In vitro release behavior and cytotoxic activity, and in vivo plasma disposition of newly synthesized macromolecular derivatives of
cisplatin (CDDP) were investigated and compared with CDDP. The derivatives included oxidized
dextran conjugate of CDDP (OX-Dex/CDDP) and dicarboxymethylated
dextran conjugate of CDDP (
DCM-Dex/CDDP). In vitro release of
platinum complex from
dextran conjugated CDDP was determined by an equilibrium dialysis method. These
dextran conjugates showed sustained release of the
platinum complex. In vitro release half-life for
DCM-Dex/CDDP was significantly longer (4.5 times) than that for OX-Dex/CDDP. In vitro cytotoxic activity of CDDP and
dextran conjugated CDDP against colon 26, mouse
colon cancer cell line, was measured using the MTT assay method. OX-Dex/CDDP showed a similar cytotoxic activity to CDDP. However, both cytotoxic activities were markedly decreased when preincubated with the medium containing serum. On the other hand,
DCM-Dex/CDDP retained residual cytotoxic activity at a significantly higher level than OX-Dex/CDDP after preincubation with the medium containing serum, although it showed the lowest cytotoxic activity. This indicated longer maintenance of the in vitro antitumor activity of
DCM-Dex/CDDP in serum compared with OX-Dex/CDDP. Plasma disposition of CDDP and
dextran conjugated CDDP was determined by
intravenous administration to rats. Although the total
platinum plasma concentration-time profile for OX-Dex/CDDP was similar to that for CDDP, its markedly higher profile was achieved when
DCM-Dex/CDDP was administered. The values of the total
platinum AUC and MRT, where AUC is the area under the
platinum concentration-time curve and MRT is the mean residence time, for
DCM-Dex/CDDP were 11.2 times and 4.8 times significantly higher than with OX-Dex/CDDP in plasma, respectively.
DCM-Dex/CDDP also showed a significantly lower total clearance compared with OX-Dex/CDDP. These results from the in vivo experiments revealed that retention of
DCM-Dex/CDDP in blood circulation was much greater than that for OX-Dex/CDDP.
DCM-Dex/CDDP thus has potential as a macromolecular derivative of CDDP for passive
tumor targeting.