Consolidated Statements of Cash Flows - USD ($) $ in Thousands	12 Months Ended
	Dec. 31, 2017	Dec. 31, 2016	Dec. 31, 2015
Cash Flows From Operating Activities:
Net Loss	$ (15,492)	$ (27,803)	$ (44,785)
Adjustments to reconcile net loss to net cash used in operating activities:
Stock-based compensation	3,409	4,009	3,198
Stock issued for milestone payments	0	0	1,350
Stock issued for exclusive channel collaboration agreement	0	0	3,000
Change in fair value of warrant liabilities	(10,738)	(11,412)	3,811
Depreciation	245	157	72
Changes in operating assets and liability:
Prepaid expenses and other current assets	1,688	7,004	(7,971)
Deposits and other assets	0	(9)	(8)
Accounts payable	27	(2,420)	3,417
Accrued expenses	(1,101)	2,330	(1,001)
Accrued employee benefits	1,761	36	(261)
Deferred rent	(3)	207	288
Net Cash Used In Operating Activity	(20,204)	(27,901)	(38,890)
Cash Flows From Investing Activity:
Purchases of property and equipment	(212)	(569)	(501)
Net Cash Used In Investing Activity	(212)	(569)	(501)
Cash Flows From Financing Activities:
Proceeds from sale of Series A Preferred Stock, net of issuance costs	11,953	0	0
Proceeds from the exercise of stock options	166	814	41
Proceeds from “at the market” stock issuances	6,358	1,509	0
Proceeds from issuance of common stock	0	25,000	46,000
Cash paid as direct offering costs	0	(616)	(3,357)
Net Cash Provided By Financing Activities	18,477	26,707	42,684
Net (decrease) increase in cash	(1,939)	(1,763)	3,293
Cash and cash equivalents at beginning of period	19,055	20,818	17,525
Cash and cash equivalents at end of period	$ 17,116	$ 19,055	$ 20,818