Inhibitors of protein farnesylation 1998

Non-thiol farnesyltransferase inhibitors: N-(4-acylamino-3-benzoylphenyl)-3-[5-(4-nitrophenyl)-2-furyl]acrylic acid amides

We have designed the nitrophenylfurylacryl-substituted benzophenone 4f as a non-thiol farnesyltransferase inhibitor utilizing a novel aryl binding site of farnesyltransferase. Variation of the 2-acylamino substituent at the benzophenone core structure of our initial lead 4f yielded several non-thiol farnesyltransferase inhibitors with improved activity. These compounds display activity in the low nanomolar range.

Non-thiol farnesyltransferase inhibitors: utilization of an aryl binding site by 5-arylacryloylaminobenzophenones

We recently described a novel aryl binding site of farnesyltransferase. The 2-naphthylacryloyl residue was developed as an appropriate substituent for our benzophenone-based AAX-peptidomimetic capable of occupying this binding site, resulting in a non-thiol farnesyltransferase inhibitor with nanomolar activity. The activity of this inhibitor is readily explained on the basis of docking studies which show the 2-naphthyl residue fitting into the aryl binding site.

Non-thiol farnesyltransferase inhibitors: structure-activity relationships of benzophenone-based bisubstrate analogue farnesyltransferase inhibitors

Investigations on the structure-activity relationships of benzophenone-based bisubstrate analogue farnesyltransferase inhibitors yielded a bisubstrate analogue farnesyltransferase inhibitor lacking any prenylic or peptidic substructures with nanomolar activity. This represents a considerable progress in comparison to those non-prenylic, non-peptidic bisubstrate analogue farnesyltransferase inhibitors we have described before which utilized AAX-peptidomimetic substructures different from the benzophenone since those inhibitors displayed activity only in the micromolar range.

Non-thiol farnesyltransferase inhibitors: N-(4-Acylamino-3-benzoylphenyl)-4-nitrocinnamic acid amides

We have developed the 4-nitrocinnamoyl substituted benzophenone 4a as a novel non-thiol farnesyltransferase inhibitor. Replacement of the p-tolyl moiety of our initial lead structure 4a by different para and ortho substituted phenyl residues as well as by 1-naphthyl resulted in derivatives with considerably enhanced activity displaying IC(50) values between 42 and 52 nM. These compounds represent novel, readily accessible non-thiol farnesyltransferase inhibitors being more active than the corresponding thiol-containing analogues.

Tomorrow's anticancer agents: inhibitors of Ras farnesylation

The purpose of this chapter is to concentrate on what can be considered as definite milestones on the way from examples of inhibitors of farnesyl-protein transferase (FPTase) to candidate drugs actually being considered for or already being evaluated in clinical trials. Emphasis will be placed on results obtained using experimental tumour models in vivo, with a detailed discussion of these results and of the questions which remain to be studied or are still unanswered. The data discussed here are almost exclusively based on published reports, with only brief reference, in the chapter "use of the FPTase inhibitors in the clinic", to some of the newer compounds reported on during recent meetings, details of which have not yet appeared in the peer-reviewed literature. For those requiring a more extensive review of the catalogue of FPTase inhibitors now discovered, some excellent reviews have been committed to this purpose [1-3].

3-Imidazolylmethylaminophenylsulfonyltetrahydroquinolines, a novel series of farnesyltransferase inhibitors

Design, synthesis and structure-activity relationship of a series of 3-imidazolylmethylaminophenylsulfonyltetrahydroquinolines as farnesyltransferase inhibitors are presented. A working pharmacophore of inhibiting farnesyltransferase by this series of inhibitors is proposed.

Inhibition of RAS-targeted prenylation: protein farnesyl transferase inhibitors revisited

The ras oncogene and its 21 kD protein product, Ras, has emerged during the last decade as a potentially exploitable target for anticancer drug development. The knowledge that Ras was readily prenylated by protein farnesyl transferase (PFTase) and that inhibition of this prenylation had functional consequences for the transformed phenotype that expressed oncogenic Ras provided the rational for the development of PFTase inhibitors. The initial enthusiasm for this approach seemed justified by the early identification of PFTase inhibitors that were able potently and specifically to block Ras processing, signalling and transformation in transformed and tumour cell lines in vitro and in certain selected animal models. More recently the recognition that geranylgeranyl transferase (GGTase) I might also be a therapeutic target is being actively researched. The last couple of years though have proved remarkable with the disclosure of a series of structurally-diverse molecules, whose major in vivo preclinical activites have been well documented against experimental animal tumours, and culminating this year in preliminary reporting of their Phase I clinical evaluations. Nevertheless, during the research and development phases of PFTase inhibitors as pharmaceutical agents for clinical use, there have been several unexpected findings which have raised intriguing and potentially crucial questions about their activities. This review aims to highlight and offer new insights into many of these issues and to bring into perspective concerns arising from basic research, as well as from clinical studies. There seems little doubt that these inhibitors of RAS-targeted prenylation represent a new generation of anticancer drugs for the preclinical researcher, whether they can be successfully exploited in clinical practice should be resolved early in the next millenium.

Imidazole-containing diarylether and diarylsulfone inhibitors of farnesyl-protein transferase

The design and syntheses of non-thiol inhibitors of farnesyl-protein transferase are described. Optimization of cysteine-substituted diarylethers led to highly potent imidazole-containing diarylethers and diarylsulfones. Polar diaryl linkers dramatically improved potency and gave highly cell active compounds.

Antitumor efficacy of hypothemycin, a new Ras-signaling inhibitor

We have devised a new drug screening assay to discover anti-cancer drugs which inhibit Ras-mediated cellular signals, by utilizing a Ras-responsive element (RRE)-driven reporter gene system. We found that hypothemycin, an anti-bacterial, reduces RRE-dependent transcription. Treatment of tumor cells with hypothemycin resulted in reduced expression of Ras-inducible genes, including MMP (matrix metalloproteinase)-1, MMP-9, transforming growth factor-beta (TGF-beta), and vascular endothelial growth factor (VEGF), but not that of the constitutively expressed gene, MMP-2. The results of zymography demonstrated that hypothemycin reduced the production of MMP-9 and MMP-3, another Ras-inducible MMP, in the culture medium. Hypothemycin selectively inhibits anchorage-independent growth of Ras-transformed cells in comparison with anchorage-dependent growth. These findings suggest that hypothemycin inhibits Ras-mediated cellular signaling. Daily treatment of tumor-bearing mice with hypothemycin resulted in significant inhibition of tumor growth. Since MMP-1, MMP-3 and MMP-9 play important roles in tumor invasion and TGF-beta and VEGF are involved in tumor angiogenesis, hypothemycin is considered to be an example of a new class of antitumor drugs, whose antitumor efficacy can be at least partly attributed to inhibition of Ras-inducible genes.

Design and in vivo analysis of potent non-thiol inhibitors of farnesyl protein transferase

Inhibitors of farnesyl protein transferase (FPTase) based upon a pseudotripeptide template are described that comprise an imidazole group substituted with a hydrophobic substituent. (1, 5)-Disubstitution of the imidazole group is shown to be the optimal array that leads to potent and selective inhibitors of FPTase. A variety of aryl and isoprenyl substituents are shown to afford effective inhibitors, and the mechanism by which these compounds inhibit FPTase has been investigated. The biochemical behavior of these compounds suggests that they bind to FPTase at the site usually occupied by the protein substrate. In experiments in cell culture, the methyl ester prodrugs of these inhibitors are cell permeant and potently inhibit the posttranslational modification of H-Ras protein. Additionally, these molecules revert the phenotype of ras transformed cells as evidenced by their ability to slow the growth of ras transformed cell lines in soft agar. One of the inhibitors, as its methyl prodrug, was evaluated in two in vivo models of tumor growth. The compound selectively inhibited the growth of tumors derived from H-ras transformed cells, in nude mice, and caused the regression of preexisting tumors in an H-ras transgenic animal model.

Non-thiol 3-aminomethylbenzamide inhibitors of farnesyl-protein transferase

The design and syntheses of non-thiol inhibitors of farnesyl-protein transferase are described. Substitutions on an imidazolylmethyl-AMBA-methionine template gave a highly potent and cell-active inhibitor.

Synthesis and evaluation of hydroxyproline-derived isoprenyltransferase inhibitors

A series of peptidomimetics based on a hydroxyproline scaffold was prepared and evaluated for inhibition of farnesyltransferase and geranylgeranyltransferase I in both enzymatic and cell-based assays. A number of analogs were potent and selective inhibitors of FTase, while one compound (22) was nonselective in the enzymatic assays but eight-fold selective for inhibition of GGTase in the cellular assay (IC50 = 0.39 microM).

Potent and orally bioavailable noncysteine-containing inhibitors of protein farnesyltransferase

Potent and orally bioavailable nonthiol-containing inhibitors of protein farnesyltransferase are described. Oral bioavailability was achieved by replacement of the pyridyl ether moiety of 1 with a 2-substituted furan ether to give 4. Potency was regained with 2,5-disubstituted furan ethers while maintaining the bioavailability inherent in 4. p-Chlorophenylfuran ether 24 is 0.7 nM in vitro (FTase) and is 32% bioavailable in the mouse, 30% bioavailable in rats, and 21% bioavailable in dogs.

Potent inhibitors of protein farnesyltransferase: heteroarenes as cysteine replacements

Synthesis and biological evaluation of heteroarenes as reduced cysteine replacements are described. Of the heteroaryl groups examined with respect to FT inhibitor FTI-276 (1), pyridyl was the replacement found to be most effective. Substitutions at C4 of the pyridyl moiety did not affect the in vitro activity. Compound 9a was found to have moderate in vivo bioavailability.