Balance Sheets - USD ($) $ in Thousands	Dec. 31, 2015	Dec. 31, 2014
Current assets:
Cash and cash equivalents	$ 34,395	$ 40,182
Prepaid expenses	3,690	804
Total current assets	38,085	40,986
Property and equipment, net	12,318	12,046
Prepaid expenses, long-term		1,678
Deferred financing costs, net	291	98
Other assets	18	18
Total assets	50,712	54,826
Current liabilities:
Accounts payable	2,387	2,631
Accrued expenses	2,653	1,062
Loan payable, current portion	2,488	5,003
Warrant liability	406	296
Total current liabilities	7,934	8,992
Loan payable, long-term	$ 13,035	$ 9,828
Commitments and contingencies (Note 13)
Stockholders' equity:
Common stock, $.0001 par value, authorized 150,000,000 shares; 22,315,612 shares issued and outstanding as of December 31, 2015 and 18,634,872 shares issued and outstanding as of December 31, 2014	$ 2	$ 2
Additional paid-in capital	194,468	170,396
Accumulated deficit	(164,727)	(134,392)
Total stockholders' equity	29,743	36,006
Total liabilities and stockholders' equity	$ 50,712	$ 54,826

Carrying value as of the balance sheet date of liabilities incurred (and for which invoices have typically been received) and payable to vendors for goods and services received that are used in an entity's business. Used to reflect the current portion of the liabilities (due within one year or within the normal operating cycle if longer).

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- Definition

Carrying value as of the balance sheet date of obligations incurred and payable, pertaining to costs that are statutory in nature, are incurred on contractual obligations, or accumulate over time and for which invoices have not yet been received or will not be rendered. Examples include taxes, interest, rent and utilities. Used to reflect the current portion of the liabilities (due within one year or within the normal operating cycle if longer).