Adaptation of a commercially available module for the production of alpha-[11C]methyl-L-tryptophan ([11C]AMT) for human use

The complex radiosynthesis of alpha-[¹¹C]methyl-L-tryptophan ([¹¹C]AMT) involves harsh chemicals and conditions, posing challenges for its implementation on commercially available synthesis modules. This study describes the adaptation of the GE TRACERlab FX2 C module for [¹¹C]AMT production using both a half-manual approach and a semi-automated method incorporating a 16-way valve system.

[¹¹C]AMT was synthesized with decay-corrected radiochemical yields of 13 ± 7.5 % (half-manual) and 10.4 ± 4.1 % (semi-automated), with radiochemical purities exceeding 95 %. The half-manual approach demonstrated higher reliability in synthesis success but required increased operator intervention, while the semi-automated method minimized radiation exposure to the operator. Key factors influencing synthesis success included the preparation and precise addition of lithium diisopropylamide and the use of a soda lime column to mitigate iodine contamination during [¹¹C]CH₃I transfer.

This work presents a practical and scalable solution for producing [¹¹C]AMT on a commercially available module, enabling its broader application in clinical research, particularly in brain imaging and pediatric oncology.