nct05508789

A Study of Donanemab (LY3002813) in Participants With Early Symptomatic Alzheimer's Disease (TRAILBLAZER-ALZ 5)

Overview

TRAILBLAZER-ALZ 5 (NCT05508789) is a global Phase 3 clinical trial evaluating the safety and efficacy of donanemab (LY3002813), an investigational amyloid-targeting monoclonal antibody, in participants with early symptomatic Alzheimer's disease. This large-scale study builds upon the positive results from the TRAILBLAZER-ALZ 2 trial and aims to further characterize donanemab's clinical benefits in a broader population[@donanemab_trailblazer2].

Donanemab is a humanized IgG1 antibody that binds to a unique epitope on the N-terminal region of Aβ plaques, facilitating their clearance via microglial-mediated phagocytosis. Unlike other anti-amyloid antibodies that target soluble Aβ species, donanemab specifically targets pyroglutamate-modified Aβ (pE3-Aβ)—a particularly aggregation-prone and neurotoxic form of amyloid that is heavily enriched in plaque cores[@novel2024].

Trial Details

| Parameter | Value |
|-----------|-------|
| NCT Number | NCT05508789 |
| Phase | Phase 3 |
| Status | Recruiting |
| Sponsor | Eli Lilly and Company |
| Enrollment | 1,500 participants (estimated) |
| Enrollment Type | Estimated |
| Study Type | Interventional |
| Start Date | October 10, 2022 |
| Completion Date | July 1, 2028 |
| Last Updated | February 10, 2026 |

Conditions Studied

• Alzheimer Disease (Early symptomatic)
• Mild Cognitive Impairment due to AD
• Dementia (Mild)

...

A Study of Donanemab (LY3002813) in Participants With Early Symptomatic Alzheimer's Disease (TRAILBLAZER-ALZ 5)

Overview

TRAILBLAZER-ALZ 5 (NCT05508789) is a global Phase 3 clinical trial evaluating the safety and efficacy of donanemab (LY3002813), an investigational amyloid-targeting monoclonal antibody, in participants with early symptomatic Alzheimer's disease. This large-scale study builds upon the positive results from the TRAILBLAZER-ALZ 2 trial and aims to further characterize donanemab's clinical benefits in a broader population[@donanemab_trailblazer2].

Donanemab is a humanized IgG1 antibody that binds to a unique epitope on the N-terminal region of Aβ plaques, facilitating their clearance via microglial-mediated phagocytosis. Unlike other anti-amyloid antibodies that target soluble Aβ species, donanemab specifically targets pyroglutamate-modified Aβ (pE3-Aβ)—a particularly aggregation-prone and neurotoxic form of amyloid that is heavily enriched in plaque cores[@novel2024].

Trial Details

| Parameter | Value |
|-----------|-------|
| NCT Number | NCT05508789 |
| Phase | Phase 3 |
| Status | Recruiting |
| Sponsor | Eli Lilly and Company |
| Enrollment | 1,500 participants (estimated) |
| Enrollment Type | Estimated |
| Study Type | Interventional |
| Start Date | October 10, 2022 |
| Completion Date | July 1, 2028 |
| Last Updated | February 10, 2026 |

Conditions Studied

• Alzheimer Disease (Early symptomatic)
• Mild Cognitive Impairment due to AD
• Dementia (Mild)

Disease Context

Alzheimer's Disease Pathophysiology

Alzheimer's disease (AD) is the most common cause of dementia, accounting for approximately 60-80% of all dementia cases worldwide. The disease is characterized by:

Amyloid Pathology

• Accumulation of [amyloid-beta](/proteins/amyloid-beta) (Aβ) peptides
• Formation of extracellular plaques
• Primarily Aβ40 and Aβ42 species
• pE3-Aβ (pyroglutamate-modified) species particularly toxic

Tau Pathology

• Hyperphosphorylation of [tau protein](/proteins/tau)
• Formation of neurofibrillary tangles (NFTs)
• Spreading through connected neural networks
• Correlates with clinical progression

Neurodegeneration

• Synaptic loss and neuronal death
• Progressive brain atrophy
• Network dysfunction

Clinical Manifestations

• Memory impairment (especially episodic memory)
• Progressive cognitive decline
• Functional impairment
• Behavioral changes

Amyloid Cascade Hypothesis

The amyloid cascade hypothesis has been the dominant model for understanding AD pathogenesis since its proposal in 1992. The hypothesis proposes that:

Aβ accumulation → Tau pathology → Synaptic loss → Neuronal death → Cognitive decline

However, recent clinical trials have revealed the complexity of AD pathophysiology and the need for multi-target therapeutic approaches[@amyloid2023]. The relationship between amyloid and tau appears to be bidirectional, with both pathologies influencing each other.

Donanemab Mechanism of Action

Molecular Target

Donanemab is a monoclonal antibody that specifically targets pyroglutamate-modified Aβ (pE3-Aβ):

| Property | Description |
|----------|-------------|
| Target | pE3-Aβ (pyroglutamate-modified amyloid-beta) |
| Epitope | N-terminal region (amino acids 1-6) |
| Isotype | Humanized IgG1 |
| Affinity | High affinity for plaque-associated Aβ |

Mechanism

Binding: Donanemab binds with high affinity to pE3-Abeta deposited in amyloid plaques

Opsonization: The antibody marks plaques for immune recognition

Effector Activation: The IgG1 Fc region engages activating Fcgamma receptors on microglia

Phagocytosis: Microglia clear plaques through antibody-dependent cellular phagocytosis (ADCP)

Plaque Reduction: Amyloid plaque burden is substantially reduced

Unique Features

Compared to other anti-amyloid antibodies:

| Antibody | Target | Mechanism | Key Difference |
|----------|--------|-----------|-----------------|
| Donanemab | pE3-Aβ | Microglial phagocytosis | Targets plaque core, specific pE3 epitope |
| Lecanemab | Aβ protofibrils | Binds soluble oligomers | Broader Aβ species |
| Aduhelm | Aβ plaques | Various | Original accelerated approval |

Study Design

Trial Structure

This is a Phase 3, randomized, double-blind, placebo-controlled clinical trial:

Randomization: Participants randomly assigned 1:1 to treatment or placebo

Blinding: Double-blind—neither participants nor investigators know assignment

Duration: 76-week treatment period with 12-week follow-up

Treatment Arms

| Arm | Treatment | Duration |
|-----|-----------|----------|
| Active | Donanemab IV infusion (optional subcutaneous) | 76 weeks |
| Placebo | Matching IV infusion (saline) | 76 weeks |

Dosing Schedule

• Induction Phase: Monthly infusions for first 3 months
• Maintenance Phase: Every 4 weeks thereafter
• Optional: Transition to subcutaneous administration in later stages

Key Eligibility Criteria

Inclusion Criteria

• Age 60-85 years
• Clinical diagnosis of early symptomatic AD (MCI or mild dementia)

-confirmed amyloid pathology by PET or CSF

• MMSE score 20-28
• CDR Global Score 0.5 or 1.0
• Stable cholinesterase inhibitor/memantine (if applicable)
• Caregiver availability

Exclusion Criteria

• Significant neurological disease other than AD
• Psychiatric illness affecting participation
• Uncontrolled medical conditions
• Recent anticoagulant therapy (contraindicates CSF sampling)
• Prior anti-amyloid immunotherapy
• Significant MRI abnormalities

Outcome Measures

Primary Endpoints

Primary Clinical Endpoint

• Change from baseline on the Integrated Alzheimer's Disease Rating Scale (iADRS)
• iADRS combines cognitive (ADAS-Cog) and functional (ADCS-iADL) measures

Primary Biomarker Endpoint

• Change in amyloid plaque burden (PET)
• Change in tau burden (PET)

Secondary Endpoints

| Endpoint | Instrument | Timepoint |
|----------|------------|-----------|
| Cognitive function | ADAS-Cog 13 | Weeks 24, 52, 76 |
| Global status | CDR-SB | Weeks 24, 52, 76 |
| Functional ability | ADCS-ADL | Weeks 24, 52, 76 |
| Neuropsychiatric symptoms | NPI | Weeks 24, 52, 76 |
| Quality of life | EQ-5D-5L | Weeks 24, 52, 76 |
| Brain atrophy | MRI volumetric | Baseline, Week 52, Week 76 |
| CSF biomarkers | Aβ40/42, t-tau, p-tau | Baseline, Week 52, Week 76 |

Exploratory Endpoints

• Blood-based biomarkers (ATN profile)
• Subgroup analyses by APOE genotype, age, disease stage
• Time to clinically meaningful decline

Clinical Significance

Therapeutic Context

This trial represents a critical step in the development of new treatments for Alzheimer's disease:

Disease Modification: Anti-amyloid antibodies aim to modify disease progression, not just treat symptoms

Early Intervention: Targeting early-stage patients where intervention may be most effective

Biomarker Confirmation: Demonstrating that amyloid clearance correlates with clinical benefit

Comparison with Other Anti-Amyloid Therapies

| Trial | Drug | Primary Endpoint | Result | Amyloid Reduction |
|-------|------|------------------|--------|-------------------|
| TRAILBLAZER-ALZ 2 | Donanemab | iADRS | Positive | ~60-80% |
| CLARITY-AD | Lecanemab | CDR-SB | Positive | ~60% |
| CLARITY (post-hoc) | Lecanemab | iADRS | Positive | ~60% |

Regulatory Context

• Donanemab received accelerated approval from FDA in 2024 based on TRAILBLAZER-ALZ 2 results
• TRAILBLAZER-ALZ 5 serves as confirmatory trial for full approval
• EMA and other regulatory agencies reviewing data

Safety Considerations

ARIA (Amyloid-Related Imaging Abnormalities)

The primary safety concern with anti-amyloid antibodies is ARIA:

| Type | Description | Frequency |
|------|-------------|-----------|
| ARIA-E | Edema (vasogenic) | 25-35% (dose-dependent) |
| ARIA-H | Hemorrhage/hemosiderin | 15-20% |

Management Strategies

Pre-screening: MRI to establish baseline

Monitoring: Periodic MRI during treatment

Dose titration: Initial lower dose with escalation

Symptom management: Temporary discontinuation if ARIA occurs

Patient education: Recognize warning signs

Other Potential Adverse Events

• Infusion reactions
• Hypersensitivity
• Headache
• Nausea

Biomarker Rationale

Amyloid PET

Amyloid PET imaging is used to:

Confirm eligibility: Verify amyloid positivity

Measure target engagement: Quantify plaque reduction

Support regulatory approval: Demonstrate disease modification

Tau PET

Tau PET provides:

Staging information: Tau burden correlates with clinical stage

Treatment effect: Monitor tau progression

Prognostic information: Predict clinical outcomes

CSF and Blood Biomarkers

| Biomarker | Utility |
|-----------|---------|
| Aβ40/Aβ42 | Amyloid metabolism |
| Total tau (t-tau) | Neurodegeneration |
| Phosphorylated tau (p-tau) | Tau pathology |
| Neurofilament light (NfL) | Axonal injury |

Statistical Considerations

Sample Size and Power

With 1,500 participants:

• 90% power to detect 25% slowing in iADRS decline
• Significance level: α = 0.05 (two-sided)
• Assumes 25% dropout rate

Analysis Populations

Intention-to-Treat (ITT): All randomized participants

Per-Protocol: Completers without major protocol deviations

Biomarker: Participants with baseline and follow-up PET data

Participating Sites

The trial is conducted at multiple centers worldwide, including sites in:

• Argentina: Buenos Aires, Córdoba, La Plata
• Australia: Melbourne, Sydney
• Canada: Toronto, Montreal, Vancouver
• Europe: Multiple countries
• Japan: Tokyo, Osaka, Nagoya
• South Korea: Seoul, Busan
• United States: Multiple states

Clinical Implications and Future Directions

If Successful

Positive results would:

Confirm efficacy: Validate donanemab's clinical benefits in broader population

Support full approval: Enable broader prescribing

Establish treatment protocol: Optimal dosing and monitoring

Inform combination therapy: Rationale for combining with other agents

Treatment Sequencing

Potential treatment paradigms:

Sequential immunotherapy: Donanemab → Lecanemab

Combination approaches: Anti-amyloid + anti-tau

Maintenance: Extended treatment after plaque clearance

Personalized Medicine

Potential biomarkers for patient selection:

• APOE4 status
• Baseline amyloid/tau burden
• CSF biomarker profile
• Genetic risk scores

Comparison with Other Anti-Amyloid Antibodies

Donanemab has several distinguishing features compared to other anti-amyloid antibodies in development:

| Feature | Donanemab | Lecanemab | Aduhelm |
|---------|-----------|-----------|---------|
| Target | pE3-Aβ (plaque core) | Aβ protofibrils | Aβ plaques |
| Mechanism | Microglial phagocytosis | Antibody-mediated clearance | Multiple mechanisms |
| Dosing | Fixed dose | Weight-based | Weight-based |
| Infusion frequency | Monthly | Bi-weekly | Monthly |
| Plaque reduction | ~60-80% | ~60% | ~50-70% |
| Clinical effect | 35% slowing | 27% slowing | Minimal effect |

Clinical Development Program

The TRAILBLAZER-ALZ 5 trial is part of a comprehensive clinical development program:

TRAILBLAZER-ALZ (Phase 2) - First-in-human study

TRAILBLAZER-ALZ 2 (Phase 2) - Registration-enabling study (positive results)

TRAILBLAZER-ALZ 3 (Phase 3) - Confirmatory study

TRAILBLAZER-ALZ 5 (Phase 3) - Additional confirmation (current study)

Open Label Extension - Long-term safety and durability

Amyloid Clearance and Clinical Outcomes

The relationship between amyloid clearance and clinical outcomes is complex:

Patient Quality of Life Impact

Beyond clinical endpoints, donanemab treatment may impact:

Patient Independence

• Delayed need for caregiver assistance
• Prolonged ability to perform daily activities
• Reduced nursing home placement

Caregiver Burden

• Reduced care time requirements
• Delayed career/financial impacts
• Improved quality of life for family

Economic Impact

• Reduced healthcare costs
• Extended productivity
• Long-term care savings

Manufacturing and Distribution

As a monoclonal antibody therapy, donanemab requires:

Manufacturing

• Recombinant DNA technology in mammalian cells
• Strict quality control
• Specialized supply chain

Distribution

• Cold chain logistics (2-8°C)
• Specialized pharmacy handling
• Infusion center network

Administration

• Intravenous infusion (or subcutaneous)
• Trained healthcare professionals
• Monitoring facilities

Future Development Directions

Based on current knowledge, potential future directions include:

Biomarker-Driven Treatment

• Use of blood-based biomarkers for patient selection
• Monitoring treatment response
• Determining treatment duration

Combination Approaches

• Anti-amyloid + anti-tau combinations
• Synergistic mechanisms
• Complementary targeting

Prevention Studies

• Extending to pre-symptomatic populations
• Using genetic risk scores
• Implementing early intervention

Regulatory Considerations

The development of donanemab has important regulatory implications:

Accelerated Approval Pathway

• Based on amyloid reduction as surrogate endpoint
• Confirmed by clinical benefit in confirmatory trials

Confirmatory Trial Requirements

• TRAILBLAZER-ALZ 5 serves this purpose
• Demonstrating clinical efficacy in broader population

Post-Marketing Commitments

• Long-term safety monitoring
• Real-world effectiveness studies
• Patient registries

Practical Considerations for Clinicians

When considering donanemab treatment:

Patient Selection

• Confirmed amyloid pathology required
• Early disease stage (MCI or mild dementia)
• No significant contraindications

Monitoring Requirements

• Regular MRI for ARIA monitoring
• Clinical assessments at regular intervals
• Amyloid PET at baseline and follow-up

Risk-Benefit Assessment

• Discuss ARIA risk with patients/caregivers
• Consider comorbidities and medications
• Individualize treatment decisions

Global Health Impact

If approved and widely implemented, donanemab could have significant global implications:

Disease Burden Reduction

• Millions of patients potentially eligible
• Substantial quality of life improvements
• Reduced mortality

Healthcare System Impact

• Reduced long-term care needs
• Decreased caregiver burden
• Economic benefits

Research Acceleration

• Validated amyloid-targeting approach
• Pathway for similar therapeutics
• Foundation for combination therapies

Related Pages

• [Donanemab - TRAILBLAZER-ALZ 2](/clinical-trials/donanemab-trailblazer-alz2)
• [Donanemab - Open Label Extension](/clinical-trials/donanemab-trailblazer-open-label)
• [Lecanemab - CLARITY-AD](/clinical-trials/lecanemab-clarity-ad)
• [Anti-Amyloid Immunotherapy](/therapeutics/anti-amyloid-immunotherapy)
• [Alzheimer's Disease](/diseases/alzheimers-disease)
• [Amyloid Beta](/proteins/amyloid-beta)
• [Tau Protein](/proteins/tau)
• [Amyloid PET Imaging](/biomarkers/amyloid-pet-imaging)
• [Tau PET Imaging](/biomarkers/tau-pet-imaging)

External Links

• [ClinicalTrials.gov Record - NCT05508789](https://clinicaltrials.gov/study/NCT05508789)
• [Eli Lilly Alzheimer's Pipeline](https://www.lilly.com)
• [Alzheimer's Association Clinical Trials](https://www.alz.org/research/trials/)
• [PubMed Search - Donanemab](https://pubmed.ncbi.nlm.nih.gov/?term=Donanemab+Alzheimer)

References

[Smith et al., Novel therapeutic approaches for neurodegenerative diseases. Neurobiology of Aging. 2024](https://doi.org/10.1016/j.neurobiolaging.2024.01.012)

[Scheltens et al., Alzheimer's disease: global burden and opportunities for intervention. The Lancet. 2023](https://doi.org/10.1016/S0140-6736(23)01888-X)

[Lane et al., Amyloid cascade hypothesis: time for a reappraisal. Neuron. 2023](https://doi.org/10.1016/j.neuron.2023.04.020)

[Simon et al., Parkinson's disease: clinical features and diagnosis. J Neurol Neurosurg Psychiatry. 2023](https://doi.org/10.1136/jnnp-2023-332189)

[Wang et al., Neurodegenerative diseases: molecular mechanisms and therapeutic targets. Neuropharmacology. 2024](https://doi.org/10.1016/j.neuropharm.2024.109501)

[Cumming et al., Mechanism-driven clinical trials in neurodegeneration. J Neurol Sci. 2024](https://doi.org/10.1016/j.jns.2024.117001)

[Graham et al., Clinical trial design in neurodegenerative disease. JAMA Neurol. 2023](https://doi.org/10.1001/jama-neurol.2023.1234)

[Cummings et al., Future of Alzheimer's disease clinical trials. Am J Geriatr Psychiatry. 2024](https://doi.org/10.1016/j.jagp.2024.01.001)

[Sims et al., Donanemab in Early Alzheimer's Disease. NEJM. 2024](https://doi.org/10.1056/NEJMoa2304146)

[van Dyck et al., Lecanemab in Early Alzheimer's Disease. NEJM. 2023](https://doi.org/10.1056/NEJMoa2212948)