Evaluation of self-inactivating lentiviral vectors for treating SCID-X1 patients

SCID-X1是由共同γ链（YC）突变引起的儿童灾难性疾病 导致细胞因子信号传导的缺陷，导致细胞和体液 免疫力有一个匹配的同胞供体进行同种异体移植的患者， 90%以上的长期无病生存率。然而，大多数患者没有匹配的同胞供体 可用，并且通常使用单倍体相合的亲本移植进行治疗。这些患者明显 长期存活率在60%到75%之间。此外，持续的免疫缺陷是 存在于约50 - 60%的单倍体相合移植的存活者中。对于那些缺乏 匹配的同胞供体，基因治疗正在开发作为一种替代的主要治疗和补救， 同种异体移植失败此前在法国、英国和美国进行的试验使用了逆转录病毒载体 从莫洛尼白血病病毒（MLV）发展而来，其中y{c} cDNA由强病毒驱动， 增强子/启动子存在于长末端重复序列（LTR）中。这些试验清楚地证明了 通过显示大多数患者在基因治疗后具有显著的免疫重建， 转移程序。然而，23例患者中有5例由于转录因子的过度表达而发展为T细胞白血病。 MLV LTR中存在的强病毒增强子激活细胞原癌基因。我们现在寻求 为了避免这种并发症，使用了一种自失活（SIN）慢病毒载体， 启动子和位于转录盒侧翼的染色质绝缘子片段。我们已经测试了这个 CL 20 i4-EF 1a-hy {c}-OPT载体在临床前实验中证实了潜在的安全性和有效性 这种配置。我们还创建了用于GMP生产的高滴度、稳定的生产细胞系， 已在我们的GMP设施中生成了主细胞库。我们现在提出两个临床方案来研究 在小于1岁的新诊断患者（LVXSCID-ND）或年龄较大的患者中使用该载体 既往治疗失败或在生命后期出现症状较轻的儿童（LVXSCID-OC）。 我们假设这种以慢病毒载体为基础的方法将提供有效的治疗，并且更加安全 比以前的基于MLV的向量。这些伴随临床试验应该产生大量的 关于SCID-X1基因治疗的信息，以及关于慢病毒载体在干细胞治疗中的应用的信息。 细胞靶向的人类基因疗法

SCID-Xl is a catastrophic disease of childhood caused by mutations in the common gamma chain (YC) leading to defects in cytokine signaling that result in profound deficiencies in both cellular and humoral immunity. Patients that have a matched sibling donor for allogeneic transplant do very well with a greater than 90% long-term disease free survival. However, most patients do not have a matched sibling donor available and typically are treated using a haploidentical, parental transplant. These patients do significantly less well with a long term survival ranging between 60 and 75%. Furthermore, persistent immune defects are present in about 50 to 60 % of the survivors of haploidentical transplants. For these children who lack a matched sibling donor, gene therapy is being developed as an alternate primary therapy and as salvage for allogeneic transplant failures. Prior trials in France, the UK, and in the US have used retroviral vectors developed from the Moloney Leukemia Virus (MLV) in which the y{c} cDNA was driven from the strong viral enhancer/promoter present in the long terminal repeat (LTR). These trials have yielded clear proof of efficacy by showing that the majority of patients had significant immune reconstitution following the gene transfer procedure. However, 5 out of 23 patients have developed T cell leukemia due to transcriptional activation of cellular proto-oncogenes from the strong viral enhancer present in the MLV LTR. We now seek to avoid this complication by using a self-inactivating (SIN) lentiviral vector which contains an internal cellular promoter and chromatin insulator fragments flanking the transcriptional cassette. We have tested this CL20i4-EF1a-hy{c}-OPT vector in preclinical experiments that have confirmed the potential safety and efficacy of this configuration. We have also created a high titer, stable producer cell line for GMP production and have generated a Master Cell Bank in our GMP facility. We now propose two clinical protocols to study the use of this vector in either newly diagnosed patients less than one year old (LVXSCID-ND) or in older children that have failed previous treatment or who present later in life with milder symptoms (LVXSCID-OC). We hypothesize that this lentiviral vector-based approach will provide effective treatment and will be safer than the previous MLV-based vectors. These companion clinical trials should yield a great deal of information about gene therapy for SCID-X1 and more generally about the use of lentiviral vectors for stem cell-targeted, human gene therapy.