https://phaidra.vetmeduni.ac.at/o:5361 FAPI Tracer en Vogue: Evaluating [68Ga]Ga-DATA5m.SA.FAPi for Molecular Imaging of Pulmonary Fibrosis Weissenböck, Victoria Victoria Weissenböck Schlederer, Michaela Michaela Schlederer Bakiri, Latifa Latifa Bakiri 0000-0002-6300-2420 Schaffenrath, Johanna Johanna Schaffenrath 0000-0003-1689-1648 Wagner, Erwin F. Erwin F. Wagner Rösch, Frank Frank Rösch Hacker, Marcus Marcus Hacker 0000-0002-4222-4083 Kenner, Lukas Lukas Kenner 0000-0003-2184-1338 University of Veterinary Medicine Vienna Philippe, Cécile Cécile Philippe 0000-0002-7203-7174 MDPI journal article open access eng Background/Objectives: Radiolabeled fibroblast activation protein inhibitors (FAPIs) are emerging as promising imaging agents assessing fibrotic diseases. This study evaluates [68Ga]Ga-DATA5m.SA.FAPi for imaging pulmonary fibrosis in two mouse models, bleomycin-induced (BLM) and a transgenic (fra-2tg) model, both displaying characteristics of human pulmonary fibrotic diseases. Methods: In the BLM model, C57BL/6 mice were treated with bleomycin or isotonic sodium chloride (controls) for 4, 5, and 6 weeks, followed by [68Ga]Ga-DATA5m.SA.FAPi PET/CT scans. Fra-2tg mice and wildtype (WT) littermates underwent at 7, 11, and 18/19 weeks of age a PET/CT scan. The selected timepoints correspond to early, middle, and late disease stages for each model. Imaging was complemented by ex vivo quantification, histological, and immunohistochemical (IHC) analyses. Results: In BLM mice, pulmonary [68Ga]Ga-DATA5m.SA.FAPi uptake showed a trend toward increase as early as 5 weeks of treatment compared with the controls, which was confirmed by ex vivo analysis (BLM: 3.31 ± 0.29%ID/g, n = 5; control: 1.61 ± 0.29%ID/g, n = 4; p = 0.0035). In fra-2tg mice, no significant differences could be detected. IHC revealed elevated pulmonary FAP expression specifically at early (BLM) and mild (fra-2tg) disease stages, whereas for BLM, tracer uptake was more pronounced at later stages. Conclusions: Our findings complement and extend observations from previous studies and support the potential of FAPI tracers as molecular imaging agents for pulmonary fibrosis. FAP Fibrosis PET Bleomycin Fra-2 http://creativecommons.org/licenses/by/4.0/ https://phaidra.vetmeduni.ac.at/api/object/o:5361/download 10.3390/ph19010034 https://phaidra.vetmeduni.ac.at/o:605 application/pdf Pharmaceuticals issn:1424-8247 VoR Pharmaceuticals 19 1 8.02 MB 2026