Objectives The Phase I safety, biodistribution and internal
radiation dosimetry study in adult healthy Japanese
males of flutemetamol (18F) injection, an in vivo b-amyloid
imaging agent, is reported and compared with previously
obtained Caucasian data.
Methods Whole-body PET scans of 6 healthy volunteers
(age 51.8–61.7 years) were acquired approximately 4 h
post-injection (administered activity 102–160 MBq). Venous
blood sampling determined 18F activity concentrations
in whole blood and plasma and high-performance
liquid chromatography (HPLC) established the percentages
of parent [18F]flutemetamol and its metabolites. Voided
urine activity was recorded. The decay-corrected and normalised
18F activity of 14 source organ regions as a function
of time was entered into the OLINDA/EXM software
to calculate the internal radiation dosimetry and effective
dose of each subject following the MIRD schema. The
pharmacokinetics, biodistribution and dosimetry profiles
were compared to data obtained from a cohort of healthy
Caucasian adult volunteers from a previous Phase I study
of [18F]flutemetamol.
Results Flutemetamol (18F) injection was well tolerated.
The highest mean initial uptakes were measured in the liver
(15.2 %), lungs (10.2 %) and brain (6.6 %). The highest
mean radiation absorbed doses were received by the gallbladder
wall (366 lGy/MBq), upper large intestine
(138 lGy/MBq) and small intestine (121 lGy/MBq). The
mean effective dose was 34.9 lSv/MBq. HPLC analysis
demonstrated that at 5-min post-injection about 75 % of
plasma 18F radioactivity was in the form of parent [18-
F]flutemetamol, reducing to 8 and 2 % at 25 and 90 min,
respectively, giving rise to less lipophilic 18F-labelled
metabolites. Comparisons with the Caucasian cohort
showed no differences that could be regarded as clinically
significant.
Conclusion The clinical safety of [18F]flutemetamol
demonstrated no differences of clinical significance in the
pharmacokinetics, biodistribution and internal radiation
dosimetry profiles between Caucasian and Japanese adults.