Condensed Consolidated Balance Sheets - USD ($) $ in Thousands	Jun. 30, 2015	Dec. 31, 2014
Current assets:
Cash and cash equivalents	$ 76,248	$ 32,780
Available for sale securities	76,541	76,138
Accounts receivable	48	48
Prepaid expenses and other current assets	2,125	1,514
Total current assets	154,962	110,480
Property and equipment, net	398	210
Other assets	305	305
Total assets	155,665	110,995
Current liabilities:
Accounts payable	2,412	2,021
Accrued expenses	3,491	4,864
Total current liabilities	5,903	6,885
Other liabilities	10	32
Total liabilities	$ 5,913	$ 6,917
Commitments and contingencies (Note 9)
Stockholders' equity:
Preferred stock $0.00001 par value, 25,000,000 shares authorized at June 30, 2015 and December 31, 2014; 0 shares issued and outstanding at June 30, 2015 and December 31, 2014
Common stock: $0.00001 par value; 175,000,000 shares authorized at June 30, 2015 and December 31, 2014; 28,882,530 and 20,370,624 shares issued and outstanding at June 30, 2015 and December 31, 2014, respectively	$ 0	$ 0
Additional paid-in capital	271,998	204,969
Treasury stock, at cost, 8,463 shares	(162)	(162)
Accumulated other comprehensive loss	(27)	(56)
Accumulated deficit	(122,057)	(100,673)
Total stockholders' equity	149,752	104,078
Total liabilities and stockholders' equity	$ 155,665	$ 110,995