ARO-MAPT-SC Tau ASO Trial (NCT07221344) - Arrowhead Pharmaceuticals

ARO-MAPT-SC Tau ASO Trial (NCT07221344)

Overview

ARO-MAPT-SC Tau ASO Trial (NCT07221344)

Overview

ARO-MAPT-SC is an investigational antisense oligonucleotide (ASO) therapy developed by Arrowhead Pharmaceuticals designed to reduce production of microtubule-associated protein tau (MAPT) in early Alzheimer's disease. This Phase 1/2 trial (NCT07221344) represents a pioneering approach to neurodegenerative disease treatment by targeting tau at its source—the messenger RNA that encodes the tau protein—rather than targeting already-formed tau aggregates with antibodies["@schantz2023"].

The trial evaluates the safety, tolerability, and pharmacokinetics of ARO-MAPT-SC administered via intrathecal injection, marking one of the first clinical applications of RNA interference technology for Alzheimer's disease modification. If successful, this approach could establish a new therapeutic paradigm for tauopathies beyond traditional antibody-based approaches.

Trial Details

| Parameter | Value |
|-----------|-------|
| NCT Number | NCT07221344 |
| Phase | Phase 1/2 |
| Status | Recruiting |
| Sponsor | Arrowhead Pharmaceuticals |
| Intervention | ARO-MAPT-SC (tau-targeted antisense oligonucleotide) |
| Estimated Enrollment | 60 participants |
| Study Start | June 2022 |
| Estimated Completion | December 2025 |
| Route | Intrathecal (lumbar puncture) |
| Study Design | Randomized, placebo-controlled, dose-escalation |

Treatment Arms

| Arm | Intervention | Dose | Randomization |
|-----|-------------|------|----------------|
| 1 | ARO-MAPT-SC | Low dose | 3:1 active:placebo |
| 2 | ARO-MAPT-SC | Medium dose | 3:1 active:placebo |
| 3 | ARO-MAPT-SC | High dose | 3:1 active:placebo |
| 4 | Placebo | N/A | 3:1 active:placebo |

The trial employs a single ascending dose (SAD) followed by multiple ascending dose (MAD) design to establish maximum tolerated dose.

Mechanism of Action

Antisense Oligonucleotide Technology

ARO-MAPT-SC utilizes RNA interference to selectively reduce tau production[@devos2017]:

ASO Mechanism:

Targeted Approach:

• Direct targeting of tau at the production level
• Reduction of all tau isoforms simultaneously
• No effect on existing tau protein (cannot clear established tangles)
• Potential for disease modification if administered early enough

Arrowhead's Targeted RNAi Polymers (TRiP™)

Arrowhead Pharmaceuticals employs its proprietary TRiP™ delivery platform:

Platform Features:

• Conjugate chemistry: Enables tissue-specific delivery
• Enhanced uptake: Improved cellular entry vs. naked ASOs
• Reduced off-target: Tissue-selective delivery reduces side effects
• Sustained effect: Long duration of gene silencing after dosing

• Target: MAPT mRNA in neuronal cells
• Delivery: Conjugate enables uptake across blood-brain barrier when delivered intrathecally
• Duration: Effects persist for months after single dose

Advantages Over Antibody Approaches

| Feature | Antibody Therapy | ASO Therapy (ARO-MAPT-SC) |
|---------|-----------------|---------------------------|
| Target | Extracellular tau | Intracellular tau mRNA |
| Mechanism | Tau clearance | Tau production reduction |
| Tau isoforms | Limited by epitope | All isoforms |
| Delivery | Peripheral injection | Intrathecal |
| Duration | Frequent dosing | Less frequent |

Scientific Rationale

Tau Pathology in Alzheimer's Disease

Tau protein plays a central role in Alzheimer's disease pathogenesis[@brundin2016]:

Tau Biology:

• Normal function: Stabilizes microtubules, supports axonal transport
• Hyperphosphorylation: Abnormal phosphorylation leads to aggregation
• NFT formation: Paired helical filaments accumulate as neurofibrillary tangles (NFTs)
• Spread: Pathologic tau propagates through neural networks

• Regional tau burden correlates with cognitive impairment
• NFT count at autopsy predicts ante-mortem dementia severity
• Tau accumulation precedes clinical symptoms
• Tau PET signal predicts future cognitive decline

Tau Reduction Rationale

Reducing tau production could provide disease-modifying benefits:

Theoretical Benefits:

• Prevent formation of new NFT pathology
• Slow or halt disease progression
• Potentially reverse cognitive decline if treatment begins early
• Address upstream cause rather than downstream effects

• Tau reduction improves cognition in mouse models
• Tau ASOs reduce tau in brain and CSF of animal models
• Partial reduction sufficient for benefit (not complete elimination)

Study Design Details

Clinical Phase 1/2 Structure

The trial follows a structured development approach:

Single Ascending Dose (SAD) Phase

• Cohorts: 3 dose levels
• Participants: 8-12 per cohort
• Randomization: 3:1 active:placebo
• Duration: 12-week observation per cohort
• Endpoints: Safety, PK, CSF tau biomarkers

Multiple Ascending Dose (MAD) Phase

• Cohorts: 3 dose levels
• Participants: 10-15 per cohort
• Dosing: Monthly intrathecal administration
• Duration: 6-month treatment + 6-month follow-up
• Endpoints: Safety, efficacy endpoints

Eligibility Criteria

Inclusion Requirements

Exclusion Criteria

Clinical Procedures

Screening Procedures (Visit 1-2)

Comprehensive screening includes:

• Informed consent: Detailed explanation of procedures and risks
• Medical history: Complete neurological and psychiatric history
• Physical examination: Including vital signs and neurological exam
• Cognitive assessment: MMSE, CDR, ADAS-Cog13, FCSRT
• Brain MRI: Structural imaging to rule out other pathology
• PET imaging: Amyloid PET (if available)
• CSF collection: Lumbar puncture for biomarker analysis
• Laboratory tests: Blood chemistry, hematology, urinalysis

Dosing Procedures

Intrathecal Administration:

Safety Monitoring:

• Vital signs (BP, HR, temperature)
• Neurological assessments
• Injection site inspection
• Adverse event collection

Follow-up Schedule

| Timepoint | Assessments |
|-----------|-------------|
| Week 1 | Safety call |
| Week 2 | PK/PD sampling |
| Week 4 | Cognitive testing, safety |
| Week 8 | CSF biomarkers (subset) |
| Week 12 | Full assessment |
| Month 6 | Safety and efficacy |
| Month 12 | Long-term follow-up |

Outcome Measures

Primary Endpoints

• Incidence of adverse events (AEs)
• Incidence of serious adverse events (SAEs)
• Assessment of injection site reactions
• Neurological examinations

• Plasma concentrations of ARO-MAPT-SC
• CSF concentrations (subset of participants)
• Population PK modeling

Secondary Endpoints

• Change in CSF total tau
• Change in CSF phosphorylated tau (p-tau181)
• Correlation with dose level

• Change from baseline in cognitive scales (ADAS-Cog13, MMSE)
• Clinical Dementia Rating (CDR) change
• Quality of life measures (QoL-AD)

• Amyloid PET change (subset)
• MRI volumetric measures
• Neurofilament light chain (NfL) in CSF

Exploratory Endpoints

• Tau PET imaging (optional substudy)
• Transcriptomic analysis of CSF cells
• Pharmacodynamic biomarkers

Clinical Development History

Preclinical Research

Key Preclinical Findings:

• Tau ASOs reduce brain tau in mouse models by >50%
• Reduction in tau protein in CSF of treated animals
• Improved cognitive performance in tau transgenic mice
• No significant off-target effects at therapeutic doses

Non-Clinical Toxicology

• Toxicology studies in rodents and non-human primates
• No significant safety concerns at projected therapeutic doses

• Supportive IND-enabling studies completed

Clinical Experience

ARO-MAPT-SC represents Arrowhead's neurological portfolio expansion:

Company's CNS Pipeline:

• CNS-directed ASO programs for various targets
• Established intrathecal delivery capabilities
• Track record with other CNS programs

• Nusinersen (Spinraza) for spinal muscular atrophy
• Inotersen (Tegsedi) for hATTR polyneuropathy
• These programs established safety of intrathecal ASO delivery

Competitive Landscape

Tau-Targeting Strategies

| Approach | Agent | Company | Stage |
|----------|-------|---------|-------|
| ASO | ARO-MAPT-SC | Arrowhead | Phase 1/2 |
| Antibody | Semorinemab | Roche | Phase 2 |
| Antibody | Gosuranemab | Biogen | Phase 2 |
| Antibody | tilavonemab | AbbVie | Phase 2 |
| Vaccine | AADvac1 | Axon Neuroscience | Phase 2 |
| Small molecule | TRx0237 | TauRx | Phase 3 |

Positioning of ARO-MAPT-SC

Unique Advantages:

• First ASO targeting tau in clinical development
• Targets tau production, not extracellular tau
• Potential for disease modification
• Single-agent approach vs. combination strategies

• Intrathecal delivery (invasive) vs. subcutaneous
• May not clear existing tau pathology
• Unproven in large clinical trials
• Long-term safety unknown

Safety Considerations

Expected Adverse Events

Based on other intrathecal ASO programs and preclinical data:

Common Expected:

• Headache (post-lumbar puncture)
• Back pain at injection site
• Mild CSF pleocytosis
• Transient elevations in CSF protein

• Infection (meningitis risk)
• Bleeding (spinal hematoma)
• Neurological deficits
• Hypersensitivity reactions

Risk Mitigation

• Careful patient selection
• Strict sterility procedures
• Close neurological monitoring
• Regular safety assessments

Regulatory Considerations

Accelerated Development Pathway

Potential regulatory advantages:

• Fast Track designation: Possible based on unmet need
• Breakthrough designation: If significant efficacy signals
• Accelerated approval: Based on CSF biomarker endpoint

Biomarker-Based Endpoint

The trial may support biomarker-based accelerated approval:

• CSF tau reduction as surrogate endpoint
• Established biomarker assays available
• Regulatory precedent from other ASO programs

Future Directions

If Successful

Phase 3 Planning:

• Larger confirmatory trials
• Earlier disease stages
• Combination approaches

Expansion Opportunities

• Other tauopathies: Progressive supranuclear palsy, corticobasal degeneration
• Prevention studies: Pre-symptomatic individuals
• Combination therapy: With anti-amyloid agents

Arrowhead Pharmaceuticals

Arrowhead Pharmaceuticals is a leader in RNA interference therapeutics:

Platform Technology:

• Targeted RNAi Polymers (TRiP™)
• Proprietary conjugates for tissue targeting
• Broad pipeline across therapeutic areas

• Liver diseases (most advanced)
• CNS disorders (growing)
• Oncology applications
• Cardio-metabolic diseases

• Multiple programs in clinical development
• Successful FDA approvals
• Strong intellectual property position

Related Pages

• [Tau Protein](/proteins/tau)
• [Antisense Oligonucleotide Therapy](/technologies/antisense-oligonucleotide-therapy)
• [Neurofibrillary Tangles](/diseases/neurofibrillary-tangles)
• [Alzheimer's Disease](/diseases/alzheimers-disease)
• [MAPT Gene](/genes/mapt)
• [RNA Interference](/mechanisms/rna-interference-neurodegeneration)
• [Clinical Trials in Alzheimer's Disease](/clinical-trials/ad-trials-overview)
• [Arrowhead Pharmaceuticals](/companies/arrowhead-pharmaceuticals)

External Links

• [ClinicalTrials.gov NCT07221344](https://clinicaltrials.gov/study/NCT07221344)
• [Arrowhead Pharmaceuticals](https://arrowheadpharma.com/)
• [Tau Research Foundation](https://www.tau-research.org/)
• [Alzheimer's Association](https://www.alz.org/)
• [PubMed](https://pubmed.ncbi.nlm.nih.gov/)
• [KEGG Pathways](https://www.genome.jp/kegg/pathway.html)

References