CONDENSED BALANCE SHEETS - USD ($) $ in Thousands	Mar. 31, 2020	Dec. 31, 2019
Current assets:
Cash and cash equivalents	$ 27,909	$ 40,019
Short-term investments	5,578	2,774
Prepaid expenses and other current assets	2,422	3,475
Total current assets	35,909	46,268
Property and equipment, net	80	97
Operating lease right-of-use asset	1,007	1,054
Other assets	70	70
Total assets	37,066	47,489
Current liabilities:
Accounts payable	941	457
Accrued expenses	7,385	7,461
Operating lease liability	162	163
Future tranche right liability	25,725	46,436
Total current liabilities	34,213	54,517
Warrant liability, long-term	2,140	3,241
Operating lease liability, net of current portion	857	899
Total liabilities	37,210	58,657
Commitments and contingencies
Stockholders’ equity (deficit)
Common stock, $0.001 par value, Authorized — 70,000 shares; Issued and outstanding — 30,607 and 29,672 at March 31, 2020 and December 31, 2019, respectively	31	30
Additional paid-in capital	711,898	709,692
Accumulated deficit	(712,073)	(720,890)
Total stockholders’ deficit	(144)	(11,168)
Total liabilities and stockholders’ deficit	37,066	47,489
Series B1 redeemable convertible preferred stock (Note 7); Designated — 278 shares, Issued and outstanding — 24 shares at March 31, 2020 and December 31, 2019
Stockholders’ equity (deficit)
Preferred stock
Series A convertible preferred stock; Designated — 1,500 shares, Issued and outstanding — 1 share
Stockholders’ equity (deficit)
Preferred stock