In addition to AC1 and AC8, the original hit and four prioritized analogs were also tested against two other AC sub-families represented by AC2 and AC5. AC2 is a member of the group II subfamily and is conditionally activated by G subunits. AC5 is a group III sub-family enzyme and is inhibited by Ca 2+ . It was found that when AC2 is activated by PMA that the scaffold generally potentiates AC2 activity by up to 50%, although analog 38 displayed the relatively little potentiation. This phenomenon has been previously observed for other AC1 inhibitors reported by our group and at this point it is difficult to posit what this may mean physiologically, if anything, as there is very little understood about AC2 activity in vivo. AC2 is expressed in the brain, lung, skeletal muscle and heart yet there is very little understood about its physiological function and a lack of animal knockout models and selective inhibitors has kept the function elusive. As for AC5 activity the scaffold appeared to have no modulatory effects against this enzyme that differed from the DMSO-treated controls. Therefore, the pyrimidinone scaffold appears to be selective for targeting AC1 over other isoforms.