Condensed Consolidated Balance Sheets - USD ($) $ in Thousands	Mar. 31, 2018	Dec. 31, 2017
Current assets:
Cash and cash equivalents	$ 45,731	$ 40,777
Marketable securities	43,339	61,275
Tax incentive receivable	932	946
Prepaid expenses and other current assets	1,420	1,927
Total current assets	91,422	104,925
Tax incentive receivable	581
Property and equipment, net	479	528
Other assets	132	57
Total assets	92,614	105,510
Current liabilities:
Accounts payable	3,796	3,020
Accrued expenses	3,661	4,273
Total current liabilities	7,457	7,293
Notes payable, long-term	20,160	20,000
Total liabilities	27,617	27,293
Commitments and contingencies (Note 7)
Stockholders' equity:
Preferred stock; $0.001 par value per share; 5,000,000 shares authorized as of March 31, 2018 and December 31, 2017; no shares issued and outstanding as of March 31, 2018 and December 31, 2017
Common stock, $0.001 par value per share; 115,000,000 shares authorized as of March 31, 2018 and December 31, 2017; 27,558,883 and 27,489,457 shares issued and outstanding as of March 31, 2018 and December 31, 2017, respectively	28	27
Additional paid-in capital	370,551	367,825
Accumulated deficit	(305,533)	(289,577)
Accumulated other comprehensive loss	(49)	(58)
Total stockholders' equity	64,997	78,217
Total liabilities and stockholders' equity	$ 92,614	$ 105,510

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).