Intensive Chemotherapy Induces Cardiotoxicity via Reverse Electron Transport

Chemotherapy-induced cardiotoxicity has emerged as an important focus in oncology, driven by the growing number of cancer survivors. Intensive chemotherapies (iCT) used in the treatment of acute myeloid leukemia (AML) often lead to significant adverse cardiac events, which can reduce therapeutic benefits, limit treatment options, or even necessitate discontinuation--particularly for patients with pre-existing cardiac conditions, resulting in a loss of therapeutic opportunity. This study shows that the iCT triggers severe mitochondrial dysfunction in cardiac tissue, mirroring effects seen in ischemia-reperfusion models. Specifically, iCT results in succinate accumulation and elevated reactive oxygen species production, consistent with reverse electron transport phenomenon. Importantly, these effects were entirely prevented with RET inhibitors such as malonate or S1QEL1.1. In vivo, we demonstrate that malonate administration successfully prevents iCT-induced cardiotoxicity, maintaining left ventricular ejection fraction and fibrosis levels comparable to controls. Additionally, in an MLL-AF9-driven AML model, malonate sensitized leukemic cells to iCT. These findings support the dual potential of malonate: as an OXPHOS metabolism inhibitor to overcome chemoresistance in AML, while also reducing cardiotoxic risk for already vulnerable patients. One Sentence Summary: This study demonstrates that malonate prevents chemotherapy-induced cardiotoxicity by inhibiting mitochondrial reverse electron transport (RET), preserving cardiac function, and simultaneously sensitizing AML cells to intensive chemotherapy.