Casopitant mesylate (GW679769B) is a potent, selective, brain permeable and orally active neurokinin 1 (NK1) receptor antagonist. Casopitant mesylate is a second in the class of antiemetics that acts to antagonise the emetogenic effect of substance P. Casopitant mesylate is also a substrate and a weak-to-moderate inhibitor of CYP3A4. Casopitant mesylate can be used for chemotherapy-induced nausea and vomiting (CINV) and postoperative nausea and vomiting (PONV)[1][2].

In a ferret-model of Cisplatin- induced emesis, Casopitant (GW679769) inhibits retching and vomiting and reduced nausea-like behaviours in a dose-dependent manner. The pharmacokinetics and brain penetration of casopitant are studied in the ferret-model of cisplatin-induced emesis. Following a single intraperitoneal dose, radioactive labeled Casopitant ([14C]Casopitant) is rapidly absorbed, with plasma and brain concentrations being approximately equal at two hours post-dosing. [14C]Casopitant is found in the brain as the parent compound and two major oxidative metabolites (M1 and M2), accounting for approximately 76%, 19%, and 3% of the radioactivity, respectively; suggesting that the pharmacologic activity of Casopitant in the ferret is largely attributable to the parent compound. Casopitant possesses a high affinity for brain NK1 receptors in the ferret[2].

[1]. Ruhlmann C, et al. Casopitant: a novel NK(1)-receptor antagonist in the prevention of chemotherapy-induced nausea and vomiting. Ther Clin Risk Manag. 2009 Apr;5(2):375-84.
[2]. Minthorn E, et al. Pharmacokinetics and brain penetration of casopitant, a potent and selective neurokinin-1 receptor antagonist, in the ferret. Drug Metab Dispos. 2008 Sep;36(9):1846-52.