Cindy R Fischer, Cristina Müller, Josefine Reber, Adrienne Müller, Stefanie D Krämer, Simon M Ametamey, Roger Schibli
Center for Radiopharmaceutical Sciences of ETH, PSI and USZ, Institute of Pharmaceutical Sciences, ETH Zurich, Zurich, Switzerland.
Bioconjugate chemistry 2012 Apr 18The folate receptor (FR) is upregulated in various cancer types (FR-α isoform) and in activated macrophages (FR-β isoform) which are involved in inflammatory and autoimmune diseases, but its expression in healthy tissues and organs is highly restricted to only a few sites (e.g kidneys). Therefore, the FR is a promising target for imaging and therapy of cancer and inflammation using folate-based radiopharmaceuticals. Herein, we report the synthesis and evaluation of a novel folic acid conjugate with improved properties suitable for positron emission tomography (PET). [(18)F]-fluoro-deoxy-glucose folate ([(18)F]3) was synthesized based on the click chemistry approach using 2-deoxy-2-[(18)F]fluoroglucopyranosyl azide and a folate alkyne derivative. The novel radiotracer [(18)F]3 was produced in good radiochemical yields (25% d.c.) and high specific radioactivity (90 GBq/μmol). Compared to previously published (18)F-folic acid derivatives, an increase in hydrophilicity was achieved by using a glucose entity as a prosthetic group. Biodistribution and PET imaging studies in KB tumor-bearing mice showed a high and specific uptake of the radiotracer in FR-positive tumors (10.03 ± 1.12%ID/g, 60 min p.i.) and kidneys (42.94 ± 2.04%ID/g, 60 min p.i.). FR-unspecific accumulation of radioactivity was only found in the liver (9.49 ± 1.13%ID/g, 60 min p.i.) and gallbladder (17.59 ± 7.22%ID/g, 60 min p.i.). No radiometabolites were detected in blood, urine, and liver tissue up to 30 min after injection of [(18)F]3. [(18)F]-fluoro-deoxy-glucose-folate ([(18)F]3) is thus a promising PET radioligand for imaging FR-positive tumors. © 2012 American Chemical Society
Cindy R Fischer, Cristina Müller, Josefine Reber, Adrienne Müller, Stefanie D Krämer, Simon M Ametamey, Roger Schibli. 18F]fluoro-deoxy-glucose folate: a novel PET radiotracer with improved in vivo properties for folate receptor targeting. Bioconjugate chemistry. 2012 Apr 18;23(4):805-13
PMID: 22372827
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