Statements of Cash Flows (USD $) In Thousands, unless otherwise specified	12 Months Ended
	Dec. 31, 2014	Dec. 31, 2013
Operating activities
Net loss	$ (21,313)	$ (17,935)
Adjustments to reconcile net loss to net cash used for operating activities:
Share-based compensation expense	8,992	12,373
Third party share-based compensation expense	63	0
Issuance of common stock for services	25	0
Depreciation expense	17	5
Changes in operating assets and liabilities:
Restricted cash	0	(37)
Prepaid clinical expenses	(1,528)	0
Prepaid expenses and other current assets	(94)	(18)
Accounts payable	(104)	742
Accrued expenses	739	80
Accrued payroll and related expenses	324	56
Net cash used for operating activities	(12,879)	(4,734)
Investing Activities
Purchase of property and equipment	(258)	(43)
Net cash used for investing activities	(258)	(43)
Financing Activities
Net proceeds from the issuance of common stock	53,063	6,751
Proceeds from the issuance of Series F Convertible Preferred Stock	0	3,250
Net cash provided by financing activities	53,063	10,001
Net increase in cash and cash equivalents	39,926	5,224
Cash and cash equivalents at beginning of period	8,629	3,405
Cash and cash equivalents at end of period	48,555	8,629
Supplemental disclosure of cash flow information:
Redemption of Series D-1 Convertible Preferred Stock and Series C-2 Convertible Preferred Stock Warrants	0	4,568
Dividends paid in Series C-1 and C-2 Convertible Preferred Stock	0	801
Conversion Of Series C-1 And D-1 Preferred Stock Into Common Stock [Member]
Supplemental disclosure of cash flow information:
Conversion of temporary equity into common stock	3,099	124
Conversion of Series F Preferred Stock into Common Stock [Member]
Supplemental disclosure of cash flow information:
Conversion of temporary equity into common stock	452	0
Exchange Of Series C-2 For Series C-1 Preferred Stock [Member]
Supplemental disclosure of cash flow information:
Conversion of temporary equity into common stock	$ 0	$ 557