Amyloid-β PET Radioligands in Alzheimer’s Disease: From Plaque Detection to Biomarker-Guided Patient Stratification and Therapeutic Monitoring

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Abstract
Amyloid-β (Aβ) positron emission tomography allows direct in vivo visualization of insoluble fibrillar Aβ deposition and has been used to detect Alzheimer’s disease pathology across the clinical continuum, from preclinical stages to overt dementia. Aβ tracers progressed from the prototypical [11C]Pittsburgh Compound-B ([11C]PiB), which is limited by [11C] half-life, to [18F]-labeled agents, including [18F]Florbetapir, [18F]Florbetaben, and [18F]Flutemetamol, which allowed centralized production and wide clinical use, with [18F]NAV4694 currently in development. In this narrative review, we sought to examine the principal Aβ positron emission tomography radioligands and their methodological framework, including visual reads, the standardized uptake value ratio, and the Centiloid scale, which harmonized quantitative output across tracers, scanners, and protocols and may enable cross-site comparison in multicenter studies and disease-modifying trials. The regulatory approval of lecanemab and donanemab has recently expanded the clinical use of Aβ positron emission tomography. Beyond diagnostic confirmation, the modality can currently confirm eligibility for anti-Aβ therapy, enrich trial populations, monitor target engagement through serial Centiloid measurements, and inform treatment discontinuation at predefined clearance thresholds. However, significant limitations remain, including the imperfect correlation between a high Aβ plaque burden and clinical cognitive decline that constrains its standalone diagnostic utility, tracer-specific variability, restricted accessibility, and the inability of fibril-targeted tracers to image the soluble oligomeric species most directly engaged by anti-Aβ antibodies. Probes for non-fibrillar species and computational tools for assisted interpretation are likely to shape the field in the near future.
Funding Information
  • Ministero della Salute (Ricerca Corrente)

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