Balance Sheets - USD ($) $ in Thousands	Dec. 31, 2016	Dec. 31, 2015
Current assets:
Cash and cash equivalents	$ 48,750	$ 34,395
Prepaid expenses	2,768	3,690
Total current assets	51,518	38,085
Property and equipment, net	12,330	12,318
Other assets	18	18
Total assets	63,866	50,421
Current liabilities:
Accounts payable	2,050	2,387
Accrued expenses	3,352	2,653
Loan payable, current portion	5,104	2,336
Warrant liability	172	406
Total current liabilities	10,678	7,782
Loan payable, long-term	10,899	12,896
Commitments and contingencies (Note 13)
Stockholders' equity:
Common stock, $.0001 par value, authorized 150,000,000 shares; 28,759,731 shares issued and outstanding as of December 31, 2016 and 22,315,612 shares issued and outstanding as of December 31, 2015;	3	2
Additional paid-in capital	235,754	194,468
Accumulated deficit	(193,468)	(164,727)
Total stockholders' equity	42,289	29,743
Total liabilities and stockholders' equity	$ 63,866	$ 50,421

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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Data Type:	xbrli:monetaryItemType
Balance Type:	credit
Period Type:	instant

- 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).