Consolidated Balance Sheets - USD ($) $ in Thousands	Sep. 30, 2019	Dec. 31, 2018
Current assets:
Cash and cash equivalents	$ 45,882	$ 55,671
Marketable securities	0	22,923
Accounts receivable	880	1,668
Prepaid expenses and other current assets	1,216	740
Total current assets	47,978	81,002
Operating lease, right-of-use asset	5,634
Property and equipment, net	2,170	3,251
Restricted cash	1,255	1,255
Other assets	847	419
Total assets	57,884	85,927
Current liabilities:
Accounts payable	1,594	1,519
Accrued expenses and other current liabilities	6,538	5,477
Operating lease liability	1,581
Deferred revenue	14,717	17,949
Total current liabilities	24,430	24,945
Deferred rent		748
Operating lease liability, net of current portion	4,831
Total liabilities	29,261	25,693
Commitments and contingencies (Note 8)
Stockholders’ equity:
Preferred stock, $0.001 par value; 10,000,000 shares authorized; no shares issued or outstanding
Common stock, $0.001 par value; 150,000,000 shares authorized; 30,663,054 shares and 30,057,970 shares issued and outstanding at September 30, 2019 and December 31, 2018, respectively	30	30
Additional paid-in capital	154,782	152,275
Accumulated other comprehensive loss		(12)
Accumulated deficit	(126,189)	(92,059)
Total stockholders’ equity	28,623	60,234
Total liabilities and stockholders’ equity	$ 57,884	$ 85,927