crth2 receptor Compound was determined to be a potent
Compound was determined to be a potent inhibitor of human DGAT-1 and to effectively suppress DGAT-1-mediated triglyceride synthesis in the HT-29 intestinal cells (). While comparable in activity to both and , is significantly more potent than the dihydro-analog . Since and are predicted to have very similar conformations, the ∼25-fold reduction in DGAT-1 inhibitory activity is likely driven by the amino functionality of . As predicted from the initial conformational analysis, -stereoisomer has DGAT-1 inhibitory activity comparable to . SAR studies on have shown that neutral, isosteric replacements of the carboxylic crth2 receptor functionality can retain potent DGAT-1 inhibitory activity, suggesting they serve a hydrogen bond acceptor role in binding to the enzyme. However, incorporation of primary amide (), nitrile () or oxadiazole () functionalities in this series led to substantially reduced DGAT-1 inhibitory potencies relative to acid . This divergent SAR between the two series is likely the result of a subtle difference in trajectories of the phenylcyclohexyl sidechain relative to their respective bicyclic cores. There is literature precedence for the metabolic activation of the methylene carbons adjacent to the ring oxygen(s) of dioxanes and benzopyrans resulting in ring-opened electrophilic carbonyl species. Based on the potential for this metabolic pathway being operative with , a steric block approach was pursued in parallel to a metabolic pathway analysis of . From multiple options for such an approach, incorporation of a quaternary center at the side chain attachment juncture was selected for initial follow-up. Compound was found to be a relatively weak inhibitor of DGAT-1 in both microsomal enzyme preparations and the triglyceride synthesis whole cell assay. The high similarity between predicted conformations of and suggests that the methyl group is making an unfavorable interaction with the enzyme. Further extensions of this steric block approach were not pursued following the findings that is very stable in human liver microsomes () and there is no evidence for the formation of electrophilic species in this setting. The design goal of achieving improved passive permeability was realized in compound (7.7×10cm/s vs 1×10cm/s for ). As predicted, incorporation of the dioxinyl-based bicyclic core raised log nearly one order of magnitude relative to , driving the improved passive permeability. However, the overall polarity of log=0.74) is still in favorable property space as evidenced by the lack of turnover in human liver microsomes () and low clearance (2mL/min/kg) observed in rat. A clean profile (IC >10μM) against a broad panel of receptor, enzyme and channel targets is also consistent with the moderate lipophilicity of . This carboxylic acid has low QTc potential (8% inhibition of hERG channel at 30μM) and was negative in Ames/in vitro micronucleus genetic toxicology screens. In a four-day rat toleration study (5, 50 and 500mg/kg), produced no treatment related changes in clinical signs, hematology or histopathology.