18. Evenamide, a Putative Antipsychotic, Targets Abnormal Electrical Activity and Glutamatergic Abnormalities to Improve Psychotic Symptoms in Patients With Schizophrenia: Results From a Phase II, Placebo-Controlled Trial

Abstract

Background: Increasing evidence implicates hippocampal hyperactivity and glutamatergic (Glu) dysfunction in the dysregulation of excitatory and inhibitory circuits leading to positive/negative symptoms and cognitive deficits associated with schizophrenia (SCZ). Existing antipsychotic drugs that target dopaminergic/serotoninergic (DA/5-HT) transmission are associated with a large proportion of patients experiencing inadequate therapeutic benefit. Evenamide, a new, highly selective, voltage-gated Na+ channel antagonist, reduces hyperexcitability, inhibits Glu release, and shows antipsychotic efficacy in multiple animal models of psychiatric disease in monotherapy and as an add-on to 1st and 2nd generation antipsychotics. Addition of evenamide to marketed antipsychotics would lead to reduction of hippocampal hyperactivity and Glu dysfunction, with modulation of mesolimbic and mesocortical DA/5-HT activity, thus providing unique benefits. Methods: This double-blind, 28-day, placebo-controlled, Phase 2 study evaluated safety, tolerability, and preliminary evidence of efficacy of evenamide as an add-on to a stable dose of risperidone or aripiprazole in SCZ outpatients. Selected patients (CGI-Severity of mild to moderately severe; PANSS total score <80) received placebo or evenamide (15–25 mg bid). Dose escalation from 15–20 to 25 mg bid was done weekly in an inpatient setting, based on tolerability. These doses are associated with plasma levels that overlap exposures (>20 ng/ml) measured at effective doses in animal models. Evaluations of vital signs, ECGs, extra-pyramidal symptom (EPS), and laboratory tests were performed weekly, and plasma levels of evenamide were measured at each dose level to determine PK–PD relationships. Preliminary evidence of efficacy was assessed by changes from baseline on the PANSS total score, CGI-Severity and Change, and the Strauss-Carpenter Level of Functioning scale. Results: Ninety patients were randomized at 5 centers (United States-2; India-3). Most patients tolerated evenamide, based on an absence of severe side-effects, as well as the high proportion of patients able to achieve and maintain the highest dose level. There are no reports of EPS, sedation, weight gain, cardiac changes, or sexual dysfunction. Conclusion: Despite the lack of interactions with DA/5-HT systems, evenamide improves positive/negative symptoms in preclinical models of psychiatric diseases, independent of the stimulus used to produce the perturbation. The combination of evenamide as an add-on to marketed antipsychotics in patients showing inadequate response would combine reduction of aberrant electrical activity and Glu transmission, with blockade of 5HT2/D2 receptors, thus producing a novel therapeutic option. Results from the Phase II trial will be presented.