Peptide conjugated oligonucleotides for a phase I/IIa clinical trial in Spinal Muscular Atrophy

脊髓性肌萎缩症（SMA）是婴儿死亡的主要遗传原因，由SMN1基因功能丧失引起。SMN1突变导致运动神经元变性，并伴有骨骼肌萎缩等外周表现。SMA是一种罕见的常染色体隐性遗传病，发病率约为1:10 000活产。大多数受影响的SMA婴儿通常有严重的疾病形式，平均预期寿命约为2岁（SMA I型）。然而，病情较轻的儿童（II型和III型）可存活2年以上，但伴有严重的活动障碍和合并症（呼吸功能不全、脊柱侧凸、发育不良），限制了正常功能和生存。SMA的严重程度与患者产生的功能性SMN蛋白水平直接相关。与SMN1密切相关的基因是SMN2，尽管该基因通常只产生约10%的全功能SMN蛋白。然而，一些SMA患者有额外的SMN2基因拷贝，因为后者基因的拷贝数在一般人群中是多态的，因此可以产生更多功能的SMN蛋白。这减轻了疾病的严重程度，这类患者通常病程较轻。大多数SMN2基因产物不具有功能，因为该基因通过选择性剪接产生两种不同的mRNA，即大多数mRNA缺乏外显子7，仅产生部分功能蛋白。目前治疗SMA最有效的方法是通过使用剪接开关寡核苷酸（SSOs）对SMN2前mrna进行剪接修饰，以提高SMN蛋白的水平。sso是单链dna样分子，可以结合并改变SMN2前mrna的加工过程，从而产生该基因的功能拷贝。一种通过修饰SMN2剪接产生功能性SMN蛋白的SSO （Nusinersen）最近被FDA和EMA批准用于临床。虽然这代表了SMA的重大发展，但第一代SSO不会穿透血脑屏障（BBB），因此通过反复侵入性鞘内注射到脊髓周围的液体中给药。这对于充分的脊髓药物输送是必要的，但作为长期治疗是不实用的，而且它也不能治疗疾病的全身特征，特别是在严重的病例中。成功开发针对SMA的SSO疗法的主要挑战是将SSO药物全身递送到除运动神经元外的所有参与疾病发病机制的受影响组织，包括骨骼肌和神经肌肉连接、肝脏和自主神经等外周组织。我们已经开发了一种基于短细胞穿透肽的新平台技术，当通过直接化学附着在SSO上时，它可以高效地渗透到细胞和组织中，如大脑、脊髓和肌肉，而这些是大型SSO药物非常难以到达的。因此，当前项目的主要目标是确定、开发和测试用于SMA的先进的下一代肽- sso。为了实现这一目标，我们将：-根据对~5肽- sso候选物的进一步研究，选择最合适的肽，以确定其在小鼠中的活性和安全性-根据药品和保健监管机构的要求，将该先导肽- sso在两个物种（大鼠和非人灵长类动物）中进行全面的安全性评估。为了获得在SMA患者中进行临床试验的批准-在12名受影响较轻的II型和III型SMA患者中进行首次I/IIa期临床试验，这些患者代表了最常见的SMA患者，其中许多人由于脊柱异常而不适合鞘内给药。该临床试验将确定该药物的安全性和初步有效性，并将成为在大量患者中进行更详细研究的前奏

Spinal muscular atrophy (SMA) is the leading genetic cause of infant mortality, arising from loss-of-function of the SMN1 gene. Mutations in SMN1 result in motor neuron degeneration, accompanied by peripheral manifestations including skeletal muscle atrophy. SMA is rare autosomal recessive disease with an incidence of ~1:10,000 live births. Most affected SMA infants typically have a severe form of the disease with a mean life expectancy of ~2 years in age (SMA Type I). However children with less severe disease (SMA Type II and III) can survive beyond 2 years but with severe mobility problems and comorbidities (respiratory insufficiency; scoliosis; failure to thrive) that limit normal functioning and survival. SMA severity relates directly to the level of functional SMN protein that a patient produces. A closely related gene to SMN1 is SMN2, although this gene typically only produces ~10% of fully functional SMN protein. However some SMA patients have additional copies of the SMN2 gene as the copy number of this latter gene is polymorphic in the general population, and hence can produce more functional SMN protein. This mitigates disease severity and such patients typically have a milder disease course. Most SMN2 gene product is not functional because the gene generates two distinct mRNAs via alternative splicing i.e. most of the mRNA lacks exon 7 and generates only partially functional protein. The most effective therapy currently for SMA is splice modification of the SMN2 pre-mRNA through use of SPLICE SWITCHING OLIGONUCLEOTIDES (SSOs) to increase levels of SMN protein. SSOs are single-stranded, DNA-like molecules that can bind to and alter the processing of SMN2 pre-mRNA to generate functional copy of the gene. A SSO (Nusinersen) which modifies SMN2 splicing to generate functional SMN protein has recently been approved for clinical use by the FDA and EMA. While this represents a major development for SMA, this first generation SSO does not penetrate the blood brain barrier (BBB) and is therefore administered through repeated invasive intrathecal injections into the fluid around the spinal cord. This is necessary for adequate spinal cord drug delivery but is not practical as a long-term therapy and moreover it also fails to treat systemic features of the disease, especially important in severe cases.The major challenge to successful development of an SSO therapy for SMA is systemic delivery of the SSO drug to all affected tissues involved in disease pathogenesis in addition to motor neurons, including peripheral tissues such as skeletal muscle and neuromuscular junctions, liver and autonomic nerves. We have developed a novel platform technology based on short cell penetrating peptides, which when attached to SSOs via direct chemical attachment provide highly effective penetration into cells and into tissues such as the brain and spinal cord and muscles which are exceptionally difficult to reach for large SSO drugs.The major OBJECTIVE of the current project is therefore to identify, develop and test an advanced NEXT GENERATION peptide-SSO for SMA. To achieve this we will:- Select the most suitable peptide based on further study of ~5 peptide-SSO candidates to determine their activity and safety properties in mice- Take this lead peptide-SSO and carry out a full safety assessment of the drug in two species (rats and non-human primates) as required by the Medicines and Healthcare Regulatory Agency, in order to obtain approval to undertake a clinical trial in SMA patients - Carry out a first-in-man phase I/IIa clinical trial in 12 less severely affected Type II and III SMA patients, who represent the most prevalent SMA patients, many of whom are not eligible candidates for intrathecal administration of drugs due to spinal abnormalities. This clinical trial will determine safety and inital effectiveness of the drug and will be a prelude to more detailed studies in larger numbers of patients