BIIB080 (development code MAPTRx, formerly IONIS-MAPTRx) is an antisense oligonucleotide (ASO) therapy developed by Biogen and Ionis Pharmaceuticals for the treatment of Alzheimer's disease and other tauopathies. It represents a novel gene-silencing approach that reduces tau protein production at the mRNA level, offering a fundamentally different mechanism from antibody-based tau immunotherapies.
BIIB080 works through antisense oligonucleotide-mediated gene silencing:
- Target: MAPT mRNA (messenger RNA encoding the tau protein)
- Mechanism: ASO binds to MAPT mRNA and promotes its degradation by RNase H1
- Result: Reduced production of total tau protein, including all isoforms
- Delivery: Intrathecal administration (lumbar puncture) to reach the central nervous system
Unlike antibody therapies that clear tau after it's produced, BIIB080 prevents tau production at the source. This approach may be particularly effective for driven by tau overexpression or overproduction.
- Direct Tau Reduction: Reduces all tau species including phosphorylated and aggregation-prone forms
- Disease-Modifying: Targets the root cause of tau pathology rather than symptoms
- Proven Target Engagement: Demonstrated dose-dependent CSF tau reduction in humans
- Broad Applicability: Potential utility in multiple tauopathies including AD, PSP, CBD, and FTD
First-in-human studies evaluated the safety, tolerability, and pharmacokinetics of BIIB080 in healthy volunteers and patients with mild Alzheimer's disease.
- Status: Completed
- Publication: Results published in Nature Medicine (2022)
- Key Results:
- Dose-dependent reduction in CSF total tau (up to 50-60% reduction)
- Dose-dependent reduction in CSF phosphorylated tau species
- Acceptable safety profile
A Phase 1/2 study further evaluated BIIB080 in patients with mild Alzheimer's disease:
- Status: Completed
- Results: Published in JAMA Neurology (2023)
- Key Findings:
- Sustained dose-dependent reductions in CSF total tau
- Effects maintained over extended treatment period
- Validated the ASO approach for tau reduction
BIIB080 advanced to a Phase II trial for Alzheimer's disease:
- Status: Active/recruiting as of early 2026
- Indication: Early Alzheimer's disease
- Primary Endpoints: Safety, tolerability, and cognitive endpoints
- Secondary Endpoints: CSF tau reduction, tau PET imaging
BIIB080 has also been evaluated in frontotemporal dementia (FTD) with tau pathology:
- Status: Completed
- Publication: Results published in Nature Medicine (2023)
- Results: Demonstrated target engagement in FTD patients
Clinical trials for BIIB080 utilize comprehensive biomarker approaches:
- CSF Total Tau: Primary pharmacodynamic biomarker - direct measurement of tau protein in cerebrospinal fluid
- CSF Phospho-tau: Measurement of phosphorylated tau species (p-tau181, p-tau217)
- Tau PET Imaging: [^18F]flortaucipir to assess regional tau burden
- Plasma Biomarkers: Emerging plasma p-tau assays as less invasive markers
BIIB080 (MAPTRx) is in active Phase II clinical development by Biogen for Alzheimer's disease. The program has received Fast Track designation from the FDA, highlighting its potential to address an unmet medical need.
The ASO approach represents one of the most promising tau-targeted therapies due to:
- Direct demonstration of tau reduction in human CSF
- Gene-level intervention preventing tau production
- Potential for disease modification rather than symptomatic treatment