Potent Cyclic Peptide Inhibitors Disrupt the FANCM–RMI Interaction

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.