Breakthroughs in Medicinal Chemistry: New Targets and Mechanisms, New Drugs, New Hopes is a series of Editorials, which are published on a biannual basis by the Editorial Board of the Medicinal ...Chemistry section of the journal Molecules ....
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Different azides and alkynes have been coupled via Cu-catalyzed 1,3-dipolar Huisgen cycloaddition to afford a novel family of N1- and C5-substituted 1,2,3-triazole derivatives that ...feature the propargylamine group typical of irreversible MAO-B inhibitors at the C4-side chain of the triazole ring. All the synthesized compounds were evaluated against human MAO-A and MAO-B. Structure–activity relationships and molecular modeling were utilized to gain insight into the structural and chemical features that enhance the binding affinity and selectivity between the two enzyme isoforms. Several lead compounds, in terms of potency (submicromolar to low micromolar range), MAO-B selective recognition, and brain permeability, were identified. One of these leads (MAO-B IC50 of 3.54μM, selectivity MAO-A/MAO-B index of 27.7) was further subjected to reversibility and time-dependence inhibition studies, which disclosed a slow and irreversible inhibition of human MAO-B. Overall, the results support the suitability of the 4-triazolylalkyl propargylamine scaffold for exploring the design of multipotent anti-Alzheimer compounds endowed with irreversible MAO-B inhibitory activity.
Multitarget anti-Alzheimer agents are the focus of very intensive research. Through a comprehensive bibliometric analysis of the publications in the period 1990-2020, we have identified trends and ...potential gaps that might guide future directions. We found that: (i) the number of publications boomed by 2011 and continued ascending in 2020; (ii) the linked-pharmacophore strategy was preferred over design approaches based on fusing or merging pharmacophores or privileged structures; (iii) a significant number of in vivo studies, mainly using the scopolamine-induced amnesia mouse model, have been performed, especially since 2017; (iv) China, Italy and Spain are the countries with the largest total number of publications on this topic, whereas Portugal, Spain and Italy are the countries in whose scientific communities this topic has generated greatest interest; (v) acetylcholinesterase, β-amyloid aggregation, oxidative stress, butyrylcholinesterase, and biometal chelation and the binary combinations thereof have been the most commonly pursued, while combinations based on other key targets, such as tau aggregation, glycogen synthase kinase-3β, NMDA receptors, and more than 70 other targets have been only marginally considered. These results might allow us to spot new design opportunities based on innovative target combinations to expand and diversify the repertoire of multitarget drug candidates and increase the likelihood of finding effective therapies for this devastating disease.
Simultaneous modulation of several key targets of the pathological network of Alzheimer's disease (AD) is being increasingly pursued as a promising option to fill the critical gap of efficacious ...drugs against this condition.
A short series of compounds purported to hit multiple targets of relevance in AD has been designed, on the basis of their distinct basicities estimated from high-level quantum mechanical computations, synthesized, and subjected to assays of inhibition of cholinesterases, BACE-1, and Aβ42 and tau aggregation, of antioxidant activity, and of brain permeation.
Using, as a template, a lead rhein-huprine hybrid with an interesting multitarget profile, we have developed second-generation compounds, designed by the modification of the huprine aromatic ring. Replacement by 1,8-naphthyridine or thieno3,2-epyridine systems resulted in decreased, although still potent, acetylcholinesterase or BACE-1 inhibitory activities, which are more balanced relative to their Aβ42 and tau antiaggregating and antioxidant activities.
Second-generation naphthyridine- and thienopyridine-based rhein-huprine hybrids emerge as interesting brain permeable compounds that hit several crucial pathogenic factors of AD.
Dual binding site acetylcholinesterase inhibitors have recently emerged as a new class of anti-Alzheimer agents with potential to positively modify the course of the disease. These compounds exhibit ...a multifunctional pharmacological profile arising from interaction with several biological targets involved upstream and downstream in the neurodegenerative cascade of Alzheimer's disease (AD). The primary target of these compounds is the enzyme acetylcholinesterase (AChE). Interaction of dual binding site AChE inhibitors with AChE results in a potent inhibitory activity of AChE and AChE-induced β-amyloid peptide (Aβ) aggregation. Some dual binding site AChE inhibitors take on added value a significant ability to additionally inhibit the enzymes butyrylcholinesterase and BACE-1, involved in the co-regulation of the hydrolysis of the neurotransmitter acetylcholine and in Aβ formation, respectively. The structural determinants which mediate the interaction of dual binding site AChE inhibitors with these three important enzymes for AD treatment are herein reviewed.
The therapeutic arsenal for the treatment of Alzheimer's disease (AD) remains confined to a group of four inhibitors of AChE and one NMDA receptor antagonist, which are used to provide a relief of ...the very late symptoms of the dementia, i.e. the cognitive and functional decline. In line with the growing body of evidence of the pivotal role of the beta-amyloid peptide (Abeta) in the pathogenesis of AD, alternative classes of drugs targeting mainly the formation or the aggregation of Abeta are actively pursued by the pharmaceutical industry, as they could positively modify the course of AD, stopping or slowing down disease progression. While the first amyloid-directed disease-modifying drugs go ahead with their clinical development and could reach the market as soon as 2009, mounting preclinical and clinical evidences is pointing towards a disease-modifying role also for currently marketed anti-Alzheimer AChE inhibitors (AChEIs), particularly for donepezil. In this review, the neuroprotective effects exhibited by currently commercialized AChEIs will be briefly discussed, together with the secondary mechanisms through which they could exert such effects. This review will focus also on particular classes of AChEIs, namely dual binding site AChEIs, which are being purposely designed to target Abeta aggregation and / or other biological targets that contribute to AD pathogenesis, thus constituting very promising disease-modifying anti-Alzheimer drug candidates.
In Plasmodium falciparum the bifunctional enzyme glucose-6-phosphate dehydrogenase‒6-phosphogluconolactonase (PfG6PD‒6PGL) is involved in the catalysis of the first reaction of the pentose phosphate ...pathway. Since this enzyme has a key role in parasite development, its unique structure represents a potential target for the discovery of antimalarial drugs. Here we describe the first 3D structural model of the G6PD domain of PfG6PD‒6PGL. Compared to the human enzyme (hG6PD), the 3D model has enabled the identification of a key difference in the substrate-binding site, which involves the replacement of Arg365 in hG6PD by Asp750 in PfG6PD. In a prospective validation of the model, this critical change has been exploited to rationally design a novel family of substrate analog-based inhibitors that can display the necessary selectivity towards PfG6PD. A series of glucose derivatives featuring an α-methoxy group at the anomeric position and different side chains at position 6 bearing distinct basic functionalities has been synthesized, and their PfG6PD and hG6PD inhibitory activities and their toxicity against parasite and mammalian cells have been assessed. Several compounds displayed micromolar affinity (Ki up to 23 μM), favorable selectivity (up to > 26-fold), and low cytotoxicity. Phenotypic assays with P. falciparum cultures revealed high micromolar IC50 values, likely as a result of poor internalization of the compounds in the parasite cell. Overall, these results endorse confidence to the 3D model of PfG6PD, paving the way for the use of target-based drug design approaches in antimalarial drug discovery studies around this promising target.
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•The first structure of P. falciparum glucose-6-phosphate dehydrogenase is reported.•A key difference in the binding pocket of Plasmodium and human enzymes has been found.•A series of substrate analogs was designed as inhibitors of the Plasmodium enzyme.•They target selectively the Plasmodium enzyme with moderate potency and low toxicity.•The 3D structural model paves the way for the design of novel antimalarial drugs.
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We have synthesized a series of dimers of (+)-(7R,11R)-huprine Y and evaluated their activity against Trypanosoma brucei, Plasmodium falciparum, rat myoblast L6 cells and human ...acetylcholinesterase (hAChE), and their brain permeability. Most dimers have more potent and selective trypanocidal activity than huprine Y and are brain permeable, but they are devoid of antimalarial activity and remain active against hAChE. Lead optimization will focus on identifying compounds with a more favourable trypanocidal/anticholinesterase activity ratio.
The current pharmacological approach to Alzheimer's disease (AD) treatment, mostly based on acetylcholinesterase inhibitors (AChEIs), is being revisited, especially in terms of the temporal frames ...and the potential benefits of their noncanonic actions, raising the question of whether inhibitors of AChE might also act in a disease-modifying manner. Besides, in the last decades, the pharmacophoric moieties of known AChEIs have been covalently linked to other pharmacophores in the pursuit of multitarget hybrid molecules that are expected to induce long-lasting amelioration of impaired neurotransmission and clinical symptoms but also to exert disease-modifying effects. Our research consortium has synthesized and defined the pharmacological profile of new AChEIs derivatives of potential interest for the treatment of AD. Among these, huprines and derivatives have been characterized successfully. Huprine X, a reversible AChE inhibitor, designed by molecular hybridization of tacrine and huperzine A, has been shown to affect the amyloidogenic process in vitro, and the AD-related neuropathology in vivo in mice models of the disease. More recently, we have shown that a group of donepezil-huprine heterodimers exerts a highly potent and selective inhibitory action on AChE both in vitro and ex vivo, simultaneously interacting with both peripheral and catalytic binding sites, and inhibiting the β-amyloid aggregation, whereas some levetiracetam-huprine hybrids have been shown to reduce epileptiform activity, neuroinflammation and amyloid burden in an animal model of AD. Here, we summarize the behavioural correlates of these noncanonic actions as assessed in three distinct biological scenarios: middle-age, cognitive deficits associated with ageing and AD-like phenotype in mice. Besides the improvement in the hallmark cognitive symptomatology without inducing side effects, these drugs have shown to be able to modulate emotional and anxiety-like behaviours or to reduce spontaneous seizures, all of them related to the so-called 'behavioural and psychological symptoms of dementia'. Overall, the studies show that these novel multitarget anticholinesterasics exert noncanonic actions providing symptomatic and disease-modifying benefits of potential interest for the management of AD.
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