Consolidated Statements of Operations - USD ($)	12 Months Ended
	Dec. 31, 2017	Dec. 31, 2016
Income Statement [Abstract]
Revenue	$ 115,000	$ 260,000
Operating expenses
Research and development	2,881,000	5,678,000
General and administrative	7,590,000	8,413,000
Impairment charges	5,800,000	9,547,000
Total operating expenses	16,271,000	23,638,000
Loss from operations	(16,156,000)	(23,378,000)
Other income (expense)
Change in fair value of derivative liabilities	2,010,000	4,538,000
Other income	6,000
Other expenses		(554,000)
Total other income, net	2,016,000	3,984,000
Loss before taxes	(14,140,000)	(19,394,000)
Income tax benefit	1,302,000	556,000
Net loss	(12,838,000)	(18,838,000)
Excess of fair value of consideration transferred on conversion of Series B redeemable convertible preferred stock		(3,580,000)
Accretion of Series B redeemable convertible preferred stock		(1,858,000)
Net loss attributable to common stockholders	$ (12,838,000)	$ (24,276,000)
Per share information:
Net loss per share of common stock - basic	$ (2.01)	$ (24.67)
Weighted average number of shares of common stock outstanding - basic	6,387,425	983,846
Net loss per share of common stock - diluted	$ (2.18)	$ (24.67)
Weighted average number of shares of common stock outstanding - diluted	6,574,117	983,846