– MS31 trihydrochloride is a selective, high-affinity, fragment-like inhibitor of the methyl-lysine read-write protein spindlin 1 (SPIN1). MS31 trihydrochloride effectively disrupts the interaction of SPIN1 with H3K4me3 protein (IC50: 77 nM, AlphaLISA; 243 nM, FP). MS31 trihydrochloride effectively inhibits the binding of trimethyl lysine containing peptides to SPIN1 and is not toxic to non-tumorigenic cells.