Balance Sheets - USD ($) $ in Thousands	Jun. 30, 2018	Dec. 31, 2017
Current assets:
Cash and cash equivalents	$ 22,465	$ 35,952
Prepaid expenses	200	762
Total current assets	22,665	36,714
Property and equipment, net	13,924	13,863
Other assets	18	18
Total assets	36,607	50,595
Current liabilities:
Accounts payable	1,078	2,784
Accrued expenses	1,751	852
Loan payable, curent portion	7,525	10,607
Warrant liability		29
Total current liabilities	10,354	14,272
Commitments and contingencies (Note 10)
Stockholders' equity
Common stock, $.0001 par value, 150,000,000 shares authorized, 34,377,329 and 34,186,342 issued and outstanding at June 30, 2018 and December 31, 2017, respectively	3	3
Additional paid-in capital	260,199	258,092
Accumulated deficit	(233,949)	(221,772)
Total stockholders' equity	26,253	36,323
Total liabilities and stockholders' equity	$ 36,607	$ 50,595

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).