X4 Pharmaceuticals (XFOR) Investor Day 2026 summary

Clinical development and milestones

• 4WARD is a global, double-blind, placebo-controlled Phase III trial targeting 126 patients with primary chronic neutropenia; participants receive mavorixafor or placebo, with or without G-CSF. Co-primary endpoints are ANC response above 500/µL and annualized infection rate.

• Blinded baseline data through September 2026 showed median ANC of 483/µL, 68% with ≥3 infections and 37% using G-CSF; enrollment was evenly split between moderate and severe disease, with no new safety signals reported.

• 4WARD enrollment is expected to complete in Q4 2026; topline data are expected in Q1 2028. Positive results could support U.S. FDA approval in late 2028 or early 2029.

• Planned Phase IIb 4STEPS will enroll ~25 patients on stable G-CSF; after mavorixafor initiation, it will assess G-CSF cessation and dose reductions while maintaining ANC. First patients are expected in Q1 2027, with topline data expected Q1 2028.

• 4STEPS includes a 4-week G-CSF observation period, 8-week run-in, stepwise G-CSF reductions over 16–20 weeks and 24-week maintenance, with ANC-based dose decisions.

Market opportunity and treatment need

• Claims analysis identified ~95,000 U.S. PCN patients aged 12+; ~30,000 had ANC <1,000/µL and ≥1 infection, and ~15,000 had ≥2 infections, aligning with 4WARD eligibility and the initial symptomatic base case.

• The potential U.S. population could extend to ~30,000 patients with ANC <1,000/µL and ≥1 infection, subject to FDA labeling.

• PCN is often underdiagnosed; current options are G-CSF injections and antibiotics, with no approved oral PCN therapy or new treatment class in more than 30 years.

• In 2025, ~6,300 U.S. PCN patients were hospitalized due to infections, with a mean stay of 4 days per infection.

• Patient research found injection fatigue, social restrictions and work or school disruption; ~90% of surveyed hematologists intended to prescribe mavorixafor assuming FDA approval.

Mavorixafor profile and positioning

• Once-daily oral CXCR4 antagonist designed to mobilize neutrophils into circulation; evaluated alone and with G-CSF in PCN and approved in the U.S. and EU as XOLREMDI for patients aged 12+ with WHIM syndrome.

• Clinicians described potential use as initial therapy for untreated patients or those intolerant of G-CSF, and alongside G-CSF for patients seeking dose reduction or discontinuation.

• In a Phase II chronic neutropenia study, common treatment-related adverse events were mild-to-moderate nausea and diarrhea, with no drug-related serious adverse events; clinicians described GI effects as generally manageable and often improving after 1–2 months.

• Clinicians highlighted reduced infection severity, hospital admissions and ER visits as meaningful outcomes; infections in 4WARD are adjudicated by a blinded committee.