In vivo tumour imaging employing regional delivery of novel gallium radiolabelled polymer composites

Background Understanding the regional vascular delivery of particles to tumour sites is a prerequisite for developing new diagnostic and therapeutic composites for treatment of oncology patients. We describe a novel imageable 67Ga-radiolabelled polymer composite that is biocompatible in an animal tumour model and can be used for preclinical imaging investigations of the transit of different sized particles through arterial networks of normal and tumour-bearing organs. Results Radiolabelling of polymer microspheres with 67Ga was achieved using a simple mix and wash method, with tannic acid as an immobilising agent. Final in vitro binding yields after autoclaving averaged 94.7%. In vivo stability of the composite was demonstrated in New Zealand white rabbits by intravenous administration, and intrahepatic artery instillations were made in normal and VX2 tumour implanted rabbit livers. Stability of radiolabel was sufficient for rabbit lung and liver imaging over at least 3 hours and 1 hour respectively, with lung retention of radiolabel over 91%, and retention in both normal and VX2 implanted livers of over 95%. SPECT-CT imaging of anaesthetised animals and planar imaging of excised livers showed visible accumulation of radiolabel in tumours. Importantly, microsphere administration and complete liver dispersal was more easily achieved with 8 μm diameter MS than with 30 μm MS, and the smaller microspheres provided more distinct and localised tumour imaging. Conclusion This method of producing 67Ga-radiolabelled polymer microspheres is suitable for SPECT-CT imaging of the regional vascular delivery of microspheres to tumour sites in animal models. Sharper distinction of model tumours from normal liver was obtained with smaller MS, and tumour resolution may be further improved by the use of 68Ga instead of 67Ga, to enable PET imaging.

Clinical Translational Evaluation of Al18F-NOTA-FAPI for Fibroblast Activation Protein Targeted Tumour Imaging

PurposeIn this study, a novel Al18F-NOTA-FAPI probe was developed for fibroblast activation protein (FAP) targeted tumour imaging, which was available to achieve curie level radioactivity by automatic synthesizer. The tumour detection efficacy of Al18F-NOTA-FAPI was further validated both in preclinical and clinical translational studies. MethodsThe radiolabeling procedure of Al18F-NOTA-FAPI was optimized. Cell uptake and competitive binding assay were completed with U87MG and A549 cell lines, to evaluate the affinity and specificity of Al18F-NOTA-FAPI probe. The biodistribution, pharmacokinetics, radiation dosimetry and tumour imaging efficacy of Al18F-NOTA-FAPI probe were researched with healthy Kunming (KM) and/or U87MG model mice. After the approval of ethical committee, Al18F-NOTA-FAPI probe was translated into clinical for the PET/CT imaging of first 10 cancer patients. ResultsThe radiolabeling yield of Al18F-NOTA-FAPI was 33.8 ± 3.2% through manually operation (n = 10), with the radiochemical purity over than 99% and the specific activity of 9.3-55.5 MBq/nmol. Whole body effective dose of Al18F-NOTA-FAPI was estimated to be 1.24E-02 mSv/MBq, lower than several other FAPI probes ( 68Ga-FAPI-04, 68Ga-FAPI-46 and 68Ga-FAPI-74). In U87MG tumour bearing mice, Al18F-NOTA-FAPI showed good tumor detection efficacy from the results of micro PET/CT imaging and biodistribution studies. In organ biodistribution study of human patients, Al18F-NOTA-FAPI showed lower SUVmean than 2-[18F]FDG in most organs, especially in liver (1.1 ± 0.2 vs. 2.0 ± 0.9), brain (0.1 ± 0.0 vs. 5.9 ± 1.3), and bone marrow (0.9 ± 0.1 vs. 1.7 ± 0.4). Meanwhile, Al18F-NOTA-FAPI do not show extensive bone uptakes, and was able to find out more tumour lesions than 2-[18F]FDG in the PET/CT imaging of several patients. ConclusionAl18F-NOTA-FAPI probe was successfully fabricated and applied in fibroblast activation protein targeted tumour PET/CT imaging, which showed excellent imaging quality and tumour detection efficacy in U87MG tumour bearing mice as well as in human cancer patients.