Note 15 — Subsequent Events

Subsequent to December 2019, the Company granted 52,791 stock options to Board members, and 57,000 stock options to executives, that are subject to cancellation in the event the Company does not obtain shareholder approval of an increase in the shares reserved for issuance under the Plan at the 2020 Annual Shareholder Meeting, and 3,000 stock options to employees under the Plan. The estimated fair value of these stock options, calculated using the Black-Scholes option valuation model, was $173,184, of which $169,339 is expected to be recognized during the year ended December 31, 2020.

In March 2020, 616,648 warrants with a weighted-average exercise price of $24.28 per share expired.

In March 2020, the World Health Organization declared the outbreak of a novel coronavirus ("COVID-19") as a pandemic, which continues to spread throughout the United States. The ultimate extent of the impact of COVID-19 on the financial performance of the Company will depend on future developments, including the duration and spread of COVID-19, and the overall economy, all of which are highly uncertain and cannot be predicted. If the financial markets and/or the overall economy are impacted for an extended period, the Company's operating results may be materially and adversely affected.