Click strategies for multifunctional anti-Alzheimer agents – Multi-click

Alzheimer Disease is a multifaceted illness requiring the combination of synergetic treatment strategies. We have thus chosen to use new click reactions to prepare new multi-target directed ligands (MTDLs) that will act simultaneously on the different players in AD pathology and, thereby, will allow a more efficient treatment of AD. The MTDLs prepared during this project combine at least two functionalities, among which acetylcholinesterase (AChE) inhibition, an action against Abeta aggregation, anti-oxidative properties, BACE-1 inhibition, GSK-3 beta inhibition or alpha 7 nAChR activation.

The MTDLs prepared during this project combine at least two functionalities, among which acetylcholinesterase (AChE) inhibition, an action against Abeta aggregation, anti-oxidative properties, BACE-1 inhibition, GSK-3 beta inhibition or alpha 7 nAChR activation. Several series of pharmacophores conveniently functionalized with a linker bearing a reactive function (e.g. azide or alkyne) have been prepared, and the desired MTDLs have been assembled using Huisgen cycloaddition. Some of the prepared MTDLs showed promising in vitro results for the inhibitions of enzymes and receptors involved in the neurodegenerative diseases (e.g alpha 7 nicotinic receptors and kinases GSK-3). Moreover, selective and sensitive near-infrared fluorescent probes for acetylcholinesterase have been developed through the same click strategy,during this project, with the final goal to use this biomarker for the evaluation of AD progression in vivo.
New click reaction such as irreversible Kondrat'Eva hetro-Diels-Alder cycloaddition has been sucessfully applied to bioconjugate reaction, but its application to in situ click chemistry on BACE-1 failed. Aldolisation reaction gave also deceptive results in in situ click chemistry. despite promising preliminary results, application of amidation reaction was given up, since its application was in the mean-time published by another group.

Selective and sensitive near-infrared fluorescent probes for acetylcholinesterase which have been developed during this project are presently used by two academic laboratoiries in Marseille and in denemark. New internationals collaborations have been initiated during this project, with Pr Marco Catto (Bari, Italy), and Pr Ye-Chun Xu (Shanghai Institute of Materia Medica, Shanghai, China).. A new project of multi-target directed ligands will be submitted to obtain a PhD fellowship through the Vinci program (Université Franco-Italienne), and a program PHC “Galilée” in collaboration with Pr. Marco Catto in Bari (Italy) will be submitted in January 2018

14 intern,ational publications and one patent. Further publications remain to be done,, since we are awaiting for the biological results of the synthezized compounds.

The objective of this project is to evaluate new "click" reactions adaptable to kinetic target guided synthesis (TGS), such as described by K. B. Sharpless et al. ten years ago. In situ click chemistry has indeed proven to be a new and elegant paradigm for drug discovery. Based on our successful experience on the use of Huisgen cycloaddition on human acetycholinesterase (AChE), which allowed us to estimate scopes and limitations of this reaction, four new reactions will be targeted, namely the “Aubé”, “Pictet-Spengler” and “carbonyle-ène” reactions, as well as the “Kondrat' Eva's“ cycloaddition for which we already have obtained encouraging preliminary results.
Our ultimate goal is to exploit these reactions to produce molecules that will aid fighting Alzheimer's disease (AD). AD is a neurodegenerative process occurring in the central nervous system (CNS). It is the most common cause of dementia in elderly. It is clinically characterized by a loss of memory and cognition, associated to a deterioration of the basal-forebrain cholinergic-neurons network and a consequent lack of acetylcholine (ACh) around brain cells. While the process leading to the development of AD is complex and multifactorial, and the etiology of AD is not completely known, it is nowadays clear that AD is a multifaceted illness requiring the combination of synergetic treatment strategies. Although several research strategies have been envisaged in the last decades, these molecules only alleviate the symptoms of the illness, and do not cure it. The current view of AD physiopathology is indeed that its onset and progression are the result of a complex network of genetic predispositions, enzymatic activities, receptors expression, protein interactions, alteration of metal concentrations, cell cycle survival disruption, ion homeostasis dysregulation, protein misfolding, etc. The “multifactorial hypothesis” led to the proposal that the multi-target-directed ligands strategy is needed to treat the disease more efficiently. The first objective in this project will, therefore, be to use the classical Huisgen reaction as well as the above-mentioned, newly-developed click reactions, so as to prepare new multi-target directed ligands (MTDLs) that will act simultaneously on the different players in AD pathology and, thereby, allow a more efficient treatment of the disease. The envisaged MTDLs should combine at least two functionalities, among which acetylcholinesterase (AChE) inhibition, an action against Abeta aggregation, anti-oxidative properties, BACE-1 inhibition, GSK-3 beta inhibition or alpha 7 nAChR activation. The second objective of the project is to use the more complex in situ click chemistry approach for the discovery of potent MTDLs. It is using this methodology, also coined kinetic target guided synthesis (TGS), that Sharpless et al. indeed obtained the most potent AChE inhibitors with a femtomolar inhibitory activity. As for our first objective, we will expand the toolkit of click-reactions beyond the classical Huisgen reaction, so as to produce a wider diversity of possible ligands. Additionally, and based on our already-existing know-how, we will expand the in situ click chemistry to another enzyme involved in AD, viz. BACE-1, which is one of the two enzymes involved in the proteolytic release of the amyloid-beta peptide.