Antitubercular polyhalogenated phenothiazines and phenoselenazine with reduced binding to CNS receptors.

Targeting energy metabolism in Mycobacterium tuberculosis (Mtb) is a new paradigm in the search for innovative anti-TB drugs. NADH:menaquinone oxidoreductase is a non-proton translocating type II NADH dehydrogenase (NDH-2) that is an essential enzyme in the respiratory chain of Mtb and is not found in mammalian mitochondria. Phenothiazines (PTZs) represent one of the most known class of NDH-2 inhibitors, but their use as anti-TB drugs is currently limited by the wide range of potentially serious off-target effects. In this work, we designed and synthesized a series of new PTZs by decorating the scaffold in an unconventional way, introducing various halogen atoms. By replacing the sulfur atom with selenium, a dibromophenoselenazine 20 was also synthesized. Among the synthesized poly-halogenated PTZs (HPTZs), dibromo and tetrachloro derivatives 9 and 11, along with the phenoselenazine 20, emerged with a better anti-TB profile than the therapeutic thioridazine (TZ). They targeted non-replicating Mtb, were bactericidal, and synergized with rifampin and bedaquiline. Moreover, their anti-TB activity was found to be related to the NDH-2 inhibition. Most important, they showed a markedly reduced affinity to dopaminergic and serotonergic receptors respect to the TZ. From this work emerged, for the first time, as the poly-halogenation of the PTZ core, while permitting to maintain good anti-TB profile could conceivably lead to fewer CNS side-effects risk, making more tangible the use of PTZs for this alternative therapeutic application.

Identification of compounds inhibiting prion replication and toxicity by removing PrPC from the cell surface.

The vast majority of therapeutic approaches tested so far for prion diseases, transmissible neurodegenerative disorders of human and animals, tackled PrPSc , the aggregated and infectious isoform of the cellular prion protein (PrPC ), with largely unsuccessful results. Conversely, targeting PrPC expression, stability or cell surface localization are poorly explored strategies. We recently characterized the mode of action of chlorpromazine, an anti-psychotic drug known to inhibit prion replication and toxicity by inducing the re-localization of PrPC from the plasma membrane. Unfortunately, chlorpromazine possesses pharmacokinetic properties unsuitable for chronic use in vivo, namely low specificity and high toxicity. Here, we employed HEK293 cells stably expressing EGFP-PrP to carry out a semi-automated high content screening (HCS) of a chemical library directed at identifying non-cytotoxic molecules capable of specifically relocalizing PrPC from the plasma membrane as well as inhibiting prion replication in N2a cell cultures. We identified four candidate hits inducing a significant reduction in cell surface PrPC , one of which also inhibited prion propagation and toxicity in cell cultures in a strain-independent fashion. This study defines a new screening method and novel anti-prion compounds supporting the notion that removing PrPC from the cell surface could represent a viable therapeutic strategy for prion diseases.

Discovery of potent p38α MAPK inhibitors through a funnel like workflow combining in silico screening and in vitro validation.

This work describes the rational discovery of novel chemotypes of p38α MAPK inhibitors using a funnel approach consisting of several computer-aided drug discovery methods and biological experiments. Among the identified hits, four compounds belonging to different chemical families showed IC50 values lower than 10 µM. In particular, the 1,4-benzodioxane derivative 5 turned out to be a potent and efficient p38α MAPK inhibitor having IC50 = 0.07 µM, and LEexp and LipE values of 0.38 and 4.8, respectively; noteworthy, the compound had also a promising kinase selectivity profile and the capability to suppress p38α MAPK effects in human immune cells. Overall, the collected findings highlight that the applied strategy has been successful in generating chemical novelty in the inhibitor kinase field, providing suitable chemical candidates for further inhibitor optimization.

A Journey around the Medicinal Chemistry of Hepatitis C Virus Inhibitors Targeting NS4B: From Target to Preclinical Drug Candidates.

Hepatitis C virus (HCV) infection is a global health burden with an estimated 130-170 million chronically infected individuals and is the cause of serious liver diseases such as cirrhosis and hepatocellular carcinoma. HCV NS4B protein represents a validated target for the identification of new drugs to be added to the combination regimen recently approved. During the last years, NS4B has thus been the object of impressive medicinal chemistry efforts, which led to the identification of promising preclinical candidates. In this context, the present review aims to discuss research published on NS4B functional inhibitors focusing the attention on hit identification, hit-to-lead optimization, ADME profile evaluation, and the structure-activity relationship data raised for each compound family taken into account. The information delivered in this review will be a useful and valuable tool for those medicinal chemists dealing with research programs focused on NS4B and aimed at the identification of innovative anti-HCV compounds.

Re-evolution of the 2-phenylquinolines: ligand-based design, synthesis, and biological evaluation of a potent new class of Staphylococcus aureus NorA efflux pump inhibitors to combat antimicrobial resistance.

Overexpression of efflux pumps is an important mechanism by which bacteria evade the effects of antimicrobial agents that are substrates. NorA is a Staphylococcus aureus efflux pump that confers reduced susceptibility to many structurally unrelated agents, including fluoroquinolones, biocides, and dyes, resulting in a multidrug resistant (MDR) phenotype. In this work, a series of 2-phenylquinoline derivatives was designed by means of ligand-based pharmacophore modeling in an attempt to identify improved S. aureus NorA efflux pump inhibitors (EPIs). Most of the 2-phenylquinoline derivatives displayed potent EPI activity against the norA overexpressing strain SA-1199B. The antibacterial activity of ciprofloxacin, when used in combination with some of the synthesized compounds, was completely restored in SA-1199B and SA-K2378, a strain overexpressing norA from a multicopy plasmid. Compounds 3m and 3q also showed potent synergistic activity with the ethidium bromide dye in a strain overexpressing the MepA MDR efflux pump.

Preclinical evaluation of 1H-benzylindole derivatives as novel human immunodeficiency virus integrase strand transfer inhibitors.

We have identified 1H-benzylindole analogues as a novel series of human immunodeficiency virus (HIV) integrase inhibitors with antiretroviral activities against different strains of HIV type 1 (HIV-1), HIV-2, and simian immunodeficiency virus strain MAC(251) [SIV(MAC(251))]. Molecular modeling and structure-activity relationship-based optimization resulted in the identification of CHI/1043 as the most potent congener. CHI/1043 inhibited the replication of HIV-1(III(B)) in MT-4 cells at a 50% effective concentration (EC(50)) of 0.60 microM, 70-fold below its cytotoxic concentration. Equal activities against HIV-1(NL4.3), HIV-2(ROD), HIV-2(EHO), and SIV(MAC(251)) were observed. CHI/1043 was equally active against virus strains resistant against inhibitors of reverse transcriptase or protease. Replication of both X4 and R5 strains in peripheral blood mononuclear cells was sensitive to the inhibitory effect of CHI/1043 (EC(50), 0.30 to 0.38 microM). CHI/1043 inhibited integrase strand transfer activity in oligonucleotide-based enzymatic assays at low micromolar concentrations. Time-of-addition experiments confirmed CHI/1043 to interfere with the viral replication cycle at the time of retroviral integration. Quantitative Alu PCR corroborated that the anti-HIV activity is based upon the inhibition of proviral DNA integration. An HIV-1 strain selected for 70 passages in the presence of CHI/1043 was evaluated genotypically and phenotypically. The mutations T66I and Q146K were present in integrase. Cross-resistance to other integrase strand transfer inhibitors, such as L-708,906, the naphthyridine analogue L-870,810, and the clinical drugs GS/9137 and MK-0518, was observed. In adsorption, distribution, metabolism, excretion, and toxicity studies, antiviral activity was strongly reduced by protein binding, and metabolization in human liver microsomes was observed. Transport studies with Caco cells suggest a low oral bioavailability.

3D pharmacophore models for 1,2,3,4-tetrahydroisoquinoline derivatives acting as anticonvulsant agents.

A 3D pharmacophore model predicting anticonvulsant activity was obtained for a series of 6,7-dimethoxy-1,2,3,4-tetrahydroisoquinoline derivatives recently disclosed as a new class of noncompetitive AMPA receptor antagonists. The training set included 17 compounds with varying potency against audiogenic seizures in DBA/2 mice. The best statistical hypothesis, generated with the HypoGen module of Catalyst 4.9, consisted of five features: two hydrogen bond acceptors, two hydrophobic features, and one hydrophobic aromatic region, providing a model with a correlation coefficient of 0.919. The obtained model was an efficient tool in the design of some new anticonvulsant agents containing the tetrahydroisoquinoline scaffold. Moreover, in order to explain the different degree of efficacy of the newly designed N-substituted derivatives, excluded volumes were also considered.

Efficient 3D database screening for novel HIV-1 IN inhibitors.

We describe the use of pharmacophore modeling as an efficient tool in the discovery of novel HIV-1 integrase (IN) inhibitors. A three-dimensional hypothetical model for the binding of diketo acid analogues to the enzyme was built by means of the Catalyst program. Using these models as a query for virtual screening, we found several compounds that contain the specified 3D patterns of chemical functions. Biological testing shows that our strategy was successful in searching for new structural leads as HIV-1 IN inhibitors.

Synthesis and anticonvulsant properties of tetrahydroisoquinoline derivatives.

As a follow up of our previous structure-activity relationship and molecular modeling studies, we synthesized a novel series of 1-aryl-6,7-dimethoxy-1,2,3,4-tetrahydroisoquinoline derivatives as potential non-competitive AMPA receptor antagonists. When tested for their ability to prevent sound-induced seizures in DBA/2 mice, some of these novel compounds showed high anticonvulsant potency.

Discovery of a novel and highly potent noncompetitive AMPA receptor antagonist.

N-Acetyl-1-aryl-6,7-dimethoxy-1,2,3,4-tetrahydroisoquinoline derivatives were designed and synthesized as potential noncompetitive AMPA receptor antagonists on the basis of molecular modeling studies. Sound-induced seizure testing showed that this class of compounds possessed anticonvulsant properties. In particular, 10c was more potent than talampanel (2), a noncompetitive AMPA receptor antagonist currently being investigated in phase III trials as an antiepileptic agent. Furthermore, electrophysiological studies indicated that 10c was a highly effective noncompetitive-type modulator of the AMPA receptor.