Consolidated Balance Sheets (USD $) In Thousands, unless otherwise specified	Dec. 31, 2012	Dec. 31, 2011
Current assets:
Cash and cash equivalents	$ 14,776	$ 4,541
Short-term investments	16,615
Prepaid expenses and other current assets	574	44
Total current assets	31,965	4,585
Property and equipment, net	756
Other assets	93
Total assets	32,814	4,585
Current liabilities:
Accounts payable	875	276
Accrued expenses and other liabilities	1,211	399
Total current liabilities	2,086	675
Other non-current liabilities	7	87
Total liabilities	2,093	762
Commitments and contingencies (Note 10)
Stockholder's equity (deficit):
Preferred stock, $0.001 par value;5,000,000 shares authorized, no shares issued and outstanding
Common stock, $0.001 par value; 100,000,000 and 23,000,000 shares authorized at December 31, 2012 and December 31, 2011, respectively; 14,268,068 and 3,529,406 shares issued at December 31, 2012 and December 31, 2011, respectively; 12,622,919 and 1,209,752 shares outstanding at December 31, 2012 and December 31, 2011, respectively	14	2
Additional paid-in capital	46,847	245
Accumulated other comprehensive loss	(6)
Deficit accumulated during the development stage	(16,134)	(2,624)
Total stockholders' equity (deficit)	30,721	(2,377)
Total liabilities, preferred stock and stockholders' equity (deficit)	32,814	4,585
Series A convertible preferred stock
Current liabilities:
Convertible preferred stock		$ 6,200