A First-in-man PET study of 2-amino-[3-11C] isobutyric acid for the amino acid transport system A: biodistribution and dosimetry in healthy volunteers

Purpose : To conduct the first-in-human evaluation of the novel PET tracer [3- ¹¹ C]AIB, which primarily targets System A amino acid transport, by assessing its biodistribution, radiation dosimetry, and safety in healthy volunteers. Methods : Six healthy male participants underwent whole-body PET/CT scans following a rapid intravenous bolus of [3- ¹¹ C]AIB (injected dose: 366.9 ± 17.9 MBq). Dynamic imaging of the upper abdomen was performed for 4 minutes post-injection, followed by static whole-body scans up to 90 minutes. Volumes of interest were drawn on major organs to derive time activity curves for dosimetry calculations. Safety was assessed through vital signs and laboratory tests before and after imaging. Results : High tracer uptake was observed in the salivary glands, pancreas, kidneys, and liver, whereas uptake in the brain and skeletal muscles remained low. The principal route of excretion was via the urinary tract. The effective dose was 5.1 µSv/MBq, corresponding to 1.9 mSv for 370 MBq injection comparable to other 11C-labeled amino acid tracers. No adverse events or significant changes in clinical assessments were noted. Conclusions : [3- ¹¹ C]AIB showed a favorable biodistribution and safety profile in healthy volunteers, supporting its potential clinical use. Its distinct uptake pattern suggests applicability for imaging tumors where System A–mediated transport and glutamine metabolism are of interest, laying the groundwork for further clinical investigations.