In April 2014, the Company adopted the Corbus Pharmaceuticals Holdings, Inc. 2014 Equity Incentive Plan (the “2014 Plan”). Pursuant to the 2014 Plan, the Company’s Board of Directors may grant incentive and nonqualified stock options and restricted stock to employees, officers, directors, consultants and advisors. Pursuant to the terms of an annual evergreen provision in the 2014 Plan, the number of shares of common stock available for issuance under the 2014 Plan shall be subject to an automatic annual increase on January 1st of each year equal to the greater of (i) seven percent (7%) of the total number of shares of common stock outstanding on December 31st of the preceding calendar year, or, (ii) the difference between (x) twenty percent (20%) of the total number of shares of common stock outstanding on December 31st of the preceding calendar year, and (y) the total number of shares of common stock reserved under the 2014 Plan on December 31st of such preceding calendar year or a lesser number of shares of common stock determined by the Company’s Board of Directors. In accordance with the terms of the 2014 Plan, effective as of January 1, 2016, the Board of Directors approved an increase in the number of shares of common stock available for issuance under the 2014 Plan in an amount of 1,250,000 shares, such amount being less than seven percent (7%) of the outstanding shares of common stock on December 31, 2015. As of March 31, 2016, there was a total of 9,916,017 shares reserved for issuance under the 2014 Plan and there were 4,624,513 shares available for future grants. Options issued under the 2014 Plan are exercisable for up to ten years from the date of issuance.

Share-based Compensation

For stock options issued and outstanding for the three months ended March 31, 2016 and 2015, respectively, the Company recorded non-cash, stock-based compensation expense of $311,238 and $301,958, respectively, net of estimated forfeitures.   

The fair value of each option award is estimated on the date of grant using the Black-Scholes option pricing model that uses the assumptions noted in the following table. Due to its limited operating history and limited number of sales of its common stock, the Company estimated its volatility in consideration of a number of factors, including the volatility of comparable public companies and, commencing in 2015, the Company also included the volatility of its own common stock. The Company uses historical data, as well as subsequent events occurring prior to the issuance of the financial statements, to estimate option exercises and employee terminations within the valuation model. The expected term of options granted to employees under the 2014 Plan, all of which qualify as “plain vanilla” per SEC Staff Accounting Bulletin 107, is based on the average of the 6.25 years. For non-employee options, the expected term is the contractual term. The risk-free rate is based on the yield of a U.S. Treasury security with a term consistent with the option.

The assumptions used principally in determining the fair value of options granted were as follows:

 

 

A summary of option activity for the three months ended March 31, 2016 and is presented below:

 

 

The weighted average grant-date fair value of options granted during the three months ended March 31, 2016 was $1.40 per share. As of March 31, 2016, there was approximately $2,128,624 of total unrecognized compensation expense, related to non-vested share-based option compensation arrangements. The unrecognized compensation expense is estimated to be recognized over a period of 3.09 years.