X4 reports data from Phase 2 clinical trial evaluating mavorixafor

X4 Pharmaceuticals (XFOR) announced positive new clinical data from its now completed Phase 2 clinical trial evaluating mavorixafor, an oral CXCR4 antagonist, in the treatment of people with chronic neutropenia, or CN. An analysis of final data from the six-month study showed that once-daily oral mavorixafor durably and meaningfully increased participants’ mean absolute neutrophil counts, or ANC. In addition, when tested in combination with injectable granulocyte colony-stimulating factor, or G-CSF, mavorixafor treatment enabled clinicians to substantially reduce G-CSF dosing while maintaining normal mean ANC levels. The Phase 2 study of mavorixafor was a six-month, open-label clinical trial that enrolled a total of 23 participants diagnosed with idiopathic, congenital, or cyclic chronic neutropenia. The analysis presented today includes results from the two study treatment groups: mavorixafor monotherapy and mavorixafor in combination with G-CSF. Consistent with previously presented analyses, results from participants receiving mavorixafor monotherapy showed that mavorixafor durably increased mean ANC from baseline, with mean ANC reaching normal levels at Month 3 and Month 6. Further analysis showed that those with severe CN achieved greater than two-fold increases in mean ANC levels out to six months, reaching levels typically targeted by physicians for patients with severe CN. Mavorixafor in combination with injectable G-CSF: New results presented demonstrated that physicians chose to reduce G-CSF dosing in nine of 12 eligible participants. Of those nine, eight had G-CSF reduced at the earliest timepoint permitted and three were taken completely off of G-CSF prior to their Month 6 visit. Mean reductions in G-CSF were 52% at Month 3 and 70% at Month 6, while mean ANC levels remained in the normal range. The three participants receiving mavorixafor who remained on stable doses of G-CSF maintained mean ANC levels in the normal range at all timepoints. X4 also announced new findings from a sub-study comparing the mean percentage of functional neutrophils in samples from healthy donors to participants from the Phase 2 CN study using two common study methods. These results demonstrated that the mean percentage of functional circulating neutrophils in CN participants in this sub-study was comparable to that of healthy donors after six months of mavorixafor dosing. The subset of participants with congenital neutropenia also had mean percentage of functional neutrophils comparable to those of healthy donors.