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
Mermaid diagram (expand to render)
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 reducedUnique 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-upTreatment 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 benefitComparison 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
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 signsOther 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 modificationTau PET
Tau PET provides:
Staging information: Tau burden correlates with clinical stage
Treatment effect: Monitor tau progression
Prognostic information: Predict clinical outcomesCSF 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 dataParticipating 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 agentsTreatment Sequencing
Potential treatment paradigms:
Sequential immunotherapy: Donanemab → Lecanemab
Combination approaches: Anti-amyloid + anti-tau
Maintenance: Extended treatment after plaque clearancePersonalized 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 durabilityAmyloid Clearance and Clinical Outcomes
The relationship between amyloid clearance and clinical outcomes is complex:
Mermaid diagram (expand to render)
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)