Blood Biomarker vs Tau PET for Treatment Monitoring

Hypothesis

Primary Hypothesis: Blood-based biomarkers (p-tau217, p-tau181, NfL, GFAP) can serve as valid surrogates for tau PET in monitoring anti-tau therapeutic response, enabling more accessible and frequent monitoring in clinical trials and practice.

Secondary Hypotheses:

Open Question Source

This experiment addresses the critical understanding gap identified in the [CBS/PSP Cure Roadmap](/mechanisms/cbs-psp-cure-roadmap) Phase 3:

• "Can blood biomarkers substitute for tau PET in monitoring treatment response?"

• Expensive ($5,000-10,000/scan)
• Limited availability (fewer than 50 US centers)
• Involves radiation exposure
• Not suitable for frequent monitoring

Validation Protocol

Study Design

Hypothesis

Primary Hypothesis: Blood-based biomarkers (p-tau217, p-tau181, NfL, GFAP) can serve as valid surrogates for tau PET in monitoring anti-tau therapeutic response, enabling more accessible and frequent monitoring in clinical trials and practice.

Secondary Hypotheses:

Open Question Source

This experiment addresses the critical understanding gap identified in the [CBS/PSP Cure Roadmap](/mechanisms/cbs-psp-cure-roadmap) Phase 3:

• "Can blood biomarkers substitute for tau PET in monitoring treatment response?"

• Expensive ($5,000-10,000/scan)
• Limited availability (fewer than 50 US centers)
• Involves radiation exposure
• Not suitable for frequent monitoring

Validation Protocol

Study Design

• Type: Prospective longitudinal biomarker correlation study embedded within Phase 2 anti-tau clinical trials
• Cohort (pooled from multiple trials):
• Anti-tau antibody trial participants (E2814, BMS-986446, Posdinemab): n=200
• Tau ASO trial participants (BIIB080): n=100
• OGA inhibitor trial participants (FNP-223): n=80
• Total: n=380

Biomarker Collection Schedule

| Timepoint | Blood (p-tau217, NfL, GFAP) | CSF (p-tau181, total tau, NfL) | Tau PET |
|-----------|------------------------------|--------------------------------|---------|
| Baseline | ✓ | ✓ | ✓ |
| Month 1 | ✓ | ✓ | |
| Month 3 | ✓ | | |
| Month 6 | ✓ | ✓ | ✓ |
| Month 9 | ✓ | | |
| Month 12 | ✓ | ✓ | ✓ |
| Month 18 | ✓ | | ✓ |
| Month 24 | ✓ | ✓ | ✓ |

Clinical Assessments

• Primary Endpoint: Correlation between blood p-tau217 % change and tau PET SUVr change at 12 months
• Secondary Endpoints:
• Correlation at other timepoints
• Correlation with clinical measures (PSP-RS, CDR, MMSE)
• Comparison across therapeutic mechanisms
• Lead/lag analysis (which biomarker changes first)

Statistical Analysis Plan

Primary Analysis

Secondary Analyses

Surrogate Endpoint Validation Framework

Using the FDA BIOMARKER qualification framework:

Expected Outcomes

Primary Outcomes

Secondary Outcomes

Exploratory Outcomes

Feasibility Assessment

Strengths

• Leverages existing clinical trial infrastructure (reduces costs)
• Multi-mechanism design enables mechanism-specific validation
• Industry partnerships provide access to trial data
• High clinical relevance for trial design

Challenges

• Requires coordination across multiple pharma-sponsored trials
• Different trial designs may limit direct comparisons
• Blood biomarker assays lack standardization across labs
• Tau PET acquisition protocols vary across sites

Timeline

| Milestone | Expected Date |
|-----------|---------------|
| Protocol development (with pharma partners) | Month 1-3 |
| Data sharing agreements | Month 3-6 |
| First patient data (pooled) | Month 6 |
| 50% enrollment | Month 12 |
| Full enrollment | Month 18 |
| 12-month primary analysis | Month 24 |
| 24-month analysis | Month 36 |
| FDA submission | Month 42 |

Cost Estimate

| Category | Cost (USD) |
|----------|------------|
| Personnel (1 FTE project manager, 1 biostatistician) | $600,000 |
| Blood biomarker assays (p-tau217, NfL, GFAP) | $400,000 |
| CSF biomarker assays | $200,000 |
| Tau PET (central reads) | $150,000 |
| Data management (harmonization across trials) | $300,000 |
| Statistical analysis | $200,000 |
| Regulatory consultation | $150,000 |
| Indirect costs (20%) | $400,000 |
| Total | $2,400,000 |

Note: Major cost share provided by pharma partners (trial sponsors)

Cross-Disease Relevance

This experiment has implications for:

• AD (similar blood vs PET questions for amyloid)
• Clinical trial design (enabling more frequent monitoring)
• Clinical practice (accessibility for patients)
• Biomarker qualification (FDA/EMA regulatory pathways)

See Also

• [CBS/PSP Cure Roadmap](/mechanisms/cbs-psp-cure-roadmap)
• [Biomarker-Guided Tau Therapy Selection](/experiments/levodopa-response-psp-biomarkers)
• [Blood NfL Trajectory Modeling for PSP](/experiments/tau-pet-therapeutic-response-prediction)
• [Experiment Priority Index](/experiments/experiment-priority-index)
• [Novel Therapy Index](/ideas/novel-therapy-index)