13. STOCK OPTIONS

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 (the "Board") 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 automatically increase on January 1 of each year by at least seven percent (7%) of the total number of shares of common stock outstanding on December 31st of the preceding calendar year, or, pursuant to the terms of the 2014 Plan, in any year, the Board may determine that such increase will provide for a lesser number of shares.

In accordance with the terms of the 2014 Plan, and pursuant to the annual evergreen provision contained in the 2014 plan, effective as of January 1, 2020, the number of shares of common stock available for issuance under the 2014 Plan increased by 4,527,103 shares, which was seven percent (7%) of the outstanding shares of common stock on December 31, 2019. As of January 1, 2020, there was a total of 23,070,842 shares reserved for issuance under the 2014 plan and there were 8,840,939 shares available for future grants. As of September 30, 2020 there were 5,228,780 shares available for future grants.

In accordance with the terms of the 2014 Plan, and pursuant to the annual evergreen provision contained in the 2014 Plan, effective as of January 1, 2021, the number of shares of common stock available for issuance under the 2014 Plan increased by 2,500,000 shares, which was less than seven percent (7%) of the outstanding shares of common stock on December 31, 2020. As of January 1, 2021, there was a total of 25,570,842 shares reserved for issuance under the 2014 Plan and there were 9,869,051 shares available for future grants. As of September 30, 2021 there were 6,071,775 shares available for future grants.

Stock-based Compensation

For stock options issued and outstanding for the three months ended September 30, 2021 and 2020, respectively, the Company recorded non-cash, stock-based compensation expense of $2,599,247 and $3,630,996, net of estimated forfeitures. For stock options issued and outstanding for the nine months ended September 30, 2021 and 2020, respectively, the Company recorded non-cash, stock-based compensation expense of $7,686,921 and $10,116,775, respectively, net of estimated forfeitures.

The fair value of each option award for employees is estimated on the date of grant using the Black-Scholes option pricing model that uses the assumptions noted in the following table. Our expected stock price volatility assumptions are based on the historical volatility of our stock over periods that are similar to the expected terms of the grants. 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 in order to estimate its forfeiture rate. The expected term of options granted under the 2014 Plan, all of which qualify as “plain vanilla” per SEC Staff Accounting Bulletin 107, is determined based on the simplified method due to the Company’s limited operating history and is 6.25 years based on the average between the vesting period and the contractual life of the option. 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 weighted average grant-date fair value of options granted during the nine months ended September 30, 2021 and 2020 was $2.02 and $3.61 per share, respectively. The aggregate intrinsic value of options exercised during the nine months ended September 30, 2021 and 2020 was approximately $1,769,714 and $1,141,083, respectively. The total fair value of options that were vested as of September 30, 2021 and 2020 was $38,806,156 and $34,180,750, respectively. As of September 30, 2021, there was approximately $14,798,875 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 2.55 years as of September 30, 2021.