The Company has authorized 150,000,000 shares of common stock, $0.0001 par value per share, of which 64,672,893 shares, and 57,247,496 shares were issued and outstanding as of December 31, 2019, and 2018, respectively.

On January 5, 2018, the Company entered into a sales agreement with Cantor Fitzgerald under which the Company had the ability to direct Cantor Fitzgerald as its sales agent to sell common stock up to an aggregate offering of up to $50 million under an “At the Market Offering” (“January 2018 Sales Agreement”). Sales of common stock under the January 2018 Sales Agreement were made pursuant to an effective registration statement for an aggregate offering of up to $50 million. During the first quarter of 2018, the Company sold 1,500,000 shares of its common stock to an institutional investor under the January 2018 Sales Agreement for which the Company received net proceeds of approximately $11.2 million. The Company did not sell any shares under the January 2018 Sales Agreement in remainder of 2018 and through February 8, 2019, the effective date of the Company’s termination of the January 2018 Sales Agreement.

On January 30, 2019, the Company consummated an underwritten public offering of shares of its common stock pursuant to which the Company sold an aggregate of 6,198,500 shares of its common stock, including 808,500 shares sold pursuant to the full exercise of the underwriters’ option to purchase additional shares, at a purchase price of $6.50 per share with gross proceeds to the Company totaling approximately $40.3 million, less issuance costs incurred of approximately $2.6 million.

During the year ended December 31, 2019 and 2018, the Company issued 107,029 and 144,069 shares of common stock upon the exercise of stock options to purchase common stock and the Company received proceeds of $386,810 and $352,645 from these exercises, respectively.

During the year ended December 31, 2019, warrants to purchase 1,283,500 shares of stock were exercised on a cashless basis resulting in the issuance of 1,119,868 shares of common stock. During the year ended December 31, 2018, warrants to purchase 5,000 shares were exercised for proceeds of $5,000.

On February 11, 2020, the Company consummated an underwritten public offering of shares of its common stock. See Note 14.