Abstract
Introduction: 64Cu-BaBaSar-RGD2 is a positron emission radiotracer taken up by integrin αvβ3, which is overexpressed in many malignancies. The aim of this study was to evaluate the biodistribution of 64Cu-BaBaSar-RGD2 in a non-human primate with positron emission tomography and to estimate the absorbed doses in major organs for human. Materials and methods: Whole-body PET imaging was done in a Siemens Biograph scanner in a male macaque monkey. After an i.v. injection of 13.1–19.7 MBq/kg of 64Cu-BaBaSar-RGD2, whole body scan was collected for a total duration of 180 min. Attenuation and scatter corrections were applied to reconstruction of the whole-body emission scan. After image reconstruction, three-dimensional volumes of interest (VOI) were hand-drawn on the PET transaxial or coronal slices of the frame where the organ was most conspicuous. Time-activity curves for each VOI were obtained, and residence time of each organ was calculated by integration of the time-activity curves. Human absorbed doses were estimated using the standard human model in OLINDA/EXM software. Results: Injection of 64Cu-BaBaSar-RGD2 was well tolerated in the macaque monkey, with no serious tracer-related adverse events observed. 64Cu-BaBaSar-RGD2 was cleared rapidly from the blood pool, with a 12.1-min biological half-time. Increased 64Cu-BaBaSar-RGD2 uptake was observed in the kidneys, and bladder, with mean percentage injected dose (ID%) values at 1 h after injection approximately 35.50 ± 6.47 and 36.89 ± 5.48, respectively. The calculated effective dose was 15.30 ± 2.21 µSv/MBq, and the kidneys had the highest absorbed dose at 108.43 ± 16.41 µGy/MBq using the non-voiding model. For an injected activity of 925 MBq 64Cu for human, the effective dose would be 14.2 ± 2.1 mSv. Discussion: Due to the limitation of the monkey number, we evaluated 64Cu-BaBaSar-RGD2 in the same monkey of three imaging sessions. Measured absorbed doses and effective doses of 64Cu-BaBaSar-RGD2 are comparable to other reported RGD-derived radiopharmaceuticals labeled with 64Cu and 18F. Therefore, 64Cu-BaBaSar-RGD2 can be safely injected into humans for studying integrin αvβ3 expression non-invasively.
Highlights
64Cu-BaBaSar-RGD2 is a positron emission radiotracer taken up by integrin αvβ3, which is overexpressed in many malignancies
To promote the clinical application of 64CuBaBaSar-RGD2 in human, we studied its biodistribution in a non-human primate after intravenous (i.v.) administration of 64Cu-BaBaSar-RGD2 and estimated the radiation exposure for humans
Based on the decay corrected activity per unit of blood sample, we found that 64Cu-BaBaSar-RGD2 was cleared rapidly from the blood
Summary
The aim of this study was to evaluate the biodistribution of 64Cu-BaBaSar-RGD2 in a non-human primate with positron emission tomography (PET) and to estimate the absorbed doses in major organs for human. Integrin αvβ is a vital component for the angiogenic process by mediating endothelial cell (EC) migration and survival during angiogenesis [4]. For neovasculature formation, ECs need to migrate into an avascular region and to extensively remodel the extracellular matrix (ECM). In this process, integrins αvβ, an immunoglobulin superfamily molecule has proved to be one of the most important cell adhesion receptors for various ECM proteins. Non-invasive detection and quantification of integrin αvβ is leading to the diagnosis of many types of cancer at their earliest stages [5]
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