ABSTRACT
Therapeutic interventions are being developed for Huntington's disease (HD), a hallmark of which is mutant huntingtin protein (mHTT) aggregates. Following the advancement to human testing of two [11C]-PET ligands for aggregated mHTT, attributes for further optimization were identified. We replaced the pyridazinone ring of CHDI-180 with a pyrimidine ring and minimized off-target binding using brain homogenate derived from Alzheimer's disease patients. The major in vivo metabolic pathway via aldehyde oxidase was blocked with a 2-methyl group on the pyrimidine ring. A strategically placed ring-nitrogen on the benzoxazole core ensured high free fraction in the brain without introducing efflux. Replacing a methoxy pendant with a fluoro-ethoxy group and introducing deuterium atoms suppressed oxidative defluorination and accumulation of [18F]-signal in bones. The resulting PET ligand, CHDI-650, shows a rapid brain uptake and washout profile in non-human primates and is now being advanced to human testing.
Subject(s)
Huntington Disease , Positron-Emission Tomography , Animals , Humans , Huntingtin Protein/genetics , Huntingtin Protein/metabolism , Ligands , Positron-Emission Tomography/methods , Huntington Disease/diagnostic imaging , Huntington Disease/drug therapy , Brain/diagnostic imaging , Brain/metabolismABSTRACT
This study describes a novel series of UDP-N-acetylglucosamine acyltransferase (LpxA) inhibitors that was identified through affinity-mediated selection from a DNA-encoded compound library. The original hit was a selective inhibitor of Pseudomonas aeruginosa LpxA with no activity against Escherichia coli LpxA. The biochemical potency of the series was optimized through an X-ray crystallography-supported medicinal chemistry program, resulting in compounds with nanomolar activity against P. aeruginosa LpxA (best half-maximal inhibitory concentration (IC50) <5 nM) and cellular activity against P. aeruginosa (best minimal inhibitory concentration (MIC) of 4 µg/mL). Lack of activity against E. coli was maintained (IC50 > 20 µM and MIC > 128 µg/mL). The mode of action of analogues was confirmed through genetic analyses. As expected, compounds were active against multidrug-resistant isolates. Further optimization of pharmacokinetics is needed before efficacy studies in mouse infection models can be attempted. To our knowledge, this is the first reported LpxA inhibitor series with selective activity against P. aeruginosa.
Subject(s)
Acyltransferases/antagonists & inhibitors , Anti-Bacterial Agents/pharmacology , Drug Discovery , Enzyme Inhibitors/pharmacology , Pseudomonas aeruginosa/drug effects , Anti-Bacterial Agents/chemistry , Crystallography, X-Ray , Drug Resistance, Bacterial/drug effects , Enzyme Inhibitors/chemistry , Escherichia coli/enzymology , Microbial Sensitivity Tests , Molecular Structure , Structure-Activity RelationshipABSTRACT
Analysis of crystals of the lithium complex of the tripodal ligand formed upon addition of adamantanone to a 1,5 diazapentadienyllithium complex reveals a long C-C bond which ruptures upon dissolution in non-co-ordinating solvents.