BALANCE SHEETS - USD ($) $ in Thousands	Jun. 30, 2019	Dec. 31, 2018
Current assets:
Cash and cash equivalents	$ 43,563	$ 61,729
Receivables	1,460	1,864
Prepaid expenses and other current assets	20,836	20,692
Total current assets	65,859	84,285
Property and equipment, net	877	1,097
Operating lease right of use assets	1,438
Deposits	130	128
Other non-current assets	4,869	9,541
Total assets	73,173	95,051
Current liabilities:
Accounts payable	941	707
Accrued expenses	8,799	8,763
Lease liability - current portion	660
Deferred rent - current portion		13
Total current liabilities	10,400	9,483
Lease liability - noncurrent portion	778
Deferred rent - noncurrent portion		4
Total liabilities	11,178	9,487
Commitments and contingencies (Note 6)
Stockholders' deficit:
Common stock, $0.001 par value; 250,000,000 shares authorized; 162,477,963 and 142,379,770 shares issued and outstanding at June 30, 2019 and December 31, 2018, respectively	162	161
Additional paid-in capital	656,216	651,732
Accumulated deficit	(594,383)	(566,329)
Total stockholders' equity	61,995	85,564
Total liabilities and stockholders' equity	$ 73,173	$ 95,051