BALANCE SHEETS - USD ($) $ in Thousands	Mar. 31, 2016	Dec. 31, 2015
Current assets:
Cash and cash equivalents	$ 124,846	$ 140,717
Receivables, net of reserves of $322 and $0 at March 31, 2016 and December 31, 2015, respectively	1,060	446
Prepaid expenses and other current assets	14,483	11,358
Total current assets	140,389	152,521
Property and equipment, net	667	581
Deposits	128	128
Other non-current assets	498	494
Total assets	141,682	153,724
Current liabilities:
Accounts payable	1,908	2,008
Accrued expenses	8,582	8,906
Deferred rent - current portion	295	348
Deferred revenue - current portion	6,489	6,861
Total current liabilities	17,274	18,123
Deferred rent, net of current portion	276	313
Deferred revenue, net of current portion	46,319	47,917
Total liabilities	$ 63,869	$ 66,353
Commitments and contingencies (Note 5)
Stockholders' equity:
Preferred stock, $0.001 par value; 30,000,000 shares authorized and no shares issued and outstanding
Common stock, $0.001 par value; 250,000,000 shares authorized; 131,802,873 and 131,718,579 shares issued and outstanding at March 31, 2016 and December 31, 2015, respectively	$ 132	$ 132
Additional paid-in capital - common stock	582,400	579,939
Accumulated deficit	(504,719)	(492,700)
Total stockholders' equity	77,813	87,371
Total liabilities and stockholders' equity	$ 141,682	$ 153,724