Statements of Cash Flows - USD ($) $ in Thousands	12 Months Ended
	Dec. 31, 2015	Dec. 31, 2014	Dec. 31, 2013
Operating activities
Net loss	$ (49,617)	$ (24,100)	$ (18,589)
Adjustments to reconcile net loss to net cash used in operating activities:
Depreciation and amortization	118	51	18
Stock-based compensation	2,253	713	423
Loss on disposal of assets		3
Amortization of debt discount	483	1,070	1,257
Change in fair value of preferred stock warrant liabilities	(1,939)	(1,181)	(272)
Noncash interest expense on convertible notes	1,068	2,393	1,422
Amortization of beneficial conversion feature	429	928	800
Amortization of debt issuance costs	74	26	20
Deferred income taxes	(4,393)
Impairment of intangible assets	17,315
Change in assets and liabilities:
Prepaid expenses and other assets	439	(1,152)	400
Restricted cash		(284)
Accounts payable and accrued expenses	2,523	2,852	(2,373)
Deferred rent	(47)	16
Net cash used in operating activities	(31,294)	(18,665)	(16,894)
Investing activities
Cash received from Merger	33,232
Purchase of property and equipment	(39)	(180)	(1)
Net cash provided by (used in) investing activities	33,193	(180)	(1)
Financing activities
Proceeds from issuance of common stock, net	41,421		63
Proceeds from borrowings in connection with term loan, net		14,794
Proceeds from convertible notes, related party	12,954	7,982	11,980
Payments on term loan		(1,833)	(2,000)
Payments on capital lease obligations	(21)	(8)
Net cash provided by financing activities	54,354	20,935	10,043
Net increase (decrease) in cash and cash equivalents	56,253	2,090	(6,852)
Cash and cash equivalents at beginning of period	6,178	4,088	10,940
Cash and cash equivalents at end of period	62,431	6,178	4,088
Supplemental disclosure of cash flow information
Cash paid for interest	1,048	479	188
Noncash activities:
Conversion of convertible notes and interest to common stock	48,222
Issuance of common stock in connection with Merger	21,291
Issuance of warrants in connection with term loan and convertible notes, related party		868	570
Beneficial conversion feature recognized upon conversion of convertible notes	396		1,123
Reclassification of warrant liability to additional paid-in capital upon conversion from warrants on convertible preferred stock to common stock	521
Reclassification of stock award liability from additional paid-in capital upon modification		399
Reclassification of stock award liability to additional paid-in capital upon expiration		292
Common stock vested			$ 2
Landlord paid leasehold improvements		259
Equipment purchased under capital leases		$ 70
Fair value of assets acquired and liabilities assumed in Merger:
Fair value of assets acquired	18,723
Fair value of liabilities assumed	(5,832)
Fair value of net assets acquired in Merger	12,891
Series A and B Preferred Stock [Member]
Noncash activities:
Conversion of preferred stock to common stock	61,982
Series F Preferred Stock [Member]
Noncash activities:
Conversion of preferred stock to common stock	24,832
Financial Advisors [Member]
Noncash activities:
Issuance of common stock in connection with Merger	$ 852