Efficacy and Safety Study of Mavorixafor in Participants With Warts, Hypogammaglobulinemia, Infections, and Myelokathexis (WHIM) Syndrome

Brief Title

Efficacy and Safety Study of Mavorixafor in Participants With Warts, Hypogammaglobulinemia, Infections, and Myelokathexis (WHIM) Syndrome

Official Title

A Phase 3, Randomized, Double-Blind, Placebo-Controlled, Multicenter Study of Mavorixafor in Patients With WHIM Syndrome With Open-Label Extension

Brief Summary

      This study has a double-blind, Randomized Placebo-Controlled Period and an Open-Label Period.
      The primary objective of the Randomized Placebo-Controlled Period is to demonstrate the
      efficacy of mavorixafor in participants with WHIM syndrome as assessed by increasing levels
      of circulating neutrophils compared with placebo, and relative to a clinically meaningful
      threshold. The primary objective of the Open-Label Period is to evaluate the safety and
      tolerability of mavorixafor in participants with WHIM syndrome. Participants are allowed to
      continue treatment in the Open-Label Period, if regionally applicable, until mavorixafor
      becomes commercially available, or until the study is terminated by the Sponsor.

Study Phase

Phase 3

Study Type


Primary Outcome

Randomized Placebo-Controlled Period: Time (in Hours) Above Threshold-Absolute Neutrophil Count (TAT-ANC in hours) of ≥ 500 Cells/Microliter (µL) over a 24-hour period

Secondary Outcome

 Randomized Placebo-Controlled Period: Time (in Hours) Above Threshold-Absolute Lymphocyte Count (TAT-ALC) of ≥ 1000 Cells/µL over a 24-hour period


WHIM Syndrome



Study Arms / Comparison Groups

Description:  Participants (adults and adolescents [12 to 17 years of age weighing >50 kilograms [kg]) will receive mavorixafor 400 milligrams (mg) once daily (QD) orally for 52 weeks in the Randomized Placebo-Controlled Period. Adolescents weighing ≤50 kg will receive mavorixafor 200 mg QD. Participants who complete the Randomized Placebo-Controlled Period or are granted Early Release due to recurrent or significant infections, as adjudicated by a blinded, independent adjudication committee (AC), will be offered the opportunity to enroll in the Open-Label Period and receive treatment with mavorixafor 400 mg once daily orally until commercial availability or study termination by the Sponsor.


* Includes publications given by the data provider as well as publications identified by National Clinical Trials Identifier (NCT ID) in Medline.

Recruitment Information

Recruitment Status


Estimated Enrollment


Start Date

October 17, 2019

Completion Date

October 2022

Primary Completion Date

September 2022

Eligibility Criteria

        Inclusion Criteria for the Randomized Placebo-Controlled Period :

          -  Have signed the current approved informed consent form. Participants under 18 years of
             age (in the Netherlands and other applicable regions, participants under 16 years of
             age) will sign an approved informed assent form and must also have a signed
             parental/legal guardian consent.

          -  Have a genotype-confirmed mutation of chemokine (C-X-C motif) receptor 4 (CXCR4)
             consistent with WHIM phenotype.

          -  Agree to use a highly effective form of contraception.

          -  Be willing and able to comply with the protocol.

          -  Have confirmed ANC ≤400 cells/µL during screening, obtained while participant has no
             clinical evidence of infection.

        Inclusion Criteria for the Open-Label Period:

          -  Completed the Randomized Period; or

          -  Granted Early Release from the Randomized Period.

        Exclusion Criteria:

          -  Has known systemic hypersensitivity to the mavorixafor drug substance, its inactive
             ingredients, or the placebo.

          -  Is pregnant or breastfeeding.

          -  Has any medical or personal condition, which in the opinion of the Investigator may
             potentially compromise the safety or compliance of the participant or may preclude the
             participant's successful completion of the clinical study.




12 Years - N/A

Accepts Healthy Volunteers



Chief Medical Officer, , 

Location Countries


Location Countries


Administrative Informations



Organization ID


Secondary IDs


Responsible Party


Study Sponsor

X4 Pharmaceuticals

Study Sponsor

Chief Medical Officer, Study Director, X4 Pharmaceuticals

Verification Date

September 2022