The naphtosultam derivative RP 62203 (fananserin) has high affinity for the dopamine D4 receptor

The dopamine D4 receptor is a potential target for novel antipsychotic drugs. Most available compounds with affinity for the dopamine D4 receptor also bind to dopamine D2 receptors. This report describe the affinity of the 5-HT2A receptor antagonist RP 62203 (fananserin) for the human dopamine D4 receptor. Fananserin displaces [3H]spiperone binding to recombinant human dopamine D4 receptors with a Ki of 2.93 nM. This compares with an affinity (Ki) of 0.37 nM for the rat 5-HT2A receptor and of 726 mM for the rat dopamine D2 receptor. [3H]Fananserin can be used to label the recombinant dopamine D4 receptor expressed in Chinese hamster ovary cells with a KD of 0.725 nM. Fananserin is, thus, the first compound to be reported that distinguishes between dopamine D4 and D2 receptors.