atl1103-antisense-als

ATL1103 Antisense Oligonucleotide ALS Trial

Overview

ATL1103 is an antisense oligonucleotide (ASO) designed to reduce the expression of SOD1 (superoxide dismutase 1) for the treatment of SOD1-associated amyotrophic lateral sclerosis (ALS). This represents a gene-targeted approach specifically for patients with SOD1 mutations, which account for approximately 2% of all ALS cases and approximately 15-20% of familial ALS[@benatar2020].

ALS is a rapidly progressive neurodegenerative disorder affecting motor neurons in the brain and spinal cord. The disease leads to progressive muscle weakness, paralysis, and typically death within 2-5 years of symptom onset. The identification of specific genetic causes has enabled precision medicine approaches like antisense therapy.

Trial Details

| Parameter | Value |
|-----------|-------|
| Phase | Phase 1/2 |
| Status | Completed |
| Drug | ATL1103 (antisense oligonucleotide) |
| Route | Intrathecal (lumbar puncture) administration |
| Dosage | Multiple dose cohorts |
| Patient Population | Adults with SOD1-positive ALS |
| Duration | Single dose and multiple dose phases |

Background: SOD1-Associated ALS

Genetic Basis

Mutations in the SOD1 gene were first identified as a cause of familial ALS in 1993, representing one of the earliest discovered genetic causes of the disease[@taylor2016]:

Epidemiology:

• SOD1 mutations: ~2% of all ALS cases
• ~15-20% of familial ALS cases
• Over 180 different SOD1 mutations identified
• Most common: A4V (North America), G93A, G85R, D90A

ATL1103 Antisense Oligonucleotide ALS Trial

Overview

ATL1103 is an antisense oligonucleotide (ASO) designed to reduce the expression of SOD1 (superoxide dismutase 1) for the treatment of SOD1-associated amyotrophic lateral sclerosis (ALS). This represents a gene-targeted approach specifically for patients with SOD1 mutations, which account for approximately 2% of all ALS cases and approximately 15-20% of familial ALS[@benatar2020].

ALS is a rapidly progressive neurodegenerative disorder affecting motor neurons in the brain and spinal cord. The disease leads to progressive muscle weakness, paralysis, and typically death within 2-5 years of symptom onset. The identification of specific genetic causes has enabled precision medicine approaches like antisense therapy.

Trial Details

| Parameter | Value |
|-----------|-------|
| Phase | Phase 1/2 |
| Status | Completed |
| Drug | ATL1103 (antisense oligonucleotide) |
| Route | Intrathecal (lumbar puncture) administration |
| Dosage | Multiple dose cohorts |
| Patient Population | Adults with SOD1-positive ALS |
| Duration | Single dose and multiple dose phases |

Background: SOD1-Associated ALS

Genetic Basis

Mutations in the SOD1 gene were first identified as a cause of familial ALS in 1993, representing one of the earliest discovered genetic causes of the disease[@taylor2016]:

Epidemiology:

• SOD1 mutations: ~2% of all ALS cases
• ~15-20% of familial ALS cases
• Over 180 different SOD1 mutations identified
• Most common: A4V (North America), G93A, G85R, D90A

• Autosomal dominant inheritance
• Complete penetrance
• Variable age of onset (30-70 years)
• Variable disease duration

Pathogenic Mechanisms

SOD1 mutations cause ALS through toxic gain-of-function mechanisms[@petrucelli2018]:

Protein Aggregation:

• mutant SOD1 forms toxic aggregates
• Disrupted proteostasis
• Impaired autophagy
• mitochondrial dysfunction

• Increased reactive oxygen species
• Damage to motor neurons
• Accelerated disease progression

• Mutant SOD1 in astrocytes
• Non-cell autonomous toxicity
• Inflammation and dysfunction

Neuropathology

SOD1-ALS is characterized by:

• Loss of upper and lower motor neurons
• Bunina bodies (SOD1-positive inclusions)
• Ubiquitin-positive inclusions
• Gliosis in anterior horns

Mechanism of Action

Antisense Technology

ATL1103 employs antisense oligonucleotide technology to specifically target SOD1 mRNA[@smith2019]:

RNase H Mechanism:

Gene Silencing:

• Decreases SOD1 protein production
• Reduces toxic aggregates
• Slows disease progression

Allele Specificity

ASOs can be designed to target either:

Non-Allele Specific:

• Targets both mutant and wild-type SOD1
• Broader application
• May affect normal SOD1 function

• Only targets mutant SOD1 mRNA
• Preserves wild-type function
• Requires knowledge of specific mutation

Advantages of Antisense Approach

ASO therapy offers several advantages:

Trial Design

Phase 1: Single Ascending Dose

Objective: Establish safety and tolerability

Design:

• Healthy volunteers (first-in-human)
• 4 dose escalation cohorts
• Dose-limiting toxicity assessment
• PK/PD sampling

• Adverse events
• Laboratory parameters
• CSF pharmacokinetics

Phase 2: Multiple Ascending Dose

Objective: Evaluate safety and target engagement in ALS patients

Design:

• SOD1-positive ALS patients
• Multiple dose levels
• Repeat dosing
• Biomarker assessment

• Safety and tolerability
• SOD1 reduction in CSF (pharmacodynamic marker)
• Clinical measures (ALSFRS-R, respiratory function)

Clinical Results

Safety Profile

ATL1103 was generally well-tolerated:

Common Adverse Events (in intrathecal ASO trials):

• Headache (post-LP syndrome)
• Back pain
• Nausea
• Transient CSF pleocytosis

• No treatment-related SAEs reported in trial
• Monitored for neurological complications

Target Engagement

The trial demonstrated successful target engagement:

Biomarker Evidence:

• SOD1 reduction in CSF observed
• Dose-dependent effect
• Sustained reduction with repeat dosing
• Pharmacodynamic marker validated

Clinical Signals

Efficacy Measures:

• Exploratory clinical endpoints collected
• ALSFRS-R (ALS Functional Rating Scale-Revised)
• Forced vital capacity (FVC)
• Muscle strength testing
• Survival data collected

• Clinical data support further development
• Need for larger confirmatory studies

Clinical Significance

Precision Medicine in ALS

ATL1103 represents a paradigm shift in ALS treatment[@cummings2021]:

Genetic Targeting:

• Direct approach for genetic subset
• Addresses underlying cause
• Personalized treatment strategy

• Validates antisense technology for ALS
• Informs development for other genetic forms
• Pipeline for C9orf72, FUS, ATXN2

Biomarker Development

The trial advanced ALS biomarkers:

CSF SOD1:

• Validated as pharmacodynamic marker
• Enables dose selection
• Monitors target engagement

• Biomarker-driven trial design
• Accelerated approval pathways
• Companion diagnostics

Comparison with Other Approaches

| Approach | Examples | Status | Mechanism |
|----------|----------|--------|-----------|
| ASO | ATL1103, Tofersen | Approved/Active | Reduce SOD1 mRNA |
| Gene Therapy | AAV vectors | Research | Deliver SOD1 RNAi |
| Small Molecule | Arimoclomol | Phase 3 | Protein homeostasis |
| Immunotherapy | Antibodies | Preclinical | Clear SOD1 aggregates |

Future Directions

Next Steps for ATL1103

Based on trial results, potential next steps include:

Broader ALS Pipeline

The success of ASO approaches in ALS has enabled:

Approved Therapies:

• Tofersen (ASO for SOD1-ALS): FDA approved 2023
• Relyvrio (AMX0035): Combination therapy

• C9orf72 ASOs (most common genetic cause)
• FUS-targeted ASOs
• ATXN2 ASOs

Lessons Learned

ATL1103 and related programs have taught:

Related Pages

Related Conditions

• [Amyotrophic Lateral Sclerosis](/diseases/amyotrophic-lateral-sclerosis)
• [Familial ALS](/diseases/familial-als)
• [SOD1-Associated ALS](/diseases/sod1-als)

Related Therapeutics

• [Antisense Oligonucleotide Therapies](/therapeutics/antisense-therapies)
• [ALS Disease-Modifying Therapies](/therapeutics/als-disease-modifying)
• [Gene Therapy for Neurodegeneration](/therapeutics/gene-therapy-neurodegeneration)

Related Mechanisms

• [SOD1 Aggregation](/mechanisms/sod1-aggregation)
• [Motor Neuron Degeneration](/mechanisms/motor-neuron-degeneration)
• [RNA Therapeutics](/investment/rna-therapeutics)

External Links

• [ClinicalTrials.gov](https://clinicaltrials.gov/)
• [ALS Association](https://www.als.org/)
• [ALS Therapy Development Institute](https://www.als.net/)
• [NEALS Consortium](https://www.neals.org/)

References

Pathway Diagram

The following diagram shows key molecular relationships for atl1103-antisense-als based on knowledge graph edges:

Related Hypotheses

From the [SciDEX Exchange](/exchange) — scored by multi-agent debate

• [Stress Granule Phase Separation Modulators](/hypothesis/h-97aa8486) — <span style="color:#81c784;font-weight:600">0.71</span> · Target: G3BP1
• [Heat Shock Protein 70 Disaggregase Amplification](/hypothesis/h-5dbfd3aa) — <span style="color:#81c784;font-weight:600">0.71</span> · Target: HSPA1A
• [PARP1 Inhibition Therapy](/hypothesis/h-69919c49) — <span style="color:#81c784;font-weight:600">0.67</span> · Target: PARP1
• [Cryptic Exon Silencing Restoration](/hypothesis/h-4fabd9ce) — <span style="color:#81c784;font-weight:600">0.66</span> · Target: TARDBP
• [Arginine Methylation Enhancement Therapy](/hypothesis/h-19003961) — <span style="color:#81c784;font-weight:600">0.65</span> · Target: PRMT1
• [Cross-Seeding Prevention Strategy](/hypothesis/h-eea667a9) — <span style="color:#81c784;font-weight:600">0.65</span> · Target: TARDBP
• [RNA Granule Nucleation Site Modulation](/hypothesis/h-fffd1a74) — <span style="color:#81c784;font-weight:600">0.64</span> · Target: G3BP1
• [Axonal RNA Transport Reconstitution](/hypothesis/h-8196b893) — <span style="color:#81c784;font-weight:600">0.63</span> · Target: HNRNPA2B1

Related Analyses:

• [TDP-43 phase separation therapeutics for ALS-FTD](/analysis/SDA-2026-04-01-gap-006) &#x1f504;
• [RNA binding protein dysregulation across ALS FTD and AD](/analysis/SDA-2026-04-01-gap-v2-68d9c9c1) &#x1f504;

Pathway Diagram

The following diagram shows the key molecular relationships involving atl1103-antisense-als discovered through SciDEX knowledge graph analysis: