Radioimmunotherapy of CD20+ Lymphomas & CD45+Leukemias

使用放射性标记的抗CD20单抗的放射免疫治疗(RIT)可使50-90%的复发淋巴瘤(NHL)患者得到缓解；然而，大多数患者最终死于复发淋巴瘤。我们小组已经证实了在异基因干细胞移植(SCT)治疗急性髓系白血病(AML)中应用放射性标记抗CD45单抗的前景，但毒性仍然很高，对于首次完全缓解(CR)的新诊断AML患者来说，治愈率仍然只有60%-65%，对于复发的AML患者，直接使用放射性标记抗CD45单抗和SCT的治愈率仍然只有20%-30%。由于放射性标记抗体在血液中的循环半衰期较长，目前RIT的疗效受到对正常组织的非特异性辐射的限制。这项建议的主要目标是开始学术研究生涯，开发创新的方法，以 通过两步链霉亲和素(SA)-生物素预靶向策略分别靶向NHL和AML肿瘤细胞表面的抗CD20和抗CD45抗原，优化RIT的疗效。在目标1中，我们将比较和对比直接放射性标记的抗CD20抗体(1F5)和使用抗CD20四价单链(ScFv)4SA融合蛋白的预靶向RIT在小鼠淋巴瘤异种移植和播散性淋巴瘤移植模型中的药代动力学、肿瘤定位和治疗效果。在DIM 2中，我们将比较放射性标记的抗人(H)CD45抗体使用常规RIT治疗白血病荷瘤小鼠的药代动力学、肿瘤定位和治疗效果，并优化了使用非放射性标记的抗hCD45(ScFv)4SA和90Y-DOTA-生物素的两步预靶向试剂盒。在目标3中，我们将评估抗CD45预靶向在小鼠同基因白血病模型中的毒性，在该模型中，靶抗原既存在于白血病细胞上，也存在于正常造血组织中。在目标4中，我们将进行一项I期临床研究，以探讨预靶向试剂盒治疗复发性惰性非霍奇金淋巴瘤或套细胞非霍奇金淋巴瘤的可行性、耐受性和潜在疗效。我们推测，使用抗CD20(ScFv)4SA和抗CD45(ScFv)4SA融合蛋白将靶向放射治疗恶性肿瘤细胞，与直接使用放射性标记抗体的传统RIT方案相比，将增强疗效并降低毒性。我们预计，这些干预措施最终将通过提高反应和存活率，同时将毒副作用降至最低，从而改善复发淋巴瘤和晚期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.