Impaired mitochondrial metabolism is a critical cancer vulnerability for MYC inhibitors.

MYC is a key driver in many aggressive and therapy-resistant cancers. We have developed and characterized a small-molecule MYC inhibitor named MYCi975. To uncover combination strategies for MYC inhibitors, we conducted a genome-wide CRISPR screen using MYCi975. This screen revealed a notable synthetic lethality when MYC inhibition was paired with disruption of mitochondrial complex I components, but not other complexes. Mechanistically, MYC inhibition reduced oxidative phosphorylation and glycolysis, triggering a compensatory up-regulation of complex I genes. Consequently, genetic or pharmacological targeting of complex I sensitized tumors to MYCi975 treatment, leading to increased purine catabolism and infiltration of CD8 T cells and macrophages into tumors. Additionally, a wide range of tumor cells with lower complex I expression showed increased MYC dependency. These results indicate that metabolic adaptation to MYC inhibition exposes a targetable weakness at complex I and provide a rational strategy for combination therapy with emerging MYC inhibitors.