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Casein Kinase 1 isoform δ (CK1δ) belongs to Protein Kinase (PK) superfamily and it is involved in several cellular processes and in neurodegenerative disorders including Alzheimer’s disease (AD), Parkinson’s disease (PD) and Amyotrophic Lateral Sclerosis (ALS). The PhD thesis is focused on the development of ATP-competitive CK1δ inhibitors by exploring heteroaromatic systems applying three main strategies: metabolic-based design, new scaffold development and molecular simplification approach. The first investigated scaffold involves the benzo[d]thiazole nucleus; Riluzole, approved drug for Amyotrophic Lateral Sclerosis (ALS), has proved to interact with the glutamatergic transmission even if the real mechanism of action is still unclear. The research group has experimentally demonstrated an activity of the candidate on CK1δ (IC50 = 16.1 μM) and to corroborate the hypothesis, since Riluzole underwent a strong hepatic metabolism, the N-hydroxylamine derivative was developed and assayed on the target obtaining an activity in the same range. Moreover, the hydrazine analogue appears as another appealing precursor. Therefore, a series of functionalized hydroxylamine and hydrazine derivatives have been developed introducing several types of alkyl and arylalkyl moieties to outline the SAR profile with encouraging results; the benzyl- and isopentyl-hydrazine derivatives proved to be the best of the series with IC50s of 1.62 μM and 0.92 μM, respectively. Moving to another heterocyclic system, a screening of in-house derivative allowed to develop a series of pyrazines exploring a new scaffold. The four positions of the system have been investigated obtaining promising results with two lead compounds reporting IC50s of 69 nM and 200 nM. Finally, starting from derivative 5-(7-amino-5-(benzylamino)-[1,2,4]triazolo[1,5-a][1,3,5]triazin-2-yl)benzen-1,3-diol that displayed activity of 180 nM, to simplify the synthetic approach and obtain a quicker and deepen SAR profile, a molecular simplification was applied. A series of 1,3,5-triazines was developed exploring several substituents even if the activities registered were in the high micromolar range. To obtain a hit compound, a molecular hybrid was achieved by combining the best derivative of the series (IC50 = 19.6 μM) and the 4-fluoro-1H-indazol-3-amine (IC50 = 24.9 μM) discovered in a fragment-based work. The hybrid displayed an activity of 3.86 μM confirming this strategy as challenging. For the most promising derivatives the CNS-prediction permeability was estimated as well as the ATP-competitive behavior. In conclusion, to validate the achieved results, a biological characterization was conducted exploring neuroprotective features as well as the decrease of phosphorylated TDP-43 (hallmark of ALS) via Western Blot analysis. Casein Kinase 1 isoform δ (CK1δ) belongs to Protein Kinase (PK) superfamily and it is involved in several cellular processes and in neurodegenerative disorders including Alzheimer’s disease (AD), Parkinson’s disease (PD) and Amyotrophic Lateral Sclerosis (ALS). The PhD thesis is focused on the development of ATP-competitive CK1δ inhibitors by exploring heteroaromatic systems applying three main strategies: metabolic-based design, new scaffold development and molecular simplification approach. The first investigated scaffold involves the benzo[d]thiazole nucleus; Riluzole, approved drug for Amyotrophic Lateral Sclerosis (ALS), has proved to interact with the glutamatergic transmission even if the real mechanism of action is still unclear. The research group has experimentally demonstrated an activity of the candidate on CK1δ (IC50 = 16.1 μM) and to corroborate the hypothesis, since Riluzole underwent a strong hepatic metabolism, the N-hydroxylamine derivative was developed and assayed on the target obtaining an activity in the same range. Moreover, the hydrazine analogue appears as another appealing precursor. Therefore, a series of functionalized hydroxylamine and hydrazine derivatives have been developed introducing several types of alkyl and arylalkyl moieties to outline the SAR profile with encouraging results; the benzyl- and isopentyl-hydrazine derivatives proved to be the best of the series with IC50s of 1.62 μM and 0.92 μM, respectively. Moving to another heterocyclic system, a screening of in-house derivative allowed to develop a series of pyrazines exploring a new scaffold. The four positions of the system have been investigated obtaining promising results with two lead compounds reporting IC50s of 69 nM and 200 nM. Finally, starting from derivative 5-(7-amino-5-(benzylamino)-[1,2,4]triazolo[1,5-a][1,3,5]triazin-2-yl)benzen-1,3-diol that displayed activity of 180 nM, to simplify the synthetic approach and obtain a quicker and deepen SAR profile, a molecular simplification was applied. A series of 1,3,5-triazines was developed exploring several substituents even if the activities registered were in the high micromolar range. To obtain a hit compound, a molecular hybrid was achieved by combining the best derivative of the series (IC50 = 19.6 μM) and the 4-fluoro-1H-indazol-3-amine (IC50 = 24.9 μM) discovered in a fragment-based work. The hybrid displayed an activity of 3.86 μM confirming this strategy as challenging. For the most promising derivatives the CNS-prediction permeability was estimated as well as the ATP-competitive behavior. In conclusion, to validate the achieved results, a biological characterization was conducted exploring neuroprotective features as well as the decrease of phosphorylated TDP-43 (hallmark of ALS) via Western Blot analysis.

Background:GSK-3β activity has been strictly related to neuroinflammation and neurodegeneration. Alzheimer’s disease is the most studied neurodegenerative disease, but GSK-3β seems to be involved in almost all neurodegenerative diseases, including Parkinson’s disease, amyotrophic lateral sclerosis, frontotemporal dementia, Huntington’s disease, and the autoimmune disease multiple sclerosis.Objective:This review aims to help researchers both working on this research topic or not to have a comprehensive overview of GSK-3β in the context of neuroinflammation and neurodegeneration.Method:Literature has been searched using PubMed and SciFinder databases by inserting specific keywords. A total of more than 500 articles have been discussed.Results:First of all, the structure and regulation of the kinase were briefly discussed, and then, specific GSK-3β implications in neuroinflammation and neurodegenerative diseases were illustrated with the help of figures, to conclude with a comprehensive overview on the most important GSK-3β and multitarget inhibitors. The structure and IC50 values at the target kinase have been reported for all the discussed compounds.Conclusion:GSK-3β is involved in several signaling pathways in neurons, glial cells and immune cells. The fine regulation and interconnection of all these pathways are at the base of the rationale use of GSK-3β inhibitors in neuroinflammation and neurodegeneration. Some compounds are now under clinical trials. Despite this, the compounds’ pharmacodynamic and ADME/Tox profiles were often not fully characterized which is deleterious in such a complex system.