X0306 4 2019-06-17 0 0001501697 X4 Pharmaceuticals, Inc XFOR 0001219023 MCGIRR DAVID W J C/O X4 PHARMACEUTICALS, INC. 955 MASSACHUSETTS AVENUE, 4TH FLOOR CAMBRIDGE MA 02139 1 0 0 0 Stock Option (right to buy) 14.75 2019-06-17 4 A 0 3427 0.00 A 2029-06-17 Common Stock 3427 3427 D 8.3333% of the shares subject to the option shall vest on July 17, 2019, with the remainder vesting in equal monthly installments of 8.3333% of the shares subject to the option until the 12-month anniversary of the date of the grant (or, if earlier, the date of the Issuer's next annual meeting of stockholders following the date of the grant), subject to the Reporting Person continuing to provide service through each such date. /s/ Adam S. Mostafa, attorney-in-fact 2019-06-19