Condensed Consolidated Balance Sheets - USD ($) $ in Thousands	Jun. 30, 2017	Dec. 31, 2016
CURRENT ASSETS:
Cash and cash equivalents	$ 116,699	$ 109,007
Prepaid expenses and other current assets	566	1,343
Total current assets	117,265	110,350
Property and equipment, net	256	400
Other assets	312	223
TOTAL ASSETS	117,833	110,973
CURRENT LIABILITIES:
Accrued liabilities	5,002	5,121
Accounts payable	521	2,604
Total current liabilities	5,523	7,725
TOTAL LIABILITIES	5,523	7,725
Commitments and Contingencies (Note 6)
STOCKHOLDERS' EQUITY:
Preferred stock, $0.001 par value; 10,000,000 shares authorized as of June 30, 2017 and December 31, 2016; nil shares issued and outstanding as of June 30, 2017 and December 31, 2016
Common stock, $0.001 par value; 500,000,000 shares authorized as of June 30, 2017 and December 31, 2016; 52,268,443 and 30,370,946 shares issued and outstanding as of June 30, 2017 and December 31, 2016	52	30
Additional paid-in capital	715,741	685,272
Accumulated deficit	(603,483)	(582,054)
TOTAL STOCKHOLDERS' EQUITY	112,310	103,248
TOTAL LIABILITIES AND STOCKHOLDERS' EQUITY	$ 117,833	$ 110,973