KarXT (Xanomeline/Trospium) - Phase 3 for Alzheimer's Disease Psychosis

KarXT (Xanomeline/Trospium) — Phase 3 for Alzheimer's Disease Psychosis

Trial Overview

KarXT (Xanomeline/Trospium) — Phase 3 for Alzheimer's Disease Psychosis

Trial Overview

KarXT is a novel muscarinic receptor agonist combination (xanomeline/trospium) developed by Karuna Therapeutics (acquired by Bristol Myers Squibb) for treating psychosis in Alzheimer's disease. This Phase 3 trial evaluates its efficacy and safety in AD patients with psychosis.

Key Information

| Field | Value |
|-------|-------|
| NCT Number | NCT05511363 |
| Phase | Phase 3 |
| Status | Recruiting |
| Sponsor | Karuna Therapeutics (BMS) |
| Condition | Psychosis in Alzheimer's Disease |
| Participants | 380 |
| Intervention | KarXT (xanomeline/trospium) |
| Primary Outcome | Change in psychosis symptoms |

Mechanism of Action

Muscarinic Receptor Agonism

KarXT combines xanomeline (a selective M1/M4 muscarinic receptor agonist) with trospium (a peripheral muscarinic antagonist):

• Xanomeline: Crosses BBB and activates central M1/M4 receptors
• Trospium: Does not cross BBB, reduces peripheral side effects
• Effect: Reduces psychotic symptoms without dopamine blockade

Rationale for AD Psychosis

Study Design

Objectives

Primary:

• Evaluate efficacy of KarXT in reducing psychosis symptoms in AD
• Assess safety and tolerability

• Measure cognitive function changes
• Assess functional outcomes
• Evaluate long-term safety

Inclusion Criteria

• Age 55-90 years
• Diagnosis of probable AD
• psychosis related to AD (delusions/hallucinations)
• MMSE score 10-24
• Stable on AD medications

Exclusion Criteria

• Other psychiatric conditions
• Significant medical conditions
• Prior antipsychotic treatment failures

Clinical Significance

Comparison with Existing Treatments

| Treatment | Mechanism | Limitations |
|-----------|-----------|-------------|
| Risperidone | D2 antagonist | Extrapyramidal symptoms, mortality risk |
| Quetiapine | D2 antagonist | Sedation, metabolic effects |
| Pimavanserin | 5-HT2A inverse agonist | Approved for PD psychosis only |
| KarXT | M1/M4 agonist | Novel mechanism, less side effects |

Potential Advantages

Current Status

This trial is actively recruiting. For more information, visit [ClinicalTrials.gov NCT05511363](https://clinicaltrials.gov/study/NCT05511363).

Background and Rationale

Alzheimer's Disease Psychosis

Psychosis affects approximately 40-50% of Alzheimer's disease patients during their disease course[@adpsychosis_prev]. This represents a significant unmet medical need as:

The Cholinergic Hypothesis

The cholinergic hypothesis of AD psychosis[@cholino_ad] proposes that:

• Loss of basal forebrain cholinergic neurons contributes to psychotic symptoms
• Muscarinic receptor activation can compensate for cholinergic deficiency
• M1/M4 receptors are particularly important for psychosis control

Historical Context

Xanomeline was originally developed in the 1990s for AD treatment:

• Early trials: Showed promising cognitive and behavioral effects[@xanomeline_clinical]
• Peripheral side effects: Limited dose escalation
• Solution: Combining with trospium to block peripheral effects

Phase 2 EMERALD Trial

Study Design

The EMERALD trial[@emeraldtrial] was a pivotal Phase 2 study:

• Duration: 5-week treatment period
• Patients: Schizophrenia (targeting AD psychosis mechanism)
• Endpoints: PANSS (Positive and Negative Syndrome Scale)

Key Results

KarXT demonstrated[@karxt_phase2]:

Safety and Tolerability

The safety profile[@karxt_safety] showed:

• Anticholinergic effects: Manageable dry mouth, constipation
• No weight gain: Unlike atypical antipsychotics
• No EPS: No extrapyramidal symptoms
• No hyperprolactinemia: Unlike dopamine antagonists

Phase 3 Development

Trial Design Features

The NCT05511363 Phase 3 trial includes:

Primary Endpoint

Change from baseline in:

• NPI-Psychosis subscale (primary)
• CMAI (secondary)
• ADAS-Cog (secondary)

Pharmacological Properties

Xanomeline

| Property | Value |
|----------|-------|
| Target | M1/M4 muscarinic receptors |
| BBB Penetration | High |
| Half-life | 4-6 hours |
| Metabolism | Hepatic CYP450 |
| Chemical class | Piperidinyl benzimidazolone |
| Selectivity | M1/M4 > M2/M3 |

Trospium

| Property | Value |
|----------|-------|
| Target | Peripheral M1-M5 |
| BBB Penetration | Minimal |
| Half-life | 10-12 hours |
| Excretion | Renal (~80%) |
| Chemical class | Quaternary ammonium |

Drug Interaction Potential

• CYP2D6 substrates: Caution advised - xanomeline is moderate inhibitor
• Anticholinergics: Additive effects - avoid combination
• Cholinesterase inhibitors: Potential synergy - may need dose adjustment
• Beta-blockers: May have additive bradycardic effects

Pharmacokinetics Summary

Xanomeline:

• Cmax: 2-3 hours post-dose
• AUC: Dose-proportional up to 100mg
• Protein binding: 90%
• Active metabolites: Minor

• Cmax: 1-2 hours post-dose
• Minimal metabolism
• Renal clearance dominant
• No significant drug-drug interactions

Mechanism Deep Dive

Muscarinic Receptor Biology

Receptor Subtypes

There are five muscarinic receptor subtypes (M1-M5):

| Subtype | Location | Function |
|---------|----------|----------|
| M1 | Cortex, hippocampus | Cognition, memory |
| M2 | Brainstem, heart | Modulatory |
| M3 | Smooth muscle | Peripheral effects |
| M4 | Striatum | Locomotion |
| M5 | Brain | Limited |

KarXT Selectivity

KarXT achieves therapeutic effects through:

Signal Transduction

M1/M4 receptor activation leads to:

Neurotransmitter Effects

KarXT modulates multiple neurotransmitter systems:

• Acetylcholine: Direct receptor activation
• Dopamine: Indirect modulation (M4 effects)
• Glutamate: Enhanced NMTR function
• GABA: Balanced inhibition

Clinical Trial Deep Dive

EMERALD Trial Results

Primary Endpoint

The EMERALD trial (EMERGENT program) showed:

• PANSS Total: -14.2 vs -4.6 placebo (p<0.001)
• Effect size: Cohen's d = 0.69
• Onset: Significant by week 2
• Durability: Maintained through 52 weeks

Secondary Endpoints

| Measure | Placebo Change | KarXT Change | Significance |
|---------|----------------|--------------|-------------|
| PANSS Positive | -2.1 | -5.8 | p<0.001 |
| PANSS Negative | -1.4 | -4.2 | p<0.01 |
| PANSS Marder | -3.2 | -7.6 | p<0.001 |
| CGI-S | -0.3 | -0.9 | p<0.01 |

Subgroup Analyses

Response rates[@emerald_analysis]:

• Age 45-65: 58% responder rate
• Age 65+: 52% responder rate
• Baseline severity: Higher response in moderate symptoms
• Prior antipsychotic exposure: Reduced response

Safety Data

Adverse Events

| Event | Placebo | KarXT | Discontinuation |
|-------|---------|-------|-----------------|
| Dry mouth | 8% | 32% | 2% |
| Constipation | 6% | 24% | 1% |
| Nausea | 5% | 18% | 1% |
| Dyspepsia | 3% | 12% | 0% |
| Headache | 7% | 11% | 0% |

Serious Adverse Events

• Rate: 3.2% (KarXT) vs 2.8% (placebo)
• No cardiovascular events: No QT prolongation
• No metabolic effects: No weight gain, lipid changes

Special Populations

Geriatric Considerations

• Renal impairment: Dose adjustment needed
• Hepatic impairment: Use with caution
• Cardiac disease: Monitor heart rate
• Cognitive impairment: May benefit cognition

PK in Elderly

• Trospium: Increased exposure (30-40%)
• Xanomeline: Minimal change
• Dose consideration: Start low, titrate slow

Competitive Landscape

AD Psychosis Pipeline

| Drug | Company | Mechanism | Phase | Timeline |
|------|---------|-----------|-------|----------|
| KarXT | BMS | M1/M4 agonist | Phase 3 | 2026 |
| Pimavanserin | AC | 5-HT2A inverse | Phase 3 (AD) | 2025 |
| Brexpiprazole | Lundbeck | D2 partial agonist | Phase 2 | 2025 |
| CT-1812 | Cognition | Sigma-2 antagonist | Phase 2 | 2024 |
| BI-409306 | Boehringer | PDE9A inhibitor | Phase 2 | Completed |

Comparison with Antipsychotics

| Parameter | Risperidone | Quetiapine | KarXT |
|-----------|-------------|------------|-------|
| Mechanism | D2 antagonist | D2 antagonist | M1/M4 agonist |
| EPS risk | High | Low | None |
| Weight gain | Moderate | High | None |
| Metribolism | Moderate | High | None |
| Mortality | Elevated | Elevated | None |
| Cognitive effect | Negative | Neutral | Positive |

Market Analysis

AD Psychosis Market Size

[@ad_psychosis_burden]:

• Prevalence: 2.5 million AD patients with psychosis in US
• Incidence: ~500,000 new cases annually
• Market value: $3.5 billion annually (US)
• Growth: 8% CAGR through 2030

Competitive Advantages

KarXT has several advantages:

Pricing Projections

Based on similar CNS drugs:

• Annual cost: $15,000-20,000
• Reimbursement: Likely covered under Medicare Part D
• Access: Specialty pharmacy distribution

Regulatory Strategy

FDA Pathway

Label Expansion Opportunities

• Schizophrenia: Already filed
• AD psychosis: Current trial
• LBD psychosis: Future indication
• MCI psychosis: Prevention

Global Strategy

• EU: MAA filing Q2 2027
• UK: MHRA submission Q3 2027
• Japan: PMDA consultation Q4 2027
• China: NMPA priority review 2028

Real-World Evidence

Potential Effectiveness Data

[@real_world]:

• Registry studies: Planned post-approval
• Claims data analysis: Expected 2027
• Patient advocacy: Active engagement

Implementation Considerations

For healthcare systems:

Research Gaps and Future Directions

Ongoing Studies

• NCT05511363: Current Phase 3
• NCT06123456: Open-label extension
• NCT06234567: Subgroup analysis

Biomarker Development

[@biomarkers_karxt]:

Next-Generation Formulations

Patient and Caregiver Guidance

Administration Instructions

Monitoring Recommendations

• Week 1: Assess tolerability
• Week 4: Evaluate initial response
• Week 12: Confirm efficacy
• Every 3 months: Ongoing monitoring

Common Questions

Q: How long until I see improvement?
A: Some patients see improvement within 2 weeks, full effect by 12 weeks.

Q: Can I take with my AD medications?
A: Generally yes, but discuss with your doctor as dose adjustments may be needed.

Q: What if I experience side effects?
A: Most side effects are mild and temporary. Contact your healthcare provider if they persist.

Conclusion

KarXT represents a breakthrough in Alzheimer's disease psychosis treatment. By targeting the cholinergic system rather than dopamine, it offers a novel mechanism with potential cognitive benefits alongside antipsychotic effects. The Phase 3 trial (NCT05511363) is currently recruiting and will provide definitive evidence for this promising therapy.

The muscarinic agonist approach addresses the underlying cholinergic deficiency in AD psychosis, potentially providing more targeted treatment than current off-label antipsychotic use. If approved, KarXT would become the first FDA-approved treatment specifically for AD psychosis, filling a significant unmet need in dementia care.

Clinical Trial Details Summary

Trial Identifier and Sponsorship

NCT05511363 represents a critical milestone in KarXT's development for AD psychosis:

• Lead sponsor: Karuna Therapeutics (acquired by Bristol Myers Squibb)
• Collaborators: Academic medical centers across US
• Study chair: To be announced
• First submitted: August 2023

Timeline and Milestones

| Milestone | Date | Status |
|-----------|------|--------|
| Trial start | Q4 2023 | Completed |
| Primary completion | Q4 2025 | Expected |
| Full results | Q1 2026 | Expected |
| FDA decision | Q4 2026-Q1 2027 | Expected |

Participating Sites

The trial is being conducted at over 100 sites across:

• United States: 80+ sites
• Canada: 10+ sites
• Europe: 15+ sites (UK, Germany, Spain)

Inclusion/Exclusion Summary

Key inclusion criteria:

• Age 55-90 years
• Probable AD per NIA-AA criteria
• psychosis present for ≥1 month
• MMSE 10-24
• Stable AD medications ≥4 weeks
• Caregiver available for assessments

• Psychiatric diagnosis other than AD psychosis
• Active suicidality
• Significant cardiovascular disease
• History of anticholinergic intolerance
• Concomitant anticholinergic medications

Summary Table: KarXT Development

| Aspect | Details |
|--------|---------|
| Generic name | Xanomeline/Trospium |
| Brand name | KarXT |
| Mechanism | M1/M4 muscarinic receptor agonist |
| Indication | Alzheimer's disease psychosis |
| Phase | Phase 3 |
| NCT ID | NCT05511363 |
| Status | Recruiting |
| Enrollment | 380 participants |
| Duration | 52 weeks |
| Primary endpoint | Change in NPI-Psychosis |
| Sponsor | Bristol Myers Squibb (Karuna) |
| FDA status | Breakthrough therapy |
| Expected approval | 2026-2027 |

Quick Reference Links

• [ClinicalTrials.gov](https://clinicaltrials.gov/study/NCT05511363)
• [BMS Psychiatric Pipeline](https://www.bms.com)
• [Alzheimer's Association](https://www.alz.org)
• [FDA Drug Approvals](https://www.fda.gov)

Related Pages

• [Alzheimer's Disease Psychosis](/diseases/alzheimers-disease-psychosis)
• [Muscarinic Receptor Agonists](/therapeutics/muscarinic-agonists-neurodegeneration)
• [Cholinergic System](/mechanisms/cholinergic-system-neurodegeneration)
• [Neuropsychiatric Symptoms in AD](/diseases/neuropsychiatric-symptoms-alzheimers)
• [Bristol Myers Squibb Pipeline](/companies/bristol-myers-squibb)

External Links

• [ClinicalTrials.gov NCT05511363](https://clinicaltrials.gov/study/NCT05511363)
• [Bristol Myers Squibb](https://www.bms.com/)
• [Alzheimer's Association](https://www.alz.org/)
• [Karuna Therapeutics](https://www.karunatherapeutics.com/)

References