posdinemab

Posdinemab (BMS-986446)

<table class="infobox infobox-therapeutic">
<tr>
<th class="infobox-header" colspan="2">posdinemab</th>
</tr>
<tr>
<td class="label">Parameter</td>
<td>Details</td>
</tr>
<tr>
<td class="label">NCT ID</td>
<td>NCT05514899</td>
</tr>
<tr>
<td class="label">Phase</td>
<td>Phase II</td>
</tr>
<tr>
<td class="label">Population</td>
<td>Early Alzheimer's disease (MCI due to AD, mild AD dementia)</td>
</tr>
<tr>
<td class="label">Status</td>
<td>Active/Recruiting</td>
</tr>
<tr>
<td class="label">Design</td>
<td>Randomized, double-blind, placebo-controlled</td>
</tr>
<tr>
<td class="label">Primary Endpoint</td>
<td>Safety, tolerability, CDR-SB change from baseline</td>
</tr>
<tr>
<td class="label">Secondary Endpoints</td>
<td>Biomarker changes (CSF tau, plasma p-tau), tau PET</td>
</tr>
<tr>
<td class="label">Antibody</td>
<td>Target</td>
</tr>
<tr>
<td class="label">Posdinemab</td>
<td>Phospho mid-domain</td>
</tr>
<tr>
<td class="label">Eilanetug (E2814)</td>
<td>MTBR</td>
</tr>
<tr>
<td class="label">Bepranemab</td>
<td>aa 235-250</td>
</tr>
<tr>
<td class="label">JNJ-63733657</td>
<td>p-tau217</td>
</tr>
<tr>
<td class="label">Semorinemab</td>
<td>N-terminus</td>
</tr>
<tr>
<td class="label">Gosuranemab</td>
<td>N-terminal</td>
</tr>
<tr>
<td class="label">Tilavonemab</td>
<td>Mid-region</td>
</tr>
<tr>
<td class="label">Zagotenemab</td>
<td>Co

Posdinemab (BMS-986446)

<table class="infobox infobox-therapeutic">
<tr>
<th class="infobox-header" colspan="2">posdinemab</th>
</tr>
<tr>
<td class="label">Parameter</td>
<td>Details</td>
</tr>
<tr>
<td class="label">NCT ID</td>
<td>NCT05514899</td>
</tr>
<tr>
<td class="label">Phase</td>
<td>Phase II</td>
</tr>
<tr>
<td class="label">Population</td>
<td>Early Alzheimer's disease (MCI due to AD, mild AD dementia)</td>
</tr>
<tr>
<td class="label">Status</td>
<td>Active/Recruiting</td>
</tr>
<tr>
<td class="label">Design</td>
<td>Randomized, double-blind, placebo-controlled</td>
</tr>
<tr>
<td class="label">Primary Endpoint</td>
<td>Safety, tolerability, CDR-SB change from baseline</td>
</tr>
<tr>
<td class="label">Secondary Endpoints</td>
<td>Biomarker changes (CSF tau, plasma p-tau), tau PET</td>
</tr>
<tr>
<td class="label">Antibody</td>
<td>Target</td>
</tr>
<tr>
<td class="label">Posdinemab</td>
<td>Phospho mid-domain</td>
</tr>
<tr>
<td class="label">Eilanetug (E2814)</td>
<td>MTBR</td>
</tr>
<tr>
<td class="label">Bepranemab</td>
<td>aa 235-250</td>
</tr>
<tr>
<td class="label">JNJ-63733657</td>
<td>p-tau217</td>
</tr>
<tr>
<td class="label">Semorinemab</td>
<td>N-terminus</td>
</tr>
<tr>
<td class="label">Gosuranemab</td>
<td>N-terminal</td>
</tr>
<tr>
<td class="label">Tilavonemab</td>
<td>Mid-region</td>
</tr>
<tr>
<td class="label">Zagotenemab</td>
<td>Conformational</td>
</tr>
</table>

Overview

Posdinemab (development code BMS-986446) is an anti-tau monoclonal antibody developed by Bristol Myers Squibb (BMS) in partnership with BioArctic AB for the treatment of Alzheimer's disease and other tauopathies[@bms][@bioarctic2024]. The antibody targets phosphorylated tau protein in the mid-domain region, representing a distinct approach from both N-terminal targeting antibodies and conformational epitope-specific antibodies.

The development of posdinemab reflects BMS's commitment to the tau immunotherapy space following the discontinuation of their earlier anti-tau program. The partnership with BioArctic brings proprietary antibody technology to the collaboration, leveraging years of research on tau pathology and antibody engineering.

Scientific Rationale

Tau Pathology in Alzheimer's Disease

Tau pathology represents a critical therapeutic target in Alzheimer's disease, with neurofibrillary tangles (NFTs) formed by hyperphosphorylated tau being closely correlated with cognitive decline[@yoshiyama2013][@wu2020]:

Pathological Cascade:

Tau Spread Hypothesis:

• Pathological tau propagates between neurons
• Trans-synaptic spread drives disease progression
• Interception may prevent further neurodegeneration

Targeting Phosphorylated Tau

Posdinemab specifically targets tau species that are phosphorylated at key pathological sites[@schofield2022]:

Rationale for Phospho-Targeting:

• Phosphorylated tau is more specific for AD pathology
• p-tau species are more aggregation-prone
• Phosphorylation creates novel epitopes for antibody binding
• p-tau levels correlate with disease severity

• Mid-domain region (aa 150-250) contains multiple pathologically relevant sites
• Accessible to antibody binding in both extracellular and intracellular compartments
• Different from N-terminal (easier access) and C-terminal (microtubule binding) regions

Mechanism of Action

Antibody Properties

Posdinemab is engineered to selectively bind phosphorylated tau in the mid-domain region[@bms][@bioarctic2024]:

Epitope Specificity:

• Targets phosphorylated epitopes in the tau mid-domain
• Prefers aggregated over monomeric tau
• Minimal binding to non-phosphorylated tau

• High affinity for pathological tau species
• Humanized IgG backbone for optimal effector function
• Designed for brain penetration

Therapeutic Mechanisms

Posdinemab achieves therapeutic benefit through multiple mechanisms[@sofruiti2019][@kolb2017]:

1. Direct Binding and Neutralization:

• Binds extracellular tau aggregates
• Prevents tau-tau interactions and propagation
• Neutralizes toxic oligomeric species

• Facilitates microglia-mediated clearance
• Enhances phagocytosis of pathological tau
• Activates complement cascade where appropriate

• Intercepts propagating tau species in extracellular space
• May block trans-synaptic transmission
• Could slow disease progression by limiting spread

Brain Penetration

Like all therapeutic antibodies, posdinemab faces the challenge of adequate brain exposure[@butchart2019]:

BBB Challenges:

• Limited transport across the blood-brain barrier
• Typical brain:plasma ratios of 0.1-1%
• Requires high dosing for therapeutic effect

• Intravenous administration
• Monthly or longer dosing intervals
• Dose selection based on preclinical and early clinical data

Clinical Development

Phase I Trial

First-in-human Phase I studies evaluated posdinemab in healthy volunteers and patients with early Alzheimer's disease[@bms]:

Study Design:

• Randomized, double-blind, placebo-controlled
• Single ascending dose (SAD) and multiple ascending dose (MAD) cohorts
• Included both healthy volunteers and early AD patients

• Safety and tolerability
• Pharmacokinetic properties
• Target engagement biomarkers (CSF tau species)
• Preliminary efficacy signals

• Demonstrated acceptable safety profile
• No dose-limiting toxicities observed
• Evidence of target engagement
• Supports advancement to Phase II

Phase II Trial (NCT05514899)

Posdinemab has advanced to Phase II clinical trials in patients with early Alzheimer's disease[@posdinemab][@nct05514899]:

Trial Design:

Study Objectives:

• Evaluate safety and tolerability
• Assess clinical efficacy (cognitive and functional measures)
• Measure biomarker effects
• Determine optimal dosing

Biomarker Strategy

Posdinemab trials incorporate comprehensive biomarker monitoring[@blennow2022][@zetterberg2019]:

Biomarkers Being Monitored:

• CSF phosphorylated tau (p-tau181, p-tau217)
• Plasma phosphorylated tau
• Tau PET imaging ([^18F]flortaucipir)
• Neurodegeneration markers (NfL, neurogranin)
• Amyloid status (for patient selection)

• Reduction in CSF p-tau with effective treatment
• Slower accumulation on tau PET
• Possible plasma p-tau changes (complex dynamics)

Comparison with Other Anti-Tau Antibodies

The anti-tau immunotherapy field has multiple programs targeting different epitopes[@bittlinger2021][@cummings2024]:

Posdinemab Differentiation

Unique Features:

Challenges:

• No clinical data published yet
• Slightly behind competitors in development timeline
• Must demonstrate efficacy in a field with multiple failures

BioArctic Partnership

Collaboration Structure

The partnership between BMS and BioArctic represents an important collaboration in the tau immunotherapy space[@bioarctic2024]:

BioArctic Contributions:

• Proprietary antibody technology platform
• Deep expertise in tau biology
• Earlier-stage research and discovery

• Clinical development expertise
• Global regulatory capabilities
• Commercial infrastructure

BioArctic's Tau Program Portfolio

BioArctic has developed multiple anti-tau antibodies:

• Posdinemab (BMS-986446): Partnered with BMS, mid-domain targeting
• BAN2401: Anti-amyloid antibody (partnered with Eisai, approved as lecanemab)
• Additional tau programs: In earlier development stages

Company Information

Bristol Myers Squibb

Headquarters: New York, New York, USA

Key Facts:

• Global biopharmaceutical company
• Strong neuroscience pipeline
• Multiple Alzheimer's disease programs

• Developed memantine (Namenda) for AD
• Amyloid-targeting programs
• Tau immunotherapy with BioArctic partnership

BioArctic AB

Headquarters: Stockholm, Sweden

Key Facts:

• Swedish biotechnology company
• Focus on neurodegenerative diseases
• Partnership-based development model

• Tau biology and antibody development
• Parkinson's disease programs
• Amyloid research (lecanemab partnership)

Current Status

As of 2024, posdinemab remains in active clinical development[@bms][@posdinemab]:

Development Timeline:

• Phase I completed
• Phase II ongoing (NCT05514899)
• Results anticipated in 2025-2026

• Phase II data readout
• Decision on Phase III advancement
• Potential regulatory interactions

Preclinical Development

Antibody Engineering

The development of posdinemab required sophisticated antibody engineering to achieve optimal therapeutic properties:

Humanization: The antibody was humanized to minimize immunogenicity and extend serum half-life. IgG1 isotype was selected for optimal effector function, enabling Fc-mediated clearance of bound tau species through engagement with Fc-gamma receptors on microglia and other immune cells.

Affinity Maturation: In vitro affinity maturation was performed to enhance binding to pathological phosphorylated tau while maintaining specificity. The antibody shows preferential binding to aggregated tau species over monomeric tau, which is critical for targeting the most toxic conformations.

Brain Penetration Optimization: Given the challenge of antibody delivery across the blood-brain barrier, the antibody was engineered to maximize brain exposure:

• Reduced aggregation propensity to improve diffusion
• Optimized Fc region for potential FcRn-mediated recycling
• Balance between brain penetration and peripheral half-life

Preclinical Efficacy Models

Posdinemab demonstrated efficacy in multiple preclinical models:

Tau Transgenic Models: In P301S tau transgenic mice, posdinemab treatment reduced:

• Soluble phosphorylated tau levels in brain tissue
• Tau aggregation as measured by AT8 immunostaining
• Neuronal loss and behavioral deficits

• Reduction in templated tau aggregation
• Blockade of trans-synaptic tau spread
• Preservation of neuronal connectivity

• Fc-dependent clearance mechanisms are operational
• Microglial activation in response to antibody-tau complexes
• Reduction in both intracellular and extracellular tau

Clinical Development

Phase I Trial

First-in-human Phase I studies evaluated posdinemab in healthy volunteers and patients with early Alzheimer's disease[@bms]:

Study Design:

• Randomized, double-blind, placebo-controlled
• Single ascending dose (SAD) and multiple ascending dose (MAD) cohorts
• Included both healthy volunteers and early AD patients

• Safety and tolerability
• Pharmacokinetic properties
• Target engagement biomarkers (CSF tau species)
• Preliminary efficacy signals

• Demonstrated acceptable safety profile
• No dose-limiting toxicities observed
• Evidence of target engagement
• Supports advancement to Phase II

Therapeutic Implications

Potential Indications

Posdinemab would potentially be indicated for:

Combination Therapy Potential

Given the complexity of AD pathology, combination approaches are expected[@cummings2024]:

Rationale:

• Anti-amyloid + anti-tau may provide complementary effects
• Addresses multiple pathological domains simultaneously
• May improve clinical outcomes over monotherapy

• BMS has anti-amyloid programs (through partnerships)
• Could potentially combine posdinemab with anti-amyloid therapy

Challenges and Future Directions

Field-Wide Challenges

The anti-tau immunotherapy field has faced significant obstacles:

• Multiple high-profile failures (gosuranemab, semorinemab, tilavonemab, zagotenemab)
• Brain penetration limitations
• Late-stage patient enrollment
• Complex biomarker-clinical relationships

Posdinemab-Specific Considerations

Advantages:

• Mid-domain phospho-tau targeting is scientifically sound
• BMS resources and experience
• BioArctic expertise in tau biology
• Active development with ongoing trials

• Similar challenges faced by other anti-tau programs
• No efficacy data yet
• Competition from anti-amyloid therapies

Cross-Links

• [Tau Protein](/proteins/tau)
• [Phosphorylated Tau Biomarkers](/biomarkers/p-tau-181)
• [Anti-Tau Immunotherapies](/therapeutics/anti-tau-immunotherapies)
• [Alzheimer's Disease](/diseases/alzheimers-disease)
• [Tau PET Imaging](/diagnostics/tau-pet)
• [Bristol Myers Squibb](/companies/bristol-myers-squibb)

See Also

• [Tau Pathology Mechanisms](/mechanisms/tau-pathology)
• [Tau Hyperphosphorylation](/mechanisms/tau-hyperphosphorylation)
• [Anti-Tau Antibody Programs](/therapeutics/anti-tau-immunotherapy-programs)
• [Tau Aggregation Inhibitors](/therapeutics/anti-tau-aggregation-therapy)
• [Clinical Trials in AD](/clinical-trials/alzheimers-disease-clinical-trials)

References