Balance Sheets - USD ($) $ in Thousands	Mar. 31, 2017	Dec. 31, 2016
Current assets
Cash and cash equivalents	$ 13,561	$ 14,528
Marketable securities	141,225	115,608
Accounts receivable	6,938	8,616
Prepaid expenses and other current assets	4,365	2,901
Total current assets	166,089	141,653
Property and equipment, net	3,360	3,105
Patents, licenses, and other intangible assets, net	10,886	10,362
Marketable securities - long term	237,865	273,340
Other assets	103	103
Total assets	418,303	428,563
Current liabilities
Accounts payable	4,275	3,880
Accrued expenses	6,502	6,692
Current portion of deferred rent	135	128
Current portion of deferred revenue	95,788	95,521
Income taxes	175	65
Total current liabilities	106,875	106,286
Deferred rent, less current portion	361	397
Deferred revenue, less current portion	7,319	7,926
Total liabilities	114,555	114,609
Commitments and contingencies
Stockholders' equity
Preferred stock, $0.01 par value: 10,000,000 authorized shares; -0- issued and outstanding shares at March 31, 2017 and December 31, 2016
Common stock, $0.01 par value: 200,000,000 authorized shares at March 31, 2017 and December 31, 2016; 46,689,447 issued and outstanding at March 31, 2017 and 46,567,978 issued and outstanding at December 31, 2016	467	466
Additional paid-in capital	557,473	552,889
Accumulated other comprehensive loss	(1,196)	(1,441)
Accumulated deficit	(252,996)	(237,960)
Total stockholders' equity	303,748	313,954
Total liabilities and stockholders' equity	$ 418,303	$ 428,563