Mavorixafor

Mavorixafor (X4P-001, formerly AMD-070/AMD-11070) is a small-molecule, orally bioavailable, selective allosteric antagonist of the CXC chemokine receptor 4 (CXCR4) that blocks the interaction between CXCR4 and its cognate ligand CXCL12 (stromal-derived factor 1 alpha, SDF-1 alpha) with an IC50 of approximately 12.5 nanomolar. The compound was first synthesized at AnorMED Inc. in the early 2000s as part of a structure-activity campaign to identify orally active CXCR4 antagonists for HIV-1 entry inhibition, and it advanced through Phase 1 clinical studies in HIV-infected subjects before development for that indication was discontinued. X4 Pharmaceuticals subsequently acquired rights to the compound and repositioned it for the treatment of warts, hypogammaglobulinemia, infections, and myelokathexis (WHIM) syndrome, an ultrarare autosomal dominant primary immunodeficiency caused by heterozygous gain-of-function mutations in the CXCR4 gene that result in pathological retention of mature leukocytes within the bone marrow.

In an open-label Phase 2 dose-escalation study of eight WHIM syndrome patients, mavorixafor at 300 to 400 mg in the published literature produced dose-dependent increases in absolute neutrophil count and absolute lymphocyte count, reduced the annualized infection rate from 4.63 to 2.14 events per year, and achieved a 75 percent reduction in cutaneous warts over 5 to 18 months without adjunctive therapy. In the pivotal Phase 3 randomized, double-blind, placebo-controlled trial of 31 WHIM syndrome patients (14 mavorixafor, 17 placebo), mavorixafor 400 mg in the published literature produced a least-squares mean time above threshold absolute neutrophil count of 15.0 hours versus 2.8 hours on placebo (P less than 0.001), a 60 percent reduction in annualized infection rate (1.7 versus 4.2 events per year; P equals 0.007), and a 3.5-fold increase in time above threshold absolute lymphocyte count over 52 weeks. On April 29, 2024, the United States Food and Drug Administration approved mavorixafor (marketed as Xolremdi) for the treatment of WHIM syndrome in patients aged 12 years and older, making it the first drug approved for this indication and the first oral CXCR4 antagonist to receive regulatory approval.

Pharmacokinetics are characterized by nonlinear, greater-than-dose-proportional absorption with a median time to peak concentration of 2.8 hours; a pronounced food effect (55 to 66 percent reduction in exposure with meals, mandating fasting administration); high plasma protein binding exceeding 93 percent; a large volume of distribution of 768 liters; metabolism predominantly through CYP3A4 with a minor contribution from CYP2D6; a terminal elimination half-life of approximately 82 hours supporting once-daily dosing; and predominant fecal elimination of metabolites. Mavorixafor is a potent inhibitor of CYP2D6 in vivo, producing up to 9-fold increases in the exposure of CYP2D6 substrate drugs, which constitutes the principal drug interaction concern and a labeled contraindication with drugs highly dependent on CYP2D6 for clearance.

The compound is generally well tolerated. The most common adverse events at the reported research dose ranges include thrombocytopenia, pityriasis, rash, rhinitis, epistaxis, vomiting, and dizziness. Concentration-dependent QTc interval prolongation has been observed at supratherapeutic doses. Embryo-fetal toxicity is expected on the basis of the CXCR4/CXCL12 signaling role in embryonic development. Beyond WHIM syndrome, mavorixafor is under clinical investigation in Waldenstrom macroglobulinemia in combination with ibrutinib, and exploratory studies have evaluated its effects on the tumor microenvironment in melanoma and renal cell carcinoma. This monograph reviews the chemistry, synthesis, discovery, molecular pharmacology, comprehensive pharmacokinetics, preclinical and clinical evidence, sourcing, handling, drug interactions, adverse-event signal, and a comparative assessment of five CXCR4-targeting agents against mavorixafor across five competency standards.