Ton GN, Weichert JP, Longino MA, Fine JP, Kwon GS. Methoxypoly(ethylene glycol)-conjugated carboxypeptidase A for solid tumor targeting.
J Control Release 2005;
104:155-66. [PMID:
15866342 DOI:
10.1016/j.jconrel.2005.01.015]
[Citation(s) in RCA: 3] [Impact Index Per Article: 0.2] [Reference Citation Analysis] [Abstract] [MESH Headings] [Grants] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 06/11/2004] [Revised: 01/25/2005] [Accepted: 01/26/2005] [Indexed: 11/16/2022]
Abstract
We have evaluated effects of mPEG modification on pharmacokinetic properties of carboxypeptidase A (CPA) in normal rats. Attachment of two or three mPEG chains to CPA resulted in the generation of mPEG2-CPA and mPEG3-CPA analogs with significantly enhanced plasma half-lives, especially during the distribution phase. Moreover, the assessment of real-time whole-body kinetics in CT26 tumor-bearing mice showed both mPEG2-CPA and mPEG3-CPA exhibited increased body retention at 48 h post-injection. In addition, tumor localization of mPEG3-CPA at 72 h was visualized and confirmed by fusion of the gamma-scintigraphy and microCT data sets. Results from the imaging studies support our hypothesis of a correlation between tumor uptake and enhanced circulatory half-life. Tissue distribution data indicated the combination of increased tumor extravasation and effective renal elimination observed with mPEG2-CPA at 48 h following administration led to the highest observed tumor-to-blood ratio of 4.8:1. Although the total concentration of mPEG3-CPA accumulated in tumor was higher than that of mPEG2-CPA and CPA at predetermined time intervals, a higher tumor-to-blood ratio was not obtained owing to a higher level of blood activity. Clearly, the attachment of an appropriate number of mPEG chains can facilitate tumor localization as effectively as can the use of a tumor-specific antibody.
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