STATEMENTS OF CASH FLOWS - USD ($) $ in Thousands	3 Months Ended
	Mar. 31, 2020	Mar. 31, 2019
Cash flows from operating activities:
Net loss	$ (18,293)	$ (13,434)
Adjustments to reconcile net loss to net cash used in operating activities:
Depreciation	142	140
Stock-based compensation	1,940	1,456
Bonus paid in common stock, net		630
(Increase) decrease in:
Receivables	2,548	1,009
Prepaid expenses and other current assets	2,585	(1,058)
Right of use asset	193	(1,589)
Deposits		(2)
Other noncurrent assets	(556)	2,817
Increase (decrease) in:
Accounts payable	(510)	152
Accrued expenses	2,206	(1,929)
Deferred rent		17
Lease liabilities	(161)	1,559
Net cash used in operating activities	(9,906)	(10,232)
Cash flows from investing activities:
Purchases of property and equipment	(513)	(10)
Net cash used in investing activities	(513)	(10)
Cash flows from financing activities:
Proceeds from exercise of stock options	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	101,680
Net increase (decrease) in cash and cash equivalents, and restricted cash	91,261	(10,242)
Cash and cash equivalents, and restricted cash, beginning of period	79,741	61,729
Cash and cash equivalents, and restricted cash, end of period	171,002	51,487
Supplementary disclosure of cash flow information:
Compensation paid in restricted stock, gross		$ 1,000
Property and equipment included in accrued expenses	$ 2,303