PF-2545920 a highly selective and potent PDE10A inhibitor with an IC50 of 0.37 nM. The PDE10A enzyme is expressed primarily in the brain, mostly in the striatum, nucleus accumbens and olfactory tubercle, and is thought to be particularly important in regulating the activity of dopamine-sensitive medium spiny neurons in the striatum which are known to be targets of conventional antipsychotic agents. n the conditioned avoidance response assay (CAR), PF-2545920 was active with an ED50 of 1 mg/kg. Administration of PF-2545920 to mice caused a dose dependent increase in striatal cGMP.