X0306 4/A 2019-03-13 2019-03-14 0 0001501697 X4 Pharmaceuticals, Inc XFOR 0001201256 WYZGA MICHAEL S C/O X4 PHARMACEUTICALS, INC. 955 MASSACHUSETTS AVENUE, 4TH FLOOR CAMBRIDGE MA 02139 1 0 0 0 Stock Option (right to buy) 10.44 2019-03-13 4 A 0 70324 A 2028-08-21 Common Stock 70324 70324 D Stock Option (right to buy) 18.66 2019-03-13 4 A 0 6854 0.00 A 2029-03-13 Common Stock 6854 6854 D Twenty-five percent (25%) of the shares subject to the option vested on August 22, 2019, and one thirty-sixth (1/36th) of the shares subject to the option shall vest each month thereafter, subject to the Reporting Person continuing to provide service through each such date. Reflects the Reporting Person's stock option to acquire 740,000 shares of X4 common stock for $0.99 per share that was assumed by the Issuer in the merger of Artemis AC Corp., a wholly-owned subsidiary of the Issuer, with and into X4 Therapeutics, Inc. (formerly X4 Pharmaceuticals, Inc.) ("X4") on March 13, 2019 (the "Merger"). 33.3333% of the shares subject to the option shall vest on March 13, 2020, with the remainder vesting in equal monthly installments of 2.7777% of the shares subject to the option until the 36-month anniversary of the date of the award, subject to the Reporting Person continuing to provide service through each such date. This amendment is being filed solely to report this additional stock option grant, which was granted automatically on March 13, 2019 pursuant to the Issuer's Director Compensation Policy upon such Reporting Person's election to the Board of Directors of the Issuer in connection with the closing of the Merger. All share and per share amounts of the Issuer's common stock and stock options reported in this Form 4/A reflect the 1-for-6 reverse stock split of the Issuer's common stock effected on March 13, 2019 after the completion of the Merger. /s/ Adam S. Mostafa, attorney-in-fact 2019-04-02