Effect of Zonisamide on Parkinsonism in Patients with Dementia with Lewy Bodies: A Phase 3 Randomized Clinical Trial

Introduction: Zonisamide is approved in Japan for treating motor dysfunction in Parkinson's disease, and might also be effective for parkinsonism in patients with dementia with Lewy bodies (DLB). Our study evaluated the safety and efficacy of zonisamide for treating parkinsonism in patients with DLB. Methods: This multicenter, randomized, double-blind, phase 3 trial was conducted in Japan between April 2015 and November 2017. Following a 4-week run-in period, outpatients diagnosed with probable DLB who had developed parkinsonism were randomized to receive oral zonisamide (25 or 50 mg/day) or placebo for 12 weeks, followed by a 40-week open-label extension. The primary endpoint was the change in Unified Parkinson's Disease Rating Scale (UPDRS) part III total score at Week 12. Results: Of 351 patients randomized, 346 (mean age, 77.2 years; 188 males) were included in the modified intention-to-treat population. At Week 12, the group difference (least squares mean +/- SEM) for changes from baseline (vs placebo) in UPDRS part III total score was -2.7 +/- 0.9 (95% confidence interval [CI]: -4.4, -0.9, P = 0.005) in the zonisamide 25-mg group and -2.6 +/- 0.9 (95% CI: -4.4, -0.8, P = 0.005) in the zoni-samide 50-mg group. Adverse events were reported in 47.1%, 48.7%, and 54.5% of patients in the placebo and zonisamide 25and 50-mg groups, and led to treatment discontinuation in 5.0%, 4.3%, and 9.8% of patients, respectively. Conclusion: Daily administration of 25or 50-mg zonisamide significantly improved motor function compared with placebo; both doses were safe and well tolerated in patients with DLB.