We recently demonstrated that Doxil loses its long-circulating properties when injected repeatedly at doses below 2 mg/m(2) in dogs. In studies using other animal species, PEGylated liposomal doxorubicin has been reported not to induce the accelerated blood clearance (ABC) phenomenon. We investigated the issue of whether Doxil can elicit the ABC phenomenon in several species. In minipigs, the ABC phenomenon was induced at 2 mg/m(2). In other animal species, the ABC phenomenon was not observed at higher doses (>2 mg/m(2)), but was observed at much lower doses (0.2 mg/m(2)). The pharmacokinetic profile of a second dose of Doxil reflected the circulating anti-PEG IgM level induced by the first dose. The ABC phenomenon was not observed at the clinically recommended DXR dose (20 mg/m(2)) in any animal species. These results indicate that Doxil can cause the ABC phenomenon in all animals tested, the extent of induction was dependent on the first dose of Doxil, and a higher Doxil dose lessened the ABC phenomenon. The current study results suggest that a careful study design including selection of animal species is important for preclinical studies using PEGylated liposomal formulations even if they contain anticancer drugs that suppress the host immune response.
Keywords: Accelerated blood clearance phenomenon; Doxil; Doxorubicin; PEGylated liposomes; Polyethylene glycol; Species difference.
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