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RecruitingNCT06056297Updated Aug 6, 2026

A Study of Mavorixafor in Participants With Congenital and Acquired Primary Autoimmune and Idiopathic Chronic Neutropenic Disorders Who Are Experiencing Recurrent and/or Serious Infections

A Phase 3 interventional study of Mavorixafor and Placebo in Neutropenia, sponsored by X4 Pharmaceuticals. Recruiting at 114 sites in 25 countries. Open to participants aged 12 Years and older. Per ClinicalTrials.gov, last updated 2026-08-06.

Sponsored by X4 Pharmaceuticals · Phase 3, Interventional, and Treatment

From the registry’s dates

  • Started Jun 2024; still recruiting 2 years 5 months later.
Phase
Phase 3
Study type
Interventional
Enrollment
176
Allocation
Randomized
Ages
12 Years and older
Sex
All
01

Study summary

The purpose of this study is to demonstrate the efficacy and evaluate the safety and tolerability of mavorixafor in participants with congenital or acquired primary autoimmune and idiopathic chronic neutropenic disorders who are experiencing recurrent and/or serious infections as assessed by demonstrating its clinical benefit and increasing levels of circulating neutrophils.

Read the detailed description

All participants will continue their pre-study background therapy, defined as the participant's current treatment regimen. Options include, but are not limited to, granulocyte-colony stimulating factor (G-CSF), immunoglobulin replacement therapy, prophylactic antibiotics, or "watchful waiting".

02

Conditions studied

  • Neutropenia

Keywords

  • Mavorixafor
  • Chronic neutropenia
  • Chronic idiopathic neutropenia
  • Severe Congenital Neutropenia (SCN)
  • C-X-C chemokine receptor 4 (CXCR4)
  • Congenital and acquired neutropenia
  • Autoimmune disease
  • Cohen syndrome
  • Barth syndrome
  • ELANE
  • G6PC3
  • GSD1b
  • Kostmann disease
  • Shwachman-Diamond syndrome
  • Autoimmune neutropenia (AIN)
03

In context

Neutropenia

316 studies on the registry are indexed under Neutropenia; 42 are open to participants now.

This study's planned enrollment of 176 is above the median of 82 across 230 interventional studies indexed under Neutropenia.

Browse Neutropenia studies →

Lead sponsor

X4 Pharmaceuticals is the lead sponsor of 13 studies on the registry; 2 are open to participants now.

Of its 10 completed or terminated interventional studies of FDA-regulated products, 3 (30%) have results posted.

Counted across the registry records on this site, refreshed daily.

04

Who can participate

Ages eligible
12 Years and older
Sexes eligible
All
Accepts healthy volunteers
No

Eligibility criteria

Key Inclusion Criteria:

  • Diagnosis of congenital or acquired primary and idiopathic chronic neutropenic disorder ≥6 months prior to the screening visit that is not attributable to medications, active or recent infections or .

  • Congenital Neutropenia, including but not limited to these classifications:

    1. Isolated with a permanent (non-cyclic) presentation, for example, elastase, neutrophil expressed (ELANE), colony stimulating factor 3 receptor (CSF3R), C-X-C chemokine receptor 2 (CXCR2), Wiskott-Aldrich syndrome (WAS)
    2. Associated with extra-hematologic manifestations, for example, Barth syndrome, Cohen syndrome, glucose-6-phosphatase catalytic subunit 3 (G6PC3), Kostmann disease
    3. Associated with metabolic disorders, for example, glycogen storage disease 1b (GSD1b)
    4. Shwachman-Diamond syndrome

  • Acquired Primary Neutropenia

    1. Chronic idiopathic neutropenia
    2. Primary autoimmune neutropenia. Other chronic neutropenia (CN) disorders that may be eligible for enrollment can be clarified and approved upon discussion with study Medical Monitor.
  • Have an ANC \<1000 cells/µL during screening (single ANC value from hematology) and confirmed trough mean (mean value of multiple ANC measurements over 6 hours) at baseline visit, with no clinical evidence of systemic infection.
  • Prior history of recurrent and/or serious infections during the 12 months preceding the screening visit (that is, suffering sequelae of chronic neutropenia), as defined by having at least 2 infections in the last 12 months that meet the following criteria:
  • Infection requiring the use of antibiotics (intravenous [IV]/oral); OR
  • Infection requiring a visit to healthcare facility (including but not limited to emergency room visit, urgent care facility, primary care physician's office, or in-patient hospitalization);

AND for all potential participants:

  • Infections considered by the Investigator to be likely related to the potential participant's CN disorder.
  • Participants who are on G-CSF or other active background therapy must have been receiving these therapies during the previous 12 months while continuing to suffer from infections, be on a stable dose and dosing schedule for ≥4 weeks prior to screening visit and remain on this dose and dosing schedule throughout the study (unless ANC >10,000 cells/µL for ≥4 weeks).
  • Participants must be willing to keep their G-CSF or other background therapy doses/regimens stable (other than for safety reasons) for the duration of the study.

Key Exclusion Criteria:

  • A diagnosis of secondary neutropenia including those due to:

    1. Hypersplenism
    2. Infection
    3. Malignancy
    4. Autoimmune disease, for example, systemic lupus erythematosus, rheumatoid arthritis, inflammatory bowel disease, , thyroid disease
    5. Nutritional deficiency, for example, vitamin B12, folic acid, copper, caloric malnutrition
    6. Drug-induced cause, for example, chemotherapy, clozapine, antiretrovirals, antibiotics, monoclonal antibodies.

  • A diagnosis of any of the following:

    1. Aplastic anemia
    2. Warts, hypogammaglobulinemia, infections, and myelokathexis (WHIM) syndrome

    3. Certain CNs, including but not limited to these classifications are excluded:

      1. Isolated with a cyclic presentation, for example, elastase, neutrophil expressed (ELANE)
      2. Associated with immune dysregulation, for example, common variable immunodeficiency (CVID), autoimmune lymphoproliferative syndrome (ALPS), familial hemophagocytic lymphohistiocytosis, Chédiak-Higashi syndrome, GATA-binding protein 2 (GATA2) deficiency syndrome
      3. Associated with bone marrow failure, for example, Fanconi anemia, Diamond-Blackfan anemia
    4. Neutropenia associated with a Duffy-null phenotype (formerly known as benign ethnic neutropenia). However, a participant with an autosomal dominant pathogenic variant in a gene associated with CN on a Duffy-null background may be eligible for inclusion
  • A medical or personal condition that may potentially compromise the safety of the participant, may preclude the participant's successful completion of the clinical study, or could, in the opinion of the Investigator or the Medical Monitor, interfere with the objectives of the study.
  • Received more than 1 dose of mavorixafor in the past.
  • Received C-X-C chemokine receptor 4 (CXCR4) antagonist (other than mavorixafor) in the past 6 months.
  • Participants taking pegylated-G-CSF unless they have a diagnosis of congenital neutropenia confirmed at screening.
  • Participant is currently taking or has taken other drug \<30 days prior to the screening visit or 5 half-lives, whichever is longer.

Note: Other protocol-defined inclusion and exclusion criteria may apply.

Terms in these criteria, in plain language(5)

Underlined terms in the criteria open these too. Explained by clinicaltrials.gg, not part of the registry record. The study team decides who can take part.

Autoimmune disease

A condition in which the immune system attacks the body’s own tissues, such as rheumatoid arthritis, lupus, psoriasis, type 1 diabetes or inflammatory bowel disease.

Immunotherapy studies often leave out active autoimmune disease, and some name exceptions, such as thyroid disease on replacement hormone. Check the exceptions this study lists.

Cancer (malignancy)

Malignancy means cancer. Criteria about another or earlier malignancy ask whether you have had a different cancer, usually within a set number of years.

Some are commonly allowed, such as treated skin cancers other than melanoma and early cancers removed completely — check the exceptions this study lists.

Absolute neutrophil count (ANC)

The number of neutrophils, white blood cells that help fight infection, in a given amount of blood. Too few raises the risk of infection.

It is a count, not a percentage of the white cells. Limits are written in units that mean the same: ≥ 1.5 × 10⁹/L is ≥ 1,500 per mm³ (µL). Each lab has its own reference range.

GVHD (graft-versus-host disease)

After a transplant from a donor, the donor’s immune cells attack the recipient’s body, often the skin, gut or liver.

Investigational drug or device

A drug or device being studied in a clinical trial.

It may be new, or already approved and being studied for another use, dose or form. Criteria often leave out people who took part in another study of one within a recent period, commonly 30 days or five half-lives.

05

Study design

Phase
Phase 3
Primary purpose
Treatment
Allocation
Randomized
Intervention model
Parallel assignment
Masking
Quadruple (Participant, Care provider, Investigator, Outcomes assessor)
Enrollment
176 participants (estimated)

Study arms

  • Experimental
    Mavorixafor

    Participants will receive mavorixafor orally once daily starting from Day 1 through Week 52.

    Drug: Mavorixafor

  • Placebo comparator
    Placebo

    Participants will receive placebo to match mavorixafor orally once daily starting from Day 1 through Week 52.

    Drug: Placebo

Interventions

  • DrugMavorixafor

    Mavorixafor will be administered per schedule specified in the arm description.

    Also known as: X4P-001

  • DrugPlacebo

    Placebo will be administered per schedule specified in the arm description.

06

What researchers measure

Primary outcomes

  1. Co-primary Endpoint: Annualized Infection Rate Based on Infections Adjudicated by Blinded Infection Adjudication Committee (BIAC) During the Treatment Period

    Time frame: Up to 52 Weeks

  2. Co-primary Endpoint: Number of Participants Meeting the Definition of a Positive Absolute Neutrophil Count (ANC) Response

    Positive ANC response: Increase of ANC \>500 cells/microliter (µL) from baseline.

    Time frame: Up to 52 weeks

Secondary outcomes

  1. Infection Severity Based on Common Terminology Criteria for Adverse Events (CTCAE) Adjudicated by a BIAC During the Treatment Period

    Time frame: Up to 52 Weeks

  2. Infection Duration Based on Duration of Infections Adjudicated by a BIAC During the Treatment Period in Those Participants who Developed Infections

    Time frame: Up to 52 Weeks

  3. Antibiotic Use Due to Infection, Characterized by the Frequency of Antibiotic Use During the Treatment Period

    Time frame: Up to 52 Weeks

  4. Oral Ulcers, as Assessed by Presence or Absence of Ulcers During the Treatment Period

    Time frame: Up to 52 Weeks

  5. Change From Baseline in Patient Reported Outcomes Measurement Information System Short Form (PROMIS SF) Fatigue Questionnaire Total Score

    Time frame: Baseline, Week 52

07

Study locations

107 of 114 sites recruiting

Showing the first 100 of 114 sites across 25 countries. Choose a country and city above to see the rest.

08

References and documents

Individual participant data

Plan to share: No

No publications or documents are linked to this record.

09

Updates

Tracking since Sep 25, 2026
No changes since tracking began. The registry record was last updated on Aug 6, 2026, before this site started recording changes on Sep 25, 2026. Its history is on ClinicalTrials.gov ↗
10

Registry details

Key details

Study ID
NCT06056297
Lead sponsor
X4 Pharmaceuticals
Responsible party
Sponsor
First posted
Sep 28, 2023
Start date
Jun 6, 2024
Primary completion
Sep 2027 (estimated)
Completion
Nov 2027 (estimated)
Last update
Aug 6, 2026

Study contacts

Patient Affairs and Advocacy
Contact
clinicaltrialinfo@x4pharma.com
857-529-5779
Vice President Global Head of Clinical Development and Safety
study director · X4 Pharmaceuticals

Oversight

Data monitoring committee
Yes
FDA-regulated drug
Yes
FDA-regulated device
No
View the source record on ClinicalTrials.gov ↗

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