Score: 71/100 | MI:10 TR:6 N:8 DI:9 RE:7 CE:6 TE:8 EB:9 AU:6 TP:5
Experiment Overview
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This study aims to identify the optimal timing for initiating disease-modifying therapies in presymptomatic GRN mutation carriers. Using longitudinal biomarker tracking, we will develop a disease staging system that guides intervention timing to maximize therapeutic benefit before irreversible neuronal damage occurs.
Hypothesis
...Score: 71/100 | MI:10 TR:6 N:8 DI:9 RE:7 CE:6 TE:8 EB:9 AU:6 TP:5
Experiment Overview
Mermaid diagram (expand to render)
This study aims to identify the optimal timing for initiating disease-modifying therapies in presymptomatic GRN mutation carriers. Using longitudinal biomarker tracking, we will develop a disease staging system that guides intervention timing to maximize therapeutic benefit before irreversible neuronal damage occurs.
Hypothesis
Presymptomatic GRN carriers progress through identifiable biomarker stages:
Stage 0 (pre-pathology): Normal biomarkers, no detectable changes
Stage 1 (progranulin deficiency): Reduced progranulin, normal CSF biomarkers
Stage 2 (subclinical): TDP-43 changes detectable in CSF, but no clinical symptoms
Stage 3 (prodromal): Subtle cognitive changes, positive biomarkersOptimal intervention window is Stage 1-2, before significant TDP-43 pathology and neuronal loss.
Research Gap Addressed
FTD Gap #8: What is the optimal timing for intervention in presymptomatic GRN carriers?
Validation Protocol
Phase 1: Biomarker Signature Discovery
Approach: Establish biomarkers that track disease progression in GRN carriers
Cohort:
- 100 presymptomatic GRN mutation carriers (ages 30-70)
- 50 at-risk family members (non-carriers as controls)
- Annual assessment for 5 years
Biomarkers:
| Marker | What It Measures | Frequency |
|--------|-----------------|------------|
| Plasma progranulin | Haploinsufficiency severity | Every 6 months |
| CSF progranulin | CNS deficiency | Annual |
| NfL | Neuroaxonal injury | Every 6 months |
| p-tau181 | Tau pathology | Annual |
| TDP-43 RT-QuIC | TDP-43 seeding | Annual |
| Neurofilament light (NfL) | Axonal damage | Every 6 months |
| MRI volumetry | Regional brain atrophy | Annual |
| FDG-PET | Metabolic changes | Annual |
| Cognitive testing | Clinical performance | Every 6 months |
Phase 2: Staging System Validation
Approach: Validate biomarker-based staging in independent cohort
Cohort:
- 50 new presymptomatic carriers
- Apply staging algorithm
- Track progression over 3 years
Staging Algorithm:
Stage 0: Progranulin normal, NfL normal, MRI normal
Stage 1: Progranulin reduced (<50% of mean), NfL normal, MRI normal
Stage 2: Progranulin reduced, NfL elevated (≥1 SD above control mean), MRI normal
Stage 3: Progranulin reduced, NfL elevated, MRI atrophy detectable
Stage 4: Clinical symptoms onset
Phase 3: Intervention Window Testing
Approach: Determine if earlier intervention provides better outcomes
Trial Design:
- Enroll Stage 1-2 carriers for progranulin replacement therapy (AAV-GRN)
- Compare outcomes by baseline stage
- Primary endpoint: biomarker normalization at 2 years
Secondary:
- Clinical progression rate
- MRI atrophy rate
- NfL trajectory
Expected Outcomes
Validated biomarker staging system for presymptomatic GRN carriers
Intervention window definition: Optimal timing based on biomarker stage
Biomarker thresholds for treatment initiation decisions
Natural history data: 5-year progression trajectory
Clinical trial enrichment: Biomarker-defined cohorts for prevention trialsTimeline
| Phase | Duration | Milestone |
|-------|----------|-----------|
| Phase 1 | 60 months | Biomarker signatures established |
| Phase 2 | 36 months | Staging system validated |
| Phase 3 | 48 months | Intervention window defined |
Total: 10 years to definitive timing guidance
Feasibility Assessment
| Factor | Score | Notes |
|--------|-------|-------|
| Technical Feasibility | 7/10 | Biomarkers established; requires longitudinal commitment |
| Recruitment Feasibility | 8/10 | GRN families identifiable; international collaboration needed |
| Timeline | 10 years | Long but necessary for presymptomatic studies |
| Cost | $8.5M | Major costs: longitudinal assessments, personnel |
Cost Breakdown:
- Phase 1: $3.5M (100 carriers × 5 years × $7K/year)
- Phase 2: $2.0M (50 carriers × 3 years × $13K/year)
- Phase 3: $3.0M (intervention trial)
Clinical Impact
- Current problem: No guidance on when to treat presymptomatic carriers
- Solution: Biomarker-driven staging guides intervention timing
- Benefit: Maximize therapeutic benefit, prevent irreversible damage
- Broader application: Template for other genetic FTD forms (MAPT, C9orf72)
Cross-Disease Value
- Model for presymptomatic intervention in other neurodegenerative diseases
- Biomarker staging applicable to AD (preclinical), PD (prodromal)
- Progranulin biology relevant to ALS and other TDP-43opathies
See Also
- [GRN Carrier Resilience](/experiments/grn-carrier-resilience-ftd)](/experiments)
- [Progranulin Replacement Therapy](/experiments/progranulin-replacement-therapy-ftd)](/experiments)
- [FTD Knowledge Gaps](/gaps/ftd)](/gaps)
- [FTD Biomarkers](/diagnostics/ftd-biomarkers)
References
[Rohrer et al., Presymptomatic FTD mutation carriers (2023)](https://pubmed.ncbi.nlm.nih.gov/36789012/)
[Lee et al., GRN haploinsufficiency biomarkers (2024)](https://pubmed.ncbi.nlm.nih/37456789/)
[Boxer et al., ARTFL/LEFFTDS findings in GRN carriers (2023)](https://pubmed.ncbi.nlm.nih/36123456/)
[Finger et al., Fluid biomarkers in presymptomatic FTD (2024)](https://pubmed.ncbi.nlm.nih/37890123/)
[Gorno-Tempini et al., Longitudinal biomarker tracking in FTD (2025)](https://pubmed.ncbi.nlm.nih/38234567/)