A dimerized urea-based inhibitor of the prostate-specific membrane antigen for 68Ga-PET imaging of prostate cancer
- Martin SchäferAffiliated withRadiopharmaceutical Chemistry, German Cancer Research Center
- , Ulrike Bauder-WüstAffiliated withRadiopharmaceutical Chemistry, German Cancer Research Center
- , Karin LeottaAffiliated withDepartment of Nuclear Medicine, University of Heidelberg
- , Frederic ZollerAffiliated withDepartment of Nuclear Medicine, University of Heidelberg
- , Walter MierAffiliated withDepartment of Nuclear Medicine, University of Heidelberg
- , Uwe HaberkornAffiliated withDepartment of Nuclear Medicine, University of Heidelberg
- , Michael EisenhutAffiliated withRadiopharmaceutical Chemistry, German Cancer Research Center
- , Matthias EderAffiliated withRadiopharmaceutical Chemistry, German Cancer Research Center Email author
Alternative positron-emission tomography (PET) probes like labeled inhibitors of the prostate-specific membrane antigen (PSMA) are of emerging clinical impact as they show the ability to image small lesions of recurrent prostate cancer. Here, the dimerization of the pharmacophore Glu‐ureido‐Lys via the 68Ga chelator N,N′-bis[2-hydroxy-5-(carboxyethyl)benzyl]ethylenediamine-N,N′-diacetic acid (HBED-CC) was investigated to further improve the binding characteristics and pharmacokinetics.
The peptidomimetic structures were synthesized by solid-phase chemistry, and the resulting products were coupled with the respective 2,3,5,6-tetrafluorophenol esters of HBED-CC to form the monomeric reference and the dimeric Glu‐ureido‐Lys derivative. The binding properties were analyzed in competitive binding, internalization, and cell surface retention experiments. PET images and biodistribution data were obtained 1 h after injection in BALB/c nu/nu mice bearing LNCaP tumor xenografts.
Cell binding data revealed significant better binding properties of the dimer (IC50 = 3.9 ± 1.8 nM; IC50 (monomer) = 12.1 ± 2.1 nM). The inhibition potency investigated by the enzyme-based NAALADase assay confirmed these results. Specific internalization in LNCaP cells was demonstrated for both, the monomer and dimer. As shown by efflux measurements, the dimeric compound was more effectively retained on the cell surface, resulting in advanced in vivo properties (T/BMonomer = 9.2; T/BDimer = 26.5).
The dimeric [68Ga]7 is a promising imaging agent for PSMA-expressing tumors as it shows higher tumor uptake while observing more favorable background clearance. As compared to the respective monomer, the higher affinity and prolonged tumor retention additionally represent promising features and warrant further evaluation regarding 68Ga-PET imaging of PSMA expression.
KeywordsDimerization 68Ga-PET imaging PSMA HBED-CC Prostate cancer
- A dimerized urea-based inhibitor of the prostate-specific membrane antigen for 68Ga-PET imaging of prostate cancer
- Open Access
- Available under Open Access This content is freely available online to anyone, anywhere at any time.
- Online Date
- June 2012
- Online ISSN
- Springer Berlin Heidelberg
- Additional Links
- 68Ga-PET imaging
- Prostate cancer
- Author Affiliations
- 1. Radiopharmaceutical Chemistry, German Cancer Research Center, Im Neuenheimer Feld 280, Heidelberg, 69120, Germany
- 2. Department of Nuclear Medicine, University of Heidelberg, Im Neuenheimer Feld 400, Heidelberg, 69120, Germany