Consolidated Balance Sheets - USD ($) $ in Thousands	Sep. 30, 2019	Dec. 31, 2018
Current assets
Cash and cash equivalents	$ 79,594	$ 75,561
Marketable securities	252,125	244,200
Accounts receivable	19,175	8,587
Prepaid expenses	6,920	5,734
Other current assets	2,414	3,831
Total current assets	360,228	337,913
Marketable securities	85,408	150,819
Accounts receivable	24,345	23,012
Property and equipment, net	28,287	28,702
Operating lease right-of-use assets	5,905
Restricted cash	1,053	1,053
Other assets	4,011	2,315
Total assets	509,237	543,814
Current liabilities
Accounts payable	9,608	4,412
Accrued expenses and other current liabilities	19,231	17,164
Deferred revenue		600
Operating lease liabilities	2,506
Total current liabilities	31,345	22,176
Deferred revenue	3,333	3,333
Operating lease liabilities	4,320
Deferred rent		1,098
Financing lease obligations		5,854
Other liabilities	1,844	2,505
Total liabilities	40,842	34,966
Commitments and contingencies (Note 7)
Stockholders’ equity
Preferred stock; $0.0001 par value; 10,000 shares authorized, and no shares issued and outstanding at September 30, 2019 and December 31, 2018
Common stock; $0.0001 par value; 100,000 shares authorized at September 30, 2019 and December 31, 2018; 36,840 and 36,120 shares issued and outstanding at September 30, 2019 and December 31, 2018, respectively	4	4
Additional paid-in capital	619,386	592,580
Accumulated other comprehensive income (loss)	363	(720)
Accumulated deficit	(151,358)	(83,016)
Total stockholders’ equity	468,395	508,848
Total liabilities and stockholders’ equity	$ 509,237	$ 543,814