Fair Value of Financial Instruments (Tables)

6 Months Ended

Jun. 30, 2015

Summary of Assets and Liabilities Measured at Fair Value on Recurring Basis

The following table summarizes the assets measured at fair value on a recurring basis at June 30, 2015 (in thousands):



Description	June 30, 2015		Active Markets (Level 1)		Observable Inputs (Level 2)		Unobservable Inputs (Level 3)
Assets:
Cash and cash equivalents	$	53,494	$	53,494	$	—	$	—
Total	$	53,494	$	53,494	$	—	$	—



Description	June 30, 2015		Active Markets (Level 1)		Observable Inputs (Level 2)		Unobservable Inputs (Level 3)
Liabilities:
Warrant liability	$	96	$	—	$	—	$	96
Total	$	96	$	—	$	—	$	96

The following table summarizes the assets and liabilities measured at fair value on a recurring basis at December 31, 2014 (in thousands):



Description	December 31, 2014		Active Markets (Level 1)		Observable Inputs (Level 2)		Unobservable Inputs (Level 3)
Assets:
Cash and cash equivalents	$	54,059	$	54,059	$	—	$	—
Total	$	54,059	$	54,059	$	—	$	—



Description	December 31, 2014		Active Markets (Level 1)		Observable Inputs (Level 2)		Unobservable Inputs (Level 3)
Liabilities:
Warrant liability	$	3,219	$	—	$	—	$	3,219
Total	$	3,219	$	—	$	—	$	3,219

Summary of Assumptions Used in Valuing Warrants

The Company measures the fair value of the warrants classified as a liability at each reporting date using the Black-Scholes option pricing model using the following assumptions:



	June 30, 2015		December 31, 2014
Risk-free interest rate	0.64	%	1.10	%
Expected dividend yield	0.00	%	0.00	%
Expected term (in years)	2.42		2.92
Expected volatility	63.17	%	56.79	%

Summary of Changes in the Fair Value of the Company's Preferred Stock Warrant Liability

The following table sets forth a summary of changes in the fair value of the Company’s common stock warrant liability, which represented a recurring measurement classified within Level 3 of the fair value hierarchy, wherein fair value was estimated using significant unobservable inputs (in thousands):



Beginning balance, January 1, 2015	$	3,219
Change in fair value	(3,123		)
Ending balance, June 30, 2015	$	96