Class B Warrants to purchase 5,416,667 shares of common stock (or, Pre-Funded Warrants). Each Class B Warrant will have an exercise price per share of common stock equal to $15.00 and will expire on the date (the “Expiration Date”) that is the earlier of (a) the date that is thirty (30) calendar days following the date on which the Company issues a press release regarding topline data from its Phase III clinical trial of mavorixafor for the treatment of WHIM syndrome (or, if such date is not a business day, the following business day) and (b) 60 months from the date of issuance. Each Class B Warrant will be immediately exercisable, provided that the holder will be prohibited, subject to certain exceptions, from exercising the Class B Warrant for shares of our common stock to the extent that immediately prior to or after giving effect to such exercise, the holder, together with its affiliates and other attribution parties, would own more than 9.99% of the total number of shares of our common stock then issued and outstanding, which percentage may be changed at the holders’ election to a higher or lower percentage not in excess of 19.99% (if exceeding such percentage would result in a change of control under Nasdaq Listing Rule 5636(b) or any successor rule) upon 61 days’ notice to us subject to the terms of the Class B Warrants. If the holder is not permitted to exercise a Class B Warrant for common stock due to the foregoing limitation, then the holder may exercise the Class B Warrant for an equivalent number of Pre-Funded Warrants with an exercise price of $0.001 in substantially the same form of Pre-Funded Warrant to purchase shares of common stock described above.

If, prior to the Expiration Date, the Company sells shares of common stock or derivative securities convertible into or exercisable for common stock (other than in certain circumstances) in one or more related transactions primarily for the purpose of raising capital (each, a “Subsequent Offering”) at an Offering Weighted-Average Price below $15.00 per share, then the initial Exercise Price of the Class B Warrants will be automatically reset upon exercise to an exercise price (the “Adjusted Exercise Price”) that is the lowest Offering Weighted-Average Price per share at which the Company sells common Stock or derivative securities convertible into or exercisable for Common Stock in a Subsequent Offering prior to the exercise date; provided, however, that the Adjusted Exercise Price will not be reduced below $1.50 per share. The “Offering Weighted-Average Price” shall be calculated as the weighted-average common stock equivalent price of the equity securities sold in such transaction(s) (subject to certain exclusions), and subtracting the value of any warrants or other derivative securities sold in such offering (determining the value of such derivative securities in accordance with GAAP using the Black-Scholes Option Pricing Model and dividing the warrant or derivative value by the number of shares potentially issuable thereunder).

If there is no effective registration statement at the time of exercise, the Class B Warrants may be exercised cashlessly. This free writing prospectus and the Preliminary Prospectus Supplement also relate to the offering of the shares of our common stock (or Pre-Funded Warrants) issuable upon exercise of the Class B Warrants.