ABSTRACT

FANCM–RMI is a protein–protein interaction that maintains genome stability during DNA repair events in cancers that rely on the Alternative Lengthening of Telomeres (ALT) pathway for survival. We report the first valid chemical inhibitors of the FANCM–RMI interaction discovered by screening cyclic peptides via mRNA display. These inhibitors engage the FANCM-binding pocket of RMI1/2 with nanomolar affinity (KD = 2–10 nM) and are potent disruptors of the FANCM–RMI interaction (IC50 = 54–104 nM). X-ray crystallography and alanine scanning reveal novel binding modes and interactions between the cyclic peptides and RMI1/2 that drive high-potency inhibition. Co-immunoprecipitation studies confirm the complete disruption of the native interaction in whole osteosarcoma cell lysates. These inhibitors represent the first validated RMI binders toward developing chemical tools for interrogating the mechanistic roles of FANCM–RMI in mediating genome stability and provide a much-anticipated starting point to accelerate the development of FANCM–RMI inhibitors for intervention against ALT-driven cancers.

Alcock, L. J., T. Gao, R. Bythell-Douglas, J. Gao, H. Krishna Sudhakar, T. Huang, R. Young, Q. N. Vu, C. Deshpande, L. E. Wilkinson-White, and 4 more contributors. 2025. Potent Cyclic Peptide Inhibitors Disrupt the FANCM-RMI Interaction.AJournal of Medicinal Chemistry 68 (12): 12615-12625.

ABSTRACT

The FANCM-RMI protein–protein interaction plays an essential role in cancers that extend their telomeres through the Alternative Lengthening of Telomeres (ALT) pathway. Here, we report the first cell-active peptide inhibitors of FANCM-RMI. Screening of mRNA-displayed peptide libraries treated with trans-1,4-dibromo-2-butene led to the discovery of both linear and cyclic peptide hits that bind RMI at the FANCM interaction site. The most potent peptides engage RMI with nanomolar affinity (KD = 4–31 nM) and outcompete the native peptide mimic of FANCM (IC50 = 24–155 nM). A bound X-ray crystal structure of the top hit revealed novel interactions at the RMI binding site that were not found in the native interaction. Conjugation to a cell-penetrating peptide resulted in inhibitors that induced an antiproliferative effect in ALT-positive osteosarcoma cell lines. These inhibitors represent the first bioactive RMI binders that can be used as chemical tools for studying the involvement of FANCM-RMI in ALT-driven cancers.

Alcock, L. J., J. Mills, R. Bythell-Douglas, H. Krishna Sudhakar, C. Deshpande, T. Passioura, A. J. Deans, and Y. H. Lau. 2025. Cell-Active Peptide Inhibitors of the FANCM-RMI Interaction.Journal of Medicinal Chemistry 68 (22): 24672-24683.