:
Cash paid for interest	136
Amounts included in accrued expenses and accounts payable related to property and equipment	348	$ 1,163
Issuance costs in accounts payable and accrued expenses	184
Supplementary disclosure of noncash investing and financing activities
Warrants issued in a term loan	$ 788