ANTIEMETIC EFFECTS OF YM060, A POTENT AND SELECTIVE SEROTONIN (5HT)3-RECEPTOR ANTAGONIST, IN FERRETS AND DOGS

YM060, (R)-5-[(1-methyl-3-indolyl)carbonyl]-4,5,6,7-tetrahydro-1H-benzimidazole hydrochloride, is a new serotonin (5HT)3-receptor antagonist. We examined the effects of YM060 on chemotherapeutic agent-, apomorphine- and copper sulfate-induced emesis. Intravenous YM060 potently prevented cisplatin (10 mg/kg, i.v.)-induced emesis with ED50 values of 0.06 (0.05-0.07)-mu-g/kg, i.v. in ferrets. Based on the ED50 values, YM060 was 300, 20 and 100 times more potent than ondansetron, granisetron and the S-isomer of YM060, respectively. The relative potencies of these drugs described above were similar to those in the previously reported 5HT3-receptor antagonism. YM060 given orally also potently inhibited cisplatin (10 mg/kg, i.p.)- and cyclophosphamide (200 mg/kg, i.p.)-induced emesis in ferrets with ED50 values of 0.1 (0.09-0.11) and 0.02 (0.16-0.27)-mu-g/kg, p.o., respectively. All tested 5HT3-receptor antagonists including YM060 failed to prevent apomorphine (0.1 mg/kg, s.c.)-induced emesis in dogs and copper sulfate (1%, 10 ml, p.o.)-induced emesis in ferrets. Our data indicate that YM060 is a highly potent inhibitor of chemotherapeutic agent-induced emesis and that the antiemetic effect of YM060 may be depend on 5HT3-receptor antagonism.