# Feasibility Assessment: Microglial Synaptic Pruning in Neurodegeneration
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## Executive Summary
Of the seven hypotheses, five retain sufficient credibility to warrant clinical-development scrutiny. Hypotheses 3 (CX3CL1-CX3CR1) and 4 (metabolic rewiring) fall below the operational threshold—0.50 and 0.40, respectively—not because the biology is impossible, but because the mechanistic specificity is insufficient to generate high-confidence therapeutic predictions, and because both face prohibitive translation obstacles (human genetic disconnect for H3; unspecific mechanism for H4). The five surviving hypotheses share a common structural weakness: they all propose mechanisms that operate in a pre-symptomatic window of 10–20 years, meaning therapeutic intervention, if valid, would need to begin before clinical diagnosis—raising enormous trial design and regulatory challenges. Nonetheless, these hypotheses differ substantially in tractability, and the most feasible path to clinic lies in the complement cascade (H1) via an existing antibody scaffold, with TREM2 (H2) as a well-genetically-validated but mechanistically more complex backup. Trained immunity (H5) is conceptually rich but presents the most challenging biomarker and regulatory pathway. Tau (H6) and sexual dimorphism (H7) are viable but niche—relevant for distinct subpopulations or specific tauopathy indications rather than broad AD.
**Overall portfolio recommendation:** Pursue H1 as primary development target, H2 as genetically-validated secondary, H5 as mechanistic differentiation play, H6 for PSP/CBD specifically, and H7 for patient stratification biomarker development rather than standalone indication.
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## Revised Confidence Scores
| # | Hypothesis | Original | Skeptic Critique Weight | Revised | Verdict |
|---|-----------|----------|----------------------|---------|---------|
| H1 | Complement over-pruning (C1q/C3/CR3) | 0.85 | Valid on causality, translation; invalid on core mechanism | **0.70** | Viable — strongest preclinical dataset and human genetics support |
| H2 | TREM2 loss-of-function | 0.80 | Valid on mechanism specificity and paradox framing | **0.65** | Viable — genetics robust, but mechanism is multivalent |
| H3 | CX3CL1-CX3CR1 disruption | 0.72 | Valid on human genetic disconnect, redundancy | **0.50** | **Cut** — insufficient human genetic validation to justify BBB-penetrant GPCR program |
| H4 |