Note 5 – Stock-based Compensation

We did not grant any stock options to employees or non-employees during the three months ended March 31, 2021 or 2020. At March 31, 2021, we had outstanding options to purchase 152,806 shares of our common stock of which options for the purchase of 115,750 shares of our common stock were vested. All the options outstanding have exercise prices higher than the closing market price at March 31, 2021.

At March 31, 2021, we also had 122,782 shares of unvested restricted stock that was granted in 2020 outstanding.

During the three months ended March 31, 2021, we issued 12,500 restricted stock units (RSUs) and 100,000 warrants to a consultant for services to be provided in 2021. We valued the RSUs based on the closing share price on the date of grant. The fair value of the warrants granted was estimated using the Black-Scholes option pricing model at the date of grant. We also agreed to grant 64,556 RSUs and 30,000 stock options to our employees and a consultant in accordance with our employment/consulting agreements. These RSUs and stock options are subject to shareholder approval; thus, they are not included in the number of potentially dilutive securities.

We recorded $308,298 and $98,663 of stock-based compensation expense for the three months ended March 31, 2021 and 2020, respectively.