This study tests a new drug called ONO-2020 for people with mild to moderate Alzheimer's disease (a condition affecting memory and thinking). The study is Phase 2, meaning researchers are checking its safety and effectiveness. The study is double-blind (neither participants nor researchers know who receives the real drug or a placebo, which is a fake treatment), and involves different groups, called parallel-group. Participants will take ONO-2020 or a placebo once a day for 26 weeks (about six months) and continue to be monitored for 4 weeks after stopping. The study involves 240 participants, with some undergoing special tests.

• The study lasts for about 30 weeks including follow-up.
• Participants must have a caregiver to assist with study requirements.
• Important to have a stable medication routine if currently on Alzheimer's treatment.