Production of [89Zr]Oxinate4 and cell labeling for human use

468 Introduction: Imaging of radiolabeled White Blood Cell (WBC) is an important tool for investigation of several conditions such as infectious/inflammatory disease. The radiopharmaceuticals available for clinical WBC labeling are gamma-emitter and so are suitable only for SPECT. PET technology opens a range of options for better and more sensitive imaging techniques compared to SPECT and thus there is a need for a suitable PET tracer for cell labeling. In this work, we describe our experience in the production of [89Zr]Oxinate4 for human use and cell labeling from benchtop to bedside. Methods: We developed a PET radiopharmaceutical suitable for human use based on oxine for WBC labeling. To do so, we optimized the benchtop chemistry varying several aspects such as buffer used to neutralize [89Zr]Oxalate, incubation time and temperature, organic solvent, glassware to perform the labeling, quality control, and filters to sterilize the final product. The optimized conditions were used to scale-up the production, which required another modification of several parameters. Briefly, the optimized production condition was: 5 mg of oxine was diluted in dichloromethane (DCM) and mixed in neutralized [89Zr]Oxalate already diluted in 5 mL of trace metal water. The mixture was incubated at room temperature for 30 minutes under vigorous agitation. The organic phase was separated, completely evaporated and suspended in 45 mL of dimethylsulfoxide (DMSO). The final formulation containing 200 µg of polysorbate 80, 12 mg of HEPES in 2 mL of 0.9% sodium chloride, was filtered into a sterile borosilicate type I vial. WBC were isolated from 120 mL of whole blood from healthy donors and labeled with 640 - 1500 µCi of [89Zr]Oxinate4 for 20 - 30 minutes at room temperature. After the incubation, the cells were washed, and the final activity recorded. Results: [89Zr]Oxinate4 was successful produced with yield of 67 ± 14.54% (N=5) and met all acceptance criteria for human use, which include non-residual solvents (DCM <600 ppm and DMSO <5000 ppm), adequate pH (7.0), high radiochemical purity (99.67 ± 0.74%), endotoxin-free and sterility. The final radioactivity concentration was 1.93 ± 0.55 mCi/mL high enough to allow the use of less than 1 mL for WBC labeling as previous studies showed lower volumes resulted in higher cell labeling yields. Over 2.0x10^8 WBC cells were isolated from 120 ml of whole blood with a high cell viability rate (81.0 ± 3.24%). The radioactivity incorporated into the cells was 327.86 ± 116.87 µCi which resulted in a labeling efficiency of 30.87 ± 9.58% and satisfactory preservation of cell viability (75.5 ± 12.85%). Conclusions: This study demonstrated the production results of [89Zr]Oxinate4 for human use and its application on WBC labeling. This radiopharmaceutical is suitable for theoretically any cell labeling and is already being used in different preclinical projects across UAB. The translation of this technique into human use will provide insight into several disease mechanisms, advancing and benefiting the scientific community as a whole. Acknowledgments: This project was supported by UAB Radiology. We acknowledge the support of all team members from Dr. Younger’s group, and UAB Cyclotron Facility.