Nonmyeloablative allogeneic PBSC in globin disorders

由于一个或多个珠蛋白分子亚单位的缺失/减少或异常产生而导致的血液病，如地中海贫血和血红蛋白病，共同构成了人类最常见的单基因疾病组。长期以来，人们一直认为，旨在取代缺失或有缺陷的珠蛋白基因的策略具有潜在的疗效，而针对造血干细胞的基因转移策略一直是这一目标的核心。当然，异基因骨髓移植已经被证明是有效的，但程序性毒性限制了应用。异基因骨髓移植是一种基于造血干细胞的基因转移，通过用正常基因的捐赠者替换整个患病器官来完成。为了扩大应用范围，我们探索了非清髓性移植方案，这些方案旨在允许移植异基因造血干细胞，而不会出现传统骨髓清除性条件处理的毒性。使用动员的外周血干细胞作为来源，我们证明了在没有骨髓切除的情况下，转移性癌症患者的移植是可靠的，并将这些观察扩展到因合并疾病而不符合常规清髓移植条件的患者。虽然清楚地确定了在不去除骨髓的情况下在人类身上实现造血植入的能力，但程序性毒性，主要是移植物抗宿主病，仍然太高，不适用于非恶性疾病。因此，我们回到了动物模型，最近开发了一种低强度的调节方案，旨在促进对同种异体移植的耐受性。基于诱导耐受的独特机制，我们在动员外周血异基因移植排斥反应的小鼠模型中，比较了小剂量照射后雷帕霉素和环孢素的免疫抑制作用。只有接受雷帕霉素治疗的小鼠表现出长期的造血细胞嵌合体，在4个月以上的随访中达到了75%以上。为了将这些观察结果应用于成人镰状细胞性贫血，我们确定了在具有镰状细胞特征的个体中动员外周血干细胞的安全性和可行性，因为这些杂合子代表了兄弟姐妹捐赠者池的大约一半。我们启动了一项针对成人镰状细胞性贫血和地中海贫血的临床试验，最近报告了我们在前10名患者中的结果。自那份报告以来，累计值已超过30，结果与86%的无病存活率相似。该方案已被修改，以积累多达50个，一些次要终点，如神经认知功能，在兄弟姐妹捐赠者之前和每年进行测量，作为对照，疼痛，生活质量，肾功能，肺功能，心功能。此外，我们已经开始计划在CD3+T细胞嵌合体为50%的患者中逐步减少免疫抑制，大多数受试者现在已经停止了免疫抑制，混合嵌合体稳定。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细胞嵌合体表明了手术耐受性。这些结果现在也被报道了。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。我们几乎达到了50名成功移植患者的应计上限，这将使我们能够完成对次要结果的分析，包括对患者在随访期间与其兄弟姐妹捐赠者进行广泛的神经心理测试。对数据的第一次横断面分析已于今年发表，我们现在正在进行前瞻性研究。考虑到可获得的人类白细胞抗原相合的同胞供者的患者数量有限，我们还继续在单倍体环境中测试这种方法，在一项测试移植后环磷酰胺剂量递增的方案中。我们的第一个协议测试是今年刚刚发布的，一个新的协议现在正在运行。新方案的收益现在正在进行中，方案现在由我们小组中一名新的终身教职跟踪调查员Courtney Fitzhugh博士运行，并将由她报告。目前正在开发一种新的方案，测试额外的c-Kit抗体降低混合供者嵌合体患者比例的能力。

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 are almost at our accrual 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 study. Given the limited number of patients with an available HLA-matched sibling donor, we have also moved on to test this approach in the haplo-idendtical setting in a protocol testing escalating doses of post-graft cyclophosphamide. Our first protocol testing this was just published this year and a new protocol is now active. Accrual to the new protocol is now ongoing, and the protocols now being run by a new tenure-track investigator in our group, Dr. Courtney Fitzhugh, and will be reported upon by her. 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 being developed.