The basic principle of the targeted delivery approach is that the conjugation of a drug to a tumorspecific molecule renders the drug inactive until it reaches the target site. Monoclonal antibodies (mAbs), which have shown high binding specificity for tumor-specific antigens, could be used as targeting agents. Paclitaxel has brought significant impact on the current cancer chemotherapy, but seriously suffers from the lack of tumor specificity. A series of paclitaxel-monoclonal antibody conjugates via C-2 ester linkage were reported. Taking into account the fact that the cytotoxicity of paclitaxel is not good enough and thus not applicable to this target delivery prodrug approach, new taxoids bearing methyldisulfanyl(alkanoyl) groups were designed, synthesized, and their activities evaluated. A highly cytotoxic C-10 methyldisulfanylpropanoyl taxoid, was conjugated to monoclonal antibodies recognizing the epidermal growth factor receptor (EGFR). These conjugates were shown to possess remarkable target-specific antitumor activity in vivo against EGFR-expressing A431 tumor xenografts in SCID mice, resulting in complete inhibition of tumor growth in all the treated mice without any noticeable toxicity to the animals.
Keywords: paclitaxel, monoclonal antibody, antibody-drug conjugates, cancer, anti-cancer agents, targeted delivery, tumor selectivity
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