Synthetic Epoxy–Phenanthridine–Triazole Conjugates Induce Dual Redox Imbalance and Metabolic Remodeling in Breast Cancer Cells: An Integrative Mechanistic Evaluation from Synthesis to Mitochondrial Collapse

Because of resistance and the absence of effective targeted therapies, breast cancer, particularly the hormone receptor-positive (HR+) and triple-negative breast cancer (TNBC) types, presents significant therapeutic problems. One promising therapeutic approach is to target the redox vulnerabilities of cancer cells. In this work, new epoxy-functionalized phenanthridine–triazole conjugates (RM58, RM60, RM61, and RM75) are evaluated as dual redox modulators in models of breast cancer. Using molecular docking and molecular dynamics simulations (100 ns) against a panel of 14 potential protein targets linked to breast cancer, these compounds are shown to have high affinity and stable binding to important redox-regulatory proteins, such as glutathione S-transferase and thioredoxin. Dose-dependent cytotoxicity was demonstrated in vitro in MCF-7 (HR+) and MDA-MB-231 (TNBC) cell lines, with RM75 and RM60 showing the strongest effects. According to mechanistic research, these substances cause oxidative stress overload by causing a considerable buildup of intracellular reactive oxygen species and the depletion of glutathione and thioredoxin. Specifically in the TNBC model, this redox imbalance led to robust caspase-3/7-mediated apoptosis, loss of membrane potential, and mitochondrial dysfunction. Untargeted LC–MS/MS metabolomic profiling revealed clear metabolic reprogramming, with significant changes found in the pathways. These findings show that a sequence of metabolic alterations and cellular apoptosis is induced by the dual disruption of antioxidant defenses. These integrative results suggest that antioxidant disruption by epoxy–phenanthridine conjugates leads to metabolic collapse and apoptosis, highlighting RM75 as a promising redox-active lead. However, in vivo efficacy, pharmacokinetics, and safety studies are needed to advance this scaffold toward clinical evaluation.