Discovery of Novel 2‑((Pyridin-3-yloxy)methyl)piperazines as α7 Nicotinic Acetylcholine Receptor Modulators for the Treatment of Inflammatory Disorders

Herein we report the design, synthesis, and structure–activity relationships for a new class of α7 nicotinic acetylcholine receptor (nAChR) modulators based on the 2-((pyridin-3-yloxy)­methyl)­piperazine scaffold. The oxazolo­[4,5-<i>b</i>]­pyridine, (<b><i>R</i></b>)-<b>18</b>, and 4-methoxyphenylurea, (<b><i>R</i></b>)-<b>47</b>, were identified as potent and selective modulators of the α7 nAChR with favorable in vitro safety profiles and good oral bioavailability in mouse. Both compounds were shown to significantly inhibit cellular infiltration in a murine model of allergic lung inflammation. Despite the structural and in vivo functional similarities in the compounds, only (<b><i>R</i></b>)-<b>18</b> was shown to be an agonist. Compound (<b><i>R</i></b>)-<b>47</b> demonstrated silent agonist activity. These data support the hypothesis that the anti-inflammatory activity of the α7 nAChR is mediated by a signal transduction pathway that is independent of ion current

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

<div><p>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.</p></div

PPA and total PA in mouse and rat blood.

<p>Concentration-versus-time plots of PPA and PA after a single oral administration of fosmetpantotenate at 100, 300, or 700 mg/kg in CD1 mice (N = 4 per time point) or Sprague Dawley rats (N = 3 per time point).</p

Mean half—Life of fosmetpantotenate and diastereomers after incubation with blood from various species at 37°C for 60 min^a.

<p>Mean half—Life of fosmetpantotenate and diastereomers after incubation with blood from various species at 37°C for 60 min<a href="http://www.plosone.org/article/info:doi/10.1371/journal.pone.0192028#t002fn001" target="_blank">^a</a>.</p

Effects of 1 μM fosmetpantotenate TID for 5 consecutive days in shRNA PanK2 knockdown human neuroblastoma cells.

<p>(A) Intracellular CoA concentrations, n = 3. (B) Western blot densitometry values. β-actin was used for normalization. Two experiments in duplicate. Two sided t-test; *p ≤0.05, **p ≤0.01, ***p ≤0.001. Gel images can be found in <a href="http://www.plosone.org/article/info:doi/10.1371/journal.pone.0192028#pone.0192028.s002" target="_blank">S2 Fig</a>.</p

Apparent in vitro permeability of diastereomers of fosmetpantotenate, PA, and PPA in a blood—Brain barrier permeability model using co-cultured porcine brain endothelial cells and rat astrocytes^a.

<p>Apparent in vitro permeability of diastereomers of fosmetpantotenate, PA, and PPA in a blood—Brain barrier permeability model using co-cultured porcine brain endothelial cells and rat astrocytes<a href="http://www.plosone.org/article/info:doi/10.1371/journal.pone.0192028#t003fn001" target="_blank">^a</a>.</p

Fosmetpantotenate, PPA, and total PA in monkey blood and brain striatal dialysate.

<p>Single oral administration to cynomolgus monkeys (100 and 300 mg/kg).</p

Scheme depicting the different metabolic paths to CoA formation from either pantothenic acid or fosmetpantotenate.

<p>Scheme depicting the different metabolic paths to CoA formation from either pantothenic acid or fosmetpantotenate.</p

Fosmetpantotenate, PPA, and total PA in monkey blood.

<p>Concentrations of fosmetpantotenate, PPA, and PA after a single oral administration of fosmetpantotenate in cynomolgus monkeys at 300 mg/kg (N = 2).</p

Fosmetpantotenate, PPA, and total PA in mouse brain striatal dialysate.

<p>Single administration of fosmetpantotenate in C57Bl6 mice (700 mg/kg orally or 125 μg intrastriatally).</p