CNversyt and Megan Rodden ALS Trials

Overview

The CNversyt and Megan Rodden clinical trials represent cutting-edge gene silencing approaches for treating specific genetic forms of amyotrophic lateral sclerosis (ALS). These trials focus on targeting the underlying genetic causes of ALS, particularly mutations in the [C9orf72](/genes/c9orf72) gene, which accounts for approximately 40% of familial ALS cases, as well as SOD1 and FUS mutations["@brown2017"][@gene2022].

Gene silencing therapies represent a paradigm shift in ALS treatment, moving from symptomatic management to disease-modifying approaches that target the root cause of neurodegeneration. By reducing the production of toxic proteins, these therapies aim to slow or halt disease progression["@ago2024"].

Trial Details

Overview

The CNversyt and Megan Rodden clinical trials represent cutting-edge gene silencing approaches for treating specific genetic forms of amyotrophic lateral sclerosis (ALS). These trials focus on targeting the underlying genetic causes of ALS, particularly mutations in the [C9orf72](/genes/c9orf72) gene, which accounts for approximately 40% of familial ALS cases, as well as SOD1 and FUS mutations["@brown2017"][@gene2022].

Gene silencing therapies represent a paradigm shift in ALS treatment, moving from symptomatic management to disease-modifying approaches that target the root cause of neurodegeneration. By reducing the production of toxic proteins, these therapies aim to slow or halt disease progression["@ago2024"].

Trial Details

CNversyt Trial (NCT04931836)

• Phase: Phase 1/2
• Status: Ongoing
• Sponsor: Wave Life Sciences
• Target: C9orf72 gene
• Approach: Antisense oligonucleotide (ASO)
• Delivery: Intrathecal (spinal) injection
• Objective: Reduce C9orf72 protein expression in CNS

Megan Rodden Trial (NCT05053035)

• Phase: Phase 1/2
• Status: Ongoing
• Sponsor: Neu Decode Therapeutics
• Target: C9orf72 gene
• Approach: Modified antisense oligonucleotide with enhanced delivery
• Innovation: Next-generation ASO chemistry for improved brain penetration

Additional C9orf72 Trials

• NCT04768972 - C9orf72 ASO trial (Wave Life Sciences)
• NCT04615988 - Biogen ASO for C9orf72-ALS
• Additional studies in planning stages

Mechanism of Action

Gene silencing approaches employ different molecular strategies to reduce the production of toxic proteins:

Antisense Oligonucleotides (ASOs)

• Bind specifically to mutant mRNA through base-pairing
• Recruit RNase H to degrade the target mRNA
• Reduce translation of the toxic protein
• Are delivered via intrathecal (spinal) injection to reach the central nervous system

RNA Interference (RNAi)

• Small interfering RNAs (siRNAs) that guide the RISC complex
• Sequence-specific degradation of target mRNA
• AAV-delivered gene therapy constructs

Gene Editing (Emerging)

• Base editing to correct mutations
• Gene knockdown via CRISPRi
• Currently in preclinical development

Target Genes

C9orf72 (Chromosome 9 Open Reading Frame 72)

• Prevalence: ~40% of familial ALS, ~10% of sporadic ALS
• Mutation: Hexanucleotide repeat expansion (GGGGCC)
• Pathogenesis:
• Toxic gain-of-function from repeat-containing RNA
• Dipeptide repeat proteins (DPRs) from repeat-associated non-ATG translation
• Loss of C9orf72 protein function
• Brain Regions Affected: Motor [cortex](/brain-regions/cortex), corticospinal tract, spinal cord

SOD1 (Superoxide Dismutase 1)

• Prevalence: ~2% of ALS
• Mutation: Over 180 known pathogenic mutations
• Pathogenesis: Toxic gain-of-function, protein aggregation
• Model: First ALS gene discovered, extensive preclinical work

FUS (Fused in Sarcoma)

• Prevalence: ~4% of familial ALS
• Mutation: Missense and truncating mutations
• Pathogenesis: RNA processing dysregulation, protein aggregation

Patient Population

Inclusion Criteria

• Confirmed diagnosis of ALS
• Genetic confirmation of target mutation (C9orf72, SOD1, or FUS)
• Age 18-80 years
• Disease duration less than 5 years
• Forced vital capacity (FVC) >50% predicted

Exclusion Criteria

• Active participation in other clinical trials
• Severe comorbidities
• Previous gene therapy for ALS

Endpoints

Primary Endpoints

• Safety and tolerability (adverse events, serious adverse events)
• Maximum tolerated dose
• Pharmacokinetics (CSF drug concentration)

Secondary Endpoints

• Target engagement (mRNA reduction in CSF cells)
• Protein levels in CSF (C9orf72, SOD1, FUS)
• [Neurofilament light](/biomarkers/neurofilament-light-chain-nfl) chain (NfL) as biomarker
• Clinical efficacy measures (ALSFRS-R, ALSAQ-40)

Exploratory Endpoints

• Brain imaging metrics
• Peripheral biomarker changes
• Quality of life measures

Clinical Significance

The CNversyt and Megan Rodden trials represent several important advances:

Challenges and Considerations

• Delivery to CNS requires invasive intrathecal administration
• Off-target effects possible with ASO approaches
• Optimal timing of intervention (pre-symptomatic vs. symptomatic)
• Need for reliable biomarkers of target engagement
• Combination approaches may be needed for complete protection

C9orf72 Pathogenesis: Molecular Mechanisms

Hexanucleotide Repeat Expansion

The C9orf72 gene contains a hexanucleotide repeat expansion (GGGGCC) in the first intron, representing the most common genetic cause of both familial ALS and frontotemporal dementia (FTD)[@c9orf72_mechanism]. This expansion leads to disease through three primary mechanisms:

1. Loss of Function

• The repeat expansion reduces C9orf72 mRNA expression
• C9orf72 protein is involved in endosomal trafficking and autophagy
• Reduced function impairs lysosomal function and autophagy
• May contribute to accumulation of toxic proteins

2. RNA Toxicity

• Expanded repeat RNA forms toxic foci in the nucleus
• Sequesters RNA-binding proteins essential for normal splicing
• Disrupts RNA metabolism and nuclear export
• Creates a toxic gain-of-function at the RNA level

3. Dipeptide Repeat Protein (DPR) Toxicity

• Non-ATG translation (RAN translation) produces five DPRs
• Poly-GA, poly-GP, poly-GR, poly-PR, poly-PA accumulate in brain
• Poly-GA is most abundant and forms neuronal inclusions
• DPRs disrupt proteostasis, nucleocytoplasmic transport, and autophagy

Neuroanatomical Distribution

The C9orf72 expansion causes characteristic neuropathology:

| Brain Region | Pathology | Clinical Correlate |
|--------------|-----------|-------------------|
| Motor Cortex | Loss of upper motor neurons | Spasticity, hyperreflexia |
| Spinal Cord | Loss of lower motor neurons | Weakness, atrophy, fasciculations |
| Frontal Lobe | TDP-43 and DPR inclusions | Executive dysfunction, behavioral changes |
| Hippocampus | Variable involvement | Memory impairment |
| Basal Ganglia | Dopaminergic neuron loss | Movement abnormalities |

Phenotypic Spectrum

C9orf72-associated disease presents on a spectrum[@millers2023]:

• ALS (50-60%): Pure motor presentation
• ALS/FTD (30-40%): Combined motor and cognitive involvement
• FTD (10-20%): Cognitive/behavioral presentation without ALS
• Parkinsonism: Rare, but described

Antisense Oligonucleotide Technology

Mechanism of Action

ASOs are single-stranded DNA analogs that work through multiple mechanisms:

RNase H-Mediated Degradation

Steric Blockade

• Some ASOs don't recruit RNase H but block translation
• Interfere with ribosome assembly or RNA splicing
• Useful for specific splice-modulating applications

Chemistry Generations

ASO chemistry has evolved through generations:

| Generation | Backbone Modification | Advantages | Limitations |
|------------|---------------------|------------|--------------|
| First | Phosphodiester | Native | Rapid degradation |
| Second | Phosphorothioate | Nuclease resistance | Off-target effects |
| Third | 2'-O-methyl, 2'-MOE | Improved binding | Limited brain penetration |
| Fourth | Locked nucleic acid (LNA) | High affinity | Potential toxicity |
| Fifth | Gapmer, bridging | Optimized design | Still requires intrathecal |

Delivery Challenges

The blood-brain barrier presents a major challenge:

Current Approach: Intrathecal Delivery

• Lumbar puncture delivers ASO directly to CSF
• Diffusion distributes ASO throughout CNS
• Requires repeated dosing (monthly or quarterly)
• Invasive but effective

• Convection-enhanced delivery
• Focused ultrasound-mediated opening
• AAV-delivered gene therapy (one-time treatment)
• Exosome-based delivery systems

Clinical Trial Design

Outcome Measures

Primary Endpoints

• Safety and Tolerability
• Adverse events (AEs) and serious AEs (SAEs)
• Laboratory abnormalities (CBC, chemistry)
• CSF cell count and protein
• MRI findings
• Pharmacokinetics
• CSF ASO concentration over time
• Dose proportionality
• Half-life determination

Secondary Endpoints

• Target Engagement
• C9orf72 mRNA levels in peripheral blood mononuclear cells (PBMCs)
• CSF biomarkers (if detectable)
• Poly-GA DPR levels in CSF (emerging biomarker)
• Clinical Efficacy
• ALSFRS-R (ALS Functional Rating Scale-Revised)
• ALSAQ-40 (ALS Assessment Questionnaire)
• Slow vital capacity (SVC)
• Handheld dynamometry

Patient Selection

Key Inclusion Criteria

Key Exclusion Criteria

Trial Phases

Phase 1: First-in-Human

• Single ascending dose (SAD)
• Multiple ascending dose (MAD)
• Primary objective: Safety and tolerability
• Secondary: PK/PD

Phase 2: Dose-Finding

• Randomized, placebo-controlled
• Multiple dose levels
• Clinical outcomes
• Biomarker development

Phase 3: Registration

• Large enrollment (hundreds)
• Pivotal efficacy endpoints
• Registration trials for FDA/EMA

Biomarker Development

Target Engagement Biomarkers

Measuring ASO activity is critical for dose selection:

Genetic Biomarkers

• C9orf72 mRNA: Reduced expression indicates target engagement
• Allele-specific expression: May show differential knockdown

Protein Biomarkers

• C9orf72 protein: Direct measurement challenging (no good antibody)
• Poly-GA DPR: Most abundant, detectable in CSF
• Other DPRs: GP, GR, PR, PA in development

Disease Progression Biomarkers

Neurofilament Light Chain (NfL)

• Released when neurons are damaged
• Elevated in ALS CSF and blood
• Correlates with disease progression
• May serve as surrogate endpoint

Prognostic Biomarkers

• Age at onset: Younger may have slower progression
• Repeat size: Larger expansions correlate with earlier onset
• Family history: Can predict disease course
• Baseline function: Higher ALSFRS-R predicts slower decline

Therapeutic Pipeline Beyond CNversyt and Megan Rodden

Other C9orf72-Targeting Approaches

| Agent | Company | Mechanism | Stage |
|-------|---------|-----------|-------|
| WVE-NEO1 | Wave Life Sciences | ASO | Phase 1/2 |
| BIIB078 | Biogen/Ionis | ASO | Phase 1 |
| AO-C9orf72 | University of Edinburgh | ASO | Preclinical |
| AAV-C9orf72 RNAi | Various | Gene therapy | Preclinical |
| CRISPR-Cas9 | Various | Gene editing | Discovery |

Comparison of Approaches

ASO Advantages:

• Proven delivery to CNS
• Reversible (can stop if issues)
• Dose-adjustable
• Established regulatory pathway

• One-time treatment
• Potentially curative
• May not require repeated procedures

• Permanent correction
• Could restore normal C9orf72 function
• Still early in development

Future Directions

Combination Therapies

Single-target approaches may not be sufficient:

• ASO + Small Molecule: Combine gene silencing with neuroprotection
• ASO + Cell Therapy: Support motor neuron survival
• ASO + Antisense for DPRs: Target both C9orf72 loss and DPR toxicity

Timing of Intervention

Pre-symptomatic Treatment:

• Treat individuals with C9orf72 expansion before symptoms
• Prevent neuron loss rather than trying to reverse it
• Requires predictive genetic testing and biomarkers
• Ethical considerations around genetic testing

• Treat within first year of diagnosis
• Preserve remaining motor neurons
• May achieve maximal benefit
• Most feasible current approach

Personalized Medicine

Future treatment will be tailored based on:

• C9orf72 repeat size
• Phenotype (ALS vs. FTD)
• Disease progression rate
• Biomarker profile
• Genetic modifiers

Clinical Significance

The CNversyt and Megan Rodden trials represent several important advances:

Impact on ALS Treatment Landscape

These trials could transform ALS care if successful:

• First disease-modifying therapy for genetic ALS
• Validation of ASO platform for CNS disorders
• Foundation for treating other genetic neurodegenerative diseases
• Model for precision medicine in neurology

Challenges to Address

| Challenge | Current Approach | Future Solutions |
|-----------|-----------------|------------------|
| Invasiveness | Intrathecal delivery | Oral/in IV ASOs, gene therapy |
| Variable response | Fixed dosing | Biomarker-guided dosing |
| Incomplete knockdown | Single ASO | Multiple ASOs, combination |
| DPR toxicity | C9orf72 only | DPR-targeting approaches |

Related Pages

• [Amyotrophic Lateral Sclerosis](/diseases/amyotrophic-lateral-sclerosis)
• [C9orf72 Gene](/genes/c9orf72)
• [SOD1 Gene](/genes/sod1)
• [FUS Gene](/genes/fus)
• [Gene Therapy](/therapeutics/gene-therapy)
• [Antisense Oligonucleotide Therapy](/therapeutics/antisense-oligonucleotide-therapy)
• [RNA Interference](/mechanisms/rna-interference)
• [TDP-43 Proteinopathy](/mechanisms/tdp-43-proteinopathy)
• [Dipeptide Repeat Proteins](/mechanisms/dipeptide-repeat-proteins-als)
• [Motor Neuron Disease](/diseases/motor-neuron-disease)
• [Frontotemporal Dementia](/diseases/frontotemporal-dementia)
• [Neurofilament Light Chain](/biomarkers/neurofilament-light-chain-nfl)

Gene Silencing in Neurodegeneration: Broader Context

Comparison to Other Neurodegenerative Diseases

The gene silencing approach for ALS builds on success in other conditions:

Spinal Muscular Atrophy (SMA)

• [ASO therapy (nusinersen/Spinraza) approved in 2016](/institutions/nus)
• [Targets SMN2 gene](/genes/ar)
• Demonstrated dramatic efficacy in infants and children
• Validated ASO platform for CNS disorders

Huntington's Disease

• ASO therapies in clinical trials (tominersen, others)
• Targets mutant huntingtin protein
• Shows target engagement in CSF
• Ongoing optimization of dosing

Alzheimer's Disease

• ASO approaches targeting BACE1, tau, APP
• Earlier in development than ALS programs
• May benefit from lessons learned

Regulatory Pathway

ASO therapies have established regulatory precedent:

| Disease | Drug | Company | Approval Year |
|---------|------|---------|---------------|
| SMA | Nusinersen | Biogen/Ionis | 2016 |
| SMA | Onasemnogene | Novartis | 2019 |
| DMD | Exondys 51 | Sarepta | 2016 |
| DMD | Vyondys 53 | Sarepta | 2019 |
| HF | Waylivra | Akcea | 2019 |

This precedent supports rapid development of ALS ASOs if efficacy is demonstrated.

Manufacturing Considerations

ASO manufacturing has unique requirements:

Synthesis:

• Solid-phase synthesis using modified nucleotides
• Scale-up is technically challenging
• Quality control is critical

• Must be sterile for intrathecal delivery
• Stability requirements for storage
• Special handling for clinical supply

• Currently expensive (>$100,000/year)
• Need to reduce manufacturing costs
• Value-based pricing discussions with payers

Real-World Considerations for Patients

Access and Logistics

Patients considering trial participation should understand:

Treatment Logistics:

• Intrathecal injections require specialized center
• Initial loading dose period with frequent visits
• Maintenance dosing (monthly to quarterly)
• Travel requirements for trial sites

• Caregiver assistance for transportation
• Insurance coverage for standard care
• Financial support for travel (trial may provide)

Risk-Benefit Assessment

Potential Benefits:

• Access to cutting-edge therapy
• Close monitoring by experts
• Contribution to scientific knowledge
• Potential for disease modification

• Unknown efficacy (may not help)
• Invasive delivery method
• Potential side effects
• Time commitment

Quality of Life Considerations

ALS progression affects treatment options:

| Disease Stage | Considerations |
|---------------|----------------|
| Early (ALSFRS-R >35) | Best time to enroll, preserve function |
| Mid (ALSFRS-R 25-35) | Still possible, careful monitoring |
| Late (ALSFRS-R <25) | May exclude, respiratory compromise |

Family Considerations

Genetic Testing:

• First-degree relatives may want testing
• Counseling available through trial sites
• Implications for family planning
• Life insurance considerations

• Trials may enroll family members for biomarker studies
• Pre-symptomatic trials emerging
• Support groups helpful for families

Emerging Science and Future Outlook

Biomarker Evolution

The field is moving toward precise biomarker-guided therapy:

Current Biomarkers:

• NfL in plasma/CSF (disease progression)
• Poly-GA in CSF (target engagement, experimental)

• Poly-GP, Poly-PR in CSF
• Neuroimaging markers
• Motor unit number estimation (MUNE)

• Reflects disease progression
• Shows treatment effect
• Easily measurable (plasma preferred)
• Cost-effective for monitoring

Next-Generation ASOs

Improved ASO technologies in development:

Improvements:

• Enhanced brain penetration
• Longer duration between doses
• Reduced off-target effects
• Improved delivery to specific cell types

• Palmitoylated ASOs for better CNS delivery
• Trivalent ASOs with enhanced affinity
• Cell-type specific targeting

Gene Therapy Integration

Gene therapy may complement ASO approaches:

Viral Vectors:

• AAV9 commonly used for CNS delivery
• Single administration potential
• Long-term expression

• Lipid nanoparticles (LNPs)
• Exosomes
• Focused ultrasound

Cell Therapy Approaches

Future combinations may include:

• Neural stem cell transplantation
• Motor neuron replacement (early research)
• Support cell transplantation (astrocytes, microglia)

Conclusion

The CNversyt and Megan Rodden clinical trials represent a pivotal moment in ALS therapeutic development. By targeting the most common genetic cause of ALS directly at its source, these trials embody the promise of precision medicine for neurodegenerative diseases.

The C9orf72 hexanucleotide repeat expansion causes disease through multiple mechanisms—loss of C9orf72 function, toxic RNA foci, and dipeptide repeat proteins. ASO therapy aims to address the root cause by reducing C9orf72 expression, potentially slowing or halting disease progression.

If successful, these trials will:

The path forward requires continued scientific innovation, patient participation in clinical trials, and collaboration across the ALS research community. While challenges remain, the progress achieved in the past decade offers genuine hope for patients and families affected by this devastating disease.

External Links

• [ClinicalTrials.gov: CNversyt (NCT04931836)](https://clinicaltrials.gov/study/NCT04931836)
• [ClinicalTrials.gov: Megan Rodden (NCT05053035)](https://clinicaltrials.gov/study/NCT05053035)
• [ALSA (ALS Association)](https://www.als.net/)
• [ALS Clinical Trials](https://clinicaltrials.gov/cond/ALS)

References