Consolidated Balance Sheets - USD ($) $ in Thousands	Dec. 31, 2015	Dec. 31, 2014
Assets
Cash and cash equivalents	$ 102,138	$ 61,854
Investment securities, available-for-sale	112,994	260,632
Interest and other receivables	1,638	964
Prepaid expenses and other current assets	2,219	1,168
Total current assets	218,989	324,618
Property and equipment, net	2,203	553
Restricted cash	375
Other assets	329	287
Total assets	221,896	325,458
Liabilities and stockholders' equity
Accounts payable	1,672	2,016
Accrued liabilities	20,230	13,818
Total current liabilities	21,902	15,834
Long-term liabilities	232	135
Total liabilities	$ 22,134	$ 15,969
Commitments and contingencies (Note 10)
Stockholders' equity:
Preferred stock, $0.0001 par value; 5,000,000 shares authorized at December 31, 2015 and 2014; no shares issued and outstanding at December 31, 2015 and 2014
Common stock, $0.0001 par value; 225,000,000 shares and 150,000,000 shares authorized at December 31, 2015 and December 31, 2014, respectively; 101,938,702 shares and 100,047,331 shares issued and outstanding at December 31, 2015 and December 31, 2014, respectively	$ 10	$ 10
Additional paid-in capital	862,327	807,631
Accumulated deficit	(662,586)	(498,143)
Accumulated other comprehensive income (loss)	11	(9)
Total stockholders' equity	199,762	309,489
Total liabilities and stockholders' equity	$ 221,896	$ 325,458