zagotenemab

Zagotenemab (LY3303560)

<table class="infobox infobox-therapeutic">
<tr>
<th class="infobox-header" colspan="2">zagotenemab</th>
</tr>
<tr>
<td class="label">Parameter</td>
<td>Details</td>
</tr>
<tr>
<td class="label">Name</td>
<td>PERISCOPE-ALZ (Phase 2)</td>
</tr>
<tr>
<td class="label">NCT ID</td>
<td>NCT04592874</td>
</tr>
<tr>
<td class="label">Population</td>
<td>Early Alzheimers disease (MCI due to AD or mild AD dementia)</td>
</tr>
<tr>
<td class="label">Enrollment</td>
<td>360 participants</td>
</tr>
<tr>
<td class="label">Design</td>
<td>Randomized, double-blind, placebo-controlled</td>
</tr>
<tr>
<td class="label">Duration</td>
<td>2 years (104 weeks)</td>
</tr>
<tr>
<td class="label">Dose Groups</td>
<td>1,400 mg IV monthly, 5,600 mg IV monthly, placebo</td>
</tr>
<tr>
<td class="label">Primary Endpoint</td>
<td>Change from baseline on integrated Alzheimers Disease Rating Scale (iADRS)</td>
</tr>
<tr>
<td class="label">Secondary Endpoints</td>
<td>Clinical measures (CDR-SB, ADAS-Cog13, ADCS-ADL), biomarker endpoints, tau PET</td>
</tr>
<tr>
<td class="label">Antibody</td>
<td>Company</td>
</tr>
<tr>
<td class="label">Zagotenemab (LY3303560)</td>
<td>Eli Lilly</td>
</tr>
<tr>
<td class="label">Semorinemab (RO7105685)</td>
<td>Genentech/Roche</td>
</tr>
<tr>
<td class="label">Gosuranemab (BIIB080)</td>
<td>Biogen</td>
</tr>
<tr>
<td class="label">Tilavonemab (ABBV-8E12)</td>
<td

Zagotenemab (LY3303560)

<table class="infobox infobox-therapeutic">
<tr>
<th class="infobox-header" colspan="2">zagotenemab</th>
</tr>
<tr>
<td class="label">Parameter</td>
<td>Details</td>
</tr>
<tr>
<td class="label">Name</td>
<td>PERISCOPE-ALZ (Phase 2)</td>
</tr>
<tr>
<td class="label">NCT ID</td>
<td>NCT04592874</td>
</tr>
<tr>
<td class="label">Population</td>
<td>Early Alzheimers disease (MCI due to AD or mild AD dementia)</td>
</tr>
<tr>
<td class="label">Enrollment</td>
<td>360 participants</td>
</tr>
<tr>
<td class="label">Design</td>
<td>Randomized, double-blind, placebo-controlled</td>
</tr>
<tr>
<td class="label">Duration</td>
<td>2 years (104 weeks)</td>
</tr>
<tr>
<td class="label">Dose Groups</td>
<td>1,400 mg IV monthly, 5,600 mg IV monthly, placebo</td>
</tr>
<tr>
<td class="label">Primary Endpoint</td>
<td>Change from baseline on integrated Alzheimers Disease Rating Scale (iADRS)</td>
</tr>
<tr>
<td class="label">Secondary Endpoints</td>
<td>Clinical measures (CDR-SB, ADAS-Cog13, ADCS-ADL), biomarker endpoints, tau PET</td>
</tr>
<tr>
<td class="label">Antibody</td>
<td>Company</td>
</tr>
<tr>
<td class="label">Zagotenemab (LY3303560)</td>
<td>Eli Lilly</td>
</tr>
<tr>
<td class="label">Semorinemab (RO7105685)</td>
<td>Genentech/Roche</td>
</tr>
<tr>
<td class="label">Gosuranemab (BIIB080)</td>
<td>Biogen</td>
</tr>
<tr>
<td class="label">Tilavonemab (ABBV-8E12)</td>
<td>AbbVie</td>
</tr>
<tr>
<td class="label">Bepranemab (UCB0107)</td>
<td>UCB</td>
</tr>
<tr>
<td class="label">JNJ-63733657</td>
<td>Janssen</td>
</tr>
</table>

Overview

Zagotenemab (development code LY3303560) is a humanized anti-tau monoclonal antibody developed by [Eli Lilly and Company](/companies/eli-lilly) for the treatment of Alzheimers disease and potentially other tauopathies[@zagotenemab][@zagotenemaba]. Unlike conventional anti-tau antibodies that target linear epitopes on phosphorylated or total tau protein, zagotenemab specifically recognizes conformational epitopes present on early pathological tau aggregates, particularly oligomeric species considered to be the most toxic form of tau pathology[@mallipeddi2021][@taylor2021].

The therapeutic rationale for zagotenemab stems from the understanding that tau oligomers represent a critical pathogenic species in Alzheimers disease progression. While neurofibrillary tangles (NFTs) represent end-stage, relatively inert tau aggregates, soluble oligomers are highly toxic, propagate between neurons via trans-synaptic spread, and drive downstream neurodegeneration[@wu2020]. By targeting these early pathological conformations, zagotenemab aimed to intercept tau toxicity before extensive irreversible neuronal damage occurs.

The development of zagotenemab represents a significant effort in the tau immunotherapy field, combining cutting-edge antibody engineering with innovative clinical trial design. The PERISCOPE-ALZ Phase II trial provided the first large-scale clinical data on a conformer-specific anti-tau antibody, offering important insights into the challenges and opportunities of this therapeutic approach.

Tau Pathology in Alzheimers Disease

Normal Tau Biology

The tau protein is encoded by the [MAPT](/genes/mapt) (microtubule-associated protein tau) gene on chromosome 17q21 and plays essential roles in neuronal biology[@yoshiyama2013]:

Physiological Functions:

• Promotes microtubule assembly and stabilizes axonal microtubules
• Facilitates intracellular transport along axons
• Regulates neuronal plasticity and signal transduction
• Supports dendritic spine formation and maintenance

Pathological Tau Transformations

In Alzheimers disease, tau undergoes dramatic transformations that lead to neurodegeneration[@wu2020][@himmelstein2012]:

Hyperphosphorylation:

• Over 40 phosphorylation sites have been identified on tau
• Kinases including [GSK-3β](/entities/gsk3-beta), [CDK5](/proteins/cdk5), and MAPKs hyperphosphorylate tau
• Phosphorylation reduces taus microtubule-binding capacity
• Phosphorylated tau dissociates from microtubules and accumulates in the soma

• Hyperphosphorylated tau aggregates into soluble oligomers
• Oligomers range from dimers to large prefibrillar aggregates
• Tau oligomers are highly toxic to neurons
• Oligomers can spread between neurons via extracellular vesicles and tunneling nanotubes

• Oligomers mature into paired helical filaments (PHFs) and straight filaments
• PHFs aggregate into neurofibrillary tangles (NFTs)
• NFTs accumulate in neuronal cell bodies
• NFT burden correlates with cognitive impairment severity

The Importance of Targeting Tau Oligomers

The recognition that tau oligomers represent the most pathogenic species has shifted therapeutic strategies[@wu2020][@lowen]:

Why Oligomers Are Critical:

Conformational vs. Phosphorylated Epitopes:

• Phospho-tau antibodies target specific phosphorylation sites (e.g., pT181, pT217, pT231)
• Conformational antibodies recognize pathological 3D structures irrespective of phosphorylation
• Early oligomers may not display all phosphorylated epitopes
• Conformer-specific antibodies may detect a broader range of pathological species

Mechanism of Action

Antibody Characteristics

Zagotenemab was engineered to specifically recognize pathological conformational epitopes on early tau aggregates[@mallipeddi2021][@taylor2021]:

Epitope Specificity:

• Targets conformational epitopes unique to aggregated tau
• Recognizes soluble oligomeric and early fibrillar tau species
• Minimal binding to monomeric tau or to mature NFTs
• Does not require specific phosphorylation at known sites

• High affinity for pathological tau conformations
• Humanized IgG1 backbone for optimal effector function
• Designed to minimize off-target effects

• Derived from the mouse MCI-1 monoclonal antibody
• Humanized to reduce immunogenicity
• Engineered for optimal brain penetration and half-life

Therapeutic Mechanisms

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

1. Antibody-Mediated Clearance:

• Binds extracellular and interstitial pathological tau species
• Facilitates Fc receptor-mediated uptake by microglia
• Enhances clearance of toxic oligomers through the brains waste clearance systems

• Sequesters soluble tau oligomers in the extracellular space
• Blocks templated conversion of normal tau to pathological forms
• May prevent trans-synaptic spread of tau pathology

• Binds and neutralizes extracellular oligomers
• Prevents oligomer interaction with neuronal receptors
• May reduce downstream inflammatory signaling

Brain Penetration Challenges

Like all anti-tau antibodies, zagotenemab faces the significant challenge of achieving adequate brain exposure[@butchart2019]:

Blood-Brain Barrier (BBB) Considerations:

• Peripheral administration results in limited brain penetration
• Typical brain:plasma ratios of 0.1-1% for conventional IgG antibodies
• BBB transport depends on FcRn-mediated transcytosis
• Higher dosing may partially overcome this limitation

• Phase II used high monthly intravenous doses (1,400 mg and 5,600 mg)
• These doses far exceed typical antibody therapeutics
• Aim to achieve sufficient free antibody for target engagement

Clinical Development Program

Phase I Clinical Trials

First-in-human studies evaluated zagotenemab in healthy volunteers and patients with Alzheimers disease[@zagotenemab][@taylor2021]:

Study Design:

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

• Safety and tolerability across dose ranges
• Pharmacokinetic properties (Cmax, AUC, half-life)
• Immunogenicity (anti-drug antibody formation)
• Target engagement biomarkers (CSF tau species)
• Preliminary clinical efficacy signals

• Acceptable safety and tolerability profile at all doses tested
• No dose-limiting toxicities observed
• Evidence of target engagement (reductions in specific CSF tau species)
• Supports advancement to Phase II evaluation

Phase II Trial: PERISCOPE-ALZ

The PERISCOPE-ALZ trial represented a major milestone in tau immunotherapy development[@zagotenemaba]:

Trial Design:

Results:

• Primary endpoint: Did not meet — no statistically significant difference from placebo on iADRS
• Biomarker findings: Dose-dependent increase in plasma tau (suggests target engagement)
• Tau PET: No significant change in tau deposition
• Safety: No dose-limiting adverse events; favorable safety profile
• Status: Development discontinued in October 2021

Why Did Zagotenemab Fail?

The negative PERISCOPE-ALZ results provide critical insights into tau immunotherapy challenges:

Possible Contributing Factors:

• Early AD still represents relatively advanced pathology
• Need to treat much earlier in the disease process

• Despite high doses, antibody may not have reached adequate brain levels
• Target engagement may have been inadequate

• Plasma tau increased (suggesting target engagement)
• But this did not translate to clinical benefit
• Indicates complex relationship between biomarker changes and clinical outcomes

• May not have captured all relevant pathological species
• Different conformations may dominate at different disease stages

• iADRS may not be sensitive enough to detect subtle effects
• 2-year treatment may be insufficient to show disease modification

Comparison with Other Anti-Tau Antibodies

The tau immunotherapy field has evolved significantly, with multiple antibodies targeting different epitopes[@bittlinger2021][@cummings2022]:

Shared Challenges:

• None have demonstrated clear clinical efficacy to date
• Similar issues with brain penetration and target engagement
• Late-stage patient enrollment may be a universal problem

• Conformational epitope targeting (unique approach)
• Targeting oligomeric species specifically
• Higher dosing than most other programs

Lessons from the Zagotenemab Experience

Implications for Future Tau Immunotherapy

The PERISCOPE-ALZ results have important implications for the field[@cummings2022]:

Timing: Earlier intervention may be critical

• Need to treat at pre-symptomatic or very early prodromal stages
• Primary prevention trials may be necessary

• Plasma tau increase may not indicate meaningful target engagement
• Need biomarkers that more directly reflect downstream effects

• May need to combine anti-tau with anti-amyloid therapy
• Multi-target strategies could address multiple pathological processes

• Identify patients most likely to respond
• Exclude those with "burned out" pathology

What Worked

Despite the negative trial, certain aspects of the program provided value:

Successful Elements:

Current Status and Future Directions

Program Status

Zagotenemab (LY3303560) development has been discontinued following the negative PERISCOPE-ALZ trial results. The program no longer active in clinical development.

Legacy and Contributions

The zagotenemab program contributed to the field in several ways:

Scientific Insights:

• Validated conformer-specific antibody approach
• Demonstrated safety of high-dose anti-tau therapy
• Provided biomarker data on target engagement
• Informed understanding of tau immunotherapy challenges

• Established Phase II trial design for anti-tau antibodies
• Validated biomarker endpoints (plasma tau)
• Demonstrated feasibility of large anti-tau trials

Related Programs

Several related efforts continue in the tau immunotherapy space:

• Anti-tau antibodies targeting different epitopes
• Small molecule tau aggregation inhibitors
• Anti-sense oligonucleotides targeting MAPT
• Gene therapy approaches
• Combination strategies

References

See Also

Related Pages

• [Tau Protein](/proteins/tau)
• [Neurofibrillary Tangles](/mechanisms/neurofibrillary-tangles)
• [Tau Oligomers](/entities/tau-oligomers)
• [Alzheimer"s Disease](/diseases/alzheimers-disease)
• [Anti-Tau Immunotherapies](/therapeutics/anti-tau-immunotherapies)
• [Tau PET Imaging](/diagnostics/tau-pet-imaging)
• [Eli Lilly](/companies/eli-lilly)

Related Mechanisms

• [Tau Pathology Mechanisms](/mechanisms/tau-pathology)
• [Tau Phosphorylation](/mechanisms/tau-phosphorylation)
• [Tau Aggregation](/mechanisms/tau-aggregation)
• [Tau Spread and Propagation](/mechanisms/tau-spread-propagation)

Related Therapeutics

• [Anti-Tau Immunotherapies Overview](/therapeutics/anti-tau-immunotherapies)
• [Semorinemab](/therapeutics/semorinemab)
• [Gosuranemab](/therapeutics/gosuranemab)
• [Tilavonemab](/therapeutics/tilavonemab)

Related Hypotheses

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

• [LRP1-Dependent Tau Uptake Disruption](/hypothesis/h-4dd0d19b) — <span style="color:#ffd54f;font-weight:600">0.53</span> · Target: LRP1

• [Tau propagation mechanisms and therapeutic interception points](/analysis/SDA-2026-04-02-gap-tau-prop-20260402003221) &#x1f504;