Elevated MMP-9/TIMP-1 ratio reflects net proteolytic activity against the BBB, causing degradation of tight junction proteins (claudin-5, occludin, ZO-1) and increased permeability. This imbalance precedes measurable cognitive decline and represents a blood-accessible biomarker. The hypothesis has the strongest evidence base with the additional advantage of having clinically plausible interventions available for repurposing (anti-MMP-9 antibodies such as anrukinzumab and GS-5745). Primary limitation is the lack of specificity for neurodegeneration versus systemic inflammation.
Curated pathway from expert analysis
flowchart TD
A["MMP-9<br/>Matrix Metallopeptidase-9"]
B["TIMP-1<br/>Tissue Inhibitor"]
C["MMP-9/TIMP-1<br/>Ratio Imbalance"]
D["Claudin-5<br/>Proteolysis"]
E["BBB Tight Junction<br/>Disassembly"]
F["Neurovascular<br/>Leakage"]
G["Perivascular<br/>Neuroinflammation"]
H["Cognitive<br/>Decline"]
A --> C
B --> C
C --> D
D --> E
E --> F
F --> G
G --> H
style A fill:#b71c1c,stroke:#ef9a9a,color:#ef9a9a
style H fill:#b71c1c,stroke:#ef9a9a,color:#ef9a9a
style G fill:#b71c1c,stroke:#ef9a9a,color:#ef9a9aNo linked papers recorded for this hypothesis yet.
No curated PDB or AlphaFold mapping for MMP-9 yet. Search RCSB →
No clinical trials data linked to this hypothesis yet.
No curated ClinVar variants loaded for this hypothesis.
Run scripts/backfill_clinvar_variants.py to fetch P/LP/VUS variants.
No DepMap CRISPR Chronos data found for MMP-9 (Matrix Metallopeptidase 9).
Run python3 scripts/backfill_hypothesis_depmap.py to populate.
No resource usage or linked notebooks recorded for this hypothesis yet.
| Prediction | Predicted | Observed | Status | Conf |
|---|---|---|---|---|
| IF subjects with confirmed elevated peripheral MMP-9/TIMP-1 ratio (top quartile) and evidence of BBB leakage receive anti-MMP-9 antibody (GS-5745 or anrukinzumab) at 5mg/kg intravenous infusions at we | Mean 40-60% reduction in CSF claudin-5 degradation fragments in treatment arm vs <15% change in placebo | — no observation — | pending | 0.55 |
| IF cognitively normal adults (50-75 years) with elevated peripheral MMP-9/TIMP-1 ratio (>75th percentile of age-adjusted reference) are compared to matched controls with normal ratios over 24 months, | Mean BBB permeability increase of 35% or greater in the elevated MMP-9/TIMP-1 group vs <10% in controls | — no observation — | pending | 0.65 |