CONSOLIDATED BALANCE SHEETS - USD ($) $ in Thousands	Sep. 30, 2019	Dec. 31, 2018
Current assets:
Cash and cash equivalents	$ 156,593	$ 220,128
Marketable securities	97,823	12,735
Accounts receivable	9,503	29,583
Prepaid expenses	12,019	6,406
Other current assets	295	272
Total current assets	276,233	269,124
Property, equipment and software, net	49,966	56,712
Other assets	25,252	6,294
Total assets	351,451	332,130
Current liabilities:
Accounts payable	2,543	4,005
Accrued expenses	28,389	33,021
Deferred revenue	23,571	21,721
Deferred rent	0	1,018
Lease liabilities	2,956	0
Other current liabilities	175	175
Total current liabilities	57,634	59,940
Deferred revenue, net of current portion	10,037	19,001
Lease liabilities, net of current portion	28,582	0
Deferred rent, net of current portion	0	10,312
Total liabilities	96,253	89,253
Stockholders' equity:
Common stock, $0.01 par value -- 125,000,000 shares authorized, 48,914,284 and 42,353,301 shares outstanding at September 30, 2019 and December 31, 2018, respectively	489	424
Additional paid-in capital	866,372	732,727
Accumulated other comprehensive income (loss)	23	(3)
Accumulated deficit	(611,686)	(490,271)
Total stockholders' equity	255,198	242,877
Total liabilities and stockholders' equity	$ 351,451	$ 332,130