Non-thiol farnesyltransferase inhibitors: the concept of benzophenone-based bisubstrate analogue farnesyltransferase inhibitors

Insights into Antimalarial Activity of N-Phenyl-Substituted Cinnamanilides

Due to the urgent need of innovation in the antimalarial therapeutic arsenal, a series of thirty-seven ring-substituted N-arylcinnamanilides prepared by microwave-assisted synthesis were subjected to primary screening against the chloroquine-sensitive strain of P. falciparum 3D7/MRA-102. The lipophilicity of all compounds was experimentally determined as the logarithm of the capacity factor k, and these data were subsequently used in the discussion of structure-activity relationships. Among the screened compounds, fourteen derivatives exhibited IC₅₀ from 0.58 to 31 µM, whereas (2E)-N-(4-bromo-2-chlorophenyl)-3-phenylprop-2-enamide (24) was the most effective agent (IC₅₀ = 0.58 µM). In addition, (2E)-N-[2,6-dibromo-4-(trifluoromethyl)- phenyl]-3-phenylprop-2-enamide (36), (2E)-N-[4-nitro-3-(trifluoromethyl)phenyl]-3-phenylprop- 2-enamide (18), (2E)-N-(2-bromo-5-fluorophenyl)-3-phenylprop-2-enamide (23), and (2E)-3-phenyl-N-(3,4,5-trichlorophenyl)prop-2-enamide (33) demonstrated efficacy in the IC₅₀ range from 2.0 to 4.3 µM, comparable to the clinically used standard chloroquine. The results of a cell viability screening performed using THP1-Blue™ NF-κB cells showed that none of these highly active compounds displayed any significant cytotoxic effect up to 20 μM, which makes them promising Plasmodium selective substances for further investigations.

Multisubstrate adduct inhibitors: drug design and biological tools

In drug discovery, different methods exist to create new inhibitors possessing satisfactory biological activity. The multisubstrate adduct inhibitor (MAI) approach is one of these methods, which consists of a covalent combination between analogs of the substrate and the cofactor or of the multiple substrates used by the target enzyme. Adopted as the first line of investigation for many enzymes, this method has brought insights into the enzymatic mechanism, structure, and inhibitory requirements. In this review, the MAI approach, applied to different classes of enzyme, is reported from the point of view of biological activity.

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.

Exploration of novel aryl binding sites of farnesyltransferase using molecular modeling and benzophenone-based farnesyltransferase inhibitors

Most non-thiol CAAX-peptidomimetic farnesyltransferase inhibitors bear nitrogen-containing heterocycles in place of the terminal cysteine which are supposed to coordinate the enzyme-bound zinc. However, it has been shown that those nitrogen-containing heterocycles can be replaced by carbocyclic aromatic moieties which are unable to coordinate the zinc ion, a conclusion that resulted in the postulation of one or two hitherto unknown aryl binding sites. No indication has been given about the spatial location of these novel binding sites. Employing flexible docking of several non-thiol farnesyltransferase inhibitors known from the literature and some model compounds based on our benzophenone scaffold as well as performing GRID searches, we have identified two regions in the farnesyltransferase's active site which we suggest being the postulated aryl binding sites. One aryl binding region is located in close proximity to the zinc ion and is defined by the aromatic side chains of Tyr 300beta, Trp 303beta, Tyr 361beta, and Tyr 365beta. The second aryl binding site is defined by the side chains of Tyr 300beta, Leu 295beta, Lys 294beta, Lys 353beta, and Lys 356beta. This second aryl binding site has been used for the design of a non-thiol farnesyltransferase inhibitor (9c) with an IC(50) of 35 nM.

Discovery of a novel lead structure for anti-malarials

From a library of 61 compounds available from former studies 2,5-bis-acylaminobenzophenone 7p was identified as a lead structure for a novel class of anti-malaria agents active against multi-resistant Plasmodium falciparum strain Dd2. Some structural modifications of this initial lead demonstrated the potential for further improvement of the anti-plasmodial activity of this novel class of anti-malarials.

Structure-activity relationships of novel anti-malarial agents. Part 2: cinnamic acid derivatives

We have described compound 1 as a lead structure for a novel class of anti-malarial agents. Replacement of the 3-phenylpropionyl moiety of the lead structure 1 by a 4-propoxycinnamic acid residue resulted in a significant improvement in antimalarial activity. Compound 3q represents an important step in the development of lead structure 1 into an anti-malarial drug candidate.