Consolidated Balance Sheets (USD $) In Thousands, unless otherwise specified	Dec. 31, 2014	Dec. 31, 2013
Current assets:
Cash and cash equivalents	$ 68,840	$ 2,793
Available-for-sale investments	14,755	2,359
Prepaid expenses and other curent assets	1,006	178
Total current assets	84,601	5,330
Property and equipment, net	83	62
Deferred tax asset		267
Other non-current assets	114
Total assets	84,798	5,659
Current liabilities:
Convertible notes, including accrued interest of $0 and $112 as of December 31, 2014 and 2013, respectively		3,727
Derivative liability		1,443
Accounts payable	917	399
Accrued expenses	1,421	984
Deferred tax liability		267
Current portion of deferred revenue from sale of option to acquire company		2,948
Total current liabilities	2,338	9,768
Total liabilities	2,338	9,768
Commitments and contingencies (Note 8)
Preferred stock, $0.001 par value per share; 10,000,000 shares authorized, no shares issued and outstanding at December 31, 2014	0	0
Common stock, $0.001 par value, 100,000,000 and 100,370,203 shares authorized at December 31, 2014 and 2013, respectively; 16,448,455 and 239,905 issued and outstanding at December 31, 2014 and 2013, respectively	16
Additional paid-in capital	192,324
Accumulated deficit	(109,874)	(100,514)
Accumulated other comprehensive loss	(6)
Total stockholders’ equity (deficit)	82,460	(100,514)
Total liabilities, redeemable convertible preferred stock and stockholders’ equity (deficit)	84,798	5,659
Series A Preferred Stock [Member]
Current liabilities:
Redeemable convertible preferred stock,		34,230
Series A-1 Preferred Stock [Member]
Current liabilities:
Redeemable convertible preferred stock,		17,374
Series B Preferred Stock [Member]
Current liabilities:
Redeemable convertible preferred stock,		27,401
Series C Preferred Stock [Member]
Current liabilities:
Redeemable convertible preferred stock,		17,400
Series D Preferred Stock [Member]
Current liabilities:
Redeemable convertible preferred stock,	$ 0	$ 0