Novel Approaches to Pretargeted Radioimmunotherapy

该项目的目标是产生一种新型的聚乙二醇化双特异性二价单链（scFv）抗体（MAb）构建体，作为新的预靶向递送策略的一部分，这将大大增加转移性前列腺癌的放射免疫治疗（RIT）的治疗指数。潜在的假设是，如果RIT的治疗指数增加10倍，则转移性前列腺癌可以在没有骨髓支持的情况下通过全身靶向放射治疗（作为联合治疗的一部分）治愈。在雄激素非依赖性转移性前列腺癌患者的I期RIT研究中，我们使用钇-90（90 Y）单抗诱导了针对上皮粘蛋白（MUC-1）的治疗反应，但有效治疗需要骨髓支持。相比之下，预先靶向RIT（pRIT）的策略将非放射性构建体在前列腺癌部位的积累阶段与靶向RIT的阶段分离。 这意味着小放射性同位素源的递送，从而显著减少对正常组织的辐射，同时保留对癌症的辐射。通过提供免疫原性较低的、模块化的、特异性肿瘤靶向分子和多价放射性源来解决预靶向治疗的关键问题，所述多价放射性源在随后的注射时将以高亲合力快速结合并交联肿瘤细胞上的预靶向分子。如果需要，已经开发了进一步的策略来消除来自残留在循环中的预靶向分子的干扰。具体目标包括：1）使用>300个前列腺癌和大量正常组织的组织阵列，从特异性结合前列腺癌细胞的MUC-1免疫scFv文库中选择scFv; （（scFv）4-PEG））; 4）在体外和体内药代动力学研究中研究前列腺癌预靶向缀合物In-111 DOTA-（scFv）4-PEG和多价Y-90 DOTA的剂量/时间特性，以使荷人前列腺癌的裸鼠中的肿瘤摄取最大化; 5）如果需要，实施策略以消除血液中残留的预靶向分子的干扰; 6）开发用于在前列腺癌患者中启动药代动力学研究的方案和GMP药物 到下一个补助期。调查小组具备：必要的经验、方法和资源。我们已经进行了载体修饰，允许位点特异性scFv缀合;通过MAb证明了与恶性肿瘤和Gleason分级相关的MUC-1靶标表达模式;选择了在组织阵列上选择性染色前列腺癌的scFv。这个建议很有可能成功。

The goal of this project is to generate a novel PEGylated bispecific, bivalent single chain (scFv) antibody (MAb) construct as part of a new pretargeting delivery strategy that will greatly increase the therapeutic index of radioimmunotherapy (RIT) in metastatic prostate cancer. The underlying hypothesis is that metastatic prostate cancer can be cured without marrow support by systemically targeted radiation therapy as part of combined modality therapy, if the therapeutic index of RIT is increased by a factor of 10. In a Phase I RIT study in patients with androgen-independent metastatic prostate cancer, we have induced therapeutic response using Yttrium-90 (90Y) MAb against an epithelial mucin (MUC-1), but marrow support was needed for effective therapy. In contrast, the strategy for pretargeted RIT (pRIT) disassociates the phase of accumulation of the nonradioactive construct at the sites of prostate cancer from the phase for delivery of the small radioisotope source, thereby dramatically decreasing radiation to normal tissues while preserving the radiation to the cancer. Key issues are addressed for pretargeted therapy, by providing a less immunogenic, modular, specific tumor targeting molecule, and a multivalent radioactive source that will, on subsequent injection, quickly bind and cross link the pretargeted molecules on tumor cells with high avidity. If needed, further strategies have been developed to negate interference from pretargeting molecules that remain in the circulation. Specific Aims have included: 1) select scFv from MUC-1 immune scFv libraries that specifically bind prostate cancer cells using tissue arrays of >300 prostate cancers and an extensive panel of normal tissues; 2) produce an optimized anti-cancedanti-DOTA scFv conjugated PEG ((scFv)4-PEG)); 3) develop an optimized multivalent Y-90 DOTA structure to bind and cross link on tumor, utilizing molecular modeling and biosensor affinity; 4) study the dose/time characteristics of the prostate cancer pretargeting conjugate as In-111 DOTA-(scFv)4-PEG and the multivalent Y-90 DOTA in in vitro and in vivo pharmacokinetic studies to maximize tumor uptake in nude mice bearing human prostate cancers; 5) if needed, implement strategy to negate interference of residual pretargeting molecules in blood; 6) develop protocols and GMP pharmaceuticals for pharmacokinetic studies in prostate cancer patients to be initiated by the next grant period. The investigative team has: the requisite experience, methods and resources. We have made vector modifications allowing site specific scFv conjugation; demonstrated MUC-1 target expression patterns correlating to malignancy and Gleason grade by MAb; selected scFv that selectively stain prostate cancer on tissue arrays. This proposal has a high likelihood of success.