CONDENSED BALANCE SHEETS - USD ($) $ in Thousands	Dec. 31, 2019	Dec. 31, 2018
Current assets:
Cash and cash equivalents	$ 40,019	$ 71,431
Short-term investments	2,774
Prepaid expenses and other current assets	3,475	1,376
Total current assets	46,268	72,807
Property and equipment, net	97	207
Operating lease right-of-use asset	1,054
Other assets	70	9
Total assets	47,489	73,023
Current liabilities:
Accounts payable	457	1,134
Accrued expenses	7,461	7,884
Operating lease liability	163
Future tranche right liability	46,436
Total current liabilities	54,517	9,018
Warrant liability, long-term	3,241
Operating lease liability, net of current portion	899
Other liabilities		11
Total liabilities	58,657	9,029
Commitments and contingencies (Note 13)
Stockholders’ equity (deficit)
Common stock, $0.001 par value, Authorized — 70,000 shares; Issued and outstanding — 29,672 and 27,188 at December 31, 2019 and December 31, 2018, respectively	30	27
Additional paid-in capital	709,692	728,342
Accumulated deficit	(720,890)	(664,375)
Total stockholders’ equity (deficit)	(11,168)	63,994
Total liabilities and stockholders’ equity (deficit)	47,489	73,023
Preferred stock
Stockholders’ equity (deficit)
Preferred stock
Series A convertible preferred stock; Designated — 1,500 shares, Issued and outstanding — 1 share
Stockholders’ equity (deficit)
Preferred stock