8. Stockholders’ Equity

2019 Private Placement

On May 9, 2019, the Company entered into a Securities Purchase Agreement (the “Purchase Agreement”) with certain accredited investors (collectively, the “Investors”) for the private placement of 2,426,455 shares of the Company’s common stock at $3.10 per share (the “2019 PIPE”). The Company received aggregate gross proceeds of approximately $7.5 million, before deducting offering expenses aggregating approximately $94,000.

The Purchase Agreement also contains representations and warranties by the Company and the Investors and covenants of the Company and the Investors (including indemnification from the Company in the event of breaches of its representations and warranties), certain information rights and other rights, obligations and restrictions, which the Company believes are customary for transactions of this type.

Issuance of Common Stock in Lieu of Cash Payments

Under the terms of the Amended and Restated Non-Employee Director Compensation Plan, each non-employee member of the Company’s Board of Directors may elect to receive all or part of his or her director fees in shares of the Company’s common stock. Director fees, whether paid in cash or in shares of common stock, are payable quarterly on the last day of each fiscal quarter. The number of shares of common stock issued to directors is determined by dividing the product of: (i)(a) the fees otherwise payable to each director in cash, times (b) the percentage of fees the director elected to receive in shares of common stock, by (ii) the volume weighted average price per share of common stock over the last five trading days of the quarter. During the years ended December 31, 2019 and 2018, 29,861 shares and 57,386 shares, respectively, were issued to directors as payment for director fees, amounting to $117,163 and $113,665, in 2019 and 2018, respectively, in lieu of cash.

Stock Incentive Plans

The Company has various share-based compensation plans and share-based compensatory contracts (collectively, the “Plans”) under which it has granted share-based awards, such as stock grants, and incentive and non-qualified stock options, to employees, directors, consultants and advisors. Awards may be subject to a vesting schedule as set forth in individual award agreements. Certain of the Plans also have provided for cash-based performance bonus awards.

Since October 2017, the Company has granted share-based awards under the Company’s Second Amended and Restated 2013 Incentive Compensation Plan (the “2013 Plan”). Under the 2013 Plan, a total of 1,956,250 shares of the Company’s common stock are reserved for issuance. Of this amount, stock grants of 394,377 shares have been awarded and option grants, net of options terminated, expired or forfeited, of 1,086,234 shares were outstanding as of December 31, 2019. Accordingly, 475,639 shares remained available for grants under the 2013 Plan as of that date.

Activity with respect to stock options issued by the Company is summarized as follows: 

The following table summarizes information about stock options at December 31, 2019 (contractual life expressed in years):

The per share weighted average grant date fair value of options granted during the years ended December 31, 2019 and 2018 was $1.72 and $0.95, respectively. A summary of the status of the Company’s nonvested stock options during the years ended December 31, 2019 and 2018 is presented below:

The Company records share-based compensation expense on a straight-line basis over the related vesting period. For the years ended December 31, 2019 and 2018, share-based compensation expense was:

As of December 31, 2019, approximately $553,221 of unrecognized compensation cost related to share-based compensation arrangements granted under the Plans. That cost is expected to be recognized over a weighted-average period of 1.71 years.

The assumptions used in calculating the fair value under the Black-Scholes option-pricing model are as follows: 

Warrants 

Warrants have generally been issued in connection with financing transactions and for terms of up to five years. Common stock warrant activity for the years ended December 31, 2019 and 2018 is as follows:

Information regarding outstanding warrants at December 31, 2019 is as follows (contractual life expressed in years):