Consolidated Balance Sheets - USD ($) $ in Thousands	Dec. 31, 2016	Dec. 31, 2015
CURRENT ASSETS:
Cash and cash equivalents	$ 109,007	$ 150,180
Prepaid expenses and other current assets	1,343	1,673
Total current assets	110,350	151,853
Property and equipment, net	400	566
Other assets	223	349
TOTAL ASSETS	110,973	152,768
CURRENT LIABILITIES:
Accrued liabilities	5,121	7,016
Accounts payable	2,604	358
Other current liabilities		23
Total current liabilities	7,725	7,397
TOTAL LIABILITIES	7,725	7,397
Commitments and Contingencies (Note 6)
STOCKHOLDERS' EQUITY:
Preferred stock, $0.001 par value; 10,000,000 shares authorized as of December 31, 2016 and December 31, 2015; nil shares issued and outstanding as of December 31, 2016 and December 31, 2015
Common stock, $0.001 par value; 500,000,000 shares authorized as of December 31, 2016 and 2015; 30,370,946 and 30,058,105 shares issued and outstanding as of December 31, 2016 and 2015	30	30
Additional paid-in capital	685,272	679,528
Accumulated deficit	(582,054)	(534,187)
TOTAL STOCKHOLDERS' EQUITY	103,248	145,371
TOTAL LIABILITIES AND STOCKHOLDERS' EQUITY	$ 110,973	$ 152,768