Consolidated Statements of Cash Flows - USD ($) $ in Thousands	12 Months Ended
	Dec. 31, 2018	Dec. 31, 2017
Cash flows from operating activities:
Net loss	$ (10,277)	$ (16,240)
Adjustments to reconcile net loss to net cash used in operating activities:
Stock-based compensation expense	526	322
Warrant liability revaluation income	(921)	(4,920)
Derivative liability revaluation expense (income)	(1,662)	1,407
Loss on disposal or impairment of property and equipment	0	40
Depreciation and amortization	392	384
Amortization of discount on convertible debt converted to common shares	0	86
Decrease (increase) in operating assets:
Prepaid expenses and other current assets	380	28
Other assets	38	26
Increase (decrease) in operating liabilities:
Accounts payable	(24)	69
Related party payable	(2,203)	1,361
Accrued expenses and deferred rent	263	(342)
Accrued interest payable	771	742
Net cash used in operating activities	(12,717)	(17,037)
Cash flows from investing activities:
Purchase of property and equipment	(164)	(433)
Net cash used in investing activities	(164)	(433)
Cash flows from financing activities:
Proceeds from private placement	900	7,623
Proceeds from common stock offerings, (net of offering costs of $1,170)	8,915	9,749
Proceeds from exercise of common warrants	499	0
Proceeds from exercise of pre-funded warrants	24	0
Payment of deferred offering costs	(444)	0
Net cash provided by financing activities	9,894	17,372
Net decrease in cash and cash equivalents	(2,987)	(98)
Cash and cash equivalents, beginning of period	17,417	17,515
Cash and cash equivalents, end of period	14,430	17,417
Noncash Investing and Financing Items [Abstract]
Property and equipment in accounts payable	9	29
Offering costs in accounts payable and accrued expenses	37	444
Reduction of warrant liability upon cashless exercise of warrants	0	41
Reduction of accrued interest payable upon cashless exercise of promissory notes	0	3
Reduction in derivative liability upon cashless exercise of promissory notes	0	6
Cashless exercise of promissory notes	0	85
Dividend paid in-kind to preferred stockholders	336	264
Deemed dividend on preferred stock	$ 513	$ 4,099