Common and Preferred Stock Warrants (Tables)

12 Months Ended

Dec. 31, 2014

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Assumptions Used in Valuing Warrant

The following assumptions were used in valuing the 2010 SVB Warrant:

	February 6, 2014			December 31, 2013			December 31, 2012
Risk-free interest rate		2.45	%		2.45	%		1.26	%
Expected dividend yield		0.00	%		0.00	%		0.00	%
Expected term (in years)		6.31			6.41			7.41
Expected volatility		75.82	%		75.82	%		76.60	%

The following assumptions were used in valuing the 2012 Warrant:

	February 6, 2014			December 31, 2013			December 31, 2012			September 4, 2012
Risk-free interest rate		3.04	%		2.79	%		1.74	%		1.67	%
Expected dividend yield		0.00	%		0.00	%		0.00	%		0.00	%
Expected term (in years)		8.58			8.68			9.35			10
Expected volatility		77.90	%		77.90	%		74.00	%		76.92	%

The following assumptions were used in valuing the 2014 SVB Warrant:

	November 25, 2014
Risk-free interest rate		2.27	%
Expected dividend yield		0.00	%
Expected term (in years)		10
Expected volatility		79.28	%

The following assumptions were used in valuing the PIPE Warrants:

	December 31, 2014			December 2, 2014
Risk-free interest rate		1.10	%		0.96	%
Expected dividend yield		0.00	%		0.00	%
Expected term (in years)		2.92			3.00
Expected volatility		56.79	%		57.28	%