Radiotherapy of CD45-expressing daudi tumors in nude mice with yttrium-90-labeled, PEGylated Anti-CD45 antibody

Studies were performed to determine the suitability of using the polyethylene glycol (PEG)-labeled AHN12 anti-CD45 monoclonal antibody to deliver the high-energy 8-particle-emitting isotope 90Y to a CD451 B-cell Daudi lymphoma grown as flank tumors in athymic nude mice. The PEGylated radiolabeled antibody displayed a significantly better antitumor effect in the mouse tumorflank model (p < 0.03) and significantly better blood pharmacokinetics in normal rats (p < 0. 05) than the non-PEGylated radiolabeled antibody. Studies of two different sizes of PEG showed that rats given 43 kDa of PEGylated AHN-12, but not 5 kDa of PEGylated AHN-12, had significantly higher radiolabeled antibody blood levels and, therefore, improved pharmacokinetics ' as compared to rodents given non-PEGylated radiolabeledAHN-12 (p < 0.05). Surviving mice revealed no signs of kidney, liver, or gastrointestinal damage by histology study. Notably, in vitro studies indicated that PEGylation did not have a major effect on labeling efficiency and the binding of labeled antibody. These findings indicate that PEGylation of radiolabeled anti-CD45 antibody may be a useful and desirable means of extending blood half-life and enhancing efficacy. Also, the final outcome may be impacted by the size of the PEG molecule usedfor the modification of the blood haif-life.