9. Stock-Based Compensation

Option and Equity Plans

In May 2016, the stockholders of the Company approved a proposal to increase the number of shares of common stock available for issuance under the 2012 Employee, Director and Consultant Equity Incentive Plan (the “2012 Plan”) by 66,667 shares, from 28,535 to 95,202.

The total number of shares available for grant under the 2012 Plan at September 30, 2016 was 75,355.

Stock Options

A summary of the Company’s stock option activity for the nine months ended September 30, 2016 was as follows:

The Company estimates the fair value of each stock option on the grant date using the Black-Scholes-Merton 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 during the nine months ended September 30, 2016 and 2015:

Summary of Stock-Based Compensation Expense

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

Unrecognized stock-based compensation at September 30, 2016 was as follows (in thousands):