Immunologically specific activation of a cephalosporin derivative of mitomycin C by monoclonal antibody beta-lactamase conjugates.
The syntheses of two cephalosporin derivatives 2 and 3 of mitomycin C (1) containing 7-phenylacetamido and 7-delta-carboxybutanamido side chains, respectively, are described. These compounds were prepared for evaluation as cephalosporin prodrugs capable of being activated by mAb-beta-lactamase conjugates. In vitro cytotoxicity assays performed on H2987 lung adenocarcinoma and clone 62 melanoma cell lines indicated that compound 2 was comparable in cytotoxicity to the parent drug. In an effort to improve upon the cytotoxic differential of 2, an alternative prodrug 3 containing a polar carboxyl group in the side chain of the cephalosporin moiety was prepared. Compound 3 consistently behaved as a prodrug and was approximately 40- and 10-fold less toxic than 1 toward H2987 and clone 62, respectively. Determination of kinetic constants for hydrolysis by beta-lactamase from Enterobacter cloacae P99 indicated kcat values of 476 +/- 170 and 248 +/- 15.1 s-1 for 2 and 3, respectively. The kcat/Km ratios for 2 and 3 were found to be approximately 9.7 and 2.1 microM/s, respectively. Comparison of these kcat/Km values with those obtained for similar cephalosporin derivatives of other antitumor agents demonstrated that compounds with delta-carboxybutanamido side chains generally have slightly diminished efficiency of enzymatic hydrolysis compared to the corresponding 7-phenylacetamido analog. It was also demonstrated that the less toxic prodrug 3 was activated in an immunologically specific manner by L6-F(ab')-beta-lactamase and 96.5-F(ab')-beta-lactamase conjugates, selective for H2987 and clone 62 cells, respectively.
Vrudhula
V M
VM
Bristol-Myers Squibb Pharmaceutical Research Institute, Seattle, Washington 98121, USA.
Svensson
H P
HP
Senter
P D
PD
D000911:Antibodies, Monoclonal / Q000276:immunology*; D002511:Cephalosporins / Q000737:chemistry* / Q000276:immunology; D006801:Humans; D046911:Macromolecular Substances; D016685:Mitomycin / Q000276:immunology / Q000378:metabolism; D008937:Mitomycins; D008956:Models, Chemical; D011355:Prodrugs / Q000138:chemical synthesis; D014407:Tumor Cells, Cultured; D001618:beta-Lactamases / Q000276:immunology*
D000911:Antibodies, Monoclonal; D002511:Cephalosporins; D046911:Macromolecular Substances; D008937:Mitomycins; D011355:Prodrugs; D016685:Mitomycin; D001618:beta-Lactamases