Clinical-grade N-(4-[18F]fluorobenzoyl)-interleukin-2 for PET imaging of activated T-cells in humans

Abstract

Background: Molecular imaging of immune cells might be a potential tool for response prediction, treatment evaluation and patient selection in inflammatory diseases as well as oncology. Targeting interleukin-2 (IL2) receptors on activated T-cells using positron emission tomography (PET) with N-(4-[18F]fluorobenzoyl)-interleukin-2 ([18F]FB-IL2) could be such a strategy. This paper describes the challenging translation of the partly manual labeling of [18F]FB-IL2 for preclinical studies into an automated procedure following Good Manufacturing Practices (GMP), resulting in a radiopharmaceutical suitable for clinical use. Methods: The preclinical synthesis of [18F]FB-IL2 was the starting point for translation to a clinical production method. To overcome several challenges, major adaptations in the production process were executed. The final analytical methods and production method were validated and documented. All data with regards to the quality and safety of the final drug product were documented in an investigational medicinal product dossier. Results: Restrictions in the [18F]FB-IL2 production were imposed by hardware configuration of the automated synthesis equipment and by use of disposable cassettes. Critical steps in the [18F]FB-IL2 production comprised the purification method, stability of recombinant human IL2 and the final formulation. With the GMP compliant production method, [18F]FB-IL2 could reliably be produced with consistent quality complying to all specifications. Conclusions: To enable the use of [18F]FB-IL2 in clinical studies, a fully automated GMP compliant production process was developed. [18F]FB-IL2 is now produced consistently for use in clinical studies.