Development and Initial Characterization of the First 18F-CXCR2-Targeting Radiotracer for PET Imaging of Neutrophils

J Med Chem. 2024 Apr 25;67(8):6327-6343. doi: 10.1021/acs.jmedchem.3c02285. Epub 2024 Apr 3.

Abstract

The interleukin-8 receptor beta (CXCR2) is a highly promising target for molecular imaging of inflammation and inflammatory diseases. This is due to its almost exclusive expression on neutrophils. Modified fluorinated ligands were designed based on a squaramide template, with different modification sites and synthetic strategies explored. Promising candidates were then tested for affinity to CXCR2 in a NanoBRET competition assay, resulting in tracer candidate 16b. As direct 18F-labeling using established tosyl chemistry did not yield the expected radiotracer, an indirect labeling approach was developed. The radiotracer [18F]16b was obtained with a radiochemical yield of 15% using tert-butyl (S)-3-(tosyloxy)pyrrolidine carboxylate and a pentafluorophenol ester. The subsequent time-dependent uptake of [18F]16b in CXCR2-negative and CXCR2-overexpressing human embryonic kidney cells confirmed the radiotracer's specificity. Further studies with human neutrophils revealed its diagnostic potential for functional imaging of neutrophils.

Publication types

  • Research Support, Non-U.S. Gov't

MeSH terms

  • Fluorine Radioisotopes* / chemistry
  • HEK293 Cells
  • Humans
  • Neutrophils* / metabolism
  • Positron-Emission Tomography* / methods
  • Radiopharmaceuticals* / chemical synthesis
  • Radiopharmaceuticals* / chemistry
  • Radiopharmaceuticals* / pharmacokinetics
  • Receptors, Interleukin-8B* / metabolism

Substances

  • Receptors, Interleukin-8B
  • Fluorine Radioisotopes
  • Radiopharmaceuticals
  • CXCR2 protein, human
  • Fluorine-18