## Feasibility Assessment: Immune-Mediated Myelopathy Hypotheses
### Survival Verdict
**Hypothesis 1 (MOGAD FcγR-Mediated Demyelination) → CONDITIONAL VIABILITY**
Confidence 0.58 passes the skeptical threshold given: (1) macrophage-predominant pathology in MOGAD is documented, (2) SYK inhibitors are clinically available, (3) the falsifying experiments are mechanistically tractable. The complement issue requires incorporation rather than dismissal.
**Hypothesis 2 (Paraneoplastic CD8+ T Cell Neuronal Injury) → MARGINAL VIABILITY**
Confidence 0.41 reflects fundamental uncertainties: motor neuron RIPK3 susceptibility is unresolved, and the antibody-responsive subset contradicts an exclusively T-cell model. However, the underlying concept—that T-cell cytotoxicity contributes to irreversible paraneoplastic injury—retains plausibility and warrants targeted investigation.
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## Hypothesis 1: MOGAD FcγR-Mediated Demyelination
### Druggability: MODERATE
| Target | Druggability Status | Notes |
|--------|-------------------|-------|
| FcγRIII (CD16) | Moderate | Monoclonal antibodies (e.g., BB-109, zaltrap-derived constructs) in oncology; limited CNS penetration data |
| SYK | High | Fostamatinib approved for ITP; broad kinase inhibition reduces specificity |
| IRAK4 | Moderate | Clinical-stage small molecules (CA-4948 in trials); role in MOG-FcγR axis unproven |
**Critical gap:** FcγR inhibitors with spinal cord penetration are undocumented. Fostamatinib failed NMOSD Phase 2 (NCT02369354), but AQP4-seropositive dominance confounds interpretation for MOGAD specifically.
### Biomarkers
- **Diagnostic/stratification:** MOG-IgG titers (live cell-based assay) are standard but do not predict FcγR-pathway dominance
- **Pharmacodynamic:** CSF CXCL13, CD68+ macrophage burden on MRI (iron-sensitive sequences)
- **Emerging:** Soluble FcγRIIB/III shed ectodomains as pathway engagement markers (exploratory)
- **Genetic:** FCGR2A-H131 and FCGR3A-V158 polymorphisms modulate receptor affinity; association studies in MOGAD cohorts are feasible but not yet performed
### Model Systems
- **Strong:** Patient-derived iPSC oligodendrocytes + macrophages (3D culture)
- **Adequate:** Mouse spinal cord slice cultures with humanized FcγR
- **Weak:** Standard EAE—species antigen differences limit translation
- **Required model improvement:** Spontaneous MOGAD model with MOG-IgG seroconversion reproducing spinal-predominant lesions (currently unavailable)
### Clinical Development Constraints
| Constraint | Severity | Mitigation |
|------------|----------|------------|
| Small patient population | High | International registries (MOGAD project, COViMS); adaptive platform trial design |
| No validated outcome measure | Moderate | Use composite of EDSS, MOG-AD-EDSS, visual acuity; await regulatory qualification |
| Regulatory precedent | Low | NMOSD (eculizumab, inebilizumab) approvals provide pathway; MOGAD as distinct indication requires dialogue |
| Competition with off-label rituximab | Moderate | FcγR-targeted approach would need superiority or biomarker-selected responder demonstration |
### Safety
**Favorable signal:** Fostamatinib has established safety profile (>1,000 ITP patients, rheumatoid arthritis trials).
**Concerns:**
- Immunosuppression (neutropenia, infections) — manageable with monitoring
- Hepatotoxicity — requires liver function monitoring
- Off-target SYK effects on platelet aggregation at high doses
- Pregnancy category (FcγR engagement affects placental antibody transfer)
**MOGAD-specific advantage:** Pediatric population with acceptable risk tolerance if disability prevention is demonstrated.
### Timeline and Cost: Realistic Assessment
| Phase | Estimated Duration | Estimated Cost |
|-------|-------------------|----------------|
| Biomarker/genetic validation | 1.5–2 years | $500K–$1M |
| Preclinical (in vitro + mouse) | 2–3 years | $2–4M |
| Phase 1/2 ( FcγR inhibitor + MOGAD cohort) | 3–4 years | $15–25M |
| Pivotal trial + regulatory | 3–4 years | $30–50M |
**Total realistic estimate: 8–12 years, $50–80M**
This assumes: (1) FCGR genetic association confirms hypothesis, (2) SYK/FcγR inhibitor CNS penetration is adequate, (3) MOGAD-specific indication pathway accepted.
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## Hypothesis 2: Paraneoplastic CD8+ T Cell Neuronal Injury
### Druggability: LOW-MODERATE (with significant caveats)
| Target | Druggability Status | Notes |
|--------|-------------------|-------|
| CD8+ T cell depletion (rituximab, alemtuzumab) | High | Already in use for paraneoplastic syndromes |
| Perforin/Granzyme B pathway | Low | Intracellular granule components