The Emerging Value of Stable Freeze-Dried Kit Formulations for Fast Clinical Translation of Radiopharmaceuticals in Targeted Imaging and Therapy

Objectives:
The development of targeted molecular probe-based radiopharmaceuticals has significantly advanced personalized molecular imaging and therapy.
This paper presents the application of validated freeze-dried technology for formulating ready-to-use kits containing protein and peptide-based radiopharmaceuticals, specifically conjugated antibodies using various bifunctional chelating agents for Lu-177 labeling, and small molecules like FAPI. This innovative approach integrates essential components of radiopharmaceutical development, including chemical synthesis, radiolabeling, and preclinical validation and facilitates the successful clinical translation of these radiopharmaceuticals in nuclear medicine by enhancing stability, ease of use, and cost-effectiveness.
Additionally, we propose expanding research to include veterinary cancer patients and fostering collaboration between medical and veterinary disciplines, emphasizing a holistic approach to health and disease, contributing to the One Health initiative.
Materials and Methods:
In our laboratory, we developed and validated freeze-dried formulations for immunoconjugated antibodies, small molecules, and peptides suitable for Lutetium-177 labeling. For antibody formulations, different molar ratios of antibodies and chelators (1:20 and 1:10) were tested to obtain stable forms with minimal moisture content, preserving protein structure for radiolabeling.
Freeze-drying protocols vary based on molecule type:
- for immunoconjugates, two-day protocol ensures proper stabilization and preservation
- for small molecules and peptides, one-day protocol due to their smaller size and different stabilization needs
Cryoprotectants and lyoprotectants, including mannitol, sucrose, and polysorbate 20, were used to maintain molecular integrity during the freeze-drying process, ensuring a stable powder. Protein characterization was performed using SE-HPLC, SDS-PAGE, FT-IR, Raman spectroscopy, and MALDI-TOF-MS. Radiolabeling efficiency was determined using ITLC methods after labeling with Lu-177.
Results:
Upon reconstitution, all freeze-dried samples dissolved rapidly in under one minute, forming clear solutions without visible particles. SDS-PAGE confirmed antibody integrity, with preservation of the secondary structure and bands at 25 kDa and 50 kDa. Gel filtration chromatography showed minimal aggregate formation, with the main monomer peak representing at least 95% of the total area, within acceptable limits.