10. Equity Incentive Plans

The Company had granted stock options under an amended and restated 1997 Equity Incentive Plan (the "1997 Plan") and a 2008 Equity Incentive Plan (the "2008 Plan"). The plans provided for the granting of incentive and nonstatutory options and stock awards to consultants, directors, officers and employees. Such options are exercisable for a period of ten years and generally vest over a four-year period. In conjunction with the adoption of the 2008 Plan in April 2008, no additional grants were made from the 1997 Plan and issued options from the 1997 Plan remain outstanding. In 2014, the Company's Board of Directors approved the 2014 Equity Incentive Plan (the "2014 Plan"). The 2014 Plan is the successor to the Company's 2008 Plan and 1997 Plan. In conjunction with the adoption of the 2014 Plan in 2014, no additional grants were made from the 2008 Plan and options from the 1997 Plan and the 2008 Plan remain outstanding. As of December 31, 2015, there were 531,540 shares available for future grant under the 2014 Plan.

Through December 31, 2015, the Company granted options to certain employees and nonemployees to purchase shares of common stock at exercise prices ranging from $0.71 to $285.71 per share. The Company recorded non cash stock based compensation expense of $2,965, $1,381 and, $1,338 for the years ended December 31, 2015, 2014 and 2013, respectively, based on the fair market value of the options granted at the grant date as determined using a Black-Scholes option pricing model. Stock-based compensation expense was as follows:

	Year Ended December 31,
	2015		2014		2013
Employee	$	2,662	$	1,185	$	476
Non-employee		303		196		862

Total	$	2,965	$	1,381	$	1,338

Stock-based compensation expense related to stock options was allocated as follows:

	Year Ended December 31,
	2015		2014		2013
Research and development	$	1,161	$	617	$	862
General and administrative		1,804		764		476

Total stock-based compensation expense	$	2,965	$	1,381	$	1,338

The following assumptions were used to compute employee stock-based compensation under the Black-Scholes option pricing model:

	2015			2014			2013
Risk-free interest rate		1.92	%		1.84	%		1.73	%
Expected volatility		75.0	%		104.8	%		104.8	%
Expected dividend yield		0	%		0	%		0	%
Expected life (in years)		6.25			6.25			6.25

Risk-free interest rate. The Company bases the risk-free interest rate assumption on observed interest rates appropriate for the expected term of the stock option grants.

Expected dividend yield. The Company bases the expected dividend yield assumption on the fact that it has never paid cash dividends and has no present intention to pay cash dividends.

Expected volatility. The expected volatility assumption is based on volatilities of a peer group of similar companies whose share prices are publicly available. The peer group was developed based on comparable companies in the biotechnology and pharmaceutical industries.

Expected term. The expected term represents the period of time that options are expected to be outstanding. Because the Company does not have historic exercise behavior, management determined the expected life assumption using the simplified method, which is an average of the contractual term of the option and its ordinary vesting period.

Forfeitures. The Company reduces stock-based compensation expense for estimated forfeitures. Forfeitures are estimated at the time of grant and revised, if necessary, in subsequent periods if actual forfeitures differ from those estimates.

As of December 31, 2015, the unrecorded deferred stock-based compensation balance related to stock options was approximately $6.2 million and will be recognized over an estimated weighted-average amortization period of 1.79 years. The weighted average grant date fair value of options granted during the year ended December 31, 2015 was $6.31.

The following table summarizes the options outstanding, options vested and the options exercisable as of December 31, 2015, 2014 and 2013:

	Options			Weighted- Average Exercise Price		Weighted- Average Remaining Contractual Life (Years)	Aggregate Intrinsic Value
Options outstanding at December 31, 2013		1,163,621			3.44	7.9 years
Options granted		712,570			8.76
Options exercised		(41,904	)		1.61
Options cancelled/forfeited		(16,739	)		4.65

Options outstanding at December 31, 2014		1,817,548			5.56	7.9 years
Options granted		620,600			9.84
Options exercised		(261,936	)		2.26
Options cancelled/forfeited		(11,147	)		2.14

Options outstanding at December 31, 2015		2,165,065			7.19	7.8 years	$	6,459


Options exercisable at December 31, 2015		1,083,249			5.06	6.7 years	$	5,622


Vested and expected to vest at December 31, 2015		2,165,065			7.19	7.8 years

Intrinsic value in the above table was calculated as the difference between the Company's estimated stock price at December 31, 2015, of $9.76, and the exercise price, multiplied by the number of options. Intrinsic value for options exercised during 2015 amounts to $1,841.