XFOR: Update on Phase 2 CN Trial at ASH 2023
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Case Studies of First Three Patients from Phase 2 CN Trial Presented at ASH 2023
On December 9, 2023, X4 Pharmaceuticals, Inc. (NASDAQ:XFOR) announced that additional preliminary data from the company’s ongoing Phase 2 clinical trial of mavorixafor in patients with chronic neutropenia (CN) was presented at the 2023 American Society of Hematology (ASH) meeting. A copy of the poster can be accessed here. The data included case studies of the first three patients who completed the six-month trial. Each of the patients entered the study on granulocyte-colony stimulating factor (G-CSF) therapy.
Overall, the results showed that mavorixafor treatment continues to be well tolerated when used in combination with G-CSF. A total of four infections were reported during the first two months of the trial, however, no infections were reported during the following four months of the trial, even though two of the three patients had reductions in G-CSF therapy, which were allowed at the discretion of the treating physician. Highlights from each of the three patients are given below.
Patient 1: 24 y.o. female with chronic idiopathic neutropenia (CIN), G-CSF dosing 0.74 μg/kg/dose QOD when entering the study.
This patient had an absolute neutrophil count (ANC) at baseline that was below the lower limit of normal, however, follow treatment with mavorixafor the patient’s ANC rose to within the normal range and stayed there through Month 4. The treating physician tapered the patient’s G-CSF dose during Months 3 and 4 during which time her ANC level remained within the normal range, however by Months 5 and 6 it had returned to below the lower limit of normal.
Patient 2: 20 y.o. female with CIN, G-CSF dosing 0.38 μg/kg/dose QD when entering the study.
This patient had a baseline ANC in the normal range, which increased with the addition of mavorixafor. Her ANC was maintained at normal or near normal levels upon ≥50% reduction in G-CSF dosing, including discontinuation of G-CSF for two months. The patient's G-CSF dosing was brought back to 50% of baseline by the treating physician in Month 6 due to CN presentation.
Patient 3: 39 y.o. male with cyclic neutropenia (CyN), G-CSF dosing 0.53 μg/kg/dose QD when entering the study.
This patient had moderate neutropenia when entering the study and following mavorixafor treatment initiation a normal ANC was maintained from M2 through M6. This patient's G-CSF dose was maintained throughout the study period.
G-CSF reduction remains a high unmet need for CN patients, and the poster included feedback from CN patients as part of a survey conducted in partnership with the National Neutropenia Network. Feedback from that survey suggests that CN patients would be amenable to taking oral medication in addition to G-CSF if it reduced the dose or frequency of G-CSF, with a strong preference for a reduction in frequency. This is encouraging as the early data shows mavorixafor treatment may lead to a reduction in G-CSF dosing for some CN patients.
Conclusion
While difficult to conclude only three patients, it is encouraging that mavorixafor was well-tolerated when used in combination with G-CSF and that there were no serious adverse events reported and no adverse events led to mavorixafor dose reduction, interruption, or cessation. We believe these data support the company’s planned Phase 3 trial of mavorixafor in CN and the potential for G-CSF adjustments in this patient population. Looking ahead, we continue to anticipate the full topline data from this study to be reported in the first half of 2024. With no changes to our model, our valuation remains at $4.50.
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