Alzheimer's disease is a chronic progressive neurodegenerative disease in which the signs of dementia are prominent and, in addition to cognitive disorders, disease is also accompanied by neuropsychiatric symptoms. The etiology of the disease is not yet fully understood, but the possible causes and processes of Alzheimer's disease are associated with senile plaques, neurofibrillary tangles, disturbed cholinergic transmission, neuroinflammation and oxidative stress. Current therapeutic approaches for the treatment of Alzheimer's disease include acetylcholinesterase inhibitors, inhibitors of N-methyl-D-aspartate receptors and anti-amyloid-beta antibodies. Registered active substances are primarily used to slow down the decline in quality of life and do not affect the disease process. Because of that there is a need to find and synthesize improved active substances for the treatment of Alzheimer's disease.
Butyrylcholinesterase, whose enzyme activity is increased in the brains of patients with Alzheimer's disease, and mitogen-activated protein kinase p38α, which contribute to neuroinflammation and apoptosis of neurons, microglia and astrocytes, are potential targets for the treatment of the disease. Therefore, in our master's thesis, we synthesized four new dual inhibitors of butyrylcholinesterase and mitogen-activated protein kinase p38α. We started from the already known compound ARRY-371797, which has an inhibitory effect on both enzymes. We kept the central 5,6-disubstituted indazole skeleton, whereby the substituent in position 5 was always represented by a 2,4-difluorophenoxy group, which we predict forms pi-pi interactions in the acyl-binding pocket of butyrylcholinesterase and favorably occupies the hydrophobic region I of p38α. The N-(2-(dimethylamino)ethyl)amide substituent was retained in position 6, which is predicted to form strong cation-pi interactions with Trp82 of the choline-binding pocket of butyrylcholinesterase, and in the active site of p38α, it is expected to be directed towards the solvent and thus would not interfere with ligand binding to the ATP-binding site. In order to achieve a stronger inhibitory effect on both targets and to study the influence of different alkyl chains on the activity of the molecule, we replaced the isobutyl group at position 1 of the indazole ring with other alkyl chains. Using the Ellman method and the ADP-Glo test, we evaluated the synthesized compounds 7A-E and found that compound 7D with an isopentyl alkyl chain most strongly inhibits the BChE enzyme, and the strongest inhibitory effect on p38α MAPK was achieved with compound 7E, in which cyclohexene most likely additionally rigidifies the structure of the compound and occupies the best position in the active site of the enzyme. The inhibitory activity of compound 7E (IC50 = 87,6 nM) was even better that activity of ARRY-371797 on mitogen-activated protein kinase p38α. We achieved selectivity for butyrylcholinesterase compared to acetylcholinesterase and effective inhibitory action on mitogen-activated protein kinase p38α which represents an important starting point for the further development of agents for the treatment of AD.
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