RESUMO
Beginning with the peptide sequence Cbz-Ile-Glu(OtBu)-Ala-Leu found in PSI (3), a series of vinyl sulfones (VS) were synthesized for evaluation as inhibitors of the chymotrypsin-like activity of the 20S proteasome. Variations at the key P3 position confirmed the importance of a long side chain capped with a hydrophobic group for optimal potency, consistent with a model of binding to the S3 subsite. The tert-butyl glutamic ester initially used at P3 gave plasma unstable, insoluble compounds and was replaced with the better isostere, N-beta-neopentyl asparagine. The inhibitors were shortened by replacing the N-terminal Cbz-isoleucine with a p-tosyl group without loss of potency. Small l-amino acids were used at P2, where d-substitution was not tolerated. The resulting optimized P4-P3-P2 sequence was grafted onto a novel proteasome inhibitor warhead, 2-keto-1,3,4-oxadiazoles (KOD), to produce reversible, subnanomolar proteasome inhibitors that were 1000-fold selective versus cathepsin B (CatB), cathepsin S (CatS), and trypsin-like as well as PGPH-like proteasome activity. A number of compounds in both the VS and the KOD series exhibited growth inhibitory effects against the human prostate cancer cell line PC3 at submicromolar concentrations.
Assuntos
Oligopeptídeos/síntese química , Oxidiazóis/síntese química , Complexo de Endopeptidases do Proteassoma/metabolismo , Inibidores de Proteassoma , Sulfonas/síntese química , Compostos de Vinila/síntese química , Animais , Antineoplásicos/síntese química , Antineoplásicos/química , Antineoplásicos/farmacologia , Bovinos , Proliferação de Células/efeitos dos fármacos , Estabilidade de Medicamentos , Humanos , Técnicas In Vitro , Modelos Moleculares , Oligopeptídeos/química , Oligopeptídeos/farmacologia , Oxidiazóis/química , Oxidiazóis/farmacologia , Complexo de Endopeptidases do Proteassoma/química , Subunidades Proteicas/antagonistas & inibidores , Subunidades Proteicas/química , Subunidades Proteicas/metabolismo , Solubilidade , Relação Estrutura-Atividade , Sulfonas/química , Sulfonas/farmacologia , Compostos de Vinila/química , Compostos de Vinila/farmacologiaRESUMO
We have prepared a series of achiral aminoacetonitriles, bearing tri-ring benzamide moieties and an aminocyclohexanecarboxylate residue at P2. This combination of binding elements resulted in sub-250 pM, reversible, selective, and orally bioavailable cathepsin K inhibitors. Lead compounds displayed single digit nanomolar inhibition in vitro (of rabbit osteoclast-mediated degradation of bovine bone). The best compound in this series, 39n (CRA-013783/L-006235), was orally bioavailable in rats, with a terminal half-life of over 3 h. 39n was dosed orally in ovariectomized rhesus monkeys once per day for 7 days. Collagen breakdown products were reduced by up to 76% dose-dependently. Plasma concentrations of 39n above the bone resorption IC50 after 24 h indicated a correlation between functional cellular and in vivo assays. Inhibition of collagen breakdown by cathepsin K inhibitors suggests this mechanism of action may be useful in osteoporosis and other indications involving bone resorption.