IMMUNOTOXINS AND RECOMBINANT TOXIN THERAPY OF CANCER

我们继续开发和改进重组免疫毒素， 癌症的治疗 我们的主要努力是把 单链免疫毒素B3（Fv）PE 38进入临床。 临床 试验于1995年2月开始，迄今已有10名患者 参加了一项涉及结肠癌患者的试验， 乳腺癌和其他上皮癌。 LMB-7的改进形式 已经通过以一种新的方法稳定Fv相互作用， 其中二硫键被基因工程改造到框架中， 将Fv片段结合在一起。 这些二硫键连接的 免疫毒素在人血浆中在37度下稳定14天。 含有dsFv结构域的重组免疫毒素显示出更好的抗肿瘤活性 在动物模型中的活性高于没有免疫抑制剂的单链免疫毒素。 非特异性毒性增加。 我们也在开发更小的 重组免疫毒素应该更好地穿透肿瘤， 免疫原性更低。我们还人源化了B3的Fv部分， 抗体作为制备免疫原性较低的重组 免疫毒素 我们还使用dsFv方法制备了 二硫键连接的T细胞受体非常稳定， 特异性针对MHC II类肽复合物，并可用于 结构研究。 我们在PE中鉴定了几个B细胞表位 并正在构建突变分子，其中这些表位具有 改变序列以产生免疫原性较低的免疫毒素。 我们 我已经制造了抗Tac抗体的dsFv片段，表明它可以被 放射性标记有效，并将迅速定位于IL 2受体- 荷瘤裸鼠体内生长。 这种药物可能对 IL-2受体携带者的诊断和治疗 恶性肿瘤。 我们正在利用噬菌体抗体展示， 改进现有抗体和开发新抗体。 我们有 修改了方法，使二硫键连接的Fv显示在 噬菌体表面，这些噬菌体比单个噬菌体稳定得多 链Fv，并应产生不同类型的抗体。 我们有 开始研究免疫毒素抗性的可能机制， 分离了几个cDNA，当它们高水平表达时， 抗假单胞菌毒素、白喉毒素和肿瘤的细胞 坏死α和β。 这些毒素的作用机制是 正在研究中。

We have continued to develop and improve recombinant immunotoxins for the treatment of cancer. Our major effort has been to bring the single chain immunotoxin, B3(Fv)PE38, into the clinic. A clinical trial was initiated in February 1995 and to date ten patients have been enrolled in this trial involving patients with colon cancer, breast cancer and other epithelial cancers. Improved forms of LMB-7 have been made by stabilizing the Fv interaction in a new approach in which a disulfide bond is genetically engineered into the framework regions to hold the Fv fragments together. These disulfide-linked immunotoxins are stable at 37 degrees for 14 days in human plasma. Recombinant immunotoxins containing dsFv domains show better antitumor activity in animal models than single chain immunotoxins without an increase in nonspecific toxicity. We are also developing smaller recombinant immunotoxins which should penetrate tumors better and be less immunogenic. We have also humanized the Fv portion of the B3 antibody as a first step in making less immunogenic recombinant immunotoxins. We have also used the dsFv approach to make a disulfide-linked T cell receptor which is extremely stable, binds specifically to MHC class II peptide complex and could be useful for structural studies. We have identified several B cell epitopes in PE and are constructing mutant molecules in which these epitopes have an altered sequence in order to make less immunogenic immunotoxins. We have made a dsFv fragment of the anti-Tac antibody, showed it can be radiolabeled efficiently, and will rapidly localize in IL2 receptor- bearing tumors growing in nude mice. This agent could be useful for the diagnosis and perhaps treatment of IL2 receptor-bearing malignancies. We are utilizing phage antibody display to try and improve existing antibodies and to develop new antibodies. We have modified the method so that disulfide-linked Fvs are displayed on the surface of phage and these are considerably more stable than single chain Fvs and should produce different types of antibodies. We have begun to investigate possible mechanisms of immunotoxin resistance and isolated several cDNAs which when expressed at high levels make MCF7 cells resistant to Pseudomonas toxin, diphtheria toxin and tumor necrosis alpha and beta. The mechanism by which these toxins act is under study.