Development of a 124I-labeled version of the anti-PSMA monoclonal antibody capromab for immunoPET staging of prostate cancer: Aspects of labeling chemistry and biodistribution

  • Int J Oncol. 2014 Jun;44(6):1998-2008. doi: 10.3892/ijo.2014.2376.
Vladimir Tolmachev  1 ,  Jennie Malmberg  2 ,  Sergio Estrada  2 ,  Olof Eriksson  2 ,  Anna Orlova  2
Affiliations
  • 1. Division of Biomedical Radiation Sciences, Rudbeck Laboratory, Uppsala University, Uppsala, Sweden.
  • 2. Preclinical PET Platform, Uppsala University, Uppsala, Sweden.
PMID: 24718894 DOI: 10.3892/ijo.2014.2376
Abstract

Correct staging of prostate Cancer is an unmet clinical need. Radionuclide targeting of prostate-specific membrane antigen (PSMA) with 111In-labeled capromab pendetide (ProstaScint) is a clinical option for prostate Cancer staging. We propose the use of 124I-labeled capromab to decrease the retention of radioactivity in healthy organs (due to the non-residualizing properties of the radiolabel). The use of 124I as a label should increase imaging sensitivity due to the advantages of PET as an imaging modality. Capromab targets the intracellular domain of PSMA; accumulation of radioactivity in the tumor should not depend on internalization of the antigen/antibody complex. Capromab was iodinated, and its targeting properties were compared with indium labeled counterpart in LNCaP xenografts in dual isotope mode. PSMA-negative xenografts (PC3) were used as a negative control. Radioiodinated capromab bound to PSMA specifically. Biodistribution of 125I/111In-capromab showed a more rapid clearance of iodine radioactivity from liver, spleen, kidneys, bones, colon tissue, as well as tumors. Maximum tumor uptake (13±8% ID/g for iodine and 29±9% ID/g for indium) and tumor-to-non-tumor ratios for both agents were measured 5 days post-injection (pi). High tumor accumulation and low uptake of radioactivity in normal organs were confirmed using microPET/CT 5 days pi of 124I-capromab.

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