Conditions: Alzheimer's Disease
Allocation: RANDOMIZED | Intervention model: PARALLEL
Enrollment: 240
Healthy volunteers: no

Brief summary:
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.

Detailed description:
If the double-blind treatment dose is not tolerated during the first 2 weeks, the participant will be discontinued. After the first 2 weeks, if the dose is not tolerated, the regimen may be modified according to a defined algorithm. Specifically, the participant will begin administration of a reduced dose for up to 2 weeks, followed by a re-challenge at the original dose only if tolerability issues diminish or resolve at the reduced dose.

Arms:
arm 1: Single 45 mg MK-7622 capsule once daily, taken orally. Dose escalated as follows: 15 mg MK-7622 once daily for 1 week; 30 mg MK-7622 once daily for 1 week; and 45 mg MK-7622 once daily for the remainder of treatment. arm 2: Matching placebo to MK-7622 capsule once daily, taken orally. arm 3: Single 5 mg MK-7622 capsule once daily, taken orally. arm 4: Single 15 mg MK-7622 capsule once daily, taken orally. arm 5: Single 45 mg MK-7622 capsule once daily, taken orally. Dose escalated as follows: 15 mg MK-7622 once daily for 1 week; 30 mg MK-7622 once daily for 1 week; and 45 mg MK-7622 once daily for the remainder of treatment. arm 6: Matching placebo to MK-7622 capsule once daily, taken orally.

Interventions: intervention 1: MK-7622 intervention 2: Placebo intervention 3: AChEI
Intervention descriptions: intervention 1: MK-7622 capsule intervention 2: Matching placebo to MK-7622 capsule intervention 3: One of the following AChEIs, as prescribed by the participant's primary care physician:

Donepezil: 10 mg total daily dose, administered orally

Rivastigmine: 9.5 or 13.3 mg/24 hours, administered by transdermal patch; or 6-12 mg total daily dose administered orally

Galantamine: 16-24 mg total daily dose, administered orally

Protocol document: