STATEMENTS OF CASH FLOWS - USD ($) $ in Thousands	6 Months Ended
	Jun. 30, 2020	Jun. 30, 2019
Cash flows from operating activities:
Net loss	$ (36,889)	$ (28,054)
Adjustments to reconcile net loss to net cash used in operating activities:
Depreciation	390	296
Stock-based compensation	3,601	4,255
(Increase) decrease in:
Receivables	(742)	404
Prepaid expenses and other current assets	6,838	(144)
Right of use asset	389
Deposits		(2)
Other noncurrent assets	(634)	4,672
Increase (decrease) in:
Accounts payable	176	234
Accrued expenses	3,320	36
Deferred rent		17
Lease liabilities	(361)	(33)
Net cash used in operating activities	(23,912)	(18,319)
Cash flows from investing activities:
Purchases of property and equipment	(4,000)	(77)
Net cash used in investing activities	(4,000)	(77)
Cash flows from financing activities:
Repurchase of common stock		(370)
Proceeds from exercise of stock options	16	600
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	101,692	230
Net increase (decrease) in cash and cash equivalents, and restricted cash	73,780	(18,166)
Cash and cash equivalents, and restricted cash, beginning of period	79,741	61,729
Cash and cash equivalents, and restricted cash, end of period	153,521	43,563
Supplementary disclosure of cash flow information:
Compensation paid in restricted stock, gross		$ 1,000
Property and equipment included in accrued expenses	$ 1,026