IC50 value: 8.7 pIC50 
Target: 5-HT2A agonist
in vitro: ACP-103 competitively antagonized the binding of [(3)H]ketanserin to heterologously expressed human 5-HT(2A) receptors with a mean pK(i) of 9.3 in membranes and 9.70 in whole cells. ACP-103 displayed potent inverse agonist activity in the cell-based functional assay receptor selection and amplification technology (R-SAT), with a mean pIC(50) of 8.7. ACP-103 demonstrated lesser affinity (mean pK(i) of 8.80 in membranes and 8.00 in whole cells, as determined by radioligand binding) and potency as an inverse agonist (mean pIC(50) 7.1 in R-SAT) at human 5-HT(2C) receptors, and lacked affinity and functional activity at 5-HT(2B) receptors, dopamine D(2) receptors, and other human monoaminergic receptors.
in vivo: ACP-103 attenuated head-twitch behavior (3 mg/kg p.o.), and prepulse inhibition deficits (1-10 mg/kg s.c.) induced by the 5-HT(2A) receptor agonist (+/-)-2,5-dimethoxy-4-iodoamphetamine hydrochloride in rats and reduced the hyperactivity induced in mice by the N-methyl-d-aspartate receptor noncompetitive antagonist 5H-dibenzo[a,d]cyclohepten-5,10-imine (dizocilpine maleate; MK-801) (0.1 and 0.3 mg/kg s.c.; 3 mg/kg p.o.), consistent with a 5-HT(2A) receptor mechanism of action in vivo and antipsychotic-like efficacy . Single doses of ACP-103 (20-300 mg) resulted in dose-proportionate mean C(max) values (9-152 ng/mL) and AUC(0-infinity) (706-10 798 h x ng/mL), and multiple doses (50-150 mg) resulted in dose-proportionate mean C(max,ss) (93-248 ng/mL) and AUC(0-infinity,ss) (1839-4680 h x ng/mL). The half-life of ACP-103 was approximately 55 hours, with a t(max) at 6 hours. ACP-103 reduced tacrine-induced tremulous jaw movements in rats. In addition, ACP-103 administered in combination with levodopa caused a dose-related reduction in dyskinesias in monkeys.