Radioimmunotherapy of CD20+ Lymphomas & CD45+Leukemias

使用放射性标记的抗CD 20单克隆抗体（Ab）的放射免疫治疗（RIT）可诱导50-90%的复发性淋巴瘤（NHL）患者缓解;然而，大多数患者最终死于复发性淋巴瘤。我们的研究小组已经证明了在异基因干细胞移植（SCT）治疗急性髓性白血病（AML）的背景下给予放射性标记的抗CD 45单克隆抗体的前景，但毒性仍然很高，首次完全缓解（CR）的新诊断AML移植患者的治愈率仍然只有60-65%，而直接使用放射性标记的抗CD 45 Ab和SCT治疗复发性AML的治愈率仍然只有20-30%。由于放射性标记的抗体在血流中的循环半衰期较长，因此RIT的疗效目前受到将辐射非特异性递送至正常组织的限制。该提案的主要目标是启动学术研究生涯，开发创新方法， 使用两步链霉亲和素（SA）-生物素预靶向策略优化RIT的功效，以分别靶向NHL和AML肿瘤细胞表面的抗CD 20和抗CD 45抗原。在目标1中，我们将在小鼠淋巴瘤异种移植物和播散性淋巴瘤移植模型中比较和对比直接放射性标记的抗CD 20 Ab（1F 5）和使用抗CD 20四价单链（scFv）4SA融合蛋白预靶向RIT，然后递增剂量放射性标记的DOTA-生物素的药代动力学、肿瘤定位和治疗效果。在dim 2中，我们将比较使用常规RIT接受放射性标记的抗人（h）CD 45 Ab治疗的荷白血病小鼠的药代动力学、肿瘤定位和治疗功效，以及使用非放射性标记的抗hCD 45（scFv）的优化两步预靶向KIT治疗的荷白血病小鼠的药代动力学、肿瘤定位和治疗功效4SA，然后是90 y-DOTA-生物素。在目标3中，我们将在小鼠同基因白血病模型中评估抗CD 45预靶向的毒性，其中靶抗原存在于白血病细胞以及正常造血组织上。在目标4中，我们将进行一项I期临床研究，以研究预靶向KIT治疗复发性惰性NHL或套细胞NHL患者的可行性、耐受性和潜在疗效。我们假设，与采用直接放射性标记抗体的常规RIT方案相比，使用抗CD 20（scFv）4SA和抗CD 45（scFv）4SA融合蛋白特异性靶向恶性细胞的放射将增强疗效并降低治疗毒性。我们预计，这些干预措施将通过提高缓解率和生存率，同时最大限度地减少毒性，最终提高复发性淋巴瘤和晚期AML患者的预后。

Radioimmunotherapy (RIT) using radiolabeled anti-CD20 monoclonal antibodies (Ab) induces remissions in 50-90% of relapsed lymphoma (NHL) patients; however, most patients eventually succumb to recurrent lymphoma. Our group has documented the promise of radiolabeled anti-CD45 monoclonal Abs administered in the setting of allogeneic stem cell transplantation (SCT) for acute myeloid leukemia (AML), but toxicity remains high and cure rates are still only 60-65% for patients with newly diagnosed AML transplanted in first complete remission (CR) and 20-30% for relapsed AML using directly radiolabeled anti-CD45 Ab and SCT. The efficacy of RIT is currently limited by non-specific delivery of radiation to normal tissues, as a result of the long circulating half-life of radiolabeled antibodies in the bloodstream. The primary objective of this proposal is to launch an academic research career developing innovative approaches to optimize the efficacy of RIT using a two-step streptavidin(SA)-biotin pretargeting strategy to target the anti-CD20 and anti-CD45 antigens on the surface of NHL and AML tumor cells, respectively. In Aim 1, we will compare and contrast the pharmacokinetics, tumor localization, and therapeutic efficacies obtained with directly radiolabeled anti-CD20 Ab (1F5) and pretargeted RIT using an anti-CD20 tetravalent single chain (scFv)4SA fusion protein followed by escalating doses of radiolabeled DOTA-biotin in murine lymphoma xenograft and disseminated lymphoma transplant models. In dim 2, we will compare the pharmacokinetics, tumor localization, and therapeutic efficacies of leukemia bearing mice treated with radiolabeled anti-human (h)CD45 Ab using conventional RIT, and optimized two-step pretargeting KIT utilizing non-radiolabeled anti-hCD45 (scFv)4SA followed by 90y-DOTA-biotin. In Aim 3, we will assess the toxicities of anti-CD45 pretargeting in a murine syngeneic leukemia model in which the target antigen is present on both leukemia cells as well as normal hematopoietic tissues. In Aim 4, we will conduct a phase I clinical study to investigate the feasibility, tolerability, and potential efficacy of pretargeted KIT for patients with relapsed indolent NHL or mantle cell NHL. We hypothesize that targeting radiation specifically to malignant cells using anti-CD20 (scFv)4SA and anti-CD45 (scFv)4SA fusion proteins will augment the efficacy and decrease the toxicity of therapy compared with conventional RIT regimens employing directly radiolabeled Abs. We anticipate that these interventions will ultimately enhance the prognosis for patients with relapsed lymphomas and advanced AML by increasing the response and survival rates, while simultaneously minimizing toxicities.