The synthesis and structure–activity relationship (SAR) of a novel series of aryl piperazine napthyridinone D2 partial agonists is described. Our goal was to optimize the affinities for the D2, 5-HT2A and 5-HT1A receptors, such that the D2/5-HT2A ratio was greater than 5 to ensure maximal occupancy of these receptors when the D2 occupancy reached efficacious levels. This strategy led to identification of PF-00217830 (2) with robust inhibition of sLMA ...