Consolidated Statements of Cash Flows - USD ($) $ in Thousands	12 Months Ended
	Dec. 31, 2016	Dec. 31, 2015	Dec. 31, 2014
Cash Flows From Operating Activities:
Net Loss	$ (27,803)	$ (44,785)	$ (19,784)
Adjustments to reconcile net loss to net cash used in operating activities:
Stock-based compensation	4,009	3,198	2,459
Stock issued for milestone payments	0	1,350	0
Stock issued for exclusive channel collaboration agreement	0	3,000	0
Change in fair value of warrant liabilities	(11,412)	3,811	(620)
Depreciation	157	72	20
Changes in operating assets and liabilities:
Prepaid expenses and other current assets	7,004	(7,971)	43
Deposits and other assets	(9)	(8)	(2)
Accounts payable	(2,420)	3,417	854
Accrued expenses	2,330	(1,001)	416
Accrued employee benefits	36	(261)	535
Deferred rent	207	288	0
Net Cash Used In Operating Activities	(27,901)	(38,890)	(16,079)
Cash Flows From Investing Activities:
Purchases of property and equipment	(569)	(501)	(48)
Net Cash Used In Investing Activities	(569)	(501)	(48)
Cash Flows From Financing Activities:
Proceeds from issuance of common stock	25,000	46,000	20,668
Cash paid as direct offering costs	(616)	(3,357)	(1,645)
Proceeds from issuance of common stock for stock option exercises	814	41	4
Proceeds from "at the market" stock issuance	1,509	0	0
Net Cash Provided By Financing Activities	26,707	42,684	19,027
Net (decrease) increase in cash	(1,763)	3,293	2,900
Cash at beginning of period	20,818	17,525	14,625
Cash at end of period	19,055	20,818	17,525
Supplemental disclosures of cash flow information:
Cash paid for interest	0	0	0
Cash paid for taxes	$ 0	$ 0	$ 0