Monoamine oxidase B (MAO-B) is responsible for dopamine metabolism and plays a key role in oxidative stress by changing the redox state of neuronal and glial cells. To date, no disease-modifying therapy for Parkinson’s disease (PD) has been identified. However, MAO-B inhibitors have emerged as a viable therapeutic strategy for PD patients. Herein, a novel series of indole-based small molecules was synthesized as new MAO-B inhibitors with the potential to counteract the induced oxidative stress in PC12 cells. At a single dose concentration of 10 µM, 10 compounds out of 30 were able to inhibit MAO-B with more than 50%. Among them, compounds 7b, 8a, 8b, and 8e showed 84.1, 99.3, 99.4, and 89.6% inhibition over MAO-B and IC₅₀ values of 0.33, 0.02, 0.03, and 0.45 µM, respectively. When compared to the modest selectivity index of rasagiline (II, a well-known MAO-B inhibitor, SI > 50), compounds 7b, 8a, 8b and 8e showed remarkable selectivity indices (SI > 305, 3649, 3278, and 220, respectively). A further kinetic study displayed a competitive mode of action for 8a and 8b over MAO-B with Ki values of 10.34 and 6.63 nM. Molecular docking studies of the enzyme-inhibitor binding complexes in MAO-B revealed that free NH and substituted indole derivatives share a common favorable binding mode: H-bonding with a crucial water “anchor” and Tyr326. Whereas in MAO-A the compounds failed to form favorable interactions, which explained their high selectivity. In addition, compounds 7b, 8a, 8b, and 8e exhibited safe neurotoxicity profiles in PC12 cells and partially reversed 6-hydroxydopamine- and rotenone-induced cell death. Accordingly, we report compounds 7b, 8a, 8b, and 8e as novel promising leads that could be further exploited for their multi-targeted role in the development of a new oxidative stress-related PD therapy.

Recently, multitargeted drugs are considered a potential approach in treating cancer. In this study, twelve in-house indole-based derivatives were preliminary evaluated for their inhibitory activities over VEGFR-2, CDK-1/cyclin B and HER-2. Compound 15l showed the most inhibitory activities among the tested derivatives over CDK-1/cyclin B and HER-2. Compound 15l was tested for its selectivity in a small kinase panel. It showed dual selectivity for CDK-1/cyclin B and HER-2. Moreover, in vitro cytotoxicity assay was assessed for the selected series against nine NCI cell lines. Compound 15l showed the most potent inhibitory activities among the tested compounds. A deep in silico molecular docking study was conducted for compound 15l to identify the possible binding modes into CDK-1/cyclin B and HER-2. The docking results revealed that compound 15l displayed interesting binding modes with the key amino acids in the binding sites of both kinases. In vitro and in silico studies demonstrate the indole-based derivative 15l as a selective dual CDK-1 and HER-2 inhibitor. This emphasizes a new challenge in drug development strategies and signals a significant milestone for further structural and molecular optimization of these indole-based derivatives in order to achieve a drug-like property.

Although the sea ecosystem offers a broad range of bioactivities including anticancer, none of the FDA-approved antiproliferative protein kinase inhibitors are derived from a marine source. In a step to develop new marine-inspired potent kinase inhibitors with antiproliferative activities, a new series of hybrid small molecules (5a–5g) was designed and synthesized based on chemical moieties derived from two marine natural products (Meridianin E and Leucettamine B). Over a panel of 14 cancer-related kinases, a single dose of 10 µM of the parent hybrid 5a possessing the benzo[d][1,3]dioxole moiety of Leucettamine B was able to inhibit the activity of FMS, LCK, LYN, and DAPK1 kinases with 82.5 ± 0.6, 81.4 ± 0.6, 75.2 ± 0.0, and 55 ± 1.1%, respectively. Further optimization revealed the most potent multiple kinase inhibitor of this new series (5g) with IC₅₀ values of 110, 87.7, and 169 nM against FMS, LCK, and LYN kinases, respectively. Compared to imatinib (FDA-approved multiple kinase inhibitor), compound 5g was found to be ~ 9- and 2-fold more potent than imatinib over both FMS and LCK kinases, respectively. In silico docking simulation models of the synthesized compounds within the active site of FMS, LCK, LYN, and DAPK1 kinases offered reasonable explanations of the elicited biological activities. In an in vitro anticancer assay using a library of 60 cancer cell lines that include blood, lung, colon, CNS, skin, ovarian, renal, prostate, and breast cancers, it was found that compound 5g was able to suppress 60 and 70% of tumor growth in leukemia SR and renal RXF 393 cell lines, respectively. Moreover, an ADME study indicated a suitable profile of compound 5g concerning cell permeability and blood-brain barrier (BBB) impermeability, avoiding possible CNS side effects. Accordingly, compound 5g is reported as a potential lead towards novel antiproliferative marine-derived kinase modulators.

New quinazoline derivatives were designed based on the structural modification of the reported inhibitors to enhance their selectivity toward Aurora A. The synthesized compounds were tested over Aurora A, and a cytotoxicity assay was performed over NCI cell lines to select the best candidate for further evaluation. Compound 6e (2-(3-bromophenyl)-8-fluoroquinazoline-4-carboxylic acid) was the most potent compound among the tested derivatives. A Kinase panel assay was conducted for compound 6e over 14 kinases to evaluate its selectivity profile. Further cell cycle and apoptosis analysis were evaluated for compound 6e over the MCF-7 cell line at its IC₅₀ of 168.78 µM. It arrested the cell cycle at the G1 phase and induced apoptosis. Molecular docking was performed to explore the possible binding mode of compound 6e into the active site. It showed significant binding into the main pocket in addition to potential binding interactions with the key amino acid residues. Accordingly, compound 6e can be considered a potential lead for further structural and molecular optimization of the quinazoline-based carboxylic acid scaffold for Aurora A kinase selective inhibition with apoptosis properties.