Flortaucipir (¹⁸F) is a fluorine-18-labeled positron emission tomography (PET) diagnostic agent used for imaging aggregated tau protein in the brain. It is marketed as TAUVID and is used to estimate the density and distribution of aggregated tau neurofibrillary tangles in adults being evaluated for Alzheimer's disease.
Chemically, Flortaucipir F-18 is 7-(6-[¹⁸F]fluoropyridin-3-yl)-5H-pyrido[4,3-b]indole. The FDA-approved product has a molecular weight of 262.27 g/mol and molecular formula C₁₆H₁₀[¹⁸F]N₃. PubChem identifies the CAS number as 1522051-90-6 and the FDA UNII as T1JP1KYU9O.
Flortaucipir F-18 is a molecular imaging agent designed to cross the blood-brain barrier and bind to aggregated tau protein. The resulting PET signal allows physicians to visualize the distribution of tau pathology in the brain.
The radioactive isotope fluorine-18 decays by positron emission and has a physical half-life of approximately 109.8 minutes. The principal photons useful for PET imaging are 511 keV gamma photons produced following positron-electron annihilation.
Flortaucipir F-18 is used with PET imaging to estimate the density and distribution of aggregated tau neurofibrillary tangles in the brain. It is intended for adults undergoing evaluation for Alzheimer's disease and other causes of cognitive decline.
A positive tau PET scan indicates the presence of aggregated tau pathology but does not by itself establish a specific clinical diagnosis. The FDA labeling states that the interpretation of TAUVID images should be performed together with clinical evaluation and other diagnostic information.
After intravenous administration, Flortaucipir F-18 crosses the blood-brain barrier and binds to aggregated tau structures. The fluorine-18 radionuclide emits positrons, which ultimately generate detectable 511-keV photons. PET imaging then produces a spatial distribution of tracer uptake corresponding to regions containing tau pathology.
TAUVID is supplied as a sterile, non-pyrogenic, clear, colorless solution for intravenous injection. Each milliliter contains up to 2 micrograms of flortaucipir and 300–3,700 MBq (8.1–100 mCi) of flortaucipir F-18 at end of synthesis. The formulation also contains L-cysteine hydrochloride monohydrate, dibasic sodium phosphate, hydrochloric acid, dehydrated alcohol and 0.9% sodium chloride injection. The labeled pH range is 5.5–7.5.
Fluorine-18 has a physical half-life of 109.8 minutes. It decays through positron emission to stable oxygen-18. The principal PET imaging photons are 511 keV.
Flortaucipir F-18 is a specialized radiopharmaceutical and therefore requires radiopharmaceutical-specific quality controls rather than conventional API tests alone.
Relevant quality attributes include:
FDA's chemistry review specifically evaluates flortaucipir F-18 using radiochemical identity, radiochemical purity, specific activity, strength, radionuclidic identity and radionuclidic purity.
Flortaucipir F-18 requires specialized radiopharmaceutical handling because it contains radioactive fluorine-18. Appropriate radiation shielding, controlled handling, transportation and disposal procedures are required according to applicable regulations.
| Parameter | Specification |
|---|---|
| Appearance | White to off-white crystalline powder |
| Identification | IR & HPLC compliant |
| Assay (HPLC) | 98.0% – 102.0% |
| Loss on Drying | NMT 1.0% |
| Residue on Ignition | NMT 0.5% |
| Heavy Metals | NMT 10 ppm |
| pH (1% Solution) | 2.0 – 4.0 |