a) Warrants

The following table summarizes the changes in warrants outstanding of the Company during the nine-month period ended September 30, 2019:

Effective March 5, 2019, the Company entered into an amendment to an outstanding warrant to purchase up to an aggregate of 5.0 million shares of our common stock, originally issued to Cotterford Company Limited, a significant stockholder, in connection with an equity financing completed on or about August 10, 2018. The amendment temporarily reduced the exercise price of such warrant from $3.00 per share to $2.90 per share through the close of business on March 8, 2019. As a result of this amendment, $196,957 of financing costs was recorded in other expenses.

On March 8, 2019, Cotterford Company Limited partially exercised its warrant and purchased 1,724,138 shares of our common stock at $2.90 per share resulting in gross proceeds to the Company of $5.0 million.

On May 3, 2019, Cotterford Company Limited partially exercised its warrant and purchased 1,666,667 shares of our common stock at $3.00 per share resulting in gross proceeds of $5.0 million to the Company.

On July 1, 2019, the Company modified the performance criteria for certain vesting milestones on an employee warrant agreement and as a result the Company re-measured warrants held by the employee, to purchase 125,000 shares of common stock at an exercise price of $2.47 per share, resulting in $11,829 of additional warrant expense to be recorded over the vesting period. These warrants vest on achievement of certain business objectives and expire 3 years from the date of vesting.

On July 24, 2019, Cotterford Company Limited exercised the remainder of its remaining warrant and purchased 1,609,195 shares of our common stock at $3.00 per share resulting in gross proceeds of $4.8 million to the Company.

During, the first three quarters of 2019, warrants to purchase an aggregate of 5,754,475 shares of our common stock were exercised (including the exercises by Cotterford Company Limited referenced above) for gross cash proceeds to the Company of approximately of $16.5 million. Refer to Note 6 for the details of these exercises.

Below is a table summarizing the warrants issued and outstanding as of September 30, 2019, which have an aggregate weighted average remaining contractual life of 2.77 years.

Warrant expense of $6,379 and $6,453 was recorded in the nine months ended September 30, 2019 and September 30, 2018, respectively. Total remaining unrecognized compensation cost related to non-vested warrants is approximately $22,462 and is expected to be recognized over a period of 1.3 years. As of September 30, 2019, the total intrinsic value of outstanding warrants was $610,742.

b) Options

The following table summarizes the changes in options outstanding of the Company during the nine-month period ended September 30, 2019:

Effective February 11, 2019, the Company granted stock options to purchase 730,000 shares of common stock to various Company personnel (including directors, executives, members of management and employees) for services to the Company. These options vest on February 11, 2020 and expire 5 years after the vesting date, with an exercise price of $3.25 per share. The Company has calculated the estimated fair market value of these options at $1,569,816, using the Black-Scholes model and the following assumptions: term 6 years, stock price $3.16, exercise price $3.25, 77.86% volatility, 2.52% risk free rate, and no forfeiture rate. Subsequent to the February 2019 grant, stock options to purchase 30,000 shares of common stock subject to the grant were forfeited.

Below is a table summarizing the options issued and outstanding as of September 30, 2019, all of which were issued pursuant to the 2011 Equity Incentive Plan (for option issuances prior to 2016) or the 2015 Plan (for option issuances commencing in 2016) and which have an aggregate weighted average remaining contractual life of 3.22 years. As of September 30, 2019, a total of 1,099,000 shares of common stock remained available for future issuance under the 2015 Plan.

Stock option expense of $1,084,312 and $1,875,507 was recorded in the nine months ended September 30, 2019 and September 30, 2018, respectively. Total remaining unrecognized compensation cost related to non-vested stock options is approximately $571,344 and is expected to be recognized over a period of 0.36 years. As of September 30, 2019, the total intrinsic value of outstanding stock options was $7,285,702.