Pharmacokinetic change of nanoparticulate formulation "Lactosome" on multiple administrations

Technology Research Laboratory, Shimadzu Corporation, Kyoto 619-0237, Japan.
International immunopharmacology (Impact Factor: 2.71). 07/2012; 14(3):261-6. DOI: 10.1016/j.intimp.2012.07.011
Source: PubMed

ABSTRACT Lactosome, which is a polymer micelle composed of poly(lactic acid)-b-poly(sarcosine), was applied successfully for solid tumor imaging. Lactosome is considered to escape from the reticuloendothelial system recognition, and shows prolonged in vivo blood clearance time. In vivo disposition of Lactosome, however, changed upon multiple dosages. Lactosome at the 2nd dosage was cleared from the blood stream by trapping at liver. This accelerated blood clearance (ABC) phenomenon is explained by production of anti-Lactosome IgM and IgG(3) through the immune response related with B-lymphocyte cells. The memory effect of B-lymphocyte cells lasted nearly for six months in mouse. The epitope moiety of Lactosome is concluded to be poly(sarcosine) based on the competitive inhibition assay. Since the ABC phenomenon was also reported with PEGylated liposome, nanoparticles in general may be potential in triggering the immune system.

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    ABSTRACT: Lactosome is a polymeric micelle composed of amphiphilic polydepsipeptide, poly(sarcosine)64-block-poly(l-lactic acid)30 (AB-type), which accumulates in solid tumors through the enhanced permeability and retention (EPR) effect. However, lactosome on multiple administrations changed its pharmacokinetics from accumulation in tumors to liver due to the production of antilactosome IgM, which was triggered by the first administration. This phenomenon is called the accelerated blood clearance (ABC). In order to reduce the production of antilactosome IgM, a novel nanoparticle composed of (poly(sarcosine)23)3-block-poly(l-lactic acid)30 (A3B-type) was prepared. The A3B-type lactosome at the second administration showed an in vivo disposition similar to that at the first administration due to suppression of antibody production. This study involving the AB- and A3B-type lactosomes, with variation of conditions, revealed that the high local density of poly(sarcosine) chains of the A3B-type lactosome should relate to the prevention of a polymeric micelle from interacting B-cell receptors.
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