Targeting melanoma resistance: Novel oxindole and non-oxindole-based benzimidazole derivatives as potent dual inhibitors of BRAF and ABL2 kinases.

Melanoma is one of the deadliest forms of cancer. The disease is incurable for many due to its aggressive, metastatic characteristics and its elevated resistance. Herein, we design and synthesize two series of target compounds oxindole-based (7a-h) and non-oxindole-based (8a-h) benzimidazole. Selected compounds were evaluated against mutant BRAF and ABL2 kinases upon evaluating for anti-tumor efficacy against a preliminary 60-tumor cell line panel at NCI, USA. The NCI selected six compounds (7c, 7d, 7g, 7h, 8b, and 8h) for evaluation at five doses. Compounds 8b and 8h exhibited the highest cytotoxic potency against SK-MEL-5 with IC = 1.00 and 0.54 μM, respectively. Compounds 7c and 8h were the most potent to inhibit BRAF with IC = 0.072 and 0.088 μM, respectively. While compounds 7c and 8b showed the most potent inhibitory activity against ABL2 kinases (IC = 0.143 and 0.236 μM, respectively). Compound 8h diminished P-glycoprotein expression by 0.2732. Molecular docking findings showed that compound 8b exhibits the highest binding affinity for the ABL2 kinase enzyme. Cytotoxicity assays in resistant melanoma cells showed IC values of 12.3 μM (A375) and 20.1 μM (A375-R), demonstrating potency comparable to vemurafenib. Western blot analysis showed that 8h effectively inhibited p-CrkL (Abl2 signaling) and p-ERK1/2 (BRAF pathway) in A375-R melanoma cells. Compounds 8h, 7c, and 8b demonstrated the highest binding affinities for BRAF. Compound 8h causes cell cycle arrest at the G1 phase, inhibiting progression to the S phase and subsequent phases (28.55 % compared to 39.02 %) and G2/M phase (13.33 % compared to 16.35 %). Furthermore, the apoptotic efficacy of 8h demonstrated a significant increase in the percentage of late apoptotic cells, reaching 13.89 % in treated cells, in contrast to 0.15 % in untreated cells. In Silico ADME profiling indicated that the proposed compounds are suitable drug candidates.