Condensed Consolidated Statements of Cash Flows - USD ($) $ in Thousands	3 Months Ended
	Mar. 31, 2016	Mar. 31, 2015
Cash flows from operating activities:
Net loss	$ (3,189)	$ (11,651)
Adjustments to reconcile net loss to net cash used in operating activities:
Depreciation and amortization	20	15
Stock-based compensation expense	136	401
Change in fair value of common stock warrants	(1,170)	6,174
Inducement charge for Series C warrants	0	3,050
Change in fair value of contingent consideration	19	0
Change in operating assets and liabilities:
Accounts receivable	(31)	(8)
Inventory	(102)	(97)
Prepaid expenses and other assets	(49)	(7)
Accounts payable	627	199
Accrued compensation and other current liabilities	(317)	115
Other long-term liabilities	72	0
Net cash used in operating activities	(3,984)	(1,809)
Cash flows from investing activities:
Purchase of property and equipment	(19)	(1)
Net cash used in investing activities	(19)	(1)
Cash flows from financing activities:
Proceeds from sale of Series A preferred convertible stock	5,071	0
Initial public offering costs paid	0	(530)
Proceeds from exercise of common stock options	0	12
Repayment of credit line	0	(102)
Net cash provided by financing activities	5,000	3,382
Net increase in cash and cash equivalents	997	1,572
Cash and cash equivalents, beginning of period	5,495	7,957
Cash and cash equivalents, end of period	6,492	9,529
Supplemental disclosures of noncash investing and financing information
Conversion of Series A preferred to common stock	1,665	0
Reduction in initial public offering costs payable	0	45
Fixed asset costs included in accounts payable	11	0
Series B Warrant transaction costs accrued and included in accrued compensation and other current liabilities	0	131
Series A Convertible Preferred Stock [Member]
Cash flows from financing activities:
Initial public offering costs paid	(71)	0
Series A Warrant Liability [Member]
Cash flows from financing activities:
Gross proceeds upon exercise of warrants	0	156
Series A Warrant Liability [Member] | Cash Exercise [Member]
Supplemental disclosures of noncash investing and financing information
De-recognition warrant liability	0	42
Private Placement Series B Warrants [Member]
Cash flows from financing activities:
Gross proceeds upon exercise of warrants	0	3,832
Tender Offer Series B Warrants [Member]
Cash flows from financing activities:
Gross proceeds upon exercise of warrants	0	189
Series B Warrant Liability [Member]
Cash flows from financing activities:
Series B warrant transaction costs paid	0	(175)
Series B Warrant Liability [Member] | Cash Exercise [Member]
Supplemental disclosures of noncash investing and financing information
De-recognition warrant liability	0	6,748
Series B Warrant Liability [Member] | Cash Less Exercise [Member]
Supplemental disclosures of noncash investing and financing information
De-recognition warrant liability	$ 593	$ 417