Condensed Consolidated Balance Sheets - USD ($) $ in Thousands	Jun. 30, 2019	Dec. 31, 2018
CURRENT ASSETS:
Cash and cash equivalents	$ 78,831	$ 106,046
Prepaid expenses and other current assets	3,761	2,706
Total current assets	82,592	108,752
Property and equipment, net	134	168
Operating lease right-of-use asset	671
Other assets	778	549
TOTAL ASSETS	84,175	109,469
CURRENT LIABILITIES:
Accrued and other liabilities	7,064	8,812
Accounts payable	1,203	1,287
Current portion of term loan	668
Total current liabilities	8,935	10,099
Term loan	4,303	4,891
Operating lease liability	466
TOTAL LIABILITIES	13,704	14,990
Commitments and Contingencies (Note 8)
STOCKHOLDERS' EQUITY:
Preferred stock, $0.001 par value; 10,000,000 shares authorized as of June 30, 2019 and December 31, 2018; nil shares issued and outstanding as of June 30, 2019 and December 31, 2018
Common stock, $0.001 par value; 500,000,000 shares authorized as of June 30, 2019 and December 31, 2018; 74,688,283 and 74,365,965 shares issued and outstanding as of June 30, 2019 and December 31, 2018	74	74
Additional paid-in capital	775,719	771,817
Accumulated deficit	(705,322)	(677,412)
TOTAL STOCKHOLDERS' EQUITY	70,471	94,479
TOTAL LIABILITIES AND STOCKHOLDERS' EQUITY	$ 84,175	$ 109,469