In 2005, the Company approved the 2005 Equity Incentive Plan (the “2005 Plan”). The 2005 Plan provides for the granting of options, restricted stock or other stock-based awards to employees, officers, directors, consultants and advisors. During 2010, the maximum number of shares of Common Stock that may be issued pursuant to the 2005 Plan was increased to 891,222 shares. The Board of Directors (the “Board”) is responsible for administration of the 2005 Plan. The Company’s Board determines the term of each option, the option exercise price, the number of shares for which each option is granted and the rate at which each option is exercisable. Nonqualified stock options may be granted to any officer, employee, consultant or director at an exercise price per share of not less than the par value per share. Following adoption of the 2014 Equity Incentive Plan (the “2014 Plan”), no further grants were made under the 2005 Plan. General terms of the 2014 Plan remain the same as that of the 2005 Plan.

 

The Company’s Board adopted the 2014 Plan and the Employee Stock Purchase Plan (the “ESPP”) and the Company’s Stockholders approved the 2014 Plan and the ESPP Plan in February 2015. As of March 31, 2019, the maximum number of shares of Common Stock that may be issued pursuant to the 2014 Plan and the ESPP was 8,390,123 and 170,567 shares, respectively.

 

In January 2019, the number of shares of common stock issuable under the 2014 Plan automatically increased by 350,000 shares pursuant to the terms of the 2014 Plan. These additional shares are included in the total of 8,390,123 shares issuable under the 2014 Plan.

 

The following is a summary of stock option activity for the three months ended March 31, 2019 and 2018: 

 

 

During the three months ended March 31, 2019 and March 31, 2018, the Board approved the grant of options to purchase 750,000 and 275,500 shares of its Common Stock, respectively. All option grants were pursuant to the 2014 Plan.

For the three months ended March 31, 2019 and 2018, the fair value of each option grant has been estimated on the date of grant using the Black-Scholes Option Pricing Model with the following weighted-average assumptions:

 

 

Using the Black-Scholes Option Pricing Model, the estimated weighted average fair value of an option to purchase one share of common stock granted during the three months ended March 31, 2019 and 2018 was $0.47 and $0.55, respectively.

 

The following is a summary of restricted stock activity for the three months ended March 31, 2019 and March 31, 2018:

 

 

The total stock-based compensation expense for employees and non-employees is included in the accompanying Condensed Consolidated Statements of Operations and as follows: 

 

 

The fair value of options granted for the three months ended March 31, 2019 and March 31, 2018 was approximately $355,300 and $151,200, respectively. As of March 31, 2019 and March 31, 2018, there was approximately $1,358,000 and $945,000 of total unrecognized compensation expense related to unvested stock-based compensation arrangements granted, which cost is expected to be recognized over a weighted-average period of 2.19 and 1.57 years, respectively. The aggregate intrinsic value of stock options outstanding and exercisable at March 31, 2019 and March 31, 2018 was approximately $0 and $0, respectively.

 

At March 31, 2019, there were 4,033,056 shares available under the 2014 Plan and 117,090 shares available under the Company’s ESPP.