Biodistribution of a 153Gd-Folate Dendrimer, Generation = 4, in Mice With Folate-Receptor Positive and Negative Ovarian Tumor Xenografts

Abstract

RATIONALE AND OBJECTIVES: An important characteristic of targeted contrast agents is how they are tolerated in a biologic environment and their localization in the surrounding tissues in addition to target tissue. We evaluate the biodistribution of a gadolinium Gd 153-folate-dendrimer in high affinity folate-receptor (hFR) positive and negative ovarian tumor xenografts. METHODS: The 153Gd-folate-dendrimer chelate was prepared by exchanging 153Gd with nonradioactive gadolinium for 1 week, followed by extensive filtration. Athymic mice with hFR-positive (n = 3) and negative tumors (n = 3) were injected intravenously and counted using a whole-body counting system with a 80 to 150 keV counting window. RESULTS: The hFR-positive tumors accumulate 3.6% +/- 2.8% injected dose/g, whereas only background counts were found in hFR-negative tumors. The folate-dendrimer's tumor-to-blood ratio of 12.6, in hFR-positive tumors, was approximately 5.7 to 17.0 fold better than those obtained with monoclonal antibodies targeted to the folate receptor. CONCLUSIONS: Biodistribution studies confirm previous MRI findings and show that the accumulation of the folate-dendrimer requires the expression of the hFR.