Improved Targeting Strategies

我们已经证明了清髓剂量的抗CD20和抗CD45的抗CD20和抗CD45的单抗治疗复发性白血病和淋巴瘤的可行性和有效性，然后进行自体或异基因干细胞移植。这种疗法的应答率很高，许多患者被治愈。尽管有这些令人鼓舞的结果，复发仍然频繁发生，毒性很大。在这个项目中，我们将研究新的策略，以进一步提高放射免疫治疗的有效性和降低毒性，方法是增加向肿瘤细胞传递的放射性数量(通过四价融合蛋白预靶向)和通过去除未能与肿瘤结合并保留在正常器官血流中的放射性同位素的比例(通过预靶向或体外抗体吸附)。在目标1中，我们将评估抗CD20lF5(ScFv)4-链霉亲和素和抗CD45BC8(ScFv)4-链霉亲和素融合蛋白在灵长类动物体内的可行性、安全性和毒性，并将其与直接放射性标记的抗CD20(1F5)和抗CD45(BC8)抗体的药代动力学和组织渗透进行比较。在目标2中，我们将比较抗CD201F5(ScFv)4-链霉亲和素和抗CD45BC8(ScFv)4-链霉亲和素预靶向放射性生物素的生物分布和剂量学特性 直接放射性标记的抗CD20 1F5和抗CD45 BC8抗体的生物分布和剂量学特性的融合蛋白。在目标3中，我们将评估循环的、放射性标记的抗B细胞和抗髓系放射性标记抗体的体外吸附对这些放射免疫结合物在猕猴体内的药代动力学、生物分布和剂量学的影响。在目标4中，我们将建立和验证抗CD20 lF5(ScFv)4-链霉亲和素和抗CD45 BC8(ScFv)4-链霉亲和素融合蛋白的主细胞库，并在当前良好的制造实践(CGMP)条件下生产、纯化和鉴定足够的融合蛋白，以进行项目1和3的I期和II期临床试验。我们假设，与正常组织相比，预靶向和EC AT将改善肿瘤部位的辐射传输，从而使我们能够在提高肿瘤剂量的同时，保持对关键正常器官的明确、可耐受的剂量上限。根据这些研究的结果，与项目1和项目3合作，计划进行前靶向(以及可能的ECAT)的人体临床试验。

We have demonstrated the feasibility and effectiveness of treating patients with relapsed leukemia and lymphoma with myeloablative doses of radiolabeled anti-CD20 and anti-CD45 monoclonal antibodies followed by autologous or allogeneic stem cell transplantation. Response rates to this therapy are high and many patients are cured. Despite these encouraging results, relapses still occur frequently and toxicities are substantial. In this Project we will investigate novel strategies to further improve the efficacy and diminish the toxicity of radioimmunotherapy by augmenting the amount of radioactivity delivered to tumor cells (by pretargeting with tetravalent fusion proteins) and by removing the proportion of radioisotope that fails to bind to tumor and remains in the bloodstream perfusing normal organs (by pretargeting or extracorporeal antibody adsorption). In Aim 1, we will evaluate the feasibility, safety, and toxicity of administering anti-CD20 lF5(scFv)4-streptavidin and anti-CD45 BC8(scFv)4-streptavidin fusion proteins to primates and will compare and contrast the pharmacokinetics and tissue penetration of the fusion proteins with those of directly radiolabeled anti-CD20 (1F5) and anti-CD45 (BC8) antibodies. In Aim 2, we will compare the biodistributions and dosimetries of radiobiotin pretargeted using anti-CD20 1F5 (scFv)4-streptavidin and anti-CD45 BC8(scFv)4-streptavidin fusion proteins with the biodistributions and dosimetries of directly radiolabeled anti-CD20 1F5 and anti-CD45 BC8 Abs, respectively. In Aim 3 we will assess the impact of extracorporeal adsorption of circulating, radiolabeled anti-B cell and anti-myeloid radiolabeled antibodies on the pharmacokinetics, biodistribution and dosimetry of these radioimmunoconjugates in macaques. In Aim 4, we will generate and validate Master Cell Banks for the anti-CD20 lF5(scFv)4-streptavidin and the anti-CD45 BC8(scFv)4-streptavidin fusion proteins and produce, purify and characterize sufficient fusion protein under current good manufacturing practice (cGMP) conditions to conduct Phase I & II clinical trials in Projects 1 and 3. We hypothesize that pretargeting and EC AT will improve the delivery of radiation to tumor sites compared to normal tissues, thereby allowing us to escalate the tumor dose while maintaining well-defined, tolerable upper limits on the dose to critical normal organs. Based on the results of these studies, human clinical trials of pretargeting (and possibly ECAT) are planned in collaboration with Projects 1 and 3.