Vabicaserin hydrochloride (SCA 136) is a selective agonist of 5-hydroxytryptamine 2C (5-HT2C) receptor (EC50: 8 nM).

5-HT2C:8 nM (EC50)

In Chinese hamster ovary cell membranes, Vabicaserin displaces 125I-(2,5-dimethoxy)phenylisopropylamine binding from human 5-HT2C receptor sites (Ki: 3 nM) and is >50-fold selective over a number of serotonergic, noradrenergic, and dopaminergic receptors. The binding affinity determined for the human 5-HT2B receptor subtype using [3H]5HT is 14 nM. Vabicaserin is a potent and full agonist (EC50, 8 nM; Emax, 100%) in stimulating 5-HT2C receptor-coupled calcium mobilization and exhibits 5-HT2A receptor antagonism and 5-HT2B antagonist or partial agonist activity in transfected cells, depending on the level of receptor expression. Vabicaserin showed a lower affinity at the binding site (22 nM) of 5-HT2C antagonist labeled with [3H]methsulamide. Other binding studies have shown that Vabicaserin has an affinity for 5-HT2B and 5-HT1A receptors with Ki values of 14 and 112 nM, respectively [1].

The unchanged drug represents less than 19, 20, and 35% of total plasma radioactivity at all the time points examined in mice, rats, and dogs, respectively, after a single oral dose of [14C]Vabicaserin at 50, 5, and 15 mg/kg. The carbamoyl glucuronide (CG) represents approximately 7 to 36% of plasma radioactivity in mice and 2 to 28% of plasma radioactivity in dogs but is not detected in rat plasma after the single [14C]Vabicaserin dose. However, the CG is observed in rat plasma after multiple-dose administration of Vabicaserin at higher doses, and the CG is approximately 20 times less than Vabicaserin based on steady-state AUC0-24 values. The estimated plasma AUC0-24 ratios of CG to the parent drug are 1.5 and 1.7 in mice and dogs after the single [14C]Vabicaserin dose, respectively. The plasma AUC0-24 ratios for the CG to Vabicaserin at steady-state with doses used for safety assessment are less for mice (0.2-0.6) and slightly higher for dogs (1.8-4.0) compared with the single-dose values. The CG is detected in dog urine in similar amounts to the parent drug, although it is not detected in mouse or rat urine after the single [14C]Vabicaserin dose. Radioactivity in a 0- to 24-h bile collection from rats receiving a 5 mg/kg [14C]Vabicaserin dose accounts for 19 and 24% of the administered dose in males and females, respectively. Although the CG is not detected in the urine or feces of rats after a single oral administration, In male rats and 15% in female rats, it represents an average of up to 30% of biliary radioactivity. In monkeys after a single oral 25-mg/kg dose of Vabicaserin, the plasma concentrations of the CG exceeded those of Vabicaserin at all the time points (2-24 h) postdose, although the amount of CG relative to Vabicaserin decreased by 24 h postdose, with ratios of 17.5 at 2 h and 1.7 at 24 h.In monkeys, The CG to Vabicaserin AUC0-24 ratio of 12:1 indicates that the CG is a major metabolite [2].