YM348 has high affinity for cloned human 5-HT _2C receptors with a K _i value of 0.89 nM and lower affinities for human-cloned 5-HT _2B (K _i : 2.5 nM) and 5-HT _2A receptors (K _i : 13 nM). To assess the binding specificity of YM348, a broad evaluation of an additional 46 binding sites including several other 5-HT receptor subtypes (1A, 1B, 1D, 3, 4, 5A, 6, 7) is performed. IC ₅₀ values of YM348 are found to be >1 μM for all of the binding sites except for the human 5-HT _1A receptors (K _i : 130 nM), bovine 5-HT _1D receptors (K _i : 481 nM), human 5-HT ₇ receptors (K _i : 177 nM), and human α _2A receptors (K _i : 126 nM).YM348 exhibits a full-agonistic activity on human 5-HT _2A and 5-HT _2B receptors. The EC ₅₀ values of YM348 for 5-HT _2C , 5-HT _2A , and 5-HT _2B receptors are 1.0, 93 and 3.2 nM, respectively.

Oral administration of YM348 induces penile erections and hypolocomotion in rats, being completely inhibited by a selective 5-HT _2C receptor antagonist, SB242084. YM348 inhibits spontaneous activity in a dose-dependent manner with a minimum effective dose of 0.203 mg/kg.