Note 10 - Stockholders' Equity

Authorized Capital

The Company has authorized the issuance and sale of up to 80,000,000 shares of stock, consisting of 75,000,000 shares of common stock having a par value of $0.001 and 5,000,000 shares of Preferred Stock having a par value of $0.001 per share. As of December 31, 2019 and 2018, there were no shares of Preferred Stock outstanding and there were no declared but unpaid dividends or undeclared dividend arrearages on any shares of the Company's capital stock.

Controlled Equity Offering

During the year ended December 31, 2018, the Company entered into a Controlled Equity Offering Sales Agreement with Cantor Fitzgerald & Co. as sales agent. The Company issued 2,186,855 shares of its common stock under the Controlled Equity Offering program for proceeds of $19,304,081, net of commissions and professional fees of $95,778.

Stock Options

The Company has an incentive stock plan, the Amended and Restated 2011 Equity Incentive Plan, as amended (the "2011 Plan"), and has granted stock options to employees, non-employee directors and consultants from the 2011 Plan. Options granted under the 2011 Plan may be Incentive Stock Options or Non-statutory Stock Options, as determined by the Administrator at the time of grant. On June 19, 2018, the Company's stockholders approved an amendment to the 2011 Plan previously adopted by the Company's board of directors on April 20, 2018 (the "2018 Amendment"). The 2018 Amendment increased the number of shares authorized for issuance under the 2011 Plan to a total of 10,000,000. As of December 31, 2019, there were 1,190,566 shares remaining available for issuance under the 2011 Plan.

During the year ended December 31, 2019, the Company granted stock options to employees to purchase 2,779,000 shares of the Company's common stock at exercise prices that ranged between $1.43 to $3.15 per share. The options have terms of ten years. The stock options have an aggregate grant date fair value of $3,471,351.

During the year ended December 31, 2019, 441,210 stock options were exercised for cash proceeds of $552,110 and the Company cancelled 193,714 stock options.

During the year ended December 31, 2018, the Company granted stock options to employees to purchase 860,000 shares of the Company's common stock at exercise prices that ranged between $3.57 to $8.86 per share. The options have terms of ten years. The stock options have an aggregate grant date fair value of $3,337,752.

Due to the commencement of the clinical study during the quarter ended September 30, 2018, stock options to purchase 726,000 shares of the Company's common stock granted to its employees in January 2017 met the performance conditions applicable to such options and began vesting. Upon certification of achievement of the performance condition by the compensation committee of the Company's board of directors on July 18, 2018, 50% of the options became vested. The remaining shares subject to the stock options will vest over a period of 24 months subject to the continuous service of the applicable optionee. The stock options have an exercise price of $2.40 and an aggregate grant date fair value of $2,759,453.

During the year ended December 31, 2018, 602,533 stock options were exercised for cash proceeds of $494,866 and the Company cancelled 460,599 stock options.

The Company recorded stock-based compensation as follows:

The following table represents stock option activity for the years ended December 31, 2019 and 2018:

The following table summarizes information on stock options outstanding and exercisable as of December 31, 2019:

Warrants

During the year ended December 31, 2019, warrants to purchase 50,000 shares of the Company's common stock were exercised for cash proceeds of $57,500.

During the year ended December 31, 2019, warrants to purchase 6,982 shares of the Company's common stock expired and were cancelled.

During the year ended December 31, 2018, warrants to purchase up to an aggregate of 780,500 shares of the Company's common stock at an exercise price of $5.30 per share were issued in the Company's Notes offering. The Warrants had a fair value of $1,253,390 (see Note 7 "Notes Payable").

During the year ended December 31, 2018, warrants to purchase 349,315 shares of the Company's common stock were exercised for aggregate cash proceeds of $678,240.

The following table represents warrant activity for the years ended December 31, 2019 and 2018: