Maria Letizia Barreca

Discovery of 2,3-diaryl-1,3-thiazolidin-4-ones as potent anti-HIV-1 agents

Design, synthesis and anti-HIV activity of a series of 2,3-diaryl-1,3-thiazolidin-4-ones are reported. Some derivatives proved to be highly effective in inhibiting HIV-1 replication at nanomolar concentrations thereby acting as non-nucleoside HIV-1 RT inhibitors (NNRTIs). SAR studies evidenced that the nature of the substituents at the 2 and 3 positions of the thiazolidinone nucleus largely influenced the in vitro anti-HIV activity of this new class of potent antiviral agents.

Design, Synthesis, Structure-Activity Relationships, and Molecular Modeling Studies of 2,3-Diaryl-1,3-thiazolidin-4-ones as Potent Anti-HIV Agents

Starting from 1H,3H-thiazolo[3,4-a]benzimidazoles (TBZs), we performed the design, synthesis, and the structure-activity relationship studies of a series of 2,3-diaryl-1,3-thiazolidin-4-ones. Some derivatives proved to be highly effective in inhibiting HIV-1 replication at nanomolar concentrations with minimal cytotoxicity, thereby acting as nonnucleoside HIV-1 RT inhibitors (NNRTIs). Computational studies were used to delineate the ligand-RT interactions and to probe the binding of the ligands to HIV-1 RT.

Pharmacophore-Based Discovery of Small-Molecule Inhibitors of Protein–Protein Interactions between HIV-1 Integrase and Cellular Cofactor LEDGF/p75

The cellular protein lens epithelium‐derived growth factor, or transcriptional coactivator p75 (LEDGF/p75), plays a crucial role in HIV integration. The protein–protein interactions (PPIs) between HIV‐1 integrase (IN) and its cellular cofactor LEDGF/p75 may therefore serve as targets for the development of new anti‐HIV drugs. In this work, a structure‐based pharmacophore model for potential small‐molecule inhibitors of HIV‐1 IN–LEDGF/p75 interaction was developed using the LigandScout software. The 3D model obtained was used for virtual screening of our in‐house chemical database, CHIME, leading to the identification of compound CHIBA‐3002 as an interesting hit for further optimization. The rational design, synthesis and biological evaluation of four derivatives were then carried out. Our studies resulted in the discovery of a new and more potent small molecule (7, CHIBA‐3003) that is able to interfere with the HIV‐1 IN–LEDGF/p75 interaction at micromolar concentration, representing one of the first compounds to show activity against these specific PPIs. Docking simulations were subsequently performed in order to investigate the possible binding mode of our new lead compound to HIV‐1 IN. This study is a valid starting point for the identification of anti‐HIV agents with a different mechanism of action from currently available antiviral drugs.

Design, synthesis, and biological evaluation of a series of 2-hydroxyisoquinoline-1,3(2H,4H)-diones as dual inhibitors of human immunodeficiency virus type 1 integrase and the reverse transcriptase RNase H domain.

We report herein the synthesis of a series of 19 2-hydroxyisoquinoline-1,3(2H,4H)-dione derivatives variously substituted at position 7 aimed at inhibiting selectively two-metal ion catalytic active sites. The compounds were tested against HIV-1 reverse transcriptase (RT) polymerase, HIV-1 RT ribonuclease H (RNase H), and HIV-1 integrase (IN). Most compounds displayed poor inhibition of RT polymerase even at 50 microM. The majority of the synthesized compounds inhibited RNase H and IN at micromolar concentrations, and some of them were weakly selective for IN. Surprisingly, two new hits were discovered, which displayed a high selectivity for IN with submicromolar IC50 values. These enzymatic inhibitory properties may be related to the metal binding abilities of the compounds. Physicochemical studies were consistent with a 1/1 stoichiometry of the magnesium complexes in solution, and the metal complexation was strictly dependent on the enolization abilities of the compounds. Unfortunately, all tested compounds exhibited high cellular cytotoxicity in cell culture which limits their applications as antiviral agents.

A 1,8-naphthyridone derivative targets the HIV-1 Tat-mediated transcription and potently inhibits the HIV-1 replication.

The emergence of multidrug resistant HIV-1 strains and the inability of the HAART to eradicate HIV-1 virus from infected patients demand new drugs able to interfere with an alternative step of the replicative cycle. The naphthyridone 3 (HM13N), described in the present study, is a promising anti-HIV agent due to its ability to inhibit the HIV-1 Tat-mediated transcription and the potent antiviral activity observed in acutely, chronically, and latently infected cells. The absence of any tendency to select for resistance mutations in vitro adds to the potential clinical value of this type of compounds, especially as these compounds are drug-like and obey the Lipinski rules.

A Highly Intensified ART Regimen Induces Long-Term Viral Suppression and Restriction of the Viral Reservoir in a Simian AIDS Model

Stably suppressed viremia during ART is essential for establishing reliable simian models for HIV/AIDS. We tested the efficacy of a multidrug ART (highly intensified ART) in a wide range of viremic conditions (103–107 viral RNA copies/mL) in SIVmac251-infected rhesus macaques, and its impact on the viral reservoir. Eleven macaques in the pre-AIDS stage of the disease were treated with a multidrug combination (highly intensified ART) consisting of two nucleosidic/nucleotidic reverse transcriptase inhibitors (emtricitabine and tenofovir), an integrase inhibitor (raltegravir), a protease inhibitor (ritonavir-boosted darunavir) and the CCR5 blocker maraviroc. All animals stably displayed viral loads below the limit of detection of the assay (i.e. <40 RNA copies/mL) after starting highly intensified ART. By increasing the sensitivity of the assay to 3 RNA copies/mL, viral load was still below the limit of detection in all subjects tested. Importantly, viral DNA resulted below the assay detection limit (<2 copies of DNA/5*105 cells) in PBMCs and rectal biopsies of all animals at the end of the follow-up, and in lymph node biopsies from the majority of the study subjects. Moreover, highly intensified ART decreased central/transitional memory, effector memory and activated (HLA-DR+) effector memory CD4+ T-cells in vivo, in line with the role of these subsets as the main cell subpopulations harbouring the virus. Finally, treatment with highly intensified ART at viral load rebound following suspension of a previous anti-reservoir therapy eventually improved the spontaneous containment of viral load following suspension of the second therapeutic cycle, thus leading to a persistent suppression of viremia in the absence of ART. In conclusion, we show, for the first time, complete suppression of viral load by highly intensified ART and a likely associated restriction of the viral reservoir in the macaque AIDS model, making it a useful platform for testing potential cures for AIDS.

Molecular Dynamics Studies of the Wild-Type and Double Mutant HIV-1 Integrase Complexed with the 5CITEP Inhibitor: Mechanism for Inhibition and Drug Resistance

The human immunodeficiency virus type 1 (HIV-1) integrase (IN) is an essential enzyme in the life cycle of the virus and is an attractive target for the development of new drugs useful in acquired immunodeficiency syndrome multidrug therapy. Starting from the crystal structure of the 5CITEP inhibitor bound to the active site in the catalytic domain of the HIV-1 IN, two different molecular dynamics simulations in water have been carried out. In the first simulation the wild-type IN was used, whereas in the second one the double mutation T66I/M154I, described to lead to drug resistance, was introduced in the protein. Compelling differences have been observed in these two structures during analyses of the molecular dynamics trajectories, particularly in the inhibitor binding modes and in the conformational flexibility of the loop (residues 138-149) located near the three catalytic residues in the active site (Asp(64), Asp(116), Glu(152)). Because the conformational flexibility of this region is important for efficient biological activity and its behavior is quite different in the two models, we suggest a hypothetical mechanism for the inhibition and drug resistance of HIV-1 IN. These results can be useful for the rational design of more potent and selective integrase inhibitors and may allow for the design of inhibitors that will be more robust against known resistance mutations.

AMPA receptor antagonists as potential anticonvulsant drugs.

Over the last years alpha-amino-3-hydroxy-5-methyl-4-isoxazolepropionic acid glutamate receptors (AMPARs) have been intensively studied owing to their crucial role in physiological and pathological processes. Efforts targeting AMPAR have been focused on identification of ligands as potential therapeutic agents useful in the prevention and treatment of a variety of neurological and non-neurological diseases. In particular, extensive work was addressed to the discovery of selective antagonists some of which proved to be potent anticonvulsant agents.

Comparative molecular field analysis (CoMFA) and docking studies of non-nucleoside HIV-1 RT inhibitors (NNIs).

A set of TIBO derivatives endowed with reverse transcriptase (RT) inhibitory activity were analyzed by comparative molecular field analysis (CoMFA). Besides conventional steric and electrostatic fields, molecular lipophilicity potential (MLP) was also used as a third field in CoMFA. An informative and statistically significant model (q2 = 0.70, r2 = 0.90, s = 0.46) was obtained by taking into account the three field types together. The key molecular determinants governing the RT inhibition by TIBO congeners were detected at the 3-D level by a careful analysis of the CoMFA isocontour maps. To challenge the predictive ability of the CoMFA model, an external set of thiazolobenzimidazole (TBZ) derivatives were examined. Good predictions, suggesting a similar binding mode for TIBO and TBZ derivatives, emerged. Flexible docking experiments on TBZ, TIBO and other NNIs confirmed common binding characteristics, as found out also by CoMFA, and moreover a good correlation between calculated binding energies and inhibitory potency was found.

Anti-HIV agents: design and discovery of new potent RT inhibitors

This paper reports our work in the field of nonnucleoside RT inhibitors (NNRTIs). On the basis of extensive studies on 1H,3H-thiazolo[3,4-a]benzimidazole derivatives (TBZs) followed by structure-activity relationship (SAR) considerations and molecular modeling, the design and synthesis of a series of 2,3-diaryl-1,3-thiazolidin-4-ones have been performed. Some derivatives proved to be highly effective in inhibiting human immunodeficiency virus type-1 (HIV-1) replication at nanomolar concentrations with minimal toxicity, acting as reverse transcriptase (RT) inhibitors. Computational studies were used in order to probe the binding of our ligands to HIV-1-RT.