9. Stock-Based Compensation

Option and Equity Plans

In May 2015, the stockholders of the Company approved an increase in the aggregate number of common shares issuable under the 2012 Employee, Director and Consultant Equity Incentive Plan (the “2012 Plan”) by 66,667 shares to 305,746 shares. The total number of shares available for grant under the 2012 Plan at December 31, 2015 was 93,039.

Stock Options

A summary of the Company’s stock option activity for the year ended December 31, 2015 is as follows:

The aggregate intrinsic value in the table above is calculated as the difference between the estimated fair value of the Company’s stock at December 31, 2015 and the exercise price of each option.

The weighted average grant date fair value of options granted during the years ended December 31, 2015 and 2014 was $5.32 and $25.05, respectively.

The Company estimates the fair value of each stock option on the grant date using the Black-Scholes valuation model, which requires several estimates including an estimate of the fair value of the underlying common stock on grant date. The expected volatility was based on an average of the historical volatility of a peer group of similar companies. The expected term was calculated utilizing the simplified method. The risk-free interest rate was based on the U.S. Treasury yield curve in effect at the time of grant for the expected term of the option. The following weighted average assumptions were used in the calculation to estimate the fair value of options granted to employees for the years ended December 31, 2015 and 2014:

Restricted Stock Awards

Restricted stock awards (“RSA”) activity for the year ended December 31, 2015 was as follows:

The total fair value of RSAs vested during the year ended December 31, 2015 was $87,000. The Company recorded $87,000 of stock-based compensation for RSAs during the year ended December 31, 2015.

Stock-Based Awards Granted to Nonemployees

The Company from time to time grants options to purchase common stock or restricted stock to non-employees for services rendered and records expense ratably over the vesting period of each award. The Company estimates the fair value of the stock options using the Black-Scholes valuation model at each reporting date. No options were granted to non-employees during the year ended December 31, 2015. The Company granted 18,000 RSAs to non-employees and recorded stock-based compensation expense of $87,000 during the year ended December 31, 2015. The Company granted 11,029 options and 6,309 restricted stock awards to non-employees and recorded stock-based compensation expense of $712,000 during the year ended December 31, 2014.

The following assumptions were used in the Black-Scholes valuation model related to non-employee stock options granted during the year ended December 31, 2014:

Summary of Stock-Based Compensation Expense

Total stock-based compensation expense included in the consolidated statements of operations and comprehensive loss was allocated as follows (in thousands):

Unrecognized stock-based compensation at December 31, 2015 was as follows (in thousands):