Clinical Trial Information

Visit, a database of privately and publicly funded clinical studies conducted around the world. Before participating in a study, talk to your health care provider and learn about the risks and potential benefits.

A Study of Mavorixafor in Participants With Severe Congenital Neutropenia and Chronic Neutropenia Disorders

This Phase 1b study will determine the safety and tolerability of mavorixafor in participants with severe chronic idiopathic neutropenia (CIN) and selected congenital neutropenia disorders. The anticipated enrollment is up to 45 participants.

Participants must meet the following criteria:

  • Weigh ≥15 kg
  • Sign the informed consent form (ICF) and be willing and able to comply with the protocol
  • Participants with severe chronic idiopathic neutropenia (CIN):
    • Have a history of ANC ≤500 cells/microliter (μL), lasting for more than 3 months at any time since diagnosis.
    • Have been diagnosed with severe CIN more than 12 months ago that is not attributable to medications, infectious, genetic, inflammatory, autoimmune, or malignant causes.
    • Be currently treated with a steady-state G-CSF regimen for greater than (>) 15 days before receiving the first dose of study drug.
    • Have cytogenetics that do not suggest clonal evolution on the most recent bone marrow biopsy/aspirate, if performed.
    • Have no history of associated thrombocytopenia (platelets < 75,000/uL) nor anemia <10.0 g/dL before G-CSF therapy initiation.
    • Not have neutropenia secondary to another pathology, such as a systemic autoimmune disorder and in particular rheumatological or hematological.
  • Participants with selected congenital neutropenia conditions including GSD1b (GSD1b; SLC37A4), G6PC3 deficiency (G6PC3), or GATA2 deficiency (GATA2):
    • May be currently receiving steady-state G-CSF dosing or not have been on G-CSF for >15 days.
    • Must have documentation of the mutational status before enrolling in the study.

Four sites have opened:

University of Michigan
Ann Arbor, Michigan, United States, 48109
Contact: Dr. Kelly Walkovich 734-615-4368

University of Washington
Seattle, Washington, United States, 98195
Contact: Dr. David Dale 206 543 3668

University of Iowa Hospital and Clinics
Iowa City, Iowa, United States, 52242
Contact: Dr. Anjali Sharathkumar

Washington University School of Medicine
Saint Louis, Missouri, United States, 63110
Contact: Dr. David Wilson 908 887-2278

To learn more about this study, you or your doctor may contact the study research staff using the contact information provided. Please refer to this study by its identifier (NCT number): NCT04154488

Please visit the clinical trial website for additional criteria, exclusions, and additional information.



X4 Pharmaceutical’s (Cambridge, MA) Phase 3 WHIM trial is open now for enrollment, entitled “A Phase 3, Randomized, Double-Blind, Placebo-Controlled, Multicenter Trial of mavorixafor (X4P-001) in Patients with WHIM Syndrome with Open-Label Extension

WHIM (Warts, Hypogammaglobulinemia, Infections and Myelokathexis) is a rare autosomal dominant primary immunodeficiency disease caused by gain-of-function mutations in the chemokine receptor CXCR4.  CXCR4 mutations induce increased leukocyte homing and retention in the bone marrow resulting in severe chronic neutropenia and lymphopenia.

X4 Pharmaceuticals is planning to sponsor a 52-week global Phase 3 study to evaluate the safety and efficacy of mavorixafor, a once-daily oral CXCR4 antagonist, in genetically confirmed WHIM patients who are aged 12 years or older.  Mavorixafor is a first-in-class, oral, small molecule antagonist of the CXCR4 chemokine receptor that has demonstrated a favorable safety profile and dose-dependent increases in ANC and ALC in a Phase 2 study. Trial subjects will participate in a one-year trial with an opportunity to continue in the subsequent open label extension.  Travel support to study sites will be provided.

To support confirming the diagnosis of WHIM, X4 Pharmaceuticals will offer genetic testing at no charge to patients meeting eligibility criteria suggestive for the disease.  For information and support for genetic confirmation of your patients with suspected WHIM, please contact


Free genetic testing is available for people living with congenital, chronic, and/or idiopathic neutropenia to help them learn more about their condition.There are 407 genes known to cause primary immune deficiencies (PIDs), some of which may cause neutropenia. This genetic testing is only looking at the 407 genes known to cause PIDs and won’t tell you if  you’re at risk for other conditions.

You can take the test at your doctor’s office or at home. And there is no cost to you for this testing.
Click flyer for additional information and how to enroll.




X4 is joining forces with ‘Probably Genetic’ to provide PID panel testing to people who fit the symptomatic profile of WHIM syndrome-a rare genetic immunodeficiency caused by mutations in the CXCR4 gene-at not cost to them.

This funding is to help people in the Untied States who may have WHIM syndrome access no-cost genetic testing. People fill out an online symptom checker to see if they are eligible, and those eligible have a genetic test sent to them in the mail.

For more information, please see their flyer.

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