These novel LIMK inhibitors significantlydecrease p-cofilin in Fmr1 KO mice and in stem cell-derivedcortical neurons from FXS patients, thereby 85 representsa superior tool compound in vitro and in vivo to explore LIMK biologyin addition to potential treatment of LIMK pathologies such as FXS. The gene discussed is CFL1; the disease is fragile X syndrome.