title: Evaluation of the in vivo biodistribution of indium-111 and yttrium-88 labeled dendrimer-1B4M-DTPA and its conjugation with anti-Tac monoclonal antibody.
abstract: We evaluated the in vivo biodistribution of indium- and yttrium-labeled second-generation polyamidoamine dendrimer (PAMAM) conjugated with 2-(p-isothiocyanatobenzyl)-6-methyl-diethylenetriaminepentaacetic acid (1B4M), a derivative of DTPA. In addition, we conjugated PAMAM-1B4M to humanized anti-Tac IgG (HuTac) and evaluated its in vitro and in vivo properties. PAMAM-1B4M was labeled with 111In at 37-48 MBq/mg (1.0-1.3 mCi/mg) or with 88Y at 3.7-4.8 MBq/mg (0.1-0. 13 mCi/mg), and an aliquot of radiolabeled conjugate was saturated with the corresponding stable yttrium or indium. Nontumor-bearing nude mice were injected intravenously with 55.5-66.6 kBq (1.5-1.8 microCi) of 88Y-labeled PAMAM-1B4M or with 185 kBq (5 microCi) of 111In-labeled PAMAM-1B4M. The mice were then sacrificed at 15 min, 90 min, 1 day, and 4 days postinjection. Then the PAMAM-1B4M was conjugated with HuTac and labeled with 111In at 111-259 MBq/mg (3-7 mCi/mg). Another preparation of 111In-labeled HuTac-PAMAM-1B4M was saturated with stable indium. Immunoreactivity of both preparations and biodistribution in normal mice 1 h after injection and in ATAC4 and A431 tumor-bearing mice 18 h after injection were evaluated and compared with those of 111In-labeled 1B4M-HuTac. We noted significantly higher accumulations (p < 0.05) of 111In-labeled and 88Y-labeled unsaturated PAMAM-1B4M than saturated preparations in the liver, kidney, spleen, and bone at most time points. The whole-body clearance times of unsaturated preparations were significantly slower than those of saturated preparations at all time points, with the exception of 168 h for 111In-labeled PAMAM-1B4M. The saturated preparation of 111In-labeled HuTac-PAMAM-1B4M showed lower hepatic uptake (27 +/- 2%ID/g) than the unsaturated (32 +/- 2%ID/g), but greater than the HuTac-1B4M control (10 +/- 0%ID/g). The splenic uptake showed 15 +/- 1, 38 +/- 5, and 8 +/- 1%ID/g for the saturated, unsaturated, and control, respectively. The biodistribution of the dendrimer conjugated HuTac in normal organs of tumor-bearing mice was similar to nontumor-bearing mice. Specific tumor (ATAC4) uptake was higher than that in nonspecific tumor (A431). In conclusion, we evaluated the biodistribution of radiolabeled PAMAM-1B4M. We noted high accumulation in the liver, kidney, and spleen, which significantly decreased when the chelates were saturated with the stable element. A similar phenomenon was observed between unsaturated and saturated 111In-labeled HuTac-PAMAM-1B4M, indicating that the PAMAM dendrimer had a detrimental effect on biodistribution.
authors.affiliation: Department of Nuclear Medicine, National Institutes of Health Bethesda,Maryland 20892, USA.
authors.forename: H
authors.initials: H
authors.lastname: Kobayashi
authors.forename: C
authors.initials: C
authors.lastname: Wu
authors.forename: M K
authors.initials: MK
authors.lastname: Kim
authors.forename: C H
authors.initials: CH
authors.lastname: Paik
authors.forename: J A
authors.initials: JA
authors.lastname: Carrasquillo
authors.forename: M W
authors.initials: MW
authors.lastname: Brechbiel
mesh_terms: D000818:Animals; D000911:Antibodies, Monoclonal / Q000737:chemistry / Q000493:pharmacokinetics*; D001672:Biocompatible Materials / Q000737:chemistry; D050091:Dendrimers; D005260:Female; D007074:Immunoglobulin G / Q000737:chemistry; D007150:Immunohistochemistry; D007205:Indium Radioisotopes; D051379:Mice; D008819:Mice, Nude; D009374:Neoplasms, Experimental / Q000378:metabolism; D004369:Pentetic Acid / Q000031:analogs & derivatives* / Q000737:chemistry / Q000493:pharmacokinetics; D011073:Polyamines / Q000737:chemistry; D019275:Radiopharmaceuticals / Q000737:chemistry / Q000493:pharmacokinetics*; D014018:Tissue Distribution; D014183:Transplantation, Heterologous; D015021:Yttrium Radioisotopes
chemical_list: D000911:Antibodies, Monoclonal; D001672:Biocompatible Materials; D050091:Dendrimers; D007074:Immunoglobulin G; D007205:Indium Radioisotopes; C104700:PAMAM Starburst; D011073:Polyamines; D019275:Radiopharmaceuticals; D015021:Yttrium Radioisotopes; C077295:2-(4-isothiocyanatobenzyl)-6-methyldiethylenetriaminepentaacetic acid; D004369:Pentetic Acid