History of Ondansetron Use for AUD
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History of Ondansetron Use for AUD

Ondansetron History and Foundation for Treating AUD


The active pharmaceutical agent in AD04 is ondansetron (the active ingredient in Zofran®) which was granted FDA approval in 1991 for nausea and vomiting post-operatively and after chemotherapy or radiation treatment and is now commercially available in generic form. In studies of Zofran® conducted as part of its FDA review process, patients were given ondansetron acutely at dosages up to almost 100 times the dosage expected to be formulated in AD04 with the highest doses of Zofran® given intravenously (“i.v.”), which results in almost twice the exposure level as oral dosing.. Even at high doses given i.v. the studies found that ondansetron is well-tolerated and results in few adverse side effects at the currently marketed doses given i.v.. The formulation/ dosage of ondansetron used in our drug candidate (and expected to be used by us in our Phase 3 clinical trials) has the potential advantage that it contains a much lower concentration of ondansetron than the generic formulation/dosage that has been used in prior clinical trials, is dosed orally, and is available with use of a companion diagnostic biomarker. Ondansetron is a 5-HT3 receptor antagonist. Preclinical and pharmacobehavioral studies suggest that blockade of serotonin-3 receptors will influence the dopamine reward system activated by alcohol, decreasing dopamine release and attenuating craving for alcohol (Dawes, MA et al., 2005b; Johnson, BA et al., 2002; Lovinger, DM, 1999a). Early clinical studies found that the efficacy of ondansetron is limited to certain subgroups of the alcohol-dependent population and suggested the differential effect could be predicted based on age of onset of alcoholism, an indistinct concept likely confounded by genetic, regional and ethnic differences (Johnson, BA et al., 2000; Kranzler, HR et al., 2003). Recent research suggests the variable effect may be predictable based on molecular mechanism of ondansetron action and individual subject genotype of key genes in the serotonin system (Enoch, MA et al., 2010; Johnson, BA et al., 2011; Kenna, GA et al., 2009).

Ondansetron, by blocking the 5-HT3 receptor, is known to affect dopaminergic signaling in the brain; and the scientific rational for use of a 5-HT3 antagonist in the treatment of alcohol dependence is well established (Johnson, BA, 2004). Briefly, studies suggest that: the rewarding effects of alcohol involve activation of the 5-HT3 receptors leading to release of dopamine within the mesolimbic system of the brain (McBride, WJ et al., 2004). Thus, by blocking activation of the 5-HT3 receptor, ondansetron may reduce the ethanol-stimulated release of dopamine leading to reduced feelings of pleasure or reward and consequently, reduced consumption (Carboni, E et al., 1989; Costall, B et al., 1987; Hagan, RM et al., 1990; Imperato, A and Angelucci, L, 1989; Lovinger, DM, 1999b; McBride, WJ et al., 2004; Minabe, Y et al., 1991; Rasmussen, K et al., 1991; Wozniak, KM et al., 1990; Yoshimoto, K et al., 1996).