Nonmyeloablative allogeneic PBSC in globin disorders

分别由一种或多种球蛋白分子亚基的缺乏/减少或异常产生引起的血液学病症如地中海贫血和血红蛋白病一起构成最普遍的人类单基因疾病组。旨在替代缺失或缺陷的珠蛋白基因的策略长期以来一直被认为是潜在的治疗方法，靶向造血干细胞的基因转移策略一直是这一目标的核心。当然，异基因骨髓移植是一种基于造血干细胞的基因转移形式，通过用正常基因型供体的器官替换整个患病器官来完成，已被证明具有治愈性，但程序毒性限制了应用。 为了扩大应用，我们探索了非清髓性移植方案，其设计允许异基因造血干细胞植入，而没有常规骨髓清除预处理的毒性。 使用动员的外周血干细胞作为来源，我们证明了转移性癌症患者在没有骨髓消融的情况下的可靠植入，并将这些观察结果扩展到由于合并症而不适合常规清髓性移植的患者。 虽然清楚地建立了在没有骨髓消融的情况下在人体中实现造血移植的能力，但主要以移植物抗宿主病形式存在的手术毒性仍然太高，无法应用于非恶性疾病。 因此，我们回到动物模型，最近开发了一种低强度的预处理方案，旨在促进对同种异体移植物的耐受性。 基于一种独特的耐受诱导机制，我们在动员外周血同种异体移植排斥反应的小鼠模型中，比较了低剂量照射后使用雷帕霉素免疫抑制与使用环孢霉素常规免疫抑制的情况。只有用雷帕霉素治疗的小鼠表现出长期的造血嵌合体，并且在超过4个月的随访中达到的水平超过75%。 为了将这些观察结果应用于成人镰状细胞性贫血的临床，我们确定了镰状细胞性状个体外周血干细胞动员的安全性和可行性，因为这些杂合子约占同胞供体库的一半。我们对患有镰状细胞性贫血和地中海贫血的成人进行了临床试验，最近报告了我们在前10名患者中的结果。 自那份报告以来，累计已达到30多例，结果相似，无病生存率为86%。 对方案进行了修订，以累积多达50个次要终点，如之前和每年测量的神经认知功能（以其同胞供体作为对照）、疼痛、生活质量、肾功能、肺功能、心脏功能。 此外，我们已经开始在具有>50%的CD 3 + T细胞嵌合体的个体中进行有计划的免疫抑制逐渐减量，并且大多数受试者现在停止免疫抑制，具有稳定的混合嵌合体。 没有急性或慢性移植物抗宿主病，在没有长期免疫抑制的情况下观察到的混合造血嵌合体证明了操作耐受性。这些结果现在也已报告。 我们现在已经确定了足以纠正表型的嵌合体水平，并对其进行了数学建模，结果发表在《血液》杂志上。我们已经完成了50例成功移植患者的上限，这将使我们能够完成对次要结局的分析，包括与同胞供体相比，在随访期间对患者进行广泛的神经心理学测试。 第一个数据的横截面分析已经在今年发表，我们现在正在进行前瞻性研究。一个新的方案测试的能力，额外的抗体c-Kit，以减少患者的比例与混合供体嵌合体，现在已经开发和积累今年已经开始。 患者的早期结果是令人鼓舞的，但收益率仍然很低，随访时间很短。

Hematologic disorders such as the thalassemias and hemoglobinopathies, resulting from absent/reduced or abnormal production of one or more of the globin-molecule subunits, respectively, together constitute the most prevalent group of human monogenic diseases. Strategies which aim to replace the absent or defective globin gene have long been envisioned as potentially curative, and gene transfer strategies targeting hematopoietic stem cells have been central to this goal. Certainly, allogeneic bone marrow transplantation, a form of hematopoietic stem cell based gene transfer accomplished by replacement of the entire diseased organ with that from a donor with a normal genotype, has proven curative, yet procedural toxicities limit application. In order to expand application, we have explored nonmyeloablative transplant regimens which are designed to allow engraftment of allogeneic hematopoietic stem cells without the toxicity of conventional marrow ablative conditioning. Using mobilized peripheral blood stem cells as the source, we demonstrated reliable engraftment in the absence of marrow ablation in patients with metastatic cancer and extended these observations to patients ineligible for conventional myeloablative transplantation due to comorbidities. While clearly establishing the ability to achieve hematopoietic engraftment in humans without marrow ablation, procedural toxicity, mainly in the form of graft-versus-host disease, remained too high for application to nonmalignant disorders. We therefore returned to animal models and have recently developed a low intensity conditioning regimen designed to promote tolerance to the allograft. Based upon a unique mechanism for tolerance induction, we compared the use of immunosuppression with rapamycin to that with conventional immunosuppression with cyclosporine after low dose irradiation in a murine model of mobilized peripheral blood allograft rejection. Only mice treated with rapamycin demonstrated long-term hematopoietic chimerism, and the levels achieved exceeded 75% at greater than 4 months of follow up. In anticipation of moving these observations toward clinical application for adults with sickle cell anemia, we established the safety and feasibility of peripheral blood stem cell mobilization in individuals with sickle cell trait, as these heterozygotes represent approximately half of the sibling donor pool. We initiated a clinical trial for adults with sickle cell anemia and thalassemia and recently reported our results in the first 10 patients. Since that report, accrual has reached over 30, and results are similar with an 86% disease free survival. The protocol has been amended to accrue up to 50, with a number of secondary endpoints such as neurocognitive functioning measured before and yearly with their sibling donor as the control, pain, quality of life, kidney function, lung function, heart function. Additionally, we have begun a planned immunosuppression taper in individuals with >50% CD3+ T cell chimerism, and the majority of subjects are now off immunosuppression with stable mixed chimerism. There has been no acute or chronic graft versus host disease, and the mixed hematopoietic chimerism observed in the absence of long term immunosuppression demonstrates operational tolerance. These results have also now been reported. We have now determined the level of chimerism sufficient to correct the phenotype, modeled it mathematically, and the results are published in Blood. We have completed accrual to our ceiling of 50 successfully transplanted patients, and this will allow us to complete our analysis of secondary outcomes including extensive neuropsychological testing in patients during follow up compared to their sibling donor. The first, cross-sectional analysis of the data has been published this year, and we are now performing the prospective studies. A new protocol testing the ability of an additional antibody to c-Kit to reduce the proportion of patients with mixed donor chimerism is now been developed and accrual has begun this year. Early results in patients are encouraging, yet the accrual is still low and the follow up brief.