Sipoglitazar

Sipoglitazar is a peroxisome proliferator–activated receptor α, δ, and γ agonist. During phase I, a wide distribution of clearance between individuals was observed. Hypothesized to result from a polymorphism in the uridine 5′‐diphospate‐glucuronosyltransferase (UGT)2B15 enzyme, pharmacogenetic samples were collected from each individual for genotyping UGT2B15 in a subsequent phase I trial in healthy subjects (n = 524) and in 2 phase II trials in type 2 diabetes subjects (n = 627), total genotype frequency was as follows: *1/*1 (22%), *1/*2 (51%), and *2/*2 (27%). The impact of genotype on exposure was assessed using a pharmacokinetic modeling approach; the influence of genotype on efficacy was evaluated using 12‐week HbA1c change from baseline. Model analysis demonstrated UGT2B15 genotype accounted significantly for the variability in sipoglitazar clearance; however, a small fraction of subjects had a clearance that could not be explained entirely by genotype. HbA1c drop increased with daily drug dose. When stratified by both dose and genotype, HbA1c drop was larger in the UGT2B15*2/*2 compared with UGT2B15*1/*1 and UGT2B15*1/*2 genotypes (P < .05). In summary, UGT2B15 genotype is a strong predictor for sipoglitazar clearance; a greater clinical response observed in the UGT2B15*2/*2 genotype appears to confirm this. However, overlap in individual rates of clearance across genotypes remains after accounting for genotype.

Sipoglitazar was a novel, azolealkanoic acid derivative that possesses selective activity for the peroxisome proliferator-activated receptors (PPAR) PPARγ, PPARα, and PPARδ. The compound undergoes phase II biotransformation by conjugation catalyzed by UDP-glucuronosyltransferase (UGT). The aim of this analysis was to explore the influence of genetic polymorphism in UGT on the pharmacokinetics of sipoglitazar.

Three preliminary phase I clinical pharmacology studies were conducted in tandem in healthy human subjects. Genotyping was undertaken in a total of 82 subjects in the phase I program for the purpose of genotyping UGT polymorphisms. Plasma samples were collected for up to 48 h post-dose to characterize the pharmacokinetic profile following a single oral dose of the drug.

Plasma concentrations of sipoglitazar and the distribution of dose-normalized individual values for area under the plasma concentration-time curve from time 0 to infinity (AUC(0-∞)) before any stratification were considerably skewed with a multi-modal distribution. The proportion of variability in AUC(0-∞) explained by UGT2B15 was 66.7 % (P < 0.0001); the addition of other genetic or demographic factors was not statistically significant. Subjects homozygous for the UGT2B15 D85Y variant (UGT2B15*2/*2) were exposed to greater plasma concentrations of sipoglitazar than subjects homozygous for the wild-type allele UGT2B15*1/*1 (3.26-fold higher) or heterozygous allele UGT2B15*1/*2 (2.16-fold higher).

These results indicate that sipoglitazar clearance is substantially modified by UGT2B15 enzyme variants, with higher exposure observed in the UGT2B15*2/*2 genotype group.