A Dose-Finding Study of Topiramate (JNS019) in Participants With Migraine

This study is a multicenter (more than 1 site), placebo-controlled (compared to placebo), randomized (participants assigned study drug by chance), double-blind (neither the participant nor the physician know the assigned study drug), parallel-group comparison (comparison for each group at the same time) study. The study period consists of 4 phases: the observation phase, double-blind phase, exit period and follow-up period. After the double-blind phase, the participants will be transferred to the continuous treatment study. The observation phase which is started after informed consent consists of the washout period (non-treatment period with migraine preventive medication: at least 2 weeks) and baseline determination period (at least 4 weeks). The participants who complete the observation phase and meet the inclusion criteria will be randomly assigned to the topiramate 50 milligram (mg) group, topiramate 100-mg group or placebo group after registration. The double-blind phase consists of the titration period (dose-escalation, 4 weeks) and fixed-dose period (18 weeks). In the titration period, starting from 1 topiramate 25-mg tablet or 1 topiramate 25-mg placebo tablet once daily (1 tablet in the evening), the dose will be increased by 1 tablet every week up to twice daily (2 tablets in the morning, 2 tablets in the evening). After that, the twice-daily treatment (2 tablets in the morning, 2 tablets in the evening) will be continued for 7 days from Day 22 to Day 28. In the fixed-dose period, the topiramate 25-mg tablets or topiramate 25-mg placebo tablets at the same dose as that in the final treatment in titration period will be continued. The participants who are not transferred to the continuous treatment study after completion of the double-blind phase or after discontinuation during the double-blind phase will be transferred to the exit period (up to 1 week).The participants who complete the exit period will be transferred to the follow-up period, and a follow-up of the participant's safety and headache symptoms such as the migraine period rate will be conducted for 4 weeks after the completion of investigational treatment. Meanwhile, the participants who complete the double-blind phase or those who discontinue the study at Week 4 or later in the fixed-dose period during the double-blind phase due to lack of efficacy and give consent to transfer to the continuous treatment study will be transferred to the transfer period (up to 3 weeks) under blind conditions.