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.
| 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 |
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
Inheritance Pattern:
- Autosomal dominant inheritance
- Complete penetrance
- Variable age of onset (30-70 years)
- Variable disease duration
SOD1 mutations cause ALS through toxic gain-of-function mechanisms[@petrucelli2018]:
Protein Aggregation:
- mutant SOD1 forms toxic aggregates
- Disrupted proteostasis
- Impaired autophagy
- mitochondrial dysfunction
Oxidative Stress:
Glial Dysfunction:
- Mutant SOD1 in astrocytes
- Non-cell autonomous toxicity
- Inflammation and dysfunction
SOD1-ALS is characterized by:
- Loss of upper and lower motor neurons
- Bunina bodies (SOD1-positive inclusions)
- Ubiquitin-positive inclusions
- Gliosis in anterior horns
ATL1103 employs antisense oligonucleotide technology to specifically target SOD1 mRNA[@smith2019]:
RNase H Mechanism:
- ASO binds to complementary SOD1 mRNA
- RNase H recognizes the RNA-DNA hybrid
- RNase H cleaves the RNA strand
- mRNA is degraded
- Less SOD1 protein is produced
Gene Silencing:
- Decreases SOD1 protein production
- Reduces toxic aggregates
- Slows disease progression
ASOs can be designed to target either:
Non-Allele Specific:
- Targets both mutant and wild-type SOD1
- Broader application
- May affect normal SOD1 function
Allele Specific:
- Only targets mutant SOD1 mRNA
- Preserves wild-type function
- Requires knowledge of specific mutation
ASO therapy offers several advantages:
- Direct gene targeting: Addresses root cause
- High specificity: Single gene focus
- Proven delivery: Intrathecal route reaches CNS
- Reversible: Effect wears off if treatment stops
- Disease modification: Potential to slow progression
Objective: Establish safety and tolerability
Design:
- Healthy volunteers (first-in-human)
- 4 dose escalation cohorts
- Dose-limiting toxicity assessment
- PK/PD sampling
Endpoints:
- Adverse events
- Laboratory parameters
- CSF pharmacokinetics
Objective: Evaluate safety and target engagement in ALS patients
Design:
- SOD1-positive ALS patients
- Multiple dose levels
- Repeat dosing
- Biomarker assessment
Endpoints:
- Safety and tolerability
- SOD1 reduction in CSF (pharmacodynamic marker)
- Clinical measures (ALSFRS-R, respiratory function)
ATL1103 was generally well-tolerated:
Common Adverse Events (in intrathecal ASO trials):
- Headache (post-LP syndrome)
- Back pain
- Nausea
- Transient CSF pleocytosis
Serious Adverse Events:
- No treatment-related SAEs reported in trial
- Monitored for neurological complications
The trial demonstrated successful target engagement:
Biomarker Evidence:
- SOD1 reduction in CSF observed
- Dose-dependent effect
- Sustained reduction with repeat dosing
- Pharmacodynamic marker validated
Efficacy Measures:
- Exploratory clinical endpoints collected
- ALSFRS-R (ALS Functional Rating Scale-Revised)
- Forced vital capacity (FVC)
- Muscle strength testing
- Survival data collected
Observations:
- Clinical data support further development
- Need for larger confirmatory studies
ATL1103 represents a paradigm shift in ALS treatment[@cummings2021]:
Genetic Targeting:
- Direct approach for genetic subset
- Addresses underlying cause
- Personalized treatment strategy
Proof of Concept:
- Validates antisense technology for ALS
- Informs development for other genetic forms
- Pipeline for C9orf72, FUS, ATXN2
The trial advanced ALS biomarkers:
CSF SOD1:
- Validated as pharmacodynamic marker
- Enables dose selection
- Monitors target engagement
Translation to Practice:
- Biomarker-driven trial design
- Accelerated approval pathways
- Companion diagnostics
| 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 |
Based on trial results, potential next steps include:
- Confirmatory trials: Larger Phase 3 trials
- Expanded population: Broader SOD1 mutation inclusion
- Combination approaches: Synergy with other therapies
- Pre-symptomatic treatment: Treat carriers before onset
The success of ASO approaches in ALS has enabled:
Approved Therapies:
- Tofersen (ASO for SOD1-ALS): FDA approved 2023
- Relyvrio (AMX0035): Combination therapy
In Development:
- C9orf72 ASOs (most common genetic cause)
- FUS-targeted ASOs
- ATXN2 ASOs
ATL1103 and related programs have taught:
- Genetic testing importance: Essential for patient identification
- Biomarker value: CSF SOD1 enables development
- Delivery challenges: Intrathecal route is effective but invasive
- Regulatory pathways: Accelerated approval possible with biomarkers
- Benatar et al., SOD1 ALS (2020)
- Smith et al., Antisense oligonucleotides (2019)
- Cummings et al., Amyotrophic lateral sclerosis (2021)
- Petrucelli et al., ALS genetics and mechanisms (2018)
- Taylor et al., SOD1 mutations in familial ALS (2016)
- Ajroudi et al., Therapeutic targeting of SOD1 (2020)