In conjunction with the June 2017 Public Offering, the Company issued to certain affiliates of the underwriters, as compensation, warrants to purchase an aggregate of 4,313 shares of common stock at an exercise price of $125.00 per share. The warrants are exercisable at the option of the holder on or after June 21, 2018 and expire June 21, 2023.The fair value of warrants was calculated utilizing a Black-Scholes model and amounted to $63,796. The fair market value of the warrants as of the date of issuance has been included in issuance costs in additional paid-in capital.

In conjunction with the Purchase Agreement in April 2019, the Company also sold warrants to purchase up to an aggregate of 42,388 shares of common stock at an initial exercise price of $27.50 per share. The warrants are exercisable at the option of the holder on or after October 29, 2019 and expire October 29, 2024. The Company issued to certain affiliates of the underwriters, as compensation, warrants to purchase an aggregate of 4,239 shares of common stock at an initial exercise price of $27.50 per share. The warrants are exercisable at the option of the holder on or after October 29, 2019 and expire April 24, 2024.

In conjunction with the Underwriting Agreement in August 2019, the Company issued to the underwriter, as compensation, warrants to purchase an aggregate of 2,250 shares of common stock at an initial exercise price of $21.25 per share. The warrants are exercisable at the option of the holder on or after February 1, 2020 and expire August 29, 2024.

In conjunction with the Underwriting Agreement in May 2020, the Company issued to the underwriter, as compensation, warrants to purchase an aggregate of 300,000 shares of common stock at an initial exercise price of $3.14 per share. The warrants are exercisable at the option of the holder on or after November 6, 2020 and expire May 5, 2025.