MK-1167 Phase 2 AD Trial (MK-1167-008)

MK-1167 Phase 2 Clinical Trial (NCT06721156)

Overview

MK-1167 is an investigational drug being developed by Merck Sharp & Dohme LLC for the treatment of Alzheimer's disease. The Phase 2 clinical trial (Study MK-1167-008) is evaluating MK-1167 as an adjunctive therapy for patients with mild to moderate AD dementia who are already receiving acetylcholinesterase inhibitor (AChEI) therapy.

Merck, a leader in neuroscience drug development with a legacy including the development of memantine and involvement in amyloid-targeting therapies, continues to invest in novel mechanisms for Alzheimer's disease. MK-1167 represents their effort to address the significant unmet need remaining after current standard-of-care treatments.

Trial Details

| Attribute | Value |
|-----------|-------|
| Phase | Phase 2 |
| Status | Active, not recruiting (verified March 2026) |
| Sponsor | Merck Sharp & Dohme LLC |
| NCT Number | NCT06721156 |
| Enrollment | 350 participants |
| Age Range | 55-90 years |
| Duration | Up to 24 weeks |
| Intervention | MK-1167 (0.3 mg, 1 mg, 3 mg once daily) |

Background: Adjunctive Therapy in Alzheimer's Disease

Rationale for Adjunctive Treatment

MK-1167 Phase 2 Clinical Trial (NCT06721156)

Overview

MK-1167 is an investigational drug being developed by Merck Sharp & Dohme LLC for the treatment of Alzheimer's disease. The Phase 2 clinical trial (Study MK-1167-008) is evaluating MK-1167 as an adjunctive therapy for patients with mild to moderate AD dementia who are already receiving acetylcholinesterase inhibitor (AChEI) therapy.

Merck, a leader in neuroscience drug development with a legacy including the development of memantine and involvement in amyloid-targeting therapies, continues to invest in novel mechanisms for Alzheimer's disease. MK-1167 represents their effort to address the significant unmet need remaining after current standard-of-care treatments.

Trial Details

| Attribute | Value |
|-----------|-------|
| Phase | Phase 2 |
| Status | Active, not recruiting (verified March 2026) |
| Sponsor | Merck Sharp & Dohme LLC |
| NCT Number | NCT06721156 |
| Enrollment | 350 participants |
| Age Range | 55-90 years |
| Duration | Up to 24 weeks |
| Intervention | MK-1167 (0.3 mg, 1 mg, 3 mg once daily) |

Background: Adjunctive Therapy in Alzheimer's Disease

Rationale for Adjunctive Treatment

The current standard of care for Alzheimer's disease includes acetylcholinesterase inhibitors (AChEIs) such as donepezil, rivastigmine, and galantamine. These medications provide modest symptomatic benefits by increasing synaptic acetylcholine levels, but they do not address the underlying disease progression. This limitation has driven interest in adjunctive therapies that can build upon the AChEI foundation.

The adjunctive approach offers several advantages:

Current Adjunctive Strategies

Multiple approaches are being explored for adjunctive therapy in AD:

| Approach | Example | Status |
|----------|---------|--------|
| NMDA antagonist augmentation | Memantine + AChEI | Approved |
| Amyloid-targeting adjuncts | Anti-amyloid antibodies + AChEI | In development |
| Neuroprotective agents | MK-1167 + AChEI | Phase 2 |
| Anti-tau agents | Anti-tau antibodies + AChEI | In development |
| Metabolic modulators | Intranasal insulin + AChEI | Phase 2 |

Mechanism of Action

The precise mechanism of action for MK-1167 has not been publicly disclosed. As an investigational compound from Merck's pipeline, MK-1167 represents a novel therapeutic approach for Alzheimer's disease. The trial evaluates multiple dose levels to establish efficacy and safety profiles.

Potential Mechanisms

Based on Merck's research pipeline and the trial design, several mechanisms are plausible:

Phosphodiesterase Inhibition:

• Merck has historically invested in PDE inhibitors (e.g., PDE4, PDE9)
• PDE inhibition can enhance synaptic plasticity and memory
• May work synergistically with cholinergic signaling

• Neuroinflammation is a key contributor to AD progression
• Microglial modulation could provide neuroprotection
• Targeting NLRP3 inflammasome or other inflammatory pathways

• Improving synaptic resilience and plasticity
• May protect against amyloid and tau toxicity
• Could enhance cognitive function independent of disease modification

• Metabolic modulation
• Mitochondrial protection
• Metal chelation approaches

Trial Design

Study Type

• Design: Randomized, double-blind, placebo-controlled, parallel-group
• Purpose: Evaluate efficacy and safety of MK-1167 as adjunctive therapy
• Randomization: 1:1:1:1 ratio across four arms (three dose levels + placebo)

Study Phases

Inclusion Criteria

• Diagnosis of mild to moderate AD dementia (Stage 4 or 5)
• MMSE score: 12-24
• Currently receiving acetylcholinesterase inhibitor (AChEI) therapy
• Age 55-90 years
• Stable AChEI dose for ≥60 days prior to screening
• Availability of a caregiver/informant for assessments

Exclusion Criteria

• History of stroke or significant cerebrovascular disease
• Psychiatric conditions that could confound assessments
• Significant medical conditions (cardiac, hepatic, renal)
• Use of concomitant neuroactive medications
• Prior participation in MK-1167 trials

Dosing Regimen

• MK-1167 0.3 mg once daily
• MK-1167 1 mg once daily
• MK-1167 3 mg once daily
• Placebo
• Duration: Up to approximately 24 weeks

Endpoints

Primary Endpoints

• The Alzheimer's Disease Assessment Scale-Cognitive subscale (ADAS-Cog) is the gold standard for measuring cognitive function in AD clinical trials
• Score range: 0-70, higher scores indicate worse function
• A 4-point change is considered clinically meaningful

• Comprehensive safety monitoring throughout the trial
• Collection of treatment-emergent adverse events (TEAEs)

• Key tolerability metric
• Discontinuation rates inform clinical practice

Secondary Endpoints

• Clinician-rated assessment of overall change
• 7-point scale from "markedly improved" to "markedly worse"

• Measures functional abilities in daily activities
• Score range: 0-78, lower scores indicate worse function
• Particularly important for moderate-stage patients

Exploratory Endpoints

• Biomarker analyses (CSF, blood)
• Pharmacokinetic assessments
• Subgroup analyses by disease severity, age, APOE status

Trial Locations

The trial is being conducted at multiple sites across:

• North America: United States, Canada
• South America: Argentina
• Europe: Italy, Netherlands, Spain, United Kingdom
• Asia: Japan, South Korea

Pharmacological Considerations

Drug Interaction Potential

As an adjunctive therapy, understanding drug interactions is critical:

With AChEIs:

• Additive cholinergic effects possible
• Monitor for enhanced cholinergic side effects (nausea, vomiting, diarrhea)
• AChEI dose typically kept stable during trial

• Avoid concomitant antidepressants with significant anticholinergic effects
• Limit benzodiazepine use
• Exclude participants on other experimental AD treatments

Pharmacokinetic Expectations

While specific PK data is not disclosed, typical Phase 2 trials collect:

• Trough and peak plasma concentrations
• Population PK modeling
• Exposure-response relationships

Clinical Significance

This trial represents Merck's contribution to finding new treatments for Alzheimer's disease. The focus on adjunctive therapy (adding to existing AChEI treatment) is notable, as it aims to build upon the modest benefits of current standard of care.

Key Points

• Novel mechanism from a major pharmaceutical company
• Focus on adjunctive therapy approach
• Multi-dose design to find optimal dosing
• International multi-site trial

Market Context

The AD therapeutic market continues to evolve:

• Disease-modifying therapies: Leqembi (lecanemab), Kisunla (donanemab) approved
• Symptomatic treatments: AChEIs, memantine remain standard
• Adjunctive opportunities: Significant unmet need for augmenting current therapies

Regulatory Pathway

Based on the trial design and endpoints, Merck appears to be positioning MK-1167 for:

The 24-week duration aligns with typical Phase 2/3 designs for symptomatic AD agents.

Future Directions

Potential Expansion

• Phase 3 Trials: If Phase 2 is successful, larger confirmatory trials would follow
• Combination Studies: Potential evaluation with anti-amyloid antibodies
• Biomarker Development: Validation of predictive biomarkers
• Pediatric Studies: Unlikely given the indication

Competitive Landscape

MK-1167 enters a competitive space but addresses distinct needs:

| Agent | Company | Mechanism | Approach |
|-------|---------|-----------|----------|
| MK-1167 | Merck | Unknown | Adjunctive symptomatic |
| Donanemab | Lilly | Anti-amyloid | Disease-modifying |
| Lecanemab | Eisai/Biogen | Anti-amyloid | Disease-modifying |
| Sodium oligomannurate | Green Valley | Gut-brain axis | Disease-modifying |

Related Pages

• [Alzheimer's Disease](/diseases/alzheimers-disease)
• [Clinical Trials Overview](/clinical-trials/overview)
• [Acetylcholinesterase Inhibitors](/therapeutics/acetylcholinesterase-inhibitors)
• [Memantine](/therapeutics/memantine)
• [Merck Neuroscience Pipeline](/therapeutics/merck-neuroscience)

External Links

• [ClinicalTrials.gov - NCT06721156](https://clinicaltrials.gov/study/NCT06721156)
• [Merck Research Laboratories](https://www.merck.com/)

References