Condensed Balance Sheets - USD ($) $ in Thousands	Jun. 30, 2015	Dec. 31, 2014
Current assets:
Cash and cash equivalents	$ 43,191	$ 52,663
Income tax receivable	250	200
Prepaid expenses and other current assets	590	287
Total current assets	44,031	53,150
Property and equipment, net	1,710	2,084
Restricted cash	700	700
Total assets	46,441	55,934
Current liabilities:
Accounts payable and accrued expenses	3,150	1,946
Deferred revenue	89	1,452
Total current liabilities	3,239	3,398
Deferred lease obligation	$ 732	$ 874
Commitments and contingencies (Note 10)
Stockholders' equity:
Preferred stock; $0.001 par value; 5,000,000 shares authorized at June 30, 2015 and December 31, 2014, zero shares issued and outstanding at June 30, 2015 and December 31, 2014
Common stock; $0.001 par value; 100,000,000 shares authorized at June 30, 2015 and December 31, 2014, 22,836,919 shares and 22,802,039 shares issued and outstanding at June 30, 2015 and December 31, 2014, respectively	$ 23	$ 23
Additional paid-in capital	133,021	131,840
Accumulated deficit	(90,574)	(80,201)
Total stockholders' equity	42,470	51,662
Total liabilities and stockholders' equity	$ 46,441	$ 55,934

Sum of the carrying values as of the balance sheet date of obligations incurred through that date and due within one year (or the operating cycle, if longer), including liabilities incurred (and for which invoices have typically been received) and payable to vendors for goods and services received, taxes, interest, rent and utilities, accrued salaries and bonuses, payroll taxes and fringe benefits.

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- Definition

Value received from shareholders in common stock-related transactions that are in excess of par value or stated value and amounts received from other stock-related transactions. Includes only common stock transactions (excludes preferred stock transactions). May be called contributed capital, capital in excess of par, capital surplus, or paid-in capital.