Fosmetpantotenate (RE-024), a phosphopantothenate replacement therapy for pantothenate kinase-associated neurodegeneration: Mechanism of action and efficacy in nonclinical models

PLoS One. 2018 Mar 9;13(3):e0192028. doi: 10.1371/journal.pone.0192028. eCollection 2018.

Abstract

In cells, phosphorylation of pantothenic acid to generate phosphopantothenic acid by the pantothenate kinase enzymes is the first step in coenzyme A synthesis. Pantothenate kinase 2, the isoform localized in neuronal cell mitochondria, is dysfunctional in patients with pantothenate kinase-associated neurodegeneration. Fosmetpantotenate is a phosphopantothenic acid prodrug in clinical development for treatment of pantothenate kinase-associated neurodegeneration, which aims to replenish phosphopantothenic acid in patients. Fosmetpantotenate restored coenzyme A in short-hairpin RNA pantothenate kinase 2 gene-silenced neuroblastoma cells and was permeable in a blood-brain barrier model. The rate of fosmetpantotenate metabolism in blood is species-dependent. Following up to 700 mg/kg orally, blood exposure to fosmetpantotenate was negligible in rat and mouse, but measurable in monkey. Consistent with the difference in whole blood half-life, fosmetpantotenate dosed orally was found in the brains of the monkey (striatal dialysate) but was absent in mice. Following administration of isotopically labeled-fosmetpantotenate to mice, ~40% of liver coenzyme A (after 500 mg/kg orally) and ~50% of brain coenzyme A (after 125 μg intrastriatally) originated from isotopically labeled-fosmetpantotenate. Additionally, 10-day dosing of isotopically labeled-fosmetpantotenate, 12.5 μg, intracerebroventricularly in mice led to ~30% of brain coenzyme A containing the stable isotopic labels. This work supports the hypothesis that fosmetpantotenate acts to replace reduced phosphopantothenic acid in pantothenate kinase 2-deficient tissues.

Publication types

  • Research Support, Non-U.S. Gov't

MeSH terms

  • Animals
  • Blood-Brain Barrier / drug effects
  • Blood-Brain Barrier / metabolism
  • Cell Line, Tumor
  • Coenzyme A / metabolism*
  • Disease Models, Animal*
  • Humans
  • Macaca fascicularis
  • Male
  • Mice, Inbred C57BL
  • Neurons / drug effects
  • Neurons / metabolism
  • Pantothenate Kinase-Associated Neurodegeneration / drug therapy*
  • Pantothenate Kinase-Associated Neurodegeneration / metabolism
  • Pantothenic Acid / analogs & derivatives*
  • Pantothenic Acid / pharmacokinetics
  • Pantothenic Acid / pharmacology
  • Pantothenic Acid / therapeutic use
  • Phosphotransferases (Alcohol Group Acceptor) / deficiency
  • Phosphotransferases (Alcohol Group Acceptor) / genetics
  • Phosphotransferases (Alcohol Group Acceptor) / metabolism
  • Prodrugs / pharmacokinetics
  • Prodrugs / pharmacology
  • Prodrugs / therapeutic use*
  • RNA Interference
  • Rats, Sprague-Dawley
  • Species Specificity

Substances

  • Prodrugs
  • Pantothenic Acid
  • phosphopantothenic acid
  • Phosphotransferases (Alcohol Group Acceptor)
  • pantothenate kinase
  • Coenzyme A
  • fosmetpantotenate

Grants and funding

Retrophin, Inc. funded the work reported in this manuscript. The funder had no role in study design, data collection and analysis, or preparation of the manuscript.