CONSOLIDATED BALANCE SHEETS - USD ($) $ in Thousands	Dec. 31, 2019	Dec. 31, 2018
Current assets:
Cash and cash equivalents	$ 29,395	$ 52,700
Marketable securities	0	50,611
Prepaid expenses and other current assets	1,848	2,116
Total current assets	31,243	105,427
Operating lease, right-of-use assets	7,542
Property and equipment, net	7,109	8,205
Other long-term assets	478	456
Total assets	46,372	114,088
Current liabilities:
Accounts payable	1,702	4,268
Accrued expenses	7,464	8,422
Operating lease liabilities, current	1,241
Total current liabilities	10,407	12,690
Operating lease liabilities, net of current portion	6,542
Other liabilities	6	149
Total liabilities	16,955	12,839
Commitments and contingencies (Note 8)
Stockholders' equity:
Common stock, $0.001 par value; 150,000,000 shares authorized as of December 31, 2019 and 2018; 28,729,725 and 28,314,274 shares issued and outstanding as of December 31, 2019 and 2018, respectively	29	28
Additional paid-in capital	282,926	275,058
Accumulated other comprehensive loss	0	(75)
Accumulated deficit	(253,538)	(173,762)
Total stockholders' equity	29,417	101,249
Total liabilities and stockholders' equity	$ 46,372	$ 114,088