Escaping from Flatland: 3D Carborane-Based Bioisosteres of Erlotinib as Potential Anticancer Agents
Belén Dávila, Pablo Vignolo, Ignacio González, Nicole Lecot, Jenner Bonanata, María Fernanda García, Gustavo A. Echeverría, Oscar E. Piro, Hugo Cerecetto, Marcos Couto
Abstract
Phenyl rings are present in nearly 45% of approved small-molecule drugs; however, their flat, aromatic nature can lead to poor solubility, metabolic instability, and limited target selectivity. Carboranes, as three-dimensional boron-rich bioisosteres, may offer a promising alternative to address these limitations. Here, we report the design, synthesis, and biological characterization of novel carborane-based analogs of erlotinib, exploring 3D bioisosterism to enhance anticancer activity. All the carborane-based analogs displayed better in vitro biological behavior than the parent compound, with the para-derivatives (13) and (17) emerging as promising leads, showing 2.5 to >12-fold greater cytotoxicity than erlotinib and up to ∼7-fold selectivities for glioblastoma over astrocytes. Compound (17) moderately inhibited both wild-type EGFR (IC50 = 9.23 μM) and the drug-resistant EGFRT790M mutant (IC50 = 7.19 μM). Molecular docking and dynamics simulations predicted binding within the ATP catalytic site, displaying a hinge-binding mode characteristic of EGFR inhibitors. Mechanistic studies revealed apoptosis as the predominant cell death pathway. In vivo, compound (17) showed excellent acute oral safety (LD50 > 2000 mg/kg in mice) with no alterations in biochemical blood parameters. Ames testing indicated no mutagenic potential. In silico ADMET profiling predicted high intestinal absorption, absence of P-gp interaction, weak hERG inhibition, and no carcinogenicity, with only compounds (16) and (17) predicted to cross the blood–brain barrier. Chemical stability assays demonstrated that all compounds, except (18), were stable for 24 h under physiologically relevant pH conditions (2.0, 7.0, and 8.6). Overall, these findings position compound (17) as a promising lead for glioblastoma tumors. Despite modest biochemical potency, its strong cellular efficacy suggests additional mechanisms of action beyond direct EGFR inhibition. Future efforts will focus on kinome-wide profiling and transcriptomic analyses to elucidate its broader target spectrum and optimize this scaffold for clinical translation.