pede4dPharmacological phosphodiesterase 4D (PDE4D) inhibition shows therapeutic potential to restore memory function in Alzheimer's disease (AD), but will likely evoke adverse side effects. AsThe goal of this study was to determine whether a phosphodiesterase-4D (PDE4D) allosteric inhibitor (BPN14770) would improve cognitive function and behavioral outes in patients with fragile X