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

SCID-XL是一种由常见伽马链(YC)突变引起的儿童灾难性疾病 导致细胞因子信号的缺陷，导致细胞和体液的严重缺陷 豁免权。有匹配的兄弟姐妹供者进行异基因移植的患者在更大的 90%以上的长期无病存活率。然而，大多数患者没有匹配的兄弟姐妹捐赠者。 通常采用单倍体相合的双亲移植治疗。这些患者有显著的 长期存活率在60%到75%之间的情况较差。此外，持续性免疫缺陷是 在大约50%到60%的单倍体相合移植的幸存者中存在。对于这些孩子来说，他们缺乏 匹配的兄弟姐妹捐赠者，基因疗法正在作为一种替代的主要治疗方法和挽救 同种异体移植失败。此前在法国、英国和美国进行的试验都使用了逆转录病毒载体 从莫洛尼白血病病毒(MLV)发展而来，在MLV中，y{c}基因是从强病毒驱动的 增强子/启动子存在于长末端重复序列(LTR)中。这些试验已经产生了明确的证据 通过显示大多数患者跟随该基因有显著的免疫重建的疗效 移交程序。然而，23名患者中有5名由于转录水平的原因患上了T细胞白血病 从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 通过使用包含内部细胞的自失活(SIN)慢病毒载体来避免这种并发症 转录盒两侧的启动子和染色质绝缘体片段。我们已经对此进行了测试 已证实潜在安全性和有效性的临床前实验中的CL20I4-EF1a-hy{c}-opt载体 此配置的。我们还创造了一种高滴度、稳定的生产细胞系，用于GMP生产和 已经在我们的GMP设施中生成了一个主细胞库。我们现在提出两个临床方案来研究 该载体在一岁以下新诊断患者(LVXSCID-ND)或年龄较大患者中的应用 先前治疗失败或以后出现症状较轻的儿童(LVXSCID-OC)。 我们推测，这种基于慢病毒载体的方法将提供有效的治疗，并将更加安全。 而不是以前的基于MLV的向量。这些配套的临床试验应该会产生大量的 关于SCID-X1的基因治疗的信息，以及更广泛地关于慢病毒载体用于干细胞的信息 以细胞为靶点的人类基因疗法。

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.