BAY 94-9392: A novel F-18 labeled tumor specific probe for PET/CT imaging - Dosimetry

Objectives The glutamic acid derivative BAY 94-9392 ((S)-4-(3-[¹⁸F]Fluoropropyl) L-glutamic acid), a new PET tracer for the detection of malignant diseases, displayed promising results in patients with NSCLC and in breast cancer. The aim of this study was to provide dosimetry estimates for BAY 94-9392 based on human whole-body PET/CT measurements.

Methods BAY 94-9392 was prepared by a fully automated two step procedure and purified by a solid phase extraction method. PET/CT scans were performed in 5 healthy volunteers (mean age: 59 years; range 51 to 64: 2 male, 3 female). Human subjects were imaged for up to 240 min using a Siemens Biograph 64 TruePoint PET/CT scanner (7 bed positions/frame, 1 min /bed position, iterative re-construction) after i.v. injection of 299 ± 22.5 MBq BAY 94-9392. Whole body and organ-specific ROIs were created for each subject (stomach wall, heart contents, kidneys, liver, marrow, pancreas, salivary glands, spleen, thyroid and urinary bladder) and activities in the organs were quantified using the MIRD pamphlet 16 methodology. Residence times were determined for the whole body and all ROIs. Absorbed dose estimates were calculated using the FDA approved OLINDA software.

Results Due to renal excretion of the tracer, absorbed dose was highest in the kidneys and urinary bladder wall, followed by pancreas and stomach wall. The individual organ doses [mSv/MBq] were 0.11 ± 0.01 for the kidneys, 0.10 ± 0.01 for the urinary bladder wall, 0.08 ± 0.02 for the pancreas and 0.017 ± 0.005 for the stomach wall. The calculated effective dose was 0.015 ± 0.001 mSv/MBq.

Conclusions Based on the distribution and bio-kinetic data, the determined radiation dose for BAY 94-9392 was calculated to be 4.50 ± 0.30 mSv at a patient dose of 300 MBq which is comparable to that of [¹⁸F]FDG (5.7 mSv).

Research Support The trial is sponsored and supported by Bayer Schering Pharma AG, Berlin