MONOCLONAL ANTIBODY-TOXIN CONJUGATES FOR TUMOR THERAPY IN VIVO

单克隆抗体选择性结合肿瘤细胞分化 抗原在体外和体内。 自然效应机制通常 不介导单克隆抗体结合细胞的杀伤， 已经设计出了将剧毒蛋白质与 选择性杀死肿瘤细胞的抗体。 有两种方法可以将有毒蛋白质，如蓖麻毒素与抗体结合， 已用于体外杀伤抗原阳性细胞。 蓖麻毒素具有 两个亚基，a亚基阻断蛋白质合成， 而B亚基结合所有细胞上的半乳糖基团 表面，而且还有利于蓖麻毒素链的运输， 胞质液 1)蓖麻毒素A链与抗体的连接产生 具有低非靶毒性但也具有靶细胞毒性的试剂 体内应用缓慢; 2）完整蓖麻蛋白与 抗体导致非常强的靶细胞毒性，但非- 靶细胞杀伤必须通过阻断靶细胞的配体来阻止 蓖麻毒素B链与细胞结合。 这就限制了它的应用 到100 mM乳糖可以阻断蓖麻毒素的体外情况 约束力 我们已经成功地开发了几种新的方法来应用 体内免疫毒素。 1)克隆毒素，然后改变它们的 在基因水平上进行结构调整，以降低非靶细胞毒性; 2)蓖麻毒素的化学修饰以确定 蓖麻毒素半乳糖结合位点，并可能提高 蓖麻毒素连接抗体; 3）开发新的方法来阻止非- 蓖麻毒素体内靶细胞毒性研究 我们已经发现了一种 阻断蓖麻毒素半乳糖结合位点的单克隆抗体 类似于乳糖; 4）免疫毒素的鞘内施用 用于治疗脑肿瘤，其杀死2- 5log的肿瘤细胞， 动物模型和5）基因工程的制备 用于人类脑肿瘤患者临床试验的免疫毒素。

Monoclonal antibodies selectively bind tumor cell differentiating antigens in vitro and in vivo. Natural effector mechanisms often do not mediate killing of monoclonal antibody bound cells so we have devised methods of linking extremely toxic proteins to the antibodies to selectively kill tumor cells. Two methods of coupling toxic proteins, like ricin to antibodies, have been used o kill antigen positive cells in vitro. Ricin has two subunits, the a subunit blocks protein synthesis when in the cytosol and the B subunit binds galactose groups on all cell surfaces but also facilitates the transport of ricin a chain to the cytosol. 1) Linkage of the ricin a chain to antibodies yields reagents with low non-target toxicity but target cell toxicity too slow for in vivo applications; 2) Linkage of intact ricin to antibodies results in very potent target cell toxicity but the non- target cell killing must be prevented by a ligand which blocks ricin B chain binding to cells. This has limited its application to in vitro situations where 100 mM lactose can block ricin binding. We have succeeded in developing several new approaches to apply immunotoxins in vivo. 1) Cloning of toxins then altering their structure at the gene level to decrease non-target cell toxicity; 2) Chemical modification of ricin to determine the location of the ricin galactose binding site and to possibly improve efficacy of ricin linked to antibodies; 3) Develop new ways to block the non- target cell toxicity of ricin in vivo. We have discovered a monoclonal antibody which blocks the ricin galactose binding site similar to lactose; 4) Intrathecal administration of immunotoxins for therapy of brain tumors that kill 2-5 logs of tumors cells in animal models and 5) Preparation of genetically engineered immunotoxins for clinical trials of human brain tumor patients.