Structure-activity relationships of novel N-imidazoylpiperazines with potent anti-Trypanosoma cruzi activity.

Background: Chagas disease is caused by the parasite Trypanosoma cruzi, and the lack of effective and safe treatments makes identifying new classes of compounds with anti-T. cruzi activity of paramount importance. Methods: Hit-to-lead exploration of a metabolically stable N-imidazoylpiperazine was performed. Results: Compound 2, a piperazine derivative active against T. cruzi, was selected to perform the hit-to-lead exploration, which involved the design, synthesis and biological evaluation of 39 new derivatives. Conclusion: Compounds 6e and 10a were identified as optimized compounds with low micromolar in vitro activity, low cytotoxicity and suitable preliminary absorption, distribution, metabolism and excretion and physicochemical properties. Both compounds reduced parasitemia in mouse models of Chagas disease, providing a promising opportunity for further exploration of new antichagasic compounds.

Targeted Protein Degradation for Infectious Diseases: from Basic Biology to Drug Discovery.

Targeted protein degradation (TPD) is emerging as one of the most innovative strategies to tackle infectious diseases. Particularly, proteolysis-targeting chimera (PROTAC)-mediated protein degradation may offer several benefits over classical anti-infective small-molecule drugs. Because of their peculiar and catalytic mechanism of action, anti-infective PROTACs might be advantageous in terms of efficacy, toxicity, and selectivity. Importantly, PROTACs may also overcome the emergence of antimicrobial resistance. Furthermore, anti-infective PROTACs might have the potential to (i) modulate "undruggable" targets, (ii) "recycle" inhibitors from classical drug discovery approaches, and (iii) open new scenarios for combination therapies. Here, we try to address these points by discussing selected case studies of antiviral PROTACs and the first-in-class antibacterial PROTACs. Finally, we discuss how the field of PROTAC-mediated TPD might be exploited in parasitic diseases. Since no antiparasitic PROTAC has been reported yet, we also describe the parasite proteasome system. While in its infancy and with many challenges ahead, we hope that PROTAC-mediated protein degradation for infectious diseases may lead to the development of next-generation anti-infective drugs.

Chemoinformatics Studies on a Series of Imidazoles as Cruzain Inhibitors.

Natural products based on imidazole scaffolds have inspired the discovery of a wide variety of bioactive compounds. Herein, a series of imidazoles that act as competitive and potent cruzain inhibitors was investigated using a combination of ligand- and structure-based drug design strategies. Quantitative structure-activity relationships (QSARs) were generated along with the investigation of enzyme-inhibitor molecular interactions. Predictive hologram QSAR (HQSAR, r2pred = 0.80) and AutoQSAR (q2 = 0.90) models were built, and key structural properties that underpin cruzain inhibition were identified. Moreover, comparative molecular field analysis (CoMFA, r2pred = 0.81) and comparative molecular similarity indices analysis (CoMSIA, r2pred = 0.73) revealed 3D molecular features that strongly affect the activity of the inhibitors. These findings were examined along with molecular docking studies and were highly compatible with the intermolecular contacts that take place between cruzain and the inhibitors. The results gathered herein revealed the main factors that determine the activity of the imidazoles studied and provide novel knowledge for the design of improved cruzain inhibitors.

Discovery of Potent, Reversible, and Competitive Cruzain Inhibitors with Trypanocidal Activity: A Structure-Based Drug Design Approach.

A virtual screening conducted with nearly 4 000 000 compounds from lead-like and fragment-like subsets enabled the identification of a small-molecule inhibitor (1) of the Trypanosoma cruzi cruzain enzyme, a validated drug target for Chagas disease. Subsequent comprehensive structure-based drug design and structure-activity relationship studies led to the discovery of carbamoyl imidazoles as potent, reversible, and competitive cruzain inhibitors. The most potent carbamoyl imidazole inhibitor (45) exhibited high affinity with a Ki value of 20 nM, presenting both in vitro and in vivo activity against T. cruzi. Furthermore, the most promising compounds reduced parasite burden in vivo and showed no toxicity at a dose of 100 mg/kg. These carbamoyl imidazoles are structurally attractive, nonpeptidic, and easy to prepare and synthetically modify. Finally, these results further advance our understanding of the noncovalent mode of inhibition of this pharmaceutically relevant enzyme, building strong foundations for drug discovery efforts.