Experimental: CAAR-T Cell Therapy for Autoantibody-Mediated Neurotoxicity in AD

Experimental: CAAR-T Cell Therapy for Autoantibody-Mediated Neurotoxicity in AD

Hypothesis

Chimeric Autoantibody Receptor (CAAR) T cells can selectively eliminate B cells producing pathogenic autoantibodies (anti-BACE1, anti-AQP4, anti-neuronal) in Alzheimer's disease patients, reducing autoantibody-mediated synaptic dysfunction and neuronal loss while preserving protective anti-Abeta antibody-producing B cells.

Background

Autoantibodies in AD

Alzheimer's disease patients harbor multiple autoantibody populations with context-dependent effects[@autoantibodies_review; @autoantibodies_pathogenesis]:

Experimental: CAAR-T Cell Therapy for Autoantibody-Mediated Neurotoxicity in AD

Hypothesis

Chimeric Autoantibody Receptor (CAAR) T cells can selectively eliminate B cells producing pathogenic autoantibodies (anti-BACE1, anti-AQP4, anti-neuronal) in Alzheimer's disease patients, reducing autoantibody-mediated synaptic dysfunction and neuronal loss while preserving protective anti-Abeta antibody-producing B cells.

Background

Autoantibodies in AD

Alzheimer's disease patients harbor multiple autoantibody populations with context-dependent effects[@autoantibodies_review; @autoantibodies_pathogenesis]:

Pathogenic autoantibodies:

• Anti-BACE1 — inhibit β-secretase, disrupting APP processing and causing synaptic dysfunction[@bace1_autoantibody]
• Anti-AQP4 — impair glymphatic clearance through astrocyte water channel disruption[@aqp4_autoantibodies]
• Anti-HuD — target neuronal RNA-binding proteins, causing direct neuronal toxicity

• Natural anti-Aβ antibodies — facilitate Aβ clearance[@amyloid_autoantibody_natural]
• Anti-4-HNE antibodies — neutralize lipid peroxidation products

The CAAR-T Approach

CAAR-T cells are engineered T cells expressing a chimeric receptor that:

This approach has been validated in:

• Myasthenia gravis (anti-AChR CAAR-T cells)[@caar_mgw]
• Anti-NMDA receptor encephalitis (preclinical)
• Neuromyelitis optica (anti-AQP4 CAAR-T cells)

Key Challenge: Selectivity

The critical therapeutic challenge is discriminating pathogenic from protective autoantibody-producing B cells. Anti-BACE1 and anti-AQP4 B cells are clearly pathogenic targets. However, anti-Aβ antibody-producing B cells are potentially protective — CAAR-T cells should NOT target these.

Solution: Use a multi-target CAAR-T approach that specifically targets BACE1-reactive and AQP4-reactive B cell clones while preserving anti-Aβ B cell populations. Alternatively, a combinatorial approach with selective depletion of pathogenic clones before introducing anti-Aβ immunotherapy.

Experimental Design

Phase I/IIa Clinical Trial

Title: CAAR-BACE1/CAAR-AQP4 T cell therapy for autoantibody-positive Alzheimer's disease

Design: Open-label, dose-escalation, single-arm

Population:

• N = 24 patients with probable AD (NIA-AA criteria)
• MMSE 18-26 (mild-to-moderate AD)
• Seropositive for either anti-BACE1 or anti-AQP4 autoantibodies (screening)
• Age 55-80 years

• Active autoimmune disease requiring immunosuppression
• Prior B cell depletion therapy within 12 months
• Active malignancy or history of lymphoma
• Anti-Aβ therapeutic within 6 months

Intervention

Autologous CAAR-T cell infusion (single dose):

| Cohort | Cell Dose | Target |
|--------|-----------|--------|
| Cohort 1 (n=6) | 1×10^6 CAAR-T cells/kg | BACE1 or AQP4 |
| Cohort 2 (n=6) | 5×10^6 CAAR-T cells/kg | BACE1 or AQP4 |
| Cohort 3 (n=6) | 1×10^7 CAAR-T cells/kg | BACE1 or AQP4 |
| Cohort 4 (n=6) | Combinatorial (BACE1 + AQP4) | Both |

Manufacturing:

Conditioning: Optional low-dose cyclophosphamide (300 mg/m²) 3 days prior to infusion for lymphodepletion (cohorts 3-4 only)

Endpoints

Primary Endpoint (Month 6):

• Change in autoantibody levels (anti-BACE1 or anti-AQP4 titer) in serum and CSF
• Safety: incidence of grade ≥3 adverse events, cytokine release syndrome (CRS)

• Cognitive: ADAS-Cog13, MMSE, CDR-SB
• Biomarker: CSF Aβ42/40 ratio, p-tau181, t-tau, NfL
• Brain imaging: Amyloid PET (Centiloid), MRI volumetry (hippocampal volume)
• B cell reconstitution: CD19+ B cell recovery, immunoglobulin levels
• Autoantibody panel: comprehensive serum autoantibody profiling (AI-omics approach)[@autoantibodies_review]

• TCR repertoire analysis of residual B cells (assess for compensatory clones)
• Treg function recovery
• Correlation of baseline autoantibody signatures with treatment response

Monitoring

| Timepoint | Assessment |
|-----------|-----------|
| Baseline | Full workup, leukapheresis |
| Week 1 | Safety monitoring, cytokine panel (CRS grading) |
| Week 2 | B cell depletion confirmation |
| Month 1 | Safety, cognitive, CSF collection |
| Month 3 | Interim safety and biomarker assessment |
| Month 6 | Primary endpoint, full biomarker panel, PET imaging |
| Month 12 | Long-term follow-up, B cell reconstitution |

Sample Size Justification

Based on:

• Expected autoantibody titer reduction of ≥50% (primary biomarker endpoint)
• Historical variability in autoantibody levels: SD = 30%
• One-sample t-test with α = 0.05, power = 80%
• Expected dropout rate: 15%

Safety Considerations

Cytokine Release Syndrome (CRS)

• CAAR-T cells target autoantigens on B cells (not T cells or neurons), minimizing on-target/off-tumor toxicity
• Expected CRS rates lower than CD19 CAR-T (which targets all B cells)
• Grade 1-2 CRS expected in up to 40%; Grade 3-4 in <10%
• Tocilizumab and corticosteroid rescue protocols in place

B Cell Aplasia

• Selective depletion of autoantibody-producing B cells may reduce overall immunoglobulin levels
• Monitor IgG, IgM, IgA every 3 months
• IVIG replacement for symptomatic hypogammaglobulinemia

Off-Target Effects

• CAAR constructs use scFv-like autoantigen display; potential cross-reactivity assessed in vitro
• Off-tumor/off-target toxicity monitoring in first-in-human cohorts

Biomarker Companion Study

Integrated autoantibody profiling using AI-omics approach (PMID:40406128):

This creates a precision medicine framework for identifying which AD patients will benefit from CAAR-T therapy.

Statistical Analysis Plan

Primary analysis: Paired t-test (or Wilcoxon signed-rank for non-normal data) comparing baseline to month 6 autoantibody titers.

Secondary analyses:

• Mixed-effects model for repeated cognitive measures (ADAS-Cog13, CDR-SB)
• ANCOVA for biomarker changes adjusting for baseline covariates (APOE4 status, age, baseline MMSE)
• Subgroup analysis by autoantibody type (anti-BACE1 vs anti-AQP4 vs both)

Missing data: Multiple imputation under MAR assumption; sensitivity analysis under MNAR.

Success Criteria

Phase I go/no-go criteria (Month 6):

• ✓ Autoantibody titer reduced ≥50% in ≥60% of patients
• ✓ No Grade 4 CRS or unexpected safety signals
• ✓ B cell reconstitution occurring by month 9-12

• ✓ Cognitive stabilization or improvement (ADAS-Cog13 decline <3 points vs historical)
• ✓ Amyloid PET stabilization or reduction (Centiloid change <5)
• ✓ Biomarker improvements consistent with AD modification

Projected Timeline

| Milestone | Timeline |
|-----------|----------|
| IND filing | Month 0 |
| Site activation (3 sites) | Month 6 |
| First patient enrolled | Month 9 |
| Last patient enrolled | Month 24 |
| Primary endpoint (6M FU) | Month 30 |
| Data lock + top-line results | Month 33 |
| Phase II protocol finalization | Month 36 |

Budget Estimate

| Category | Cost (USD) |
|----------|------------|
| Manufacturing (24 × CAAR-T) | $1.2M |
| Clinical operations (3 sites, 30 months) | $1.8M |
| Biomarker companion studies | $400K |
| Imaging (PET/MRI) | $300K |
| Regulatory/IND | $150K |
| Data management | $200K |
| Total estimated | ~$4.1M |

Related Pages

• [Autoimmune Hypothesis in AD](/hypotheses/autoimmune-hypothesis-alzheimers-disease) — mechanistic foundation
• [Hypothesis Rankings](/hypotheses/rankings) — Autoimmune score: 59/100
• [CAAR-T cells mechanism](/mechanisms/caar-t-cell-therapy) — therapeutic approach

References

Pathway Diagram

The following diagram shows the key molecular relationships involving Experimental: CAAR-T Cell Therapy for Autoantibody-Mediated Neurotoxicity in AD discovered through SciDEX knowledge graph analysis: