Optimization of an Allysine-Targeted PET Probe for Quantifying Fibrogenesis in a Mouse Model of Pulmonary Fibrosis

Sergey Shuvaev; Rachel S Knipe; Matt Drummond; Nicholas J Rotile; Ilknur Ay; Jonah P Weigand-Whittier; Hua Ma; Iris Yuwen Zhou; Jesse D Roberts Jr; Katherine Black; Lida P Hariri; Yingying Ning; Peter Caravan

doi:10.1007/s11307-023-01845-2

Optimization of an Allysine-Targeted PET Probe for Quantifying Fibrogenesis in a Mouse Model of Pulmonary Fibrosis

Mol Imaging Biol. 2023 Oct;25(5):944-953. doi: 10.1007/s11307-023-01845-2. Epub 2023 Aug 23.

Authors

Sergey Shuvaev^{1

2

3}, Rachel S Knipe^{4

5}, Matt Drummond^{3

4}, Nicholas J Rotile^{1

2}, Ilknur Ay^{1

2}, Jonah P Weigand-Whittier², Hua Ma¹, Iris Yuwen Zhou^{1

2

3}, Jesse D Roberts Jr⁶, Katherine Black⁴, Lida P Hariri⁷, Yingying Ning^{1

2

3}, Peter Caravan^{8

9

10}

Affiliations

¹ Institute for Innovation in Imaging (i3), Boston, USA.
² Athinoula A. Martinos Center for Biomedical Imaging, Boston, USA.
³ Department of Radiology, Massachusetts General Hospital and Harvard Medical School, 149 13th Street, Charlestown, Boston, MA, 02129, USA.
⁴ Division of Pulmonary and Critical Care Medicine, Boston, USA.
⁵ Center for Immunology and Inflammatory Diseases, Massachusetts General Hospital and Harvard Medical School, Boston, MA, USA.
⁶ Department of Pediatric Anesthesiology, Mass General Hospital for Children, Boston, USA.
⁷ Department of Pathology, Massachusetts General Hospital, Boston, MA, USA.
⁸ Institute for Innovation in Imaging (i3), Boston, USA. pcaravan@mgh.harvard.edu.
⁹ Athinoula A. Martinos Center for Biomedical Imaging, Boston, USA. pcaravan@mgh.harvard.edu.
¹⁰ Department of Radiology, Massachusetts General Hospital and Harvard Medical School, 149 13th Street, Charlestown, Boston, MA, 02129, USA. pcaravan@mgh.harvard.edu.

PMID: 37610609
DOI: 10.1007/s11307-023-01845-2

Abstract

Purpose: Idiopathic pulmonary fibrosis (IPF) is a destructive lung disease with a poor prognosis, an unpredictable clinical course, and inadequate therapies. There are currently no measures of disease activity to guide clinicians making treatment decisions. The aim of this study was to develop a PET probe to identify lung fibrogenesis using a pre-clinical model of pulmonary fibrosis, with potential for translation into clinical use to predict disease progression and inform treatment decisions.

Methods: Eight novel allysine-targeting chelators, PIF-1, PIF-2, …, PIF-8, with different aldehyde-reactive moieties were designed, synthesized, and radiolabeled with gallium-68 or copper-64. PET probe performance was assessed in C57BL/6J male mice 2 weeks after intratracheal bleomycin challenge and in naïve mice by dynamic PET/MR imaging and with biodistribution at 90 min post injection. Lung hydroxyproline and allysine were quantified ex vivo and histological staining for fibrosis and aldehyde was performed.

Results: In vivo screening of probes identified ⁶⁸GaPIF-3 and ⁶⁸GaPIF-7 as probes with high uptake in injured lung, high uptake in injured lung versus normal lung, and high uptake in injured lung versus adjacent liver and heart tissue. A crossover, intra-animal PET/MR imaging study of ⁶⁸GaPIF-3 and ⁶⁸GaPIF-7 confirmed ⁶⁸GaPIF-7 as the superior probe. Specificity for fibrogenesis was confirmed in a crossover, intra-animal PET/MR imaging study with ⁶⁸GaPIF-7 and a non-binding control compound, ⁶⁸GaPIF-Ctrl. Substituting copper-64 for gallium-68 did not affect lung uptake or specificity indicating that either isotope could be used.

Conclusion: A series of allysine-reactive PET probes with variations in the aldehyde-reactive moiety were evaluated in a pre-clinical model of lung fibrosis. The hydrazine-bearing probe, ⁶⁸GaPIF-7, exhibited the highest uptake in fibrogenic lung, low uptake in surrounding liver or heart tissue, and low lung uptake in healthy mice and should be considered for further clinical translation.

Keywords: Collagen; Copper-64; Extracellular matrix; Gallium-68; Molecular imaging.