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

A Phase 1b/2, Open-Label, Multicenter Study of Mavorixafor in Patients With Congenital Neutropenia and Chronic Neutropenia Disorders

This is a 2-part study of mavorixafor in participants diagnosed with chronic neutropenia. The main goal of Part 1 (Phase 1b) is to help researchers learn more about how the investigational medicine, mavorixafor, impacts people living with chronic neutropenia (including congenital, idiopathic, and cyclic). In Part 2 (Phase 2), the safety and tolerability of chronic dosing of mavorixafor will be evaluated in a larger participant population and the impact of 6-month chronic dosing of mavorixafor on participant neutropenia.

Study Overview

• Status: Completed
• Conditions: Neutropenia
• Intervention / Treatment: Drug: Mavorixafor

Detailed Description

Part 1: Participants will receive one oral dose of mavorixafor and be monitored for 8 hours to see if neutrophil cell counts increase. Participants screened after implementation of Protocol Version 8.0, do not need to enter Part 1 and can start with the Part 2 Screening visit (Day -28 to Day -1).

Part 2: For participants enrolled in the study before implementation of Protocol Version 8.0, Part 2 will include those who completed Part 1 and exhibited a response to treatment. Eligible participants from Part 1 enrolled in the study before implementation of Protocol Version 8.0, can directly roll-over to the Baseline (Day -3 to Day -1) visit in Part 2. Participants will receive once daily oral dosing of mavorixafor for 6 months and be monitored throughout to see if neutrophil cell counts increase.

Study visits can be conducted at-home or at one of many study clinic locations, depending on the participant's preference.

• Study Type: Interventional
• Enrollment (Actual): 32
• Phase: Phase 2; Phase 1

Contacts and Locations

Study Locations

• United States
  • Florida
    • Saint Petersburg, Florida, United States, 33701
      • USF Health Department of Pediatrics
  • Iowa
    • Iowa City, Iowa, United States, 52242
      • University of Iowa Hospital and Clinics
  • Michigan
    • Ann Arbor, Michigan, United States, 48109
      • University of Michigan
  • Missouri
    • Saint Louis, Missouri, United States, 63110
      • Washington University School of Medicine
  • Pennsylvania
    • Philadelphia, Pennsylvania, United States, 19104
      • Children's Hospital of Philadelphia
  • Texas
    • Dallas, Texas, United States, 75235
      • University of Texas, Southwestern
  • Washington
    • Seattle, Washington, United States, 98195
      • University of Washington

Participation Criteria

Eligibility Criteria

• Ages Eligible for Study: 8 years and older (Child, Adult, Older Adult)
• Accepts Healthy Volunteers: No

Description

Key Inclusion Criteria:

For all participants (Parts 1 and 2):

• Sign the informed consent form (ICF) and be willing and able to comply with the protocol.
• Weigh ≥15 kg
• Agree to use a highly effective form of contraception if sexually active.

• Participants may be eligible for the study whether they are on or off granulocyte-colony stimulating factor (G-CSF) treatment.

  • Note: Participants who are on G-CSF must be on a stable dose for ≥14 days prior to the Baseline visit and should not have an ANC ≥10,000 cells/μL.
  • Note: Participants who are not on G-CSF must be off for ≥14 days prior to the Baseline visit and have an ANC ≤1000 cells/µL at the Screening visit.
  • Note: Participants with Shwachman-Diamond syndrome, Cohensyndrome, and warts, hypogammaglobulinemia, infections and myelokathexis syndrome are eligible. Other types of chronic neutropenic disorders may also be eligible for enrollment upon discussion and approval with Sponsor and Study Medical Monitor.
• Have been diagnosed with chronic neutropenia for ≥6 months prior to the Screening visit that is not attributable to medications, active or recent (≤3 months) infections, or malignant cause.

Part 2 only:

• Participants enrolled in the study before implementation of Protocol Version 8.0 must have completed Part 1 and exhibited a positive response to treatment.
• Participant has a history of symptomatic chronic neutropenia confirmed by the Investigator.

Key Exclusion Criteria (Parts 1 and 2):

• Known systemic hypersensitivity to the mavorixafor drug substance or its inactive ingredients.
• Is pregnant, breastfeeding, or plans to become pregnant over the next 8 months.
• Known history of a positive serology or viral load for human immunodeficiency virus (HIV) or a known history of acquired immune deficiency syndrome.
• Known active SARS-CoV-2 virus (COVID-19) infection or a positive test within the local accepted clinical and governmental guidelines for a communicable window.

• At the Screening Visit, has laboratory test results meeting one or more of the following criteria:

  • Positive hepatitis C virus (HCV) antibodies with confirmation by HCV-ribonucleic acid polymerase chain reaction reflex testing.
  • Positive hepatitis B surface antigen (hBsAg) or hepatitis B core antibody (hBcAb).
  • Note: If a participant tests negative for hBsAg but positive for hBcAb, the participant would be considered eligible if the participant tests positive for antibody to hBsAg reflex testing.

• At the Screening visit, has laboratory test results meeting one or more of the following criteria:

  • Hemoglobin <9.0 grams/deciliter (g/dL)
  • Platelets <30,000/μL
  • Estimated glomerular filtration rate (eGFR) ≤60 mL/minute/1.73 meter (m)^2, as estimated by the Chronic Kidney Disease Epidemiology Collaboration (CKD-EPI) equation
  • Serum aspartate transaminase >2.5 x upper limit of normal (ULN)
  • Serum alanine transaminase >2.5 x ULN
  • Total bilirubin >1.5 x ULN (unless due to Gilbert's syndrome, in which case total bilirubin greater than or equal to (≥) 3.0 x ULN and direct bilirubin >1.5 x ULN)

• ≤14 days before Day 1, received any of the following treatments:

  • Systemic glucocorticoids (>5 mg prednisone equivalent per day).
  • Medication prohibited based on cytochrome P450 (CYP)2D6 potential for interaction.
• Is taking a medication which is a strong inhibitor of CYP3A4, unless the Investigator and Medical Monitor conclude that the medication must be used during the study and is permissible with modification of mavorixafor dose.
• Has an infection requiring use of systemic antibiotics ≤4 weeks before the Baseline visit.
• Has a medical or personal condition that may potentially compromise the safety or compliance of the participant, or may preclude the participant's successful completion of the clinical study or that in the opinion of the Investigator or the Sponsor could interfere with the objectives of the study.
• Has had major surgery ≤4 weeks before the Baseline visit.
• Inability to ingest mavorixafor capsules.
• Has an active malignancy or history of (≤5 years prior to enrollment) in the study of solid, metastatic, or hematologic malignancy. Exception: basal cell carcinoma in situ of the skin that has been adequately treated.
• Diagnosed or has suspected congenital long QT syndrome. Any history of clinically significant ventricular arrhythmias (such as ventricular tachycardia, ventricular fibrillation, or torsades de pointes); any history of arrhythmia will be discussed with the sponsor's medical monitor before participant's entry into the study.
• Prolonged corrected QT interval using Fridericia's formula at the Screening visit electrocardiogram (ECG) (>450 milliseconds [ms])

Study Plan

How is the study designed?

Design Details

• Primary Purpose: Treatment
• Allocation: N/A
• Interventional Model: Single Group Assignment
• Masking: None (Open Label)

Number of Arms

1

Arms and Interventions

Participant Group / Arm

Intervention / Treatment

Experimental: Mavorixafor; Part 1: Adult participants and adolescent participants who weigh more than 50 kilograms (kg) will receive mavorixafor 400 milligrams (mg) (4 capsules of 100 mg each), orally once on Day 1. Adolescents weighing less than or equal to 50 kg will receive mavorixafor 200 mg (2 capsules of 100 mg each), orally once on Day 1. Part 2: Eligible participants from Part 1 will receive once daily dosing of mavorixafor for 6 months.

Drug: Mavorixafor; Mavorixafor capsules will be administered per dose and schedule specified in the arm.; Other Names: X4P-001

What is the study measuring?

Primary Outcome Measures

Outcome Measure	Time Frame
Number of Participants With Treatment-Emergent Adverse Events (TEAEs) After a Single Dose of Mavorixafor	Baseline through Day 1 and 7 days follow-up
Number of Participants With Treatment-Emergent Adverse Events (TEAEs) After Multiple Doses of Mavorixafor	Baseline through Month 6 and 30 days follow-up
Change From Baseline in Absolute Neutrophil Count (ANC) to 8 hours Post-dose On Day 1	Baseline, 8 hours Post-dose On Day 1
Change From Baseline in ANC to Month 6	Baseline, Month 6

Secondary Outcome Measures

Outcome Measure	Time Frame
Serum Concentration of Mavorixafor in Relation to ANC and Area Under the Curve (AUC) for ANC (AUCANC)	0 (pre-dose), 60 minutes and 2, 3, 4, 6, and 8 hours post-dose on Day 1
Serum Concentrations of Mavorixafor	0 (pre-dose) up to Month 6
Change from Baseline in Absolute Lymphocyte Count (ALC)	Baseline, Month 6
Change from Baseline in Total White Blood Cells (WBC)	Baseline, Month 6
Change from Baseline in Absolute Monocyte (AMC)	Baseline, Month 6
AUC of ANC (AUCANC)	Baseline up to Month 6
AUC of ALC (AUCALC)	Baseline up to Month 6
AUC of AMC (AUCAMC)	Baseline up to Month 6
AUC of WBC (AUCWBC)	Baseline up to Month 6

Collaborators and Investigators

• Sponsor: X4 Pharmaceuticals

Study record dates

Study Major Dates

• Study Start (Actual): October 16, 2021
• Primary Completion (Actual): August 27, 2024
• Study Completion (Actual): August 27, 2024

Study Registration Dates

• First Submitted: November 4, 2019
• First Submitted That Met QC Criteria: November 4, 2019
• First Posted (Actual): November 6, 2019

Study Record Updates

• Last Update Posted (Actual): August 6, 2025
• Last Update Submitted That Met QC Criteria: August 1, 2025
• Last Verified: August 1, 2025

More Information

Terms related to this study

• Keywords: CIN; CXCR4; Chronic congenital neutropenia; Chronic idiopathic neutropenia; SCN; Mavorixafor; Neutropenia glycogen storage disease type 1b; GSD1b; G6PC3; SLC37A4; GATA2
• Additional Relevant MeSH Terms: Cytopenia; Leukocyte Disorders; Hematologic Diseases; Leukopenia; Agranulocytosis; Neutropenia
• Other Study ID Numbers: X4P-001-104

Drug and device information, study documents

• Studies a U.S. FDA-regulated drug product: Yes
• Studies a U.S. FDA-regulated device product: No