Elisa Uliassi

Multitarget Drug Design Strategy: Quinone–Tacrine Hybrids Designed To Block Amyloid-β Aggregation and To Exert Anticholinesterase and Antioxidant Effects

We report the identification of multitarget anti-Alzheimer compounds designed by combining a naphthoquinone function and a tacrine fragment. In vitro, 15 compounds displayed excellent acetylcholinesterase (AChE) inhibitory potencies and interesting capabilities to block amyloid-β (Aβ) aggregation. The X-ray analysis of one of those compounds in complex with AChE allowed rationalizing the outstanding activity data (IC50 = 0.72 nM). Two of the compounds showed negligible toxicity in immortalized mouse cortical neurons Neuro2A and primary rat cerebellar granule neurons. However, only one of them was less hepatotoxic than tacrine in HepG2 cells. In T67 cells, both compounds showed antioxidant activity, following NQO1 induction. Furthermore, in Neuro2A, they were able to completely revert the decrease in viability induced by Aβ. Importantly, they crossed the blood-brain barrier, as demonstrated in ex vivo experiments with rats. When ex vivo results were combined with in vitro studies, these two compounds emerged to be promising multitarget lead candidates worthy of further pursuit.

The Hippo Pathway and YAP/TAZ–TEAD Protein–Protein Interaction as Targets for Regenerative Medicine and Cancer Treatment

The Hippo pathway is an important organ size control signaling network and the major regulatory mechanism of cell-contact inhibition. Yes associated protein (YAP) and transcriptional co-activator with PDZ-binding motif (TAZ) are its targets and terminal effectors: inhibition of the pathway promotes YAP/TAZ translocation to the nucleus, where they interact with transcriptional enhancer associate domain (TEAD) transcription factors and coactivate the expression of target genes, promoting cell proliferation. Defects in the pathway can result in overgrowth phenotypes due to deregulation of stem-cell proliferation and apoptosis; members of the pathway are directly involved in cancer development. The pharmacological regulation of the pathway might be useful in cancer prevention, treatment, and regenerative medicine applications; currently, a few compounds can selectively modulate the pathway. In this review, we present an overview of the Hippo pathway, the sequence and structural analysis of YAP/TAZ, the known pharmacological modulators of the pathway, especially those targeting YAP/TAZ-TEAD interaction.

Two diseases, one approach: multitarget drug discovery in Alzheimer's and neglected tropical diseases

In the past decade, scientific advances in network pharmacology have laid the foundations for a polypharmacological approach to discover new drugs for complex diseases. There is now a comprehensive understanding that many incurable diseases are multifactorial in nature and, consequently, conventional drugs directed to a single molecular target are inadequate. To achieve a desired clinical outcome, a polypharmacological approach seeks to intervene in the diseased network using either combinations of multiple drugs or single small molecules modulating multiple targets. Both these approaches are equally feasible from a clinical standpoint. However, for various reasons which will be discussed in this review, the latter approach may be favoured for Alzheimers disease (AD) and neglected tropical diseases (NTDs). With each passing year, an increasing number of multitarget drugs and drug candidates are being identified, and several proof-of-concepts for treating these two diseases have emerged. Herein, with an awareness of the obstacles and challenges faced, we explore small molecules that seek to modulate multiple targets with the ultimate goal of harnessing network pharmacology for therapeutic applications in AD and NTDs.

Toward the Development of Dual‐Targeted Glyceraldehyde‐3‐phosphate Dehydrogenase/Trypanothione Reductase Inhibitors against Trypanosoma brucei and Trypanosoma cruzi

A significant improvement in the treatment of trypanosomiases has been achieved with the recent development of nifurtimox–eflornithine combination therapy (NECT). As an alternative to drug combinations and as a means to overcome most of the antitrypanosomatid drug discovery challenges, a multitarget drug design strategy has been envisaged. To begin testing this hypothesis, we designed and developed a series of quinone–coumarin hybrids against glyceraldehyde‐3‐phosphate dehydrogenase/trypanothione reductase (GAPDH/TR). These enzymes belong to metabolic pathways that are vital to Trypanosoma brucei and Trypanosoma cruzi, and have thus been considered promising drug targets. The synthesized molecules were characterized for their dual‐target antitrypanosomal profile, both in enzyme assays and in in vitro parasite cultures. The merged derivative 2‐{[3‐(3‐dimethylaminopropoxy)‐2‐oxo‐2H‐chromen‐7‐yl]oxy}anthracene‐1,4‐dione (10) showed an IC50 value of 5.4 μM against TbGAPDH and a concomitant Ki value of 2.32 μM against TcTR. Notably, 2‐{4‐[6‐(2‐dimethylaminoethoxy)‐2‐oxo‐2H‐chromen‐3‐yl]phenoxy}anthracene‐1,4‐dione (compound 6) displayed a remarkable EC50 value for T. brucei parasites (0.026 μM) combined with a very low cytotoxicity toward mammalian L6 cells (7.95 μM). This promising low toxicity of compound 6 might be at least partially due to the fact that it does not interfere with human glutathione reductase.

A perspective on multi-target drug discovery and design for complex diseases

Diseases of infection, of neurodegeneration (such as Alzheimer’s and Parkinson’s diseases), and of malignancy (cancers) have complex and varied causative factors. Modern drug discovery has the power to identify potential modulators for multiple targets from millions of compounds. Computational approaches allow the determination of the association of each compound with its target before chemical synthesis and biological testing is done. These approaches depend on the prior identification of clinically and biologically validated targets. This Perspective will focus on the molecular and computational approaches that underpin drug design by medicinal chemists to promote understanding and collaboration with clinical scientists.

Neuroregeneration versus neurodegeneration: toward a paradigm shift in Alzheimer's disease drug discovery

Alzheimers disease represents an enormous global burden in terms of human suffering and economic cost. To tackle the current lack of effective drugs and the continuous clinical trial failures might require a shift from the prevailing paradigm targeting pathogenesis to the one targeting neural stem cells (NSCs) regeneration. In this context, small molecules have come to the forefront for their potential to manipulate NSCs, provide therapeutic tools and unveil NSCs biology. Classically, these molecules have been generated either by target-based or phenotypic approaches. To circumvent specific liabilities, nanomedicines emerge as a feasible alternative. However, this review is not intended to be comprehensive. Its purpose is to focus on recent examples that could accelerate development of neuroregenerative drugs against Alzheimers disease.

Structure-Based Design of 3-(4-Aryl-1H-1,2,3-triazol-1-yl)-Biphenyl Derivatives as P2Y14 Receptor Antagonists

UDP and UDP-glucose activate the P2Y14 receptor (P2Y14R) to modulate processes related to inflammation, diabetes, and asthma. A computational pipeline suggested alternatives to naphthalene of a previously reported P2Y14R antagonist (3, PPTN) using docking and molecular dynamics simulations on a hP2Y14R homology model based on P2Y12R structures. By reevaluating the binding of 3 to P2Y14R computationally, two alternatives, i.e., alkynyl and triazolyl derivatives, were identified. Improved synthesis of fluorescent antagonist 4 enabled affinity quantification (IC50s, nM) using flow cytometry of P2Y14R-expressing CHO cells. p-F3C-phenyl-triazole 65 (32) was more potent than a corresponding alkyne 11. Thus, additional triazolyl derivatives were prepared, as guided by docking simulations, with nonpolar aryl substituents favored. Although triazoles were less potent than 3 (6), simpler synthesis facilitated further structural optimization. Additionally, relative P2Y14R affinities agreed with predicted binding of alkynyl and triazole analogues. These triazoles, designed through a structure-based approach, can be assessed in disease models.

Molecular basis for covalent inhibition of glyceraldehyde-3-phosphate dehydrogenase by a 2-phenoxy-1,4-naphthoquinone small molecule

Glyceraldehyde‐3‐phosphate dehydrogenase (GAPDH) has recently gained attention as an antiprotozoan and anticancer drug target. We have previously identified 2‐phenoxy‐1,4‐naphthoquinone as an inhibitor of both Trypanosoma brucei and human GAPDH. Herein, through multiple chemical, biochemical, and biological studies, and through the design of analogs, we confirmed the formation of a covalent adduct, we clarified the inhibition mechanism, and we demonstrated antitrypanosomal, antiplasmodial, and cytotoxic activities in cell cultures. The overall results lent support to the hypothesis that 2‐phenoxy‐1,4‐naphthoquinone binds the GAPDH catalytic cysteine covalently through a phenolate displacement mechanism. By investigating the reactivity of 2‐phenoxy‐1,4‐naphthoquinone and its analogs with four GAPDH homologs, we showed that the covalent inhibition is not preceded by the formation of a strong non‐covalent complex. However, an up to fivefold difference in inactivation rates among homologs hinted at structural or electrostatic differences of their active sites that could be exploited to further design kinetically selective inhibitors. Moreover, we preliminarily showed that 2‐phenoxy‐1,4‐naphthoquinone displays selectivity for GAPDHs over two other cysteine‐dependent enzymes, supporting its suitability as a warhead starting fragment for the design of novel inhibitors.

Development of a Focused Library of Triazole-Linked Privileged-Structure-Based Conjugates Leading to the Discovery of Novel Phenotypic Hits against Protozoan Parasitic Infections

Protozoan infections caused by Plasmodium, Leishmania, and Trypanosoma spp. contribute significantly to the burden of infectious diseases worldwide, causing severe morbidity and mortality. The inadequacy of available treatments calls for cost‐ and time‐effective drug discovery endeavors. To this end, we envisaged the triazole linkage of privileged structures as an effective drug design strategy to generate a focused library of high‐quality compounds. The versatility of this approach was combined with the feasibility of a phenotypic assay, integrated with early ADME‐tox profiling. Thus, an 18‐membered library was efficiently assembled via Huisgen cycloaddition of phenothiazine, biphenyl, and phenylpiperazine scaffolds. The resulting 18 compounds were then tested against seven parasite strains, and counter‐screened for selectivity against two mammalian cell lines. In parallel, hERG and cytochrome P450 (CYP) inhibition, and mitochondrial toxicity were assessed. Remarkably, 10‐((1‐(3‐([1,1′‐biphenyl]‐3‐yloxy)propyl)‐1H‐1,2,3‐triazol‐5‐yl)methyl)‐10H‐phenothiazine (7) and 10‐(3‐(1‐(3‐([1,1′‐biphenyl]‐3‐yloxy)propyl)‐1H‐1,2,3‐triazol‐4‐yl)propyl)‐10H‐phenothiazine (12) showed respective IC50 values of 1.8 and 1.9 μg mL−1 against T. cruzi, together with optimal selectivity. In particular, compound 7 showed a promising ADME‐tox profile. Thus, hit 7 might be progressed as an antichagasic lead.

A Focused Library of Psychotropic Analogues with Neuroprotective and Neuroregenerative Potential

Overcoming the lack of effective treatments and the continuous clinical trial failures in neurodegenerative drug discovery might require a shift from the prevailing paradigm targeting pathogenesis to the one targeting simultaneously neuroprotection and neuroregeneration. In the studies reported herein, we sought to identify small molecules that might exert neuroprotective and neuroregenerative potential as tools against neurodegenerative diseases. In doing so, we started from the reported neuroprotective/neuroregenerative mechanisms of psychotropic drugs featuring a tricyclic alkylamine scaffold. Thus, we designed a focused-chemical library of 36 entries aimed at exploring the structural requirements for efficient neuroprotective/neuroregenerative cellular activity, without the manifestation of toxicity. To this aim, we developed a synthetic protocol, which overcame the limited applicability of previously reported procedures. Next, we evaluated the synthesized compounds through a phenotypic screening pipeline, based on primary neuronal systems. Phenothiazine 2Bc showed improved neuroregenerative and neuroprotective properties with respect to reference drug desipramine (2Aa). Importantly, we have also shown that 2Bc outperformed currently available drugs in cell models of Alzheimers and Parkinsons diseases and attenuates microglial activation by reducing iNOS expression.