A seamless phase IIa/IIb, multicenter, randomized, double-blind, placebo-controlled, parallel group trial to evaluate the efficacy and safety of MK-7622 as an adjunctive therapy to donepezil for symptomatic treatment in subjects with Alzheimer's disease

The purpose of this multicenter trial is to assess the efficacy and safety of MK-7622 compared with placebo as adjunctive therapy to acetylcholinesterase inhibitors (AChEIs) for the symptomatic treatment of participants with mild to moderate Alzheimer\'s Disease (AD). The trial consists of two stages: Stage 1 and Stage 2. In Stage 1, participants will be randomized to receive either placebo or MK-7622 45 mg once daily. In Stage 2, participants will be randomized to receive either placebo or MK-7622 (dose: 5, 15 or 45 mg once daily). Participants will be enrolled in only one stage; the duration of each stage is approximately 26 weeks. Interim analyses will be performed in both Stage 1 and Stage 2 to determine whether the trial should continue. The primary study hypotheses are the following: Stage 1 - MK-7622 45 mg once daily is superior to placebo with respect to improving cognition in participants with mild to moderate AD as assessed by mean change from baseline in the 11-item Alzheimer\'s Disease Assessment Scale-Cognitive Subscale (ADAS-Cog11) at Week 12; Stage 2 - At least one of the top two doses of MK-7622 (15 mg once daily, 45 mg once daily) is superior to placebo with respect to improving cognition in participants with mild to moderate AD as assessed by mean change from baseline in ADAS-Cog11 at Week 12.