Plerixafor

Plerixafor (INN and USAN, trade name Mozobil) is an immunostimulant used to mobilize hematopoietic stem cells in cancer patients into the bloodstream. The stem cells are then extracted from the blood and transplanted back to the patient. The drug was developed by AnorMED, which was subsequently bought by Genzyme. Plerixafor (INN and USAN, trade name Mozobil) is an immunostimulant used to mobilize hematopoietic stem cells in cancer patients into the bloodstream. The stem cells are then extracted from the blood and transplanted back to the patient. The drug was developed by AnorMED, which was subsequently bought by Genzyme. Peripheral blood stem cell mobilization, which is important as a source of hematopoietic stem cells for transplantation, is generally performed using granulocyte colony-stimulating factor (G-CSF), but is ineffective in around 15 to 20% of patients. Combination of G-CSF with plerixafor increases the percentage of persons that respond to the therapy and produce enough stem cells for transplantation. The drug is approved for patients with lymphoma and multiple myeloma. Studies in pregnant animals have shown teratogenic effects. Plerixafor is therefore contraindicated in pregnant women except in critical cases. Fertile women are required to use contraception. It is not known whether the drug is secreted into the breast milk. Breast feeding should be discontinued during therapy. Nausea, diarrhea and local reactions were observed in over 10% of patients. Other problems with digestion and general symptoms like dizziness, headache, and muscular pain are also relatively common; they were found in more than 1% of patients. Allergies occur in less than 1% of cases. Most adverse effects in clinical trials were mild and transient. The European Medicines Agency has listed a number of safety concerns to be evaluated on a post-marketing basis, most notably the theoretical possibilities of spleen rupture and tumor cell mobilisation. The first concern has been raised because splenomegaly was observed in animal studies, and G-CSF can cause spleen rupture in rare cases. Mobilisation of tumor cells has occurred in patients with leukaemia treated with plerixafor. No interaction studies have been conducted. The fact that plerixafor does not interact with the cytochrome system indicates a low potential for interactions with other drugs. In the form of its zinc complex, plerixafor acts as an antagonist (or perhaps more accurately a partial agonist) of the alpha chemokine receptor CXCR4 and an allosteric agonist of CXCR7.The CXCR4 alpha-chemokine receptor and one of its ligands, SDF-1, are important in hematopoietic stem cell homing to the bone marrow and in hematopoietic stem cell quiescence. The in vivo effect of plerixafor with regard to ubiquitin, the alternative endogenous ligand of CXCR4, is unknown. Plerixafor has been found to be a strong inducer of mobilization of hematopoietic stem cells from the bone marrow to the bloodstream as peripheral blood stem cells. Additionally, plerixafor inhibits CD20 expression on B cells by interfering with CXCR4/SDF1 axis that regulates its expression. Following subcutaneous injection, plerixafor is absorbed quickly and peak concentrations are reached after 30 to 60 minutes. Up to 58% are bound to plasma proteins, the rest mostly resides in extravascular compartments. The drug is not metabolized in significant amounts; no interaction with the cytochrome P450 enzymes or P-glycoproteins has been found. Plasma half life is 3 to 5 hours. Plerixafor is excreted via the kidneys, with 70% of the drug being excreted within 24 hours. Plerixafor is a macrocyclic compound and a bicyclam derivative, the cyclam rings being linked at the amine nitrogen atoms by a 1,4-xylyl spacer. It is a strong base; all eight nitrogen atoms accept protons readily. The two macrocyclic rings form chelate complexes with bivalent metal ions, especially zinc, copper and nickel, as well as cobalt and rhodium. The biologically active form of plerixafor is its zinc complex.