STATEMENTS OF CASH FLOWS - USD ($) $ in Thousands	3 Months Ended
	Mar. 31, 2019	Mar. 31, 2018
Cash flows from operating activities:
Net loss	$ (13,434)	$ (16,020)
Adjustments to reconcile net loss to net cash used in operating activities:
Depreciation	140	117
Stock-based compensation	1,456	3,659
Bonus paid in common stock, net	630
Change in fair value of derivative liabilities		(28)
(Increase) decrease in:
Receivables	1,009	1
Prepaid expenses and other current assets	(1,058)	(1,172)
Other noncurrent assets	2,817	(490)
Deposits	(2)
Increase (decrease) in:
Accounts payable	152	(3,811)
Accrued expenses	(1,929)	(1,030)
Deferred revenue		(146)
Deferred rent	17	(37)
Other liabilities	(30)
Net cash used in operating activities	(10,232)	(18,957)
Cash flows from investing activities:
Purchases of property and equipment	(10)	(150)
Net cash used in investing activities	(10)	(150)
Cash flows from financing activities:
Repurchase of common stock		(731)
Net cash provided by (used in) financing activities	0	(731)
Net decrease in cash and cash equivalents, and restricted cash	(10,242)	(19,838)
Cash and cash equivalents, and restricted cash, beginning of period	61,729	71,335
Cash and cash equivalents, and restricted cash, end of period	51,487	51,497
Supplementary disclosure of cash flow information:
Bonus paid in common stock, gross	$ 1,000
Series 1 Preferred Stock
Supplementary disclosure of noncash investing and financing activities:
Payment of dividends in preferred stock		$ 5,120