A novel drug, mavorixafor, appears to be safe and effective for the treatment of warts, hypogammaglobulinemia, infections, and myelokathexis (WHIM) syndrome, according to research presented at the EHA 2023 Hybrid Congress.

WHIM is a rare syndrome linked with multiple immunodeficiencies, including leukopenia and infection. It is known to be linked with gain-of-function CXCR4 variants.

A previous phase 2 trial indicated that mavorixafor — a novel, orally administered CXCR4 antagonist — is safe and potentially effective in this patient population. For this phase 3 study (ClinicalTrials.gov Identifier: NCT03995108), researchers compared the safety and efficacy of mavorixafor with that of placebo among patients with WHIM syndrome.

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The trial included 31 patients who were 12 years of age or older at diagnosis. They were randomly assigned to receive mavorixafor (14 patients) or placebo (17 patients). At baseline, in the experimental and placebo groups, 50% and 53% of patients, respectively, were at least 18 years old, 64% and 53% of patients were female, and the median absolute neutrophil counts (ANCs) were 150 and 200 cells/µL. 

The study’s primary endpoint was time above threshold ANC. Secondary endpoints included annualized infection rate, duration of infections, and total infection score.

The study met its primary endpoint. The mean time above threshold ANC was 15.04 hours in the mavorixafor group and 2.75 hours in the placebo group (P <.0001).

Furthermore, the mean time above threshold absolute lymphocyte count was 15.8 hours in the mavorixafor group and 4.55 hours in the placebo group (P <.0001).

Mavorixafor was associated with a 60% lower annualized infection rate (P =.0072) and a 40% lower total infection score.

No patients discontinued treatment because of an adverse event, and no serious treatment-related events were observed.

“Overall, these data support the filing of a new drug application,” said study presenter Jean Donadieu, MD, PhD, of Hôpital Armand-Trousseau in Paris.

Disclosures: This research was supported by X4 Pharmaceuticals.


Badolato R, Donadieu J, 4WHIM Study Group. Results of a phase 3 trial of an oral CXCR4 antagonist, mavorixafor, for treatment of patients with WHIM syndrome. EHA 2023. June 8-11, 2023. Abstract S180.