Facilitation of Autologous Hematopoietic Stem Cell Engraftment for Gene Therapy

描述（由申请人提供）：干细胞植入不足是限制移植疗法应用于涉及造血系统的遗传和恶性疾病的关键问题。实验研究已经表明，在实现来自供体干细胞的长期植入之前，宿主中通常需要耗尽骨髓中的原始干细胞。在目前的临床移植方案中，这通常是通过使用具有侵略性剂量的全身照射或白消安的受体调节来实现的。这些治疗受到严重副作用的限制。用能够选择性地耗尽骨髓微环境中的干细胞的药剂进行的替代治疗有希望提供毒性更小和更特异性的替代。我们在第一阶段提案中的目标是证明这些毒性治疗可以被一种试剂取代的概念证明，该试剂通过其在低氧张力下的存在而特异性地针对受体的真正造血干细胞（HSC）。这种策略将允许使用温和的预处理疗法，以最大限度地提高自体移植中通过基因疗法校正的干细胞的植入。具体而言，初始开发将包括给予替拉扎明（TPZ）和密切相关的TPZ类似物（SN 30000）。我们已经确定TPZ能够耗尽宿主体内缺氧的骨髓HSC，并且我们期望在同基因骨髓的小鼠受体中实现稳健且持久的供体型植入。预计我们将确定一种改进的HSC移植预处理方案，该方案与提供基因治疗的安全有效的手段一起，可以扩展到大型动物模型，并最终扩展到人类临床应用。具体目标：一。优化低氧选择性细胞毒素替拉扎明（TPZ）和SN 30000的骨髓干细胞耗竭特性; II.评估这些药物在骨髓移植模型中提供正常供体干细胞长期植入的能力。7.干细胞植入不足是限制移植治疗涉及造血系统的遗传性和恶性疾病应用的关键问题。用能够选择性地耗尽骨髓微环境中的干细胞的药剂进行的药物治疗有希望在干细胞校正基因治疗中提供毒性更小且更特异性的辐射或白消安替代物。我们还希望这种方法的发展将加速基因治疗的临床应用，以永久纠正？地中海贫血（库利氏贫血）和镰状细胞贫血，构成了一些最常见和最严重的遗传性疾病。

DESCRIPTION (provided by applicant): Insufficient stem cell engraftment is a key problem that limits the application of transplant therapies for genetic and malignant diseases involving the hematopoietic system. Experimental studies have shown that depletion of primitive stem cells in the bone marrow is often required in the host before long- term engraftment from donor stem cells is achieved. In current clinical transplant protocols, this is usually accomplished using recipient conditioning with aggressive doses of whole body irradiation or busulfan. These treatments are limited by harsh side-effects. Recipient treatment with an agent capable of selectively depleting stem cells in the bone marrow microenvironment has the promise of providing less toxic and more specific replacement. Our goal in this phase I proposal is to demonstrate the proof of concept that these toxic treatments can be substituted by an agent that is specifically directed against the true hematopoietic stem cells (HSC) of the recipient by virtue of its existence in low oxygen tension. Such a strategy would allow the use of milder conditioning therapy in maximizing the engraftment of stem cells corrected by gene therapy in autologous transplants. Specifically, the initial development will comprise of administering tirapazamine (TPZ) and a closely related TPZ analog (SN 30000). We have already identified TPZ as being capable of depleting hypoxic bone marrow HSCs in the host and where we expect to achieve robust and persistent donor-type engraftment in murine recipients of syngeneic bone marrow. It is anticipated that we will identify an improved HSC transplant conditioning regimen that, together with the safe and effective means of delivering a gene therapy, can be extended to large animal models and eventually to human clinical application. Specific Aims: I. Optimize the bone marrow stem cell depleting properties of the hypoxia-selective cytotoxin tirapazamine (TPZ) and SN 30000; II. Assess the ability of these drugs to provide for long-term engraftment of normal donor stem cells in a bone marrow transplant model.7. Project Narrative Insufficient stem cell engraftment is a key problem that limits the application of transplant therapies for genetic and malignant diseases involving the hematopoietic system. Recipient treatment with an agent capable of selectively depleting stem cells in the bone marrow microenvironment has the promise of providing less toxic and more specific replacement for either irradiation or busulfan in stem cell-corrective gene therapy. We also expect that development of such a method will accelerate the clinical application of gene therapy directed at permanently correcting ?-thalassemia (Cooley's anemia) and sickle cell anemia which constitute some of most common and serious of the genetic diseases.