Consolidated Balance Sheets - USD ($) $ in Thousands	Dec. 31, 2018	Dec. 31, 2017
CURRENT ASSETS:
Cash and cash equivalents	$ 106,046	$ 100,348
Prepaid expenses and other current assets	2,706	1,377
Total current assets	108,752	101,725
Property and equipment, net	168	154
Other assets	549	319
TOTAL ASSETS	109,469	102,198
CURRENT LIABILITIES:
Accrued liabilities	8,812	6,133
Accounts payable	1,287	1,339
Total current liabilities	10,099	7,472
Term loan	4,891
TOTAL LIABILITIES	14,990	7,472
Commitments and Contingencies (Note 7)
STOCKHOLDERS' EQUITY:
Preferred stock, $0.001 par value; 10,000,000 shares authorized as of December 31, 2018 and December 31, 2017; nil shares issued and outstanding as of December 31, 2018 and December 31, 2017
Common stock, $0.001 par value; 500,000,000 shares authorized as of December 31, 2018 and 2017; 74,365,965 and 52,395,223 shares issued and outstanding as of December 31, 2018 and 2017	74	52
Additional paid-in capital	771,817	718,751
Accumulated deficit	(677,412)	(624,077)
TOTAL STOCKHOLDERS' EQUITY	94,479	94,726
TOTAL LIABILITIES AND STOCKHOLDERS' EQUITY	$ 109,469	$ 102,198