Consolidated Balance Sheets - USD ($) $ in Thousands	Jun. 30, 2018	Dec. 31, 2017
Current assets
Cash and cash equivalents	$ 106,889	$ 46,656
Marketable securities	179,605	114,122
Accounts receivable	739	473
Prepaid expenses	3,690	5,334
Other current assets	2,347	1,412
Total current assets	293,270	167,997
Marketable securities	19,795	15,616
Accounts receivable	4,485
Property and equipment, net	16,698	13,977
Restricted cash	225	225
Other assets	1,514	862
Total assets	335,987	198,677
Current liabilities
Accounts payable	4,230	4,832
Accrued expenses and other current liabilities	12,023	9,605
Deferred revenue	600
Total current liabilities	16,853	14,437
Deferred rent, net of current portion	1,192	1,211
Other liabilities	720
Total liabilities	18,765	15,648
Commitments and contingencies (Note 6)
Stockholders’ equity
Preferred stock; $0.0001 par value; 10,000 shares authorized, and no shares issued and outstanding at June 30, 2018 and December 31, 2017
Common stock; $0.0001 par value; 100,000 shares authorized at June 30, 2018 and December 31, 2017; 32,275 and 31,295 shares issued and outstanding at June 30, 2018 and December 31, 2017, respectively	3	3
Additional paid-in capital	386,110	371,497
Accumulated other comprehensive loss	(771)	(715)
Accumulated deficit	(68,120)	(187,756)
Total stockholders’ equity	317,222	183,029
Total liabilities and stockholders’ equity	$ 335,987	$ 198,677