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

在镰状细胞病和β-地中海贫血中诱导胎儿血红蛋白是一种极端的 有希望的方法来改善这两种疾病的严重性。最近的分子研究揭示了新的 人类胎儿到成人血红蛋白开关的调节，包括BCL11A。BCL11A是一种遗传和 功能验证的γ-珠蛋白表达调控因子和靶向治疗的首选候选药物 SCD患者体内HBF的诱导。干细胞移植是治疗SCD的有效方法 细胞移植(HSCT)。移植物衰竭和与移植相关的死亡率导致显著的 SCD患者异基因造血干细胞移植相关并发症。慢性阻塞性肺病的有利结果在很大程度上取决于 配对同胞供者的可获得性以及移植物失败和移植物抗宿主病的发生率 (GVHD)。只有不到10%的SCD患者有未受影响的人类白细胞抗原相合的同胞潜在捐赠者。基因 治疗血红蛋白疾病提供了明显的优势，消除了移植物抗宿主病的风险，并需要 通过使用自体细胞确定合适的干细胞捐赠者。在SCD中以BCL11A为目标具有重要意义 基因修饰的造血细胞在红系细胞中充分敲除BCL11A的优势 干细胞(HSCs)会增加HBF的表达，同时降低突变HBs的表达。自.以来 镰状红细胞中的血红蛋白聚合高度依赖于细胞内HBs和HbS的浓度 被HBF强烈抑制，有效靶向BCL11A的载体应该可以阻止BCL11A的细胞表型 含有镰刀状的红细胞。因此，减少的血红蛋白聚合会导致显著增加 体内红细胞的半衰期。我们最近发现利用红系特异性表达microRNA 针对BCL11A的修饰shRNAs(ShRNAmiR)有效地诱导人红系细胞产生HBF 转导HSCs，在小鼠模型中很大程度上减弱了SCD对血液学的影响。基于 数学模型和临床前数据，我们预测转导人类HSCs将降低红细胞 镰刀状的范围将显著减弱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.