BALANCE SHEETS - USD ($) $ in Thousands	Mar. 31, 2019	Dec. 31, 2018
Current assets:
Cash and cash equivalents	$ 51,487	$ 61,729
Receivables	854	1,864
Prepaid expenses and other current assets	21,752	20,692
Total current assets	74,093	84,285
Property and equipment, net	967	1,097
Operating lease right of use assets	1,589
Deposits	130	128
Other non-current assets	6,724	9,541
Total assets	83,503	95,051
Current liabilities:
Accounts payable	859	707
Accrued expenses	6,836	8,763
Lease liability - current portion	644
Deferred rent - current portion		13
Total current liabilities	8,339	9,483
Lease liability - noncurrent portion	948
Deferred rent - noncurrent portion		4
Total liabilities	9,287	9,487
Commitments and contingencies (Note 6)
Stockholders' deficit:
Common stock, $0.001 par value; 250,000,000 shares authorized; 162,287,161 and 161,066,136 shares issued and outstanding at March 31, 2019 and December 31, 2018, respectively	162	161
Additional paid-in capital	653,817	651,732
Accumulated deficit	(579,763)	(566,329)
Total stockholders' equity	74,216	85,564
Total liabilities and stockholders' equity	$ 83,503	$ 95,051