CK1δ is a serine-threonine kinase involved in several pathological conditions including neuroinflammation and neurodegenerative disorders like Alzheimer's disease, Parkinson's disease, and Amyotrophic Lateral Sclerosis. Specifically, it seems that an inhibition of CK1δ could have a neuroprotective effect in these conditions. Here, a series of [1,2,4]triazolo[1,5-a][1,3,5]triazines were developed as ATP-competitive CK1δ inhibitors. Both positions 2 and 5 have been explored leading to a total of ten compounds exhibiting IC₅₀s comprised between 29.1 µM and 2.08 µM. Three of the four most potent compounds (IC₅₀ < 3 µM) bear a thiophene ring at the 2 position. All compounds have been submitted to computational studies that identified the chain composed of at least 2 atoms (e.g., nitrogen and carbon atoms) at the 5 position as crucial to determine a key bidentate hydrogen bond with Leu85 of CK1δ. Most potent compounds have been tested in vitro, resulting passively permeable to the blood-brain barrier and, safe and slight neuroprotective on a neuronal cell model. These results encourage to further structural optimize the series to obtain more potent CK1δ inhibitors as possible neuroprotective agents to be tested on models of the above-mentioned neurodegenerative diseases.

Protein kinase CK1δ (CK1δ) is a serine-threonine/kinase that modulates different physiological processes, including the cell cycle, DNA repair, and apoptosis. CK1δ overexpression, and the consequent hyperphosphorylation of specific proteins, can lead to sleep disorders, cancer, and neurodegenerative diseases. CK1δ inhibitors showed anticancer properties as well as neuroprotective effects in cellular and animal models of Parkinson’s and Alzheimer’s diseases and amyotrophic lateral sclerosis. To obtain new ATP-competitive CK1δ inhibitors, three sets of benzimidazole-2-amino derivatives were synthesized (1–32), bearing different substituents on the fused benzo ring (R) and diverse pyrazole-containing acyl moieties on the 2-amino group. The best-performing derivatives were those featuring the (1H-pyrazol-3-yl)-acetyl moiety on the benzimidazol-2-amino scaffold (13–32), which showed CK1δ inhibitor activity in the low micromolar range. Among the R substituents, 5-cyano was the most advantageous, leading to a compound endowed with nanomolar potency (23, IC₅₀ = 98.6 nM). Molecular docking and dynamics studies were performed to point out the inhibitor–kinase interactions.

Background/Objective: Casein kinase 1δ (CK1δ) plays a central role in regulating circadian rhythms, DNA repair, apoptosis, and cell proliferation, and its dysregulation is associated with both cancer and neurodegenerative diseases, making CK1δ an attractive therapeutic target. This study aimed to develop novel CK1δ inhibitors with favourable drug-like properties through the synthesis and biological evaluation of benzimidazol-2-acetamide derivatives. Methods: A novel series of benzimidazol-2-acetamide derivatives was synthesized, incorporating different substituents on the benzimidazole core (5-chloro, 5,6-dichloro, 5-nitro, and 5-cyano) and various saturated cyclic amines on the acetamide moiety. Compounds were evaluated for CK1δ inhibitory activity, while molecular docking and molecular dynamics simulations were performed to investigate their binding mode. In silico ADME predictions assessed pharmacokinetic properties, and cytotoxicity was evaluated in SH-SY5Y neuroblastoma cells. Results: The 5,6-dichloro derivatives 20 and 24, bearing piperidin-4-ylmethanamine and morpholine moieties, respectively, displayed the highest CK1δ inhibitory activity (IC₅₀ = 0.172 and 0.223 μM). The 5-cyano analogue 22 also exhibited a good potency (IC₅₀ = 0.224 μM). Computational studies confirmed an ATP-competitive binding mode and highlighted the dynamic behaviour of the solvent-exposed substituents within the CK1δ binding site. Predicted pharmacokinetic properties suggested favourable oral absorption and blood–brain barrier penetration. Compounds 20, 22, and 24 showed no cytotoxicity in SH-SY5Y cells at concentrations up to 10 μM. Conclusions: The new benzimidazol-2-acetamide derivatives exhibited good inhibitor activity against CK1δ, favourable predicted ADME properties, and low cellular toxicity. The combined experimental and computational findings provide valuable insights for the further optimization of this scaffold toward the development of therapeutics for CK1δ-related diseases.