Consolidated Statements of Cash Flows - USD ($) $ in Thousands	12 Months Ended
	Dec. 31, 2015	Dec. 31, 2014
Cash flows from operating activities:
Net loss	$ (39,842)	$ (28,702)
Adjustments to reconcile net loss to net cash used in operating activities:
Depreciation and amortization	146	85
Gain on bargain purchase		(486)
Share-based compensation expense related to employee stock options	2,675	2,032
Write-off of fixed assets	6
Amortization of debt issuance costs and debt discount	185
Changes in assets and liabilities, net of effect of acquisitions:
Increase/(decrease) in prepaid expenses and other assets	13	(58)
Increase in accounts payable	1,230	406
Increase in accrued liabilities	2,638	2,078
Net cash used in operating activities	(32,949)	(24,645)
Cash flows from investing activities:
Purchases of certificates of deposit	(13,713)	(19,435)
Proceeds from maturities of certificates of deposit	17,024	16,659
Proceeds from sales of certificates of deposit	249
Purchases of property and equipment	(165)	(147)
Security deposit for new lease		(130)
Cash obtained through acquisition		3,534
Net cash provided by investing activities	3,395	481
Cash flows from financing activities:
Proceeds from borrowings under debt facility	15,000
Costs paid in connection with debt facility	(193)
Proceeds from sale of common stock	2,140	30,201
Proceeds from sale and exercise of warrants		6,148
Payments for offering costs	(142)	(2,058)
Payments for capital lease	(7)
Net cash provided by financing activities	16,798	34,291
Net (decrease)/increase in cash and cash equivalents	(12,756)	10,127
Cash and cash equivalents at beginning of period	35,808	25,681
Cash and cash equivalents at end of period	$ 23,052	$ 35,808