CONDENSED CONSOLIDATED BALANCE SHEETS (UNAUDITED) - USD ($) $ in Thousands	Mar. 31, 2020	Dec. 31, 2019
Current assets:
Cash and cash equivalents	$ 15,047	$ 29,395
Prepaid expenses and other current assets	1,962	1,848
Total current assets	17,009	31,243
Operating lease, right-of-use assets	7,228	7,542
Property and equipment, net	6,694	7,109
Other long-term assets	471	478
Total assets	31,402	46,372
Current liabilities:
Accounts payable	3,043	1,702
Accrued expenses	6,437	7,464
Operating lease liabilities, current	1,287	1,241
Total current liabilities	10,767	10,407
Operating lease liabilities, net of current portion	6,200	6,542
Other liabilities	4	6
Total liabilities	16,971	16,955
Commitments and contingencies (Note 8)
Stockholders’ equity:
Common stock, $0.001 par value; 150,000,000 shares authorized as of March 31, 2020 and December 31, 2019; 28,963,858 and 28,729,725 shares issued and outstanding as of March 31, 2020 and December 31, 2019, respectively	29	29
Additional paid-in capital	284,538	282,926
Accumulated deficit	(270,136)	(253,538)
Total stockholders’ equity	14,431	29,417
Total liabilities and stockholders’ equity	$ 31,402	$ 46,372