Design, Synthesis, and Antiproliferative Activity of New 5-Chloro-indole-2-carboxylate and Pyrrolo[3,4- b]indol-3-one Derivatives as Potent Inhibitors of EGFR^T790M/BRAF^V600E Pathways

Mutant EGFR/BRAF pathways are thought to be crucial targets for the development of anticancer drugs since they are over-activated in several malignancies. We present here the development of a novel series of 5-chloro-indole-2-carboxylate 3a-e, 4a-c and pyrrolo[3,4-b]indol-3-ones 5a-c derivatives as potent inhibitors of mutant EGFR/BRAF pathways with antiproliferative activity. The cell viability assay results of 3a-e, 4a-c, and 5a-c revealed that none of the compounds tested were cytotoxic, and that the majority of those tested at 50 µM had cell viability levels greater than 87%. Compounds 3a-e, 4a-c, and 5a-c had significant antiproliferative activity with GI₅₀ values ranging from 29 nM to 78 nM, with 3a-e outperforming 4a-c and 5a-c in their inhibitory actions against the tested cancer cell lines. Compounds 3a-e were tested for EGFR inhibition, with IC₅₀ values ranging from 68 nM to 89 nM. The most potent derivative was found to be the m-piperidinyl derivative 3e (R = m-piperidin-1-yl), with an IC₅₀ value of 68 nM, which was 1.2-fold more potent than erlotinib (IC₅₀ = 80 nM). Interestingly, all the tested compounds 3a-e had higher anti-BRAF^V600E activity than the reference erlotinib but were less potent than vemurafenib, with compound 3e having the most potent activity. Moreover, compounds 3b and 3e showed an 8-fold selectivity index toward EGFR^T790M protein over wild-type. Additionally, molecular docking of 3a and 3b against BRAF^V600E and EGFR^T790M enzymes revealed high binding affinity and active site interactions compared to the co-crystalized ligands. The pharmacokinetics properties (ADME) of 3a-e revealed safety and good pharmacokinetic profile.