RESUMO
BACKGROUND: c-MET is a transmembrane receptor involved in many biological processes and contributes to cell proliferation and migration during cancer invasion process. Its expression is measured by immunehistochemistry on tissue biopsy in clinic, although this technique has its limitations. PET-CT could allow in vivo mapping of lesions expressing c-MET, providing whole-body detection. A number of radiopharmaceuticals are under development for this purpose but are not yet in routine clinical use. EMP100 is a cyclic oligopeptide bound to a DOTA chelator, with nanomolar affinity for c-MET. The aim of this project was to develop an automated method for radiolabelling the radiopharmaceutical [68Ga]Ga-EMP100. RESULTS: The main results showed an optimal pH range between 3.25 and 3.75 for the complexation reaction and a stabilisation of the temperature at 90 °C, resulting in an almost complete incorporation of gallium-68 after 10 min of heating. In these experiments, 90 µg of EMP-100 peptide were initially used and then lower amounts (30, 50, 75 µg) were explored to determine the minimum required for sufficient synthesis yield. Radiolysis impurities were identified by radio-HPLC and ascorbic acid and ethanol were used to improve the purity of the compound. Three batches of [68Ga]Ga-EMP100 were then prepared according to the optimised parameters and all met the established specifications. Finally, the stability of [68Ga]Ga-EMP100 was assessed at room temperature over 3 h with satisfactory results in terms of appearance, pH, radiochemical purity and sterility. CONCLUSIONS: For the automated synthesis of [68Ga]Ga-EMP100, the parameters of pH, temperature, precursor peptide content and the use of adjuvants for impurity management were efficiently optimised, resulting in the production of three compliant and stable batches according to the principles of good manufacturing practice. [68Ga]Ga-EMP100 was successfully synthesised and is now available for clinical development in PET-CT imaging.
RESUMO
OBJECTIVES: In the context of a supply disruption of mebrofenin (Cholediam)-based kits for radiolabelling with technetium-99m [99mTc], the medicine agencies allowed the importation of a back-up radiopharmaceutical diagnostic agent, etifenin (Techida), to ensure continuous management of patients with hepatobiliary disorders in nuclear medicine departments. There are still issues regarding the measurement of radiochemical purity (RCP) with these kits based on the European Pharmacopoeia and the Summary of Product Characteristics (SPC). This study aims to identify and to optimise, in a clinical context, the most suitable thin layer chromatography (TLC) method for the determination of the RCP in terms of speed of response and reliability for [99mTc]Tc-mebrofenin and [99mTc]Tc-etifenin. METHODS: [99mTc]Tc-etifenin (n=4) and [99mTc]Tc-mebrofenin (n=5) were individually controlled using six different TLC methods and one high-performance liquid chromatography (HPLC) method for impurity identification ([99mTc](TcO2)n and Na[99mTc]TcO4), RCP (%) and duration of analysis (min). Two TLC methods were selected according to the recommendations of the Pharmacopoeia and SPC, two others were exactly the same but with a heating step, and the other two corresponded to a mix between the methods of the SPC and the Pharmacopoeia that were chosen to optimise RCP determination parameters. RESULTS: Radio-HPLC analysis allowed effective separation of [99mTc]Tc-etifenin and [99mTc]Tc-mebrofenin with a retention time of 8.05±0.02 min and 8.94±0.07 min, respectively, from Na[99mTc]TcO4 (retention time 2.76±0.03 min). HPLC showed an absence of Na[99mTc]TcO4 for [99mTc]Tc-mebrofenin and 0.2% for [99mTc]Tc-etifenin. Among the TLC methods, we identified the most suitable method which ensures the most compliant RCP (98.3±0.9%) in a time of 31.5±1.1 min. Also, it allowed a time saving of 15 min compared with the methods proposed by the Pharmacopoeia and the SPCs. CONCLUSION: We propose a TLC method that accelerates quality control by an average of 15 min while guaranteeing a reliable RCP.
