Total share-based compensation related to stock options, common stock awards, and non-financing warrants was $616,933 and $2,057,519 for the three months ended September 30, 2016 and 2015, respectively, and $2,635,196 and $2,294,717 for the nine months ended September 30, 2016 and 2015, respectively.

Share-based compensation expense is classified in the condensed consolidated statements of comprehensive loss as follows:

Employee Stock Options

During the nine months ended September 30, 2016 and 2015, the Company granted 12,122 employee stock options. The key valuation assumptions used consisted of the Company’s stock price, a risk free rate of 0.54% and an expected volatility of 123% and no expected dividends. There were no employee stock options granted during the same period in 2015. In March 2016, the Company extended the exercise expiration date of certain former employee stock option awards resulting in a change in incremental value of approximately $24,000 which was charged to administrative expense. In August 2016, the Company modified the exercise price and vesting of certain employee stock option awards resulting in a change in incremental value and catch up of share-based amortization of approximately $148,000 which was charged to administrative and research and development expense.

The Company recognized compensation expense related to employee stock options of $521,746 and $1,412,992 during the three months ended September 30, 2016 and 2015, respectively, and $1,311,074 and $1,497,295 during the nine months ended September 30, 2016 and 2015, respectively.

Non-Employee Stock Options

No non-employee stock options were granted during the nine months ended September 30, 2016 or 2015 and no non-employee stock options were exercised during the nine months ended September 30, 2016 or 2015. In August 2016, the Company modified the exercise price and vesting of certain non-employee stock option awards resulting in a change in incremental value and catch up of share-based amortization of approximately $17,000 which was charged to administrative expense. The Company recognized compensation expense related to non-employee stock options of $60,435 and $177,351 during the three months ended September 30, 2016 and 2015, respectively, and $62,938 and $186,544 during the nine months ended September 30, 2016 and 2015, respectively.

Common stock awards

The Company granted 8,146 and 371,292 common stock awards during the three months ended September 30, 2016 and 2015, respectively, and 20,309 and 605,580 common stock awards during the nine months ended September 30, 2016 and 2015, respectively, based on the value of the services provided and the average stock price during each respective period. The Company recognized compensation expense related to common stock awards of $36,542 and $116,045 during the three months ended September 30, 2016 and 2015, respectively, and $144,332 and $167,045 during the nine months ended September 30, 2016 and 2015, respectively.

Warrants

In connection with certain of the Company’s collaboration agreements and consulting arrangements, the Company has issued warrants to purchase shares of common stock. On May 16, 2016, the Company modified the exercise price of 150,307 performance-based warrants held by Serum and individuals related to Serum from $25.41 to $7.92 and resulted in an incremental value expense of $204,000. Additionally, the Company issued 212,122 warrants to purchase shares of common stock to Serum with an exercise price of $7.92. The new warrants were fully vested and the Company recognized $1.37 million of expense related to the grant.

As of September 30, 2016, and December 31, 2015, warrants to purchase 758,347 shares of common stock were outstanding. These warrants were fair valued at each issuance date using the Black-Scholes option pricing model. Warrants for which a measurement date has not been reached are subject to re-measurement at each reporting period until the measurement date is reached. Expense is recognized on a straight-line basis over the expected service period or at the date of issuance, if there is not a service period. Expense for the nine months ended September 30, 2016, was $1.1 million including the incremental value recognized for the warrant modification. The Company issued no warrants in connection with collaboration agreements and consulting services during the three and nine months ended September 30, 2016.

The Company recognized warrant expense (gain) in connection with collaboration and consulting arrangements of ($1,790) and $326,123 during the three months ended September 30, 2016 and 2015, respectively, and $1,116,852 and $418,826 during the nine months ended September 30, 2016 and 2015, respectively.