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The protein farnesyltransferase inhibitor Tipifarnib as a new lead for the development of drugs against Chagas disease.

ABSTRACT: Tipifarnib (R115777), an inhibitor of human protein farnesyltransferase (PFT), is shown to be a highly potent inhibitor of Trypanosoma cruzi growth (ED(50) = 4 nM). Surprisingly, this is due to the inhibition of cytochrome P450 sterol 14-demethylase (CYP51, EC 1.14.13.70). Homology models of the T. cruzi CYP51 were used for the prediction of the binding modes of the substrate lanosterol and of Tipifarnib, providing a basis for the design of derivatives with selectivity for TcCYP51 over human PFT.

SUBMITTER: Hucke O

PROVIDER: S-EPMC3265986 | biostudies-literature | 2005 Aug

REPOSITORIES: biostudies-literature

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The protein farnesyltransferase inhibitor Tipifarnib as a new lead for the development of drugs against Chagas disease.

Hucke Oliver O Gelb Michael H MH Verlinde Christophe L M J CL Buckner Frederick S FS

Journal of medicinal chemistry 20050801 17

Tipifarnib (R115777), an inhibitor of human protein farnesyltransferase (PFT), is shown to be a highly potent inhibitor of Trypanosoma cruzi growth (ED(50) = 4 nM). Surprisingly, this is due to the inhibition of cytochrome P450 sterol 14-demethylase (CYP51, EC 1.14.13.70). Homology models of the T. cruzi CYP51 were used for the prediction of the binding modes of the substrate lanosterol and of Tipifarnib, providing a basis for the design of derivatives with selectivity for TcCYP51 over human PFT ...[more]

PMID: 16107140

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Project description:We tested the antituberculosis drug SQ109, which is currently in advanced clinical trials for the treatment of drug-susceptible and drug-resistant tuberculosis, for its in vitro activity against the trypanosomatid parasite Trypanosoma cruzi, the causative agent of Chagas disease. SQ109 was found to be a potent inhibitor of the trypomastigote form of the parasite, with a 50% inhibitory concentration (IC50) for cell killing of 50 ± 8 nM, but it had little effect (50% effective concentration [EC50], ?80 ?M) in a red blood cell hemolysis assay. It also inhibited extracellular epimastigotes (IC50, 4.6 ± 1 ?M) and the clinically relevant intracellular amastigotes (IC50, ?0.5 to 1 ?M), with a selectivity index of ?10 to 20. SQ109 caused major ultrastructural changes in all three life cycle forms, as observed by light microscopy, scanning electron microscopy (SEM), and transmission electron microscopy (TEM). It rapidly collapsed the inner mitochondrial membrane potential (??m) in succinate-energized mitochondria, acting in the same manner as the uncoupler FCCP [carbonyl cyanide 4-(trifluoromethoxy)phenylhydrazone], and it caused the alkalinization of internal acidic compartments, effects that are likely to make major contributions to its mechanism of action. The compound also had activity against squalene synthase, binding to its active site; it inhibited sterol side-chain reduction and, in the amastigote assay, acted synergistically with the antifungal drug posaconazole, with a fractional inhibitory concentration index (FICI) of 0.48, but these effects are unlikely to account for the rapid effects seen on cell morphology and cell killing. SQ109 thus most likely acts, at least in part, by collapsing ??/?pH, one of the major mechanisms demonstrated previously for its action against Mycobacterium tuberculosis. Overall, the results suggest that SQ109, which is currently in advanced clinical trials for the treatment of drug-susceptible and drug-resistant tuberculosis, may also have potential as a drug lead against Chagas disease.

Project description:Chagas disease remains one of the most neglected diseases in the world despite being the most important parasitic disease in Latin America. The characteristic chronic manifestation of chagasic cardiomyopathy is the region's leading cause of heart-related illness, causing significant mortality and morbidity. Due to the limited available therapeutic options, new drugs are urgently needed to control the disease. Sirtuins, also called Silent information regulator 2 (Sir2) proteins have long been suggested as interesting targets to treat different diseases, including parasitic infections. Recent studies on Trypanosoma cruzi sirtuins have hinted at the possibility to exploit these enzymes as a possible drug targets. In the present work, the T. cruzi Sir2 related protein 1 (TcSir2rp1) is genetically validated as a drug target and biochemically characterized for its NAD+-dependent deacetylase activity and its inhibition by the classic sirtuin inhibitor nicotinamide, as well as by bisnaphthalimidopropyl (BNIP) derivatives, a class of parasite sirtuin inhibitors. BNIPs ability to inhibit TcSir2rp1, and anti-parasitic activity against T. cruzi amastigotes in vitro were investigated. The compound BNIP Spermidine (BNIPSpd) (9), was found to be the most potent inhibitor of TcSir2rp1. Moreover, this compound showed altered trypanocidal activity against TcSir2rp1 overexpressing epimastigotes and anti-parasitic activity similar to the reference drug benznidazole against the medically important amastigotes, while having the highest selectivity index amongst the compounds tested. Unfortunately, BNIPSpd failed to treat a mouse model of Chagas disease, possibly due to its pharmacokinetic profile. Medicinal chemistry modifications of the compound, as well as alternative formulations may improve activity and pharmacokinetics in the future. Additionally, an initial TcSIR2rp1 model in complex with p53 peptide substrate was obtained from low resolution X-ray data (3.5 Å) to gain insight into the potential specificity of the interaction with the BNIP compounds. In conclusion, the search for TcSir2rp1 specific inhibitors may represent a valuable strategy for drug discovery against T. cruzi.

Dataset Information

The protein farnesyltransferase inhibitor Tipifarnib as a new lead for the development of drugs against Chagas disease.

Publications

The protein farnesyltransferase inhibitor Tipifarnib as a new lead for the development of drugs against Chagas disease.

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