Gene therapy targeting BCL11A to induce fetal hemoglobin and reduce sickle hemoglobin in patients with Sickle Cell Disease

镰状细胞病（SCD）和β-地中海贫血中胎儿血红蛋白（HbF）的诱导是一个非常重要的因素。 有希望的方法来改善这两种疾病的严重程度。最近的分子研究揭示了新的 人类胎儿到成人血红蛋白转换的调节因子，包括BCL 11 A。BCL 11 A是一种基因和 功能上经过验证的γ-珠蛋白表达调节剂，是靶向治疗的主要候选者， SCD患者HbF诱导。造血干细胞移植是治疗SCD的有效方法 细胞移植（HSCT）。移植失败和移植相关的死亡率是导致 SCD中与同种异体HSCT相关的并发症SCD的有利结局主要取决于 匹配同胞供体的可用性以及移植物衰竭和移植物抗宿主病的发生率 （GVHD）。少于10%的SCD患者有未受影响的HLA匹配的兄弟姐妹潜在供体。基因 血红蛋白病的治疗提供了消除GVHD风险的明显优势， 通过使用自体细胞鉴定合适的干细胞供体。在SCD中靶向BCL 11 A具有显著的 在源自基因修饰的造血干细胞的红系细胞中充分敲低BCL 11 A的优点 干细胞（HSC）将增加HbF表达，同时减少突变HbS的表达。以来 镰状红细胞中的血红蛋白聚合高度依赖于HbS的细胞内浓度， 被HbF强烈抑制，有效靶向BCL 11 A的载体应该防止BCL 11 A的细胞表型， 含镰状红细胞因此，血红蛋白聚合的减少将导致血红蛋白聚合的显著增加。 红细胞在体内的半衰期我们最近已经表明，使用红细胞特异性表达microRNA 靶向BCL 11 A的适应性shRNA（shRNAmiR）有效地诱导来自人红系细胞的HbF， 转导的HSC，在很大程度上减弱SCD在鼠模型中的血液学效应。基于 根据数学模型和临床前数据，我们预测人类HSC的转导将减少红细胞数量， 镰状化的范围将显著减弱SCD表型。基于这些数据，我们提出了一个 在有限的SCD患者队列中进行的试点/可行性研究确定了该方法的适用性。

Induction of fetal hemoglobin (HbF) in both sickle cell disease (SCD) and β-thalassemia is an extremely promising approach to ameliorate the severity of both diseases. Recent molecular studies have revealed new regulators of the fetal-to-adult hemoglobin switch in humans, including BCL11A. BCL11A is a genetically and functionally validated regulator of γ-globin expression and a prime candidate for targeted therapy aimed at induction of HbF in individuals with SCD. Curative treatment for SCD can be attained with hematopoietic stem cell transplantation (HSCT). Graft failure and transplant-related mortality contribute to the significant complications associated with allogeneic HSCT in SCD. Favorable outcomes in SCD are largely dependent on the availability of matched sibling donors and the incidence of graft failure and graft versus host disease (GVHD). Fewer than 10% of SCD patients have unaffected HLA-matched sibling potential donors. Gene therapy for the hemoglobinopathies offers the clear advantage of eliminating the risk of GVHD and the need to identify suitable stem cell donors by the use of autologous cells. Targeting BCL11A in SCD holds the significant advantage that adequate knockdown of BCL11A in erythroid cells derived from gene-modified hematopoietic stem cells (HSCs) will increase HbF expression while concurrently reducing expression of mutant HbS. Since hemoglobin polymerization in sickle red cells is highly dependent on the intracellular concentration of HbS and is strongly inhibited by HbF, vectors effectively targeting BCL11A should prevent the cellular phenotype of sickle-containing red cells. Reduced hemoglobin polymerization would thus lead to a pronounced increase in the red cell half-life in vivo. We have recently shown that that use of erythroid-specific expression of microRNA adapted shRNAs (shRNAmiR) targeting BCL11A effectively induces HbF in human erythroid cells derived from transduced HSCs, largely attenuating the hematologic effects of SCD in a murine model. Based on mathematical modeling and preclinical data, we predict that transduction of human HSCs will reduce red cell sickling in a range that will significantly attenuate the SCD phenotype. Based on these data, we propose a pilot/feasibility study in a limited cohort of SCD patients determine the applicability of this approach.