In April 2016, the Company’s Board of Directors and stockholders representing a majority of the Company’s outstanding stock at that time, approved the Monopar Therapeutics Inc. 2016 Stock Incentive Plan, as amended (the “Plan”), allowing the Company to grant up to an aggregate 700,000 shares of stock-based awards in the form of stock options, restricted stock units, stock appreciation rights and other stock-based awards to employees, non-employee directors and consultants. In October 2017, the Company’s Board of Directors voted to increase the stock award pool to 1,600,000 shares of common stock, which subsequently was approved by the Company’s stockholders. In April 2020, the Company’s Board of Directors voted to increase the stock award pool to 3,100,000 (and increase of 1,500,000 shares of common stock), which was approved by the Company’s stockholders in June 2020.

In January 2020, the Company's Plan Administrator Committee granted two new hire stock option grants and a consultant stock option grant to the Company’s acting chief medical office, in aggregate, for the purchase of 15,125 shares of the Company’s common stock with exercise prices ranging from $16.80 to $17.75. The stock options have a 10-year term and vest over 1 to 4 years.

In February 2020, the Company's Plan Administrator Committee (with regards to non-officer employees) and the Company's Compensation Committee, as ratified by the Board of Directors (in the case of officers and non-employee directors) granted an aggregate of 189,985 stock options with exercise prices ranging from $12.93 to $14.35 as annual equity grants to executive officers, non-employee directors and staff. All stock options have a 10-year term and vest over 1 to 4 years. The annual equity grants also included an aggregate 45,722 restricted stock units to executive officers, non-employee directors and staff which vest over 1 to 4 years.

In May 2020, the Company's Plan Administrator Committee granted stock option grants to a new hire and an employee, in aggregate, for the purchase of 4,000 shares of the Company’s common stock with exercise prices ranging from $7.61 to $7.66. All stock options have a 10-year term and vest over 4 years.

Under the Plan, the per share exercise price for the shares to be issued upon exercise of an option shall be determined by the Plan Administrator, except that the per share exercise price shall be no less than 100% of the fair market value per share on the grant date. Fair market value is established by the Company’s Board of Directors, using third party valuation reports, recent private financings or the Company’s closing prices on Nasdaq since the Company’s listing on December 19, 2019. Stock options generally expire after 10 years.

Stock option activity under the Plan was as follows:

A summary of options outstanding as of June 30, 2020 is shown below:

Restricted stock unit activity under the Plan was as follows:

During the three months ended June 30, 2020 and 2019, the Company recognized $248,889 and $164,600, respectively, of employee and non-employee director stock-based compensation expense as general and administrative expenses and $100,898 and $72,324, respectively, as research and development expenses. During the six months ended June 30, 2020 and 2019, the Company recognized $469,655 and $315,326, respectively, of employee and non-employee director stock-based compensation expense as general and administrative expenses and $201,069 and $134,665, respectively, as research and development expenses. The stock-based compensation expense is allocated on a departmental basis, based on the classification of the holder. No income tax benefits have been recognized in the condensed consolidated statements of operations and comprehensive loss for stock-based compensation arrangements.

The Company recognizes as an expense the fair value of options granted to persons (currently consultants) who are neither employees nor non-employee directors. Stock-based compensation expense for consultants which was recorded as research and development expense for the three months ended June 30, 2020 and 2019 was $17,571 and $20,708, and for the six months ended June 30, 2020 and 2019 $35,131 and $41,418, respectively.

The fair value of options granted from inception to June 30, 2020 was based on the Black-Scholes option-pricing model assuming the following factors: 4.7 to 6.2 years expected term, 55% to 85% volatility, 0.4% to 2.9% risk free interest rate and zero dividends. The expected term for options granted to date was estimated using the simplified method. There were 4,000 and 209,110 stock option grants during the three and six months ended June 30, 2020, respectively. For the three and six months ended June 30, 2020 the weighted average grant date fair value was $5.43 per share and $9.22 per share, respectively. There were no stock option grants during the three and six months ended June 30, 2019. For the three months ended June 30, 2020 and 2019, the fair value of shares vested was $0.4 million and $0.3 million, respectively. For the six months ended June 30, 2020 and 2019, the fair value of shares vested was $0.6 million and $0.5 million, respectively. At June 30, 2020, the aggregate intrinsic value of outstanding stock options was approximately $4.9 million of which approximately $4.3 million was vested and approximately $0.6 million is expected to vest (representing options to purchase up to 423,638 shares of the Company's common stock), and the weighted-average exercise price in aggregate was $4.79 which includes $2.84 for fully vested stock options and $8.79 for stock options expected to vest. At June 30, 2020, the unamortized unvested balance of stock-based compensation was approximately $3.0 million to be amortized over 2.93 years.