Design, synthesis, and pharmacological evaluation of new farnesyl protein transferase inhibitors

Synthesis of a novel conformationally restricted Val-Phe dipeptidomimetic

A method for the synthesis of (3(R,S),6S,11b(R,S))-1,3,4,6,7,11b-hexahydro-4-oxo-3-phthalimidopyrido[2,1-a]isoquinoline-6-carboxylic acid 2 as a new conformationally restricted dipeptidomimetic of Val-Phe is reported. It involved cyclisation via an intramolecular electrophilic addition at the reactive bridgehead carbon. This new scaffold can be used as a building block in the preparation of libraries of peptidomimetics.

A Simple Continuous Flow Microwave Reactor

A new simple procedure for microwave-assisted organic synthesis under continuous flow processing has been developed for use in a monomodal microwave synthesizer with direct temperature control using the instrument's in-built IR sensor. This design makes optimum use of the standing wave cavity to improve the energy efficiency of microwave-assisted flow reactions.

[Involvement of PI3K/Akt pathway in prostate cancer. Potential strategies for developing targeted therapies]

Because of the unavailability of effective therapies to block or reverse the progression of androgen-independent prostate cancer, it seems obvious to target growth signaling pathways for which frequently recurring mutations have been identified. Acquired mutations of the PTEN gene have been reported in several tumor types, including up to 30% - 60% of prostate cancer tumors. This results in constitutive activation of the PI3K/Akt pathway which then represents a major target to prevent dysfunctions in cell growth, survival and motility. Our experience and, therefore, our own tools allow us to design new inhibitors of growth factor receptor tyrosine kinase, PDK-1 and farnesyltransferase activities. These original compounds could selectively switch off one or several steps of the multifunctional pathway and constitute lead compounds in the design of new classes of potent drugs.

Discovery of Functionally Selective 7,8,9,10-Tetrahydro-7,10-ethano-1,2,4-triazolo[3,4-a]phthalazines as GABAA Receptor Agonists at the α3 Subunit

We have previously identified the 7,8,9,10-tetrahydro-7,10-ethano-1,2,4-triazolo[3,4-a]phthalazine (1) as a potent partial agonist for the alpha(3) receptor subtype with 5-fold selectivity in binding affinity over alpha(1). This paper describes a detailed investigation of the substituents on this core structure at both the 3- and 6-positions. Despite evaluating a wide range of groups, the maximum selectivity that could be achieved in terms of affinity for the alpha(3) subtype over the alpha(1) subtype was 12-fold (for 57). Although most analogues showed no selectivity in terms of efficacy, some did show partial agonism at alpha(1) and antagonism at alpha(3) (e.g., 25 and 75). However, two analogues tested (93 and 96), both with triazole substituents in the 6-position, showed significantly higher efficacy for the alpha(3) subtype over the alpha(1) subtype. This was the first indication that selectivity in efficacy in the required direction could be achieved in this series.

Novel N-(4-Piperidinyl)benzamide Antimalarials with Mammalian Protein Farnesyltransferase Inhibitory Activity

Protein farnesyltransferase of Plasmodium falciparum is a potential target in the treatment of malaria for which increased drug resistance is observed. The design, synthesis and evaluation of a series of N-(4-piperidinyl)benzamides is reported. The most potent compounds showed in vitro activity against the parasite at submicromolar concentrations.

Spectroscopic study of fluorescent peptides for prenyl transferase assays

A study of the prenyl transferase reactions was performed by fluorescence using rat brain cytosol fractions as an enzyme source. Four dansylated peptides corresponding to the C-terminal sequence of Ras isoforms were synthesised. The effects of different detergents on the farnesylation or geranylgeranylation of the four peptides were evaluated. Dose-dependent effects of dodecyl-maltoside, a non-ionic detergent, on the farnesyl transferase or geranylgeranyl transferase activities were observed with all peptide substrates. Additionally, the effect of temperature was investigated and these assays were applied to determine Michaelis-Menten constants (K(m)) of the substrates: dansyl-GCVLS (1.8 microM), dansyl-GCVVM (3.2 microM), dansyl-CVIM (3.4 microM) and dansyl-GCVLL (8.4 microM) and FPP (22.6 microM) for FTase activity. Using GGPP as co-substrate, GGTase activity was measured with K(m) values superior to 50 microM for all the three substrate dansyl-GCVLS, dansyl-GCVVM, or dansyl-CVIM, whereas values of 7.6 and 5.4 microM were calculated for the dansyl-GCVLL sequence and GGPP co-substrate, respectively. IC50 values of selective prenyl transferase inhibitors, B-581, FTI 276 and GGTI 287 have been measured to 34, 0.8 and 18 nM, respectively, using dansyl-GCVLS as substrate (FTase inhibition). When dansyl-GCVLL is used as substrate (GGTase inhibition) the IC50 values are 5100, 75 and 5 nM for B-581, FTI 276 and GGTI 287, respectively. Then, this developed method allowed to evaluate the selectivity of all the three inhibitors tested.

Potent and Selective Farnesyl Transferase Inhibitors

We recently described a novel series of CA(1)A(2)X peptidomimetics as farnesyl transferase inhibitors (FTIs). These compounds possess an N-(4-piperidinyl)benzamide scaffold mimicking A(1)A(2) residue. Extensive exploration of structure--activity relationships revealed that replacement of cysteine by substituted benzylimidazoles provided nanomolar FTIs with in vitro activities (18e, IC(50) = 4.60 nM on isolated enzyme, EC(50) = 20.0 nM for growth inhibition on a tumor cell line). The molecular docking of 18e and 19e in the active site of the enzyme provided details of key interactions with the protein and showed that the methionine or phenylalanine residue fits into the aryl binding site.

Broad-Based Quantitative Structure−Activity Relationship Modeling of Potency and Selectivity of Farnesyltransferase Inhibitors Using a Bayesian Regularized Neural Network

Inhibitors of the enzyme farnesyltransferase show potential as novel anticancer agents. There are many known inhibitors, but efforts to build predictive SAR models have been hampered by the structural diversity and flexibility of inhibitors. We have undertaken for the first time a QSAR study of the potency and selectivity of a large, diverse data set of farnesyltransferase inhibitors. We used novel molecular descriptors based on binned atomic properties and invariants of molecular matrices and a robust, nonlinear QSAR mapping paradigm, the Bayesian regularized neural network. We have built robust QSAR models of farnesyltransferase inhibition, geranylgeranyltransferase inhibition, and in vivo data. We have derived a novel selectivity index that allows us to model potency and selectivity simultaneously and have built robust QSAR models using this index that have the potential to discover new potent and selective inhibitors.

Design, Synthesis, and Evaluation of Su- gar Amino Acid Based Inhibitors of Pro- tein Prenyl Transferases PFT and PGGT-1

Eleven analogues of the C-terminal Ca(1)a(2)X motif found in natural substrates of the prenyl transferases PFT and PGGT-1 were synthesized and evaluated for their inhibition potency and selectivity against PFT and PGGT-1. Replacement of the central dipeptide part a(1)a(2) by a benzylated sugar amino acid resulted in a good and highly selective PFT inhibitor (8, IC(50) = 250 +/- 20 nM). The methyl ester of 8 (13) selectively inhibited protein farnesylation in cultured cells.

Involvement of nitric oxide in farnesyltransferase inhibitor-mediated apoptosis in chronic myeloid leukemia cells

The mechanism of action of farnesyltransferase inhibitors (FTIs) has not been fully clarified. We investigated the cytotoxic effects of various FTIs in chronic myeloid leukemia (CML), using LAMA cells and marrow cells from 40 CML patients in chronic phase. FTI-mediated cytotoxic effect was observed in LAMA cells and in 65% of primary CML cells, whereas marrow cells from controls were only weakly affected. Cytotoxic effects were partially related to enhanced apoptosis; however, Fas-receptor (FasR) and Fas-ligand (FasL) expression were not modified by FTIs. Susceptibility to FTI-mediated inhibition did not correlate with FasR/FasL expression in CD34+ CML cells. Moreover, intra-cellular activation of caspase-1 and -8 were not altered by FTIs, and their blockade did not reverse FTI toxicity. However, we observed FTI-induced activation of caspase-3, and its inhibition partially reverted FTI-induced apoptosis. FTIs did not modulate bcl2, bclxL, and bclxS expression, whereas they increased inducible nitric oxide (iNOS) mRNA and protein levels, resulting in higher NO production. Furthermore, C3 exoenzyme, a Rho inhibitor, significantly increased iNOS expression in CML cells, suggesting that FTIs may up-regulate NO formation at least partially through FTI-mediated inhibition of Rho. We conclude that FTIs induce selective apoptosis in CML cells via activation of iNOS and caspase-3.