Neil Victor Harris

RP 73163: A bioavailable alkylsulphinyl-diphenylimidazole ACAT inhibitor☆

RP 73163 5 the major metabolite of the ACAT inhibitor RP 76076 3 retains ACAT activity. This alkylsulphinyl-4,5-diphenyl-1H-imidazole has higher systemic bioavailability than the parent thioether, with plasma levels of parent compound in certain species exceeding the IC50 required for inhibition of hepatic, intestinal, artery, adrenal and macrophage ACAT for up to twelve hours after oral dosing.

Identification and optimisation of a series of substituted 5-pyridin-2-yl-thiophene-2-hydroxamic acids as potent histone deacetylase (HDAC) inhibitors

Further investigation of a series of thienyl-based hydroxamic acids that included ADS100380 and ADS102550 led to the identification of the 5-pyridin-2-yl-thiophene-2-hydroxamic acid 3c, which possessed modest HDAC inhibitory activity. Substitution at the 5- and 6-positions of the pyridyl ring of compound 3c provided compounds 5a-g, 7a, b, 9, and 13a. Compound 5b demonstrated improved potency, in vitro DMPK profile, and rat oral bioavailability, compared to ADS102550. Functionalisation of the pendent phenyl group of compounds 5b, 5e and 13a provided analogues that possessed excellent enzyme inhibition and anti-proliferative activity.

Novel Heterocyclic Dpp-4 Inhibitors for the Treatment of Type 2 Diabetes.

Novel deazaxanthine-based DPP-4 inhibitors have been identified that are potent (IC(50) <10nM) and highly selective versus other dipeptidyl peptidases. Their synthesis and SAR are reported, along with initial efforts to improve the PK profile through decoration of the deazaxanthine core. Optimisation of compound 3a resulted in the identification of compound (S)-4i, which displayed an improved in vitro and ADME profile. Further enhancements to the PK profile were possible by changing from the deazahypoxanthine to the deazaxanthine template, culminating in compound 12g, which displayed good ex vivo DPP-4 inhibition and a superior PK profile in rat, suggestive of once daily dosing in man.

Hypolipidaemic properties of a potent and bioavailable alkylsulphinyl-diphenylimidazole ACAT inhibitor (RP 73163) in animals fed diets low in cholesterol

RP 73163 ((S)-2-[5-(3,5-dimethyl-l-pyrazolyl)pent-l-yl)-sulphinyl]-5, 6-diphenylimidazole) has been shown to be a potent and specific inhibitor of acyl-CoA:cholesterol acyltransferase (EC 2.3.1.26; ACAT) in vitro using the tissues of experimental animals as sources of the enzyme. The concentrations of RP 73163 required to produce 50% inhibition of ACAT activity (IC50 values) in microsomal preparations ranged from 86 nM for rat liver to 370 nM for rabbit intestine. In whole cell assays using human hepatic (HepG2), intestinal (Caco2), and monocytic (THP-1) cell lines, RP 73163 inhibited ACAT activity with IC50 values of 266, 158, and 314 nM, respectively. The addition of RP 73163 (0.03-1.0 microM) to the medium of cultured HepG2 cells produced a concentration-dependent decrease in apolipoprotein B (apoB) secretion. The compound has high systemic bioavailability. Using a bioassay, a concentration of active inhibitor equivalent to 29 microM of parent compound was present in plasma 1 hr after oral administration of RP 73163 (50 mg.kg-1). In rats that had been fed a basal diet ad libitum or starved for 18 hr prior to blood sampling, the administration of RP 73163 (50 mg.kg-1 b.i.d. for 7 days) reduced plasma triglyceride levels by 50% without affecting the concentration of cholesterol. This hypotriglyceridaemic effect was associated with reductions in plasma very-low-density-lipoprotein (VLDL) and low-density-lipoprotein (LDL) levels. RP 73163 decreased the rate of VLDL secretion by 24% in Triton WR-1339-treated rats that had been fasted overnight but did not affect the secretion rate in animals fed ad libitum, indicating that ACAT was only important in regulating VLDL secretion under certain nutritional conditions. RP 73163 reduced the accumulation of intraperitoneally administered [3H]leucine into the plasma VLDL-apoB pool in both fed and fasted states. The results suggest that, in fed animals at least, an increase in the clearance of VLDL from the bloodstream may contribute to the hypolipidaemic activity of the compound. In rabbits with casein-induced endogenous hypercholesterolaemia, RP 73163 specifically reduced the levels of cholesterol carried by LDL. In conclusion, the hypolipidaemic actions of RP 73163, a potent and systemically bioavailable ACAT inhibitor, are consistent with a reduction in the secretion of apoB containing lipoproteins by hepatic tissue and possibly with an increase in the clearance of these particles.

RP 70676: A potent systematically available inhibitor of acyl-CoA:cholesterol O-acyl transferase (ACAT)

Abstract RP 70676 (3d) is a potent inhibitor of ACAT. It is an effective hypocholesterolaemic agent in the cholesterol-fed rabbit, and reduces the accumulation of both cholesterol and cholesterol ester in rabbit aorta and thoracic artery. The compound is readily bioavailable in rabbits with significant levels of parent compound present in plasma up to 6 hours after an oral dose.

Selective endothelin A receptor ligands. 1. Discovery and structure-activity of 2,4-disubstituted benzoic acid derivatives

Summary This paper describes the discovery of a new non-peptide endothelin A (ETA) selective ligand, 2,4-dibenzyloxybenzoic acid 3, which inhibits the binding of [125I]ET-1 to ETA receptors with an IC50 of 9 μM (ET-1 = endothelin-1). Optimisation of 3 resulted in compound 52 which had an IC50 of 1 μM. One of the analogues of 3, compound 15, was examined in a functional assay and shown to antagonise ET-1-induced contraction of rat aorta. The identification of 3 was made through the application of ChemDBS-3D searching of our corporate database. The 3D query, using an aromatic ring to a carboxylic acid group separated by 10.2 ± 1.1 A, was derived from an examination of common pharmacophoric distances found in the low energy conformations of two known ETA antagonists, the cyclic pentapeptide BQ 123 1 and myriceron caffeoyl ester 2.

Antifolate and antibacterial activities of 6-substituted 2,4-diaminoquinazolines

A series of 5-substituted 2,4-diaminoquinazolines (3) has been synthesized and evaluated as inhibitors of the enzyme dihydrofolate reductase (DHFR) from both bacterial and mammalian sources. The best compounds (e.g. 53) show good activity against Escherichia coli DHFR, but there is no significant selectivity for the bacterial over the mammalian enzyme. The structure-activity relationships for enzyme inhibition appear to be complex and not amenable to simple analysis; a hypothesis to explain the observed qualitative structure-activity relationships is proposed. The inhibitory activities of the compounds against the growth of intact bacterial cells in vitro closely parallel those for the inhibition of the isolated bacterial enzymes, suggesting that their antifolate action is responsible for their antibacterial effects. Five of the compounds were tested for their ability to cure a systemic E. coli infection in the mouse, but they showed no therapeutic effects at their maximum tolerated doses.

From virtual to clinical: The discovery of PGN-1531, a novel antagonist of the prostanoid EP4 receptor.

In this Letter, we present the results of a hit-finding and lead optimization programme against the EP4 receptor (EP4R). In a short time period, we were able to discover five structurally diverse series of hit compounds using a combination of virtual screening methods. The most favoured hit, compound 6, was demonstrated to be a competitive antagonist of the EP4R. Compound 73 was identified following several rounds of optimization, which centred on improving both the primary EP4R affinity and selectivity against the related EP2R as well as the aqueous solubility. This work culminated in the preparation of PGN-1531, the sodium salt of 73, which showed a marked improvement in solubility (>10 mg/mL). PGN-1531 is a potent and selective antagonist at EP4Rs in vitro and in vivo, with the potential to alleviate the symptoms of migraine that result from cerebral vasodilatation.

Selective endothelin A receptor antagonists. 2. Discovery and structure-activity relationships of 5-ketopentanoic acid derivatives

Summary The second in this series of papers describes the further progress made in the discovery of a potent and selective endothelin ETA receptor antagonist for the potential treatment of diseases in which endothelin has been shown to have a pathophysiological role including hypertension, ischaemic diseases and atherosclerosis. We describe herein the synthesis and structure-activity relationships of a novel series of 5-ketopentanoic acid derivatives exemplified by the lead compound 1 (IC50 0.72 μM, rat aortic ETAR). Optimisation of the in vitro binding of 1 led to the identification of a more potent compound (37) which exhibited an IC50 300-fold selectivity for the ETA receptor over the ETB receptor. This compound demonstrated functional antagonism of endothelin-induced vasoconstriction in vitro.