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性策略，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1，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2，3。 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4。我们现在已经启动了一项针对镰状细胞性贫血和地中海贫血成人的临床试验，并筛选了100多名潜在受试者，其中8名患有纯合子镰状细胞性贫血。 迄今为止，所有8例患者均接受了早期供体造血嵌合体移植，导致表型逆转。 两名患者接受了低于计划的照射剂量，一名患者需要再次移植，目前稳定，具有完全的供体红系嵌合体。 另外三对患者/供体已被确定为计划在未来几个月内进行移植。 应计正在进行中。

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 cancer1 and extended these observations to patients ineligible for conventional myeloablative transplantation due to comorbidities2,3. 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 pool4. We have now initiated a clinical trial for adults with sickle cell anemia and thalassemia, and have screened over 100 potential subjects and accrued 8 with homozygous sickle cell disease. All eight patients have thus far undergone transplantation with early donor hematopoietic chimerism resulting in reversion of the phenotype. Two patients inadvertantly received a lower than planned irradiation dose and one has required retransplantation and is currently stable with complete donor erythroid chimerism. Three additional patient/donor pairs have been identified with transplantation planned in the coming months. Accrual is ongoing.