Balance Sheets - USD ($) $ in Thousands	Jun. 30, 2017	Dec. 31, 2016
Current assets
Cash and cash equivalents	$ 11,220	$ 14,528
Marketable securities	177,269	115,608
Accounts receivable	14,876	8,616
Prepaid expenses and other current assets	7,617	2,901
Total current assets	210,982	141,653
Property and equipment, net	3,861	3,105
Patents, licenses, and other intangible assets, net	10,865	10,362
Marketable securities - long term	190,242	273,340
Other assets	214	103
Total assets	416,164	428,563
Current liabilities
Accounts payable	7,379	3,880
Accrued expenses	3,984	6,692
Current portion of deferred rent		128
Current portion of deferred revenue	95,613	95,521
Income taxes	455	65
Total current liabilities	107,431	106,286
Deferred rent, less current portion	614	397
Deferred revenue, less current portion	6,754	7,926
Total liabilities	114,799	114,609
Commitments and contingencies
Stockholders' equity
Preferred stock, $0.01 par value: 10,000,000 authorized shares; -0- issued and outstanding shares at June 30, 2017 and December 31, 2016
Common stock, $0.01 par value: 200,000,000 authorized shares at June 30, 2017 and December 31, 2016; 46,854,762 issued and outstanding at June 30, 2017 and 46,567,978 issued and outstanding at December 31, 2016	468	466
Additional paid-in capital	562,017	553,290
Accumulated other comprehensive loss	(1,240)	(1,441)
Accumulated deficit	(259,880)	(238,361)
Total stockholders' equity	301,365	313,954
Total liabilities and stockholders' equity	$ 416,164	$ 428,563