The therapeutic effect of drugs used in cancer chemotherapy has been augmented by their complexing or chemical linking to macromolecular carriers. The role of the carrier should be to deliver the drug preferentially to the tumor site. Potential carriers are either (1) nonspecific macromolecules whose preferential activity is due to the inherently higher permeability and pinocytic activity of tumor cells, (2) lysosomotropic agents such as DNA or liposomes, or (3) the more specific agents--antitumor antibodies. Conjugates of daunomycin to antitumor antibodies, prepared either by direct binding or by binding via dextran, were shown to retain both the antibody and the drug activity. Thus they exert specific cytotoxic activity toward tumor cells that the antibodies recognize. In vivo, these complexes are more active than the free drug in prolongation of survival of mice transplanted with the tumor cells. Conjugates of daunomycin with normal immunoglobulin or with dextran also show higher therapeutic efficacy in vivo, probably due to their capacity to reduce the cytotoxicity of daunomycin and/or to the higher permeability of neoplastic cells. But under certain conditions, mainly at low drug concentrations, the drug-antibody conjugates have an advantage over all others.
癌症化疗所用药物通过与大分子载体络合或化学连接，其治疗效果得到了增强。载体的作用应该是将药物优先递送至肿瘤部位。潜在的载体包括：（1）非特异性大分子，其优先活性源于肿瘤细胞固有的较高通透性和胞饮活性；（2）溶酶体亲和剂，如DNA或脂质体；（3）更具特异性的试剂——抗肿瘤抗体。通过直接结合或经由葡聚糖结合制备的柔红霉素与抗肿瘤抗体的结合物，显示出同时保留了抗体和药物活性。因此，它们对抗体所识别的肿瘤细胞发挥特异性细胞毒活性。在体内，这些复合物在延长移植有肿瘤细胞的小鼠生存期方面比游离药物更具活性。柔红霉素与正常免疫球蛋白或葡聚糖的结合物在体内也显示出更高的治疗效果，这可能是由于它们降低柔红霉素细胞毒性的能力和/或肿瘤细胞更高的通透性。但在某些条件下，主要是在低药物浓度时，药物-抗体结合物比其他所有结合物都具有优势。
