Selective
chemotherapy remains a key issue for successful treatment in
cancer therapy. The use of targeting approaches like the enhanced permeability and retention (EPR) effect of macromolecules, is consequently needed. Here, we report the preparation of a novel
catalytic antibody-
polymer conjugate for selective
prodrug activation.
HPMA copolymer was conjugated to
catalytic antibody 38C2 through an
amide bond formation between epsilon-amino group of
lysine residue from the antibody molecule and a p-nitrophenyl
ester of the
polymer. The conjugate was purified over a size exclusion column using FPLC. In the isolated fraction, one or two molecules of
polymer were conjugated to one molecule of antibody based on gel analysis. The resulting conjugate retained most of its catalytic activity (75-81%) in comparison to the free antibody. The activity was monitored with a
fluorogenic substrate and a
prodrug activation assay using HPLC. Furthermore, the conjugate was evaluated in vitro for its ability to activate an
etoposide prodrug using two different
cancer cell lines. Cells growth inhibition using the
prodrug and the conjugate was almost identical to inhibition by the free antibody and the
prodrug. For the first time, a
catalytic antibody was conjugated to a passive targeting moiety while retaining its catalytic ability to activate a
prodrug. The conjugate described in this work can be used for selective activation of
prodrug in the PDEPT (
polymer directed
enzyme prodrug therapy) approach by replacing the
enzyme component with
catalytic antibody 38C2.