Status: Recruiting
Phase: Phase 3
Sponsor: Life Molecular Imaging
Sponsor Collaborators: None
Intervention: [18F]PI-2620 tau PET imaging
Estimated Enrollment: 200 participants
Study Start: January 2023
Estimated Completion: December 2026
This Phase 3 clinical trial evaluates [18F]PI-2620, a next-generation tau positron emission tomography (PET) tracer, for histopathological validation in Alzheimer's disease (AD). PI-2620 is a tau-selective radioligand that demonstrates binding to all tau aggregate isoforms, including 3R/4R tau bundles characteristic of AD.
¶ Background and Rationale
Tau PET imaging represents a critical advancement in Alzheimer's disease diagnostics and research. While first-generation tau tracers showed limited ability to discriminate between different tauopathies and suffered from off-target binding, PI-2620 offers improved characteristics:
- High specificity: Selective binding to paired helical filaments (PHFs) and straight filaments (SFs)
- Broad isoform recognition: Binding to both 3R and 4R tau aggregates
- Kinetic properties: Improved signal-to-background ratios
- Off-target reduction: Reduced binding to monoamine oxidase sites
The histopathological validation of PI-2620 is essential for establishing its utility as a biomarker for tau pathology in AD clinical trials and clinical practice.
| Parameter |
Value |
| Design |
Single-arm imaging study |
| Allocation |
N/A (imaging study) |
| Intervention |
[18F]PI-2620 PET scan |
| Primary Outcome |
Correlation with postmortem tau pathology |
| Secondary Outcomes |
Diagnostic accuracy, sensitivity, specificity |
- Age: 65-90 years
- Cognitive status: Clinical diagnosis of Alzheimer's disease or cognitively normal controls
- Clinical diagnosis: Probable AD per NIA-AA criteria or cognitively unimpaired
- Willingness: Consent to PET scanning and potential brain donation
- Ability to undergo PET/MRI: No contraindications to imaging
- Neurological conditions: History of stroke, traumatic brain injury, or other neurodegenerative diseases
- Psychiatric conditions: Active major depression or psychosis
- Contraindications: Inability to lie still for PET/MRI scanning
- Radiation exposure: Participation in other radionuclide studies within 12 months
- Other: Severe medical conditions that may affect study participation
- Informed consent process
- Medical history review
- Cognitive assessment screening
- Physical and neurological examination
- Demiographic data collection
- Clinical assessment scales (MMSE, CDR, ADAS-Cog)
- Blood collection for biomarkers
- [18F]PI-2620 PET acquisition
- MRI for anatomical reference
The PET imaging protocol includes:
- Radiotracer administration: Intravenous injection of [18F]PI-2620 (185-370 MBq)
- Dynamic imaging: 0-90 minutes post-injection
- Standardized uptake value (SUV): Regional tau deposition quantification
- Parametric imaging: Kinetic analysis using arterial blood sampling or reference tissue models
- MRI co-registration: High-resolution T1-weighted MRI for anatomical localization
For participants undergoing brain donation:
- Postmortem correlation: Quantitative neuropathology assessment
- Immunohistochemistry: AT8, PHF1, 3R/4R tau antibodies
- Biochemical analysis: Tau protein quantification
- Histopathological correlation: Correlation between antemortem PI-2620 PET signal and postmortem neurofibrillary tangle (NFT) density using Braak staging
- Regional mapping: Regional distribution of PI-2620 binding compared to tau pathology distribution
- Diagnostic accuracy: Sensitivity and specificity of PI-2620 for detecting Alzheimer's disease vs. controls
- Discriminative ability: Ability to distinguish AD from other tauopathies (primary tauopathies)
- Cognitive correlation: Association between PI-2620 uptake and cognitive performance
- Biomarker correlation: Correlation with CSF tau and amyloid biomarkers
- Longitudinal monitoring: Change in PI-2620 signal over time
- Adverse events monitoring
- Radiation dosimetry assessment
- Vital signs and laboratory values
Alzheimer's disease is characterized by two hallmark pathologies: extracellular amyloid-beta plaques and intracellular neurofibrillary tangles (NFTs) composed of hyperphosphorylated tau protein. Tau PET imaging enables in vivo visualization ofNFT burden, providing:
- Diagnostic confirmation: Objective evidence of tau pathology
- Disease staging: Braak stage assessment in vivo
- Treatment monitoring: Objective measure for therapeutic response
- Prognostic information: Correlation with cognitive decline
PI-2620 was developed by Life Molecular Imaging (formerly Piramal Imaging) and has undergone extensive evaluation:
- Preclinical: In vitro binding studies showing high affinity for PHFs (KD ~ 2.5 nM)
- Phase 1: First-in-human studies establishing safety and radiation dosimetry
- Phase 2: Diagnostic performance studies in AD and other tauopathies
- Phase 3: Current histopathological validation trial
The trial is conducted at multiple academic memory centers with expertise in Alzheimer's disease research and neuroimaging. Specific site information is available through ClinicalTrials.gov.
This Phase 3 trial aims to establish:
- Regulatory validation: FDA/EMA approval pathway for PI-2620 as a diagnostic agent
- Clinical utility: Integration of PI-2620 into AD diagnostic workup
- Research applications: Use of PI-2620 as biomarker in AD clinical trials
- Biological insights: Understanding of in vivo tau pathology progression