A Phase 2 interventional study of Mavorixafor in Acquired Primary Autoimmune and Idiopathic Chronic Neutropenia Disorders, Chronic Neutropenia and Autoimmune Neutropenia, sponsored by X4 Pharmaceuticals. Not yet recruiting. Open to participants aged 12 Years and older. Per ClinicalTrials.gov, last updated 2026-10-29.
Sponsored by X4 Pharmaceuticals · Phase 2, Interventional, and Treatment
The purpose of this study is to evaluate the safety and tolerability of G-CSF dosage reduction with mavorixafor in participants with autoimmune neutropenia (AIN) and chronic idiopathic neutropenia (CIN) disorders as assessed by the ability to safely reduce G-CSF dosage with mavorixafor treatment while maintaining clinically acceptable absolute neutrophil count (ANC) levels.
All participants will be receiving chronic G-CSF background therapy and will continue this pre-study background therapy, defined as the participant's current treatment regimen.
316 studies on the registry are indexed under Neutropenia; 42 are open to participants now.
This study's planned enrollment of 40 is below the median of 82 across 230 interventional studies indexed under Neutropenia.
Browse Neutropenia studies →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.
Key Inclusion Criteria:
Key Exclusion Criteria:
A diagnosis of any of the following:
Note: Other protocol-defined inclusion and exclusion criteria may apply.
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.
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.
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.
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.
Explained by clinicaltrials.gg, not part of the registry record. The study team decides who can take part.
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.
Explained by clinicaltrials.gg, not part of the registry record. The study team decides who can take part.
Participants will receive mavorixafor once daily orally for 52 weeks (starting from Week 4 through 56).
Drug: Mavorixafor
Mavorixafor will be administered per schedule specified in the arm description.
Also known as: X4P-001
Number of Participants With Treatment-emergent Adverse Events (TEAEs)
Time frame: Up to Week 56
Percent Change in Average Daily G-CSF Dosage
Time frame: Week 12 through Week 28 or 32
Percentage of Participants Achieving G-CSF Cessation
Time frame: Week 28 or 32
Percentage of Participants Achieving G-CSF Dosage Reduction ≥75%
Time frame: Week 28 or 32
Percentage of Participants Achieving G-CSF Dosage Reduction by ≥ 25%/≥ 50%
Time frame: Week 12 through Week 28 or 32
Time to G-CSF Cessation
Time frame: Week 4 through Week 28 or 32
Time to G-CSF Dosage Reduction of ≥25% or ≥50% or ≥75
Time frame: Week 4 through Week 28 or 32
Change From Week 12 in Average Daily G-CSF Dosage at Week 28 or 32
Time frame: Week 12, Week 28 or 32
Change From Week 12 in Average Daily G-CSF Frequency at Week 28 or 32
Time frame: Week 12, Week 28 or 32
Change From Week 4 in Bone Pain up to Week 56, Assessed Using Patient-Reported Outcomes Measurement Information System Short Form (PROMIS SF) Pain Intensity Scale Score (Participants Aged 12 to <18 Years)
Time frame: Week 4, up to Week 56
Change From Week 4 in Bone Pain up to Week 56, Assessed Using Functional Assessment of Chronic Illness Therapy (FACIT) Bone Pain Scale Score (Participants Aged ≥18 Years)
Time frame: Week 4, up to Week 56
Change From Week 4 in Fatigue up to Week 56, Assessed Using PROMIS SF Fatigue Scale Score (Participants Aged 12 to <18 Years)
Time frame: Week 4, up to Week 56
Change From Week 4 in Fatigue up to Week 56, Assessed Using FACIT-Fatigue Scale Score (Participants Aged ≥18 years)
Time frame: Week 4, up to Week 56
No study locations are listed for this record.
Plan to share: No
No publications or documents are linked to this record.
From the registry record's own update history. This site started tracking changes on Sep 25, 2026; for anything earlier, see the record history on ClinicalTrials.gov ↗
This study is not yet recruiting, as verified in Oct 2026. You cannot join it, but the record below documents what was studied.
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Studies of the drug tested here: Mavorixafor
X4 Pharmaceuticals