Condensed Consolidated Balance Sheets - USD ($) $ in Thousands	Mar. 31, 2020	Dec. 31, 2019
CURRENT ASSETS:
Cash and cash equivalents	$ 133,534	$ 147,528
Prepaid expenses and other current assets	1,936	2,369
Total current assets	135,470	149,897
Property and equipment, net	112	113
Operating lease right-of-use asset	547	589
Other assets	662	729
TOTAL ASSETS	136,791	151,328
CURRENT LIABILITIES:
Accrued and other liabilities	5,640	7,170
Accounts payable	1,357	1,019
Warrant liabilities		45,935
Securities issuance obligation		10,485
Total current liabilities	6,997	64,609
Operating lease liability	298	374
TOTAL LIABILITIES	7,295	64,983
Commitments and Contingencies (Note 8)
STOCKHOLDERS' EQUITY:
Preferred stock, $0.001 par value; 10,000,000 shares authorized as of March 31, 2020 and December 31, 2019; nil shares issued and outstanding as of March 31, 2020 and 103,000 shares Series A convertible voting preferred stock issued and outstanding as of December 31, 2019		1
Common stock, $0.001 par value; 500,000,000 shares authorized as of March 31, 2020 and December 31, 2019; 10,395,732 and 1,867,176 shares issued and outstanding as of March 31, 2020 and December 31, 2019	10	74
Additional paid-in capital	927,085	851,957
Accumulated deficit	(797,599)	(765,687)
TOTAL STOCKHOLDERS' EQUITY	129,496	86,345
TOTAL LIABILITIES AND STOCKHOLDERS' EQUITY	$ 136,791	$ 151,328