Antitumor activity of mannan-methotrexate conjugate in vitro and in vivo

Conjugation of anticancer drugs with different carriers has been extensively studied recently as a potential method of obtaining improved drug forms. The conjugation often results in the increase of the therapeutic effect, alteration of a toxicity profile, and/or selective targeting of therapeutic agent to the tissue of interest. We have synthesized mannan-methotrexate conjugate by means of methotrexate anhydride and studied its antitumor properties both in vitro and in vivo in comparison with free methotrexate. Mannan-methotrexate conjugate showed significantly improved antitumor activity compared to free methotrexate in the model of P388 mouse leukemia disseminated in the peritoneal cavity treated with intraperitoneally injected chemotherapy. Conversely, the antitumor effects of free methotrexate and mannan-methotrexate conjugate were comparable when leukemia was implanted subcutaneously and chemotherapy agents were administered intravenously. These results suggest that mannan-methotrexate conjugate should be further investigated as a potential therapeutic agent for intraperitoneally disseminated tumors.