Fully automated preparation of radiolabeled peptides in self-shielded radiosynthesis box

Objectives In the field of PET radiopharmaceuticals appropriate shielding is crucial both for production and application of prepared radiopharmaceuticals. Hands free systems for application of PET radiopharmaceuticals are already used in everyday clinical practice. Production is however still limited to fully automated modules which demand PET dedicated shielded boxes. Introduction of new small and self-shielded radiosynthesis box (Modular-Lab MicroCell) offers a possibility to perform wide variety of fully automated synthesis in almost every hospital enviroment. Here we describe results of a fully automated synthesis of 68Ga and 177Lu radiolabeled peptides using the MicroCell.

Methods Two methods for 68Ga preparation were used - fractionated and cation exchange prepurification method. 68Ga generator (IGG100, EZAG) was eluted with 0.1M HCl. 177Lu n.c.a. was purchased from ITG. Reaction conditions such as buffers, pH range, reaction temperature, time and volume of reaction solution were optimized for labelling DOTA-Tyr3-octreotate (DOTATATE) using sterile, single-use cassettes designed for MicroCell. Dose rates were measured at surface and at 1m distance from shielded unit.

Results 40 µg of peptide (27,8 nmol) were successfully labelled with 68Ga (300MBq) with radiochemical yields >99%. Overall reaction yields were around 60%. With final purification step using SepPak (Waters) 68Ge breakthrough was < 0,001%. Dose rates at surface were 1,3 μSv/h, at 1m distance did not exceed normal background rates. 177Lu-DOTATATE synthesis (3 GBq) was reproducible with radiochemical yields of > 99%. Dose rates at surface and 1m distance did not exceed normal background rates.

Conclusions A self-shielded radiosynthesis box, with its small size and low weight, is a unique solution for Nuclear Medicine departments which lack space for standard automated synthesis systems. Results using sterile single-use cassettes show reproducible 68Ga and 177Lu peptide radiolabeling. MicroCell provides sufficient shielding for both PET and β- radioisotopes.

Research Support Eckert and Ziegler Eurotope GmbH, Berlin, Germany