X4 Pharmaceuticals (XFOR) Study Update summary

Background and Unmet Need in Chronic Neutropenia

• Chronic neutropenia affects about 50,000 patients in the U.S., with over 15,000 experiencing recurrent infections despite current treatments.

• G-CSF is the only approved therapy but is associated with injection discomfort, bone pain, and long-term risks such as myelodysplasia and leukemia.

• There is a significant need for an effective, well-tolerated oral therapy to improve quality of life and reduce infection risk.

Mavorixafor Mechanism and Prior Data

• Mavorixafor is an oral CXCR4 antagonist that mobilizes neutrophils from bone marrow to circulation.

• Previous studies in WHIM syndrome showed mavorixafor increased ANC by ~600 cells/μL and reduced infection rates by ~60%.

• FDA approval for mavorixafor in WHIM syndrome supports its safety and efficacy profile.

Phase 2 Interim Study Design and Objectives

• Open-label, six-month trial with 23 participants across monotherapy and combination (with G-CSF) arms.

• Main objectives: assess durable ANC increase, benefit in severe CN, and safety/tolerability.

• Participants included idiopathic, autoimmune, and congenital CN subtypes.

• The study also evaluated durability of response and efficacy in severe CN patients (baseline ANC <500 cells/μL).