ABSTRACT
Purpose@#PASylation® offers the ability to systematically tune and optimize the pharmacokinetics of protein tracers for molecularimaging. Here we report the first clinical translation of a PASylated Fab fragment (89Zr∙Df-HER2-Fab-PAS200) for the molecularimaging of tumor-related HER2 expression. @*Methods@#A patient with HER2-positive metastatic breast cancer received 37 MBq of 89Zr∙Df-HER2-Fab-PAS200 at a total massdose of 70 μg. PET/CT was carried out 6, 24, and 45 h after injection, followed by image analysis of biodistribution, normalorgan uptake, and lesion targeting. @*Results@#Images show a biodistribution typical for protein tracers, characterized by a prominent blood pool 6 h p.i., whichdecreased over time. Lesions were detectable as early as 24 h p.i. 89Zr∙Df-HER2-Fab-PAS200 was tolerated well. @*Conclusion@#This study demonstrates that a PASylated Fab tracer shows appropriate blood clearance to allow sensitive visualizationof small tumor lesions in a clinical setting.