Condensed Consolidated Balance Sheets - USD ($) $ in Thousands	Sep. 30, 2019	Dec. 31, 2018
Current assets:
Cash and cash equivalents	$ 58,196	$ 59,634
Short-term marketable securities	53,806	10,497
Accounts receivable	298	459
Prepaid expenses and other current assets	2,397	3,715
Total current assets	114,697	74,305
Property and equipment, net	2,446	2,694
Operating lease right-of-use assets	3,059
Other assets	1,453	1,503
Total assets	121,655	78,502
Current liabilities:
Accounts payable	7,304	10,727
Accrued expenses	8,037	12,375
Deferred revenue	4,646	46,196
Operating lease liabilities	2,145
Short-term debt	167
Other liabilities	85	127
Total current liabilities	22,384	69,425
Operating lease liabilities	1,257
Long-term debt, net	4,670
Other liabilities	299	282
Total liabilities	28,610	69,707
Commitments (Note 11)
Stockholders' equity
Preferred stock, $0.0001 par value; 25,000,000 shares authorized; 0 shares issued and outstanding at September 30, 2019 and December 31, 2018, respectively
Common stock, $0.0001 par value; 175,000,000 shares authorized; 47,882,897 and 23,234,472 shares issued and outstanding at September 30, 2019 and December 31, 2018, respectively	5	3
Additional paid-in capital	269,140	172,966
Accumulated other comprehensive income (loss)	28	(8)
Accumulated deficit	(176,128)	(164,166)
Total stockholders’ equity	93,045	8,795
Total liabilities and stockholders’ equity	$ 121,655	$ 78,502