Cathepsin B-labile dipeptide linkers for lysosomal release of doxorubicin from internalizing immunoconjugates: model studies of enzymatic drug release and antigen-specific in vitro anticancer activity.
The anticancer drug doxorubicin (DOX) has been linked to chimeric BR96, an internalizing monoclonal antibody that binds to a Lewis(y)-related, tumor-associated antigen, through two lysosomally cleavable dipeptides, Phe-Lys and Val-Cit, giving immunoconjugates 72 and 73. A self-immolative p-aminobenzyloxycarbonyl (PABC) spacer between the dipeptides and the DOX was required for rapid and quantitative generation of free drug. DOX release from model substrate Z-Phe-Lys-PABC-DOX 49 was 30-fold faster than from Z-Val-Cit-PABC-DOX 42 with the cysteine protease cathepsin B alone, but rates were identical in a rat liver lysosomal preparation suggesting the participation of more than one enzyme. Conjugates 72 and 73 showed rapid and near quantitative drug release with cathepsin B and in a lysosomal preparation, while demonstrating excellent stability in human plasma. Against tumor cell lines with varying levels of BR96 expression, both conjugates showed potent, antigen-specific cytotoxic activity, suggesting that they will be effective in delivering DOX selectively to antigen-expressing carcinomas.
Dubowchik
Gene M
GM
Bristol-Myers Squibb Pharmaceutical Research Institute, P.O. Box 5100, Wallingford, Connecticut 06492, USA. Gene.Dubowchik@bms.com
Firestone
Raymond A
RA
Padilla
Linda
L
Willner
David
D
Hofstead
Sandra J
SJ
Mosure
Kathleen
K
Knipe
Jay O
JO
Lasch
Shirley J
SJ
Trail
Pamela A
PA
D000818:Animals; D000911:Antibodies, Monoclonal / Q000493:pharmacokinetics*; D000951:Antigens, Neoplasm / Q000276:immunology; D002401:Cathepsin B / Q000378:metabolism*; D002455:Cell Division / Q000187:drug effects; D003432:Cross-Linking Reagents / Q000737:chemistry / Q000378:metabolism*; D004151:Dipeptides / Q000737:chemistry / Q000378:metabolism*; D004317:Doxorubicin / Q000138:chemical synthesis / Q000493:pharmacokinetics*; D004355:Drug Stability; D004798:Enzymes / Q000378:metabolism; D006801:Humans; D007700:Kinetics; D007983:Lewis Blood Group Antigens / Q000276:immunology; D008247:Lysosomes / Q000201:enzymology / Q000378:metabolism*; D051381:Rats; D014407:Tumor Cells, Cultured
D000911:Antibodies, Monoclonal; D000951:Antigens, Neoplasm; C092612:BR96-doxorubicin immunoconjugate; D003432:Cross-Linking Reagents; D004151:Dipeptides; D004798:Enzymes; D007983:Lewis Blood Group Antigens; C094162:Lewis Y antigen; D004317:Doxorubicin; D002401:Cathepsin B