Preclinical and Clinical Study of CNGb3 Acromatopsia and Treatment with CNTF

CNGb3 肢端视障及 CNTF 治疗的临床前和临床研究

• 批准号: 8745665
• 负责人: Paul Sieving
• 金额: $ 79.21万
• 依托单位: NATIONAL INSTITUTE ON DEAFNESS AND OTHER COMMUNICATION DISORDERS
• 依托单位国家: 美国
• 资助国家: 美国
• 起止时间: 至
• 项目状态: 未结题
• 来源: https://reporter.nih.gov/project-details/8745665
• 关键词: Accounting; Address; Adult; Adverse effects; Adverse event; Affect; Age; Animal Model; Animals; Aqueous Humor; Biological; Blindness; Blood - brain barrier anatomy; Blood Circulation; Blood-Retinal Barrier; Bolus Infusion; Canis familiaris; Cell Death; Cells; Ciliary Neurotrophic Factor; Clinical; Clinical Protocols; Clinical Research; Clinical Trials; Color Visions; Devices; Discrimination; Electroretinography; Encapsulated; Enrollment; Eye; Genes; Human; Image; Implant; Individual; Inherited; Injection of therapeutic agent; Knockout Mice; Light; Lighting; Measures; Membrane; Modeling; Molecular; Mutation; Neuraxis; Nonexudative age-related macular degeneration; Operative Surgical Procedures; Optical Coherence Tomography; Organelles; Outcome Measure; Participant; Pathologic Nystagmus; Patients; Penetration; Performance; Phase; Phase I Clinical Trials; Photophobia; Photoreceptors; Phototransduction; Polymers; Population Study; Proteins; Rattus; Recovery; Research Design; Retina; Retinal; Retinal Cone; Retinal Degeneration; Retinal Diseases; Retinal Dystrophy; Retinitis Pigmentosa; Risk; Safety; Severities; Signal Transduction; Staging; Structure; Study Subject; System; Technology; Testing; Therapeutic; Therapeutic Agents; Therapeutic Effect; Time; Toxic effect; Vertebrate Photoreceptors; Vision; Visual; Visual Acuity; Work; achromatopsia; autosomal recessive trait; base; capsule; cyclic-nucleotide gated ion channels; design; effective therapy; follow-up; gene therapy; implantable device; implantation; improved; intravitreal injection; mouse model; neurotrophic factor; phase 2 study; preclinical study; prevent; primary outcome; prospective; research study; response; retinal rods; safety study; secondary outcome; vector

Achromatopsia is a monogenic congenital retinal dystrophy that causes reduced visual acuity, extremely limited color vision discrimination, nystagmus and photophobia. It is inherited as an autosomal recessive trait. Four genes currently are known to cause the condition; CNGA3 and CNGB3 encoding the alpha- and beta-subunits, respectively, of the cyclic nucleotide gated channel type 3 (CNG3) on cone photoreceptors are responsible for the vast majority of the achromatopsia cases. Mutations in the CNGB3 genes alone account for more than 50% of individuals with achromatopsia, a retinal disorder that affects approximately 1 in every 33,000 individuals. The CNGA3 and CNGB3 proteins cooperate to form the heteromeric CNG3 conductance channel on the cone outer segment membrane. CNG3 channels are essential for converting light stimulation to activation of the cone photoreceptors and ultimately to daylight vision. In the absence of cone function, human vision is limited to rod function which is achromatic, resulting in poor acuity and saturation in bright illumination. Although achromatopsia historically was thought to be a condition in which cones were lacking or present in extremely reduced numbers, recent human studies show that a number of cones are still present even in older subjects with achromatopsia. Studies of CNGB3 and CNGA3 animal models also show that cones are present but have significant morphologic changes and progressive functional reduction with age. If cone function could be improved or restored in these subjects, they might recover augmented visual function. Gene therapy experiments have successfully treated achromat animal models, including both the naturally occurring CNGB3 mutation canine model and the CNGB3 knockout mouse model. A surprising observation was made during the gene therapy study of the CNGB3 dog achromat model: gene therapy could partially restore cone function on ERG testing in adult dogs, but only if animals were pretreated with ciliary neurotrophic factor (CNTF). Without prior treatment with CNTF, gene therapy was successful only for quite young dogs. This indicated that CNTF facilitated inducing a biological state in the adult cones in which they were receptive to gene rescue. More surprising was the finding that a bolus intravitreal injection of CNTF protein, without the CNGB3 gene vector, gave functional rescue of cones, and rescue persisted for several weeks until the CNTF from the bolus injection cleared. So, administration of CNTF protein alone, and without prior or subsequent gene vector delivery, supported recovery of light-stimulated activity of the cone photoreceptors in the CNGB3 achromat dog. CNTF is among the class of macro-biomolecules called neurotrophic factors which have been demonstrated to retard loss of photoreceptor cells during retinal degeneration. CNTF is effective in retarding vision loss from photoreceptor cell death in 13 animal models. A Phase 1 safety study in 2003-2006 was conducted at the NEI to investigate ocular delivery of CNTF in 10 subjects with end-stage retinitis pigmentosa. It passed appropriate safety milestones to mount Phase 2 studies, and the study indicated that CNTF possibly improved acuity performance in some subjects. The Phase 1 clinical trial observations and the animal studies provided the impetus for mounting a Phase 2 efficacy study for subjects with retinitis pigmentosa and dry AMD. The study design and outcome measures were based on the premise that CNTF could possibly improve visual function of cone photoreceptor cells. One major challenge is the delivery of this potentially therapeutic CNTF agent to the retina. The blood-retinal barrier prevents or inhibits the penetration of macro-molecules to the neurosensory retina, similar to the action of the blood-brain barrier in limiting transfer between the systemic circulation and the central nervous system. To address this issue, Neurotech USA, Inc., developed encapsulated cell technology (ECT) to provide controlled, sustained delivery of therapeutic agents directly into the intraocular fluids and thereby providing direct access to the retina. Cells within the ECT device are transfected with the CNTF gene and produce CNTF protein which exits through a semi-permeable polymer capsule membrane directly into the vitreous. The Neurotech NT-501 ECT device measures approximately 1mm x 6 mm and can readily be retrieved from the eye, providing an added level of safety. The previous Phase 1 and Phase 2 studies in RP and AMD have clearly demonstrated that CNTF is released by the implanted device and have also demonstrated that CNTF reaches and modifies the retina. Human clinical trials are being conducted to explore the safety and efficacy of these CNTF ocular implants on retinal structure and function in 5 patients with acromatopsia due to CNGB3 mutations(see below). To further explore the efficacy of CNTF in achromatopsia, we are delivering CNTF by intravitreal injection to the mouse model, which has a deletion of the CNGB3 gene. The model shows a severe and early reduction in cone function, while maintaining relatively good rod function as measured by the electrotretinogram (ERG). We previously showed that intravitreal injection of CNTF into normal rat eye suppresses rod function by down-regulating molecular mechanisms involved in converting light to visual signals (phototransduction). However, as mentioned above, it protects photoreceptors in several inherited and light induced models of retinal degeneration. Recently, it was shown that CNTF also protects cones from degeneration in one of these models, and actually partially restores the functional organelle for light reception, the cone outer segment. This indicates the possible anatomical basis for the recovery of cone function in humans and and CNGB3 dogs mentioned above. Using the CNGB3 mouse model of achromatopsia will allow us to explore potential mechanisms of cone rescue as well as conditions that enhance and prolong this affect. Clinical protocol: CNTF Implants for CNGB3 Achromatopsia ClinicalTrials.gov identifier: NCT01648452 Objective: The objective of this study is to evaluate the safety of ocular NT-501 device with encapsulated NT-201 cells releasing Ciliary Neurotrophic Factor (CNTF) to the retina of participants affected with CNGB3 achromatopsia. Study Population: Five participants affected with CNGB3 achromatopsia are enrolled, with one eye treated per participant. Design: This is a Phase I/II, prospective, single-center study. One eye of each participant received a vitreous NT-501 device implant releasing CNTF. The study will be completed once the final participant has received three years of follow-up. Outcome Measures: The primary outcome is the number and severity of adverse events and systemic and ocular toxicities at six months post-implantation. Additional safety of ocular CNTF implants in participants with CNGB3 achromatopsia will be determined from assessment of retinal function, ocular structure and occurrence of adverse events at all time points. Secondary outcomes include changes in visual function including visual acuity and color vision, electroretinogram (ERG) responses, and retinal imaging with optical coherence tomography (OCT).

全色盲是一种单基因先天性视网膜营养不良症，会导致视力下降、色觉辨别能力极其有限、眼球震颤和畏光。 它作为常染色体隐性遗传。目前已知有四种基因会导致这种情况： CNGA3 和 CNGB3 分别编码视锥细胞上环核苷酸门控通道 3 型 (CNG3) 的 α 和 β 亚基，是绝大多数色盲病例的原因。仅 CNGB3 基因突变就导致了超过 50% 的全色盲患者，这种视网膜疾病大约每 33,000 人中就有 1 人受影响。 CNGA3 和 CNGB3 蛋白协同作用，在锥体外节膜上形成异聚 CNG3 电导通道。 CNG3 通道对于将光刺激转化为视锥细胞的激活并最终转化为日光视觉至关重要。在没有锥函数的情况下，人的视觉仅限于消色差的杆函数，导致在明亮照明下的敏锐度和饱和度较差。 尽管全色盲在历史上被认为是一种视锥细胞缺乏或数量极少的病症，但最近的人类研究表明，即使在患有全色盲的老年受试者中，仍然存在许多视锥细胞。 CNGB3 和 CNGA3 动物模型的研究还表明，视锥细胞存在，但随着年龄的增长，其形态发生显着变化，并且功能逐渐降低。如果这些受试者的视锥细胞功能能够得到改善或恢复，他们可能会恢复增强的视觉功能。 基因治疗实验已成功治疗消色差动物模型，包括自然发生的 CNGB3 突变犬模型和 CNGB3 基因敲除小鼠模型。在 CNGB3 犬消色差模型的基因治疗研究中，我们发现了一个令人惊讶的观察结果：基因治疗可以部分恢复成年犬 ERG 测试中的视锥细胞功能，但前提是动物接受了睫状神经营养因子 (CNTF) 预处理。如果事先未接受 CNTF 治疗，基因治疗仅对幼犬有效。这表明 CNTF 促进了成年视锥细胞的生物状态的诱导，使它们能够接受基因拯救。更令人惊讶的是，我们发现玻璃体内快速浓注CNTF蛋白（不含CNGB3基因载体）可以对视锥细胞进行功能性拯救，并且这种拯救持续了数周，直到快速浓注中的CNTF被清除为止。因此，单独施用 CNTF 蛋白，并且没有事先或随后的基因载体递送，支持 CNGB3 消色差狗中视锥细胞光感受器的光刺激活性的恢复。 CNTF 属于一类称为神经营养因子的大生物分子，已被证明可以延缓视网膜变性期间感光细胞的损失。 CNTF 可有效延缓 13 种动物模型中感光细胞死亡导致的视力丧失。 NEI 于 2003 年至 2006 年进行了一项 1 期安全性研究，以研究 CNTF 在 10 名患有终末期色素性视网膜炎的受试者中的眼部递送情况。它通过了适当的安全里程碑来开展第二阶段研究，研究表明 CNTF 可能会改善某些受试者的敏锐度表现。一期临床试验观察结果和动物研究为针对色素性视网膜炎和干性 AMD 受试者开展二期疗效研究提供了动力。研究设计和结果测量的前提是CNTF可能改善视锥细胞的视觉功能。 一个主要挑战是将这种具有潜在治疗作用的 CNTF 试剂输送到视网膜。血-视网膜屏障防止或抑制大分子渗透到神经感觉视网膜，类似于血脑屏障限制体循环和中枢神经系统之间传输的作用。为了解决这个问题，Neurotech USA, Inc. 开发了封装细胞技术 (ECT)，以受控、持续地将治疗剂直接输送到眼内液中，从而提供直接进入视网膜的途径。 ECT 装置内的细胞被 CNTF 基因转染，并产生 CNTF 蛋白，该蛋白通过半透聚合物胶囊膜直接进入玻璃体。 Neurotech NT-501 ECT 设备尺寸约为 1 毫米 x 6 毫米，可以轻松从眼睛中取出，从而提高了安全性。之前在 RP 和 AMD 中进行的 1 期和 2 期研究已经清楚地证明了 CNTF 是由植入设备释放的，并且还证明了 CNTF 到达并修改了视网膜。目前正在进行人体临床试验，以探讨这些 CNTF 眼部植入物对 5 名因 CNGB3 突变而患有肢视症的患者视网膜结构和功能的安全性和有效性（见下文）。 为了进一步探讨 CNTF 在全色盲中的功效，我们通过玻璃体内注射将 CNTF 递送到 CNGB3 基因缺失的小鼠模型中。 该模型显示视锥细胞功能严重且早期下降，同时根据视网膜电图（ERG）测量，视杆细胞功能保持相对良好。我们之前表明，将 CNTF 玻璃体内注射到正常大鼠眼中，可以通过下调将光转化为视觉信号（光转导）的分子机制来抑制视杆细胞功能。然而，如上所述，它可以保护几种遗传性和光诱导的视网膜变性模型中的光感受器。最近，研究表明，CNTF 还可以保护其中一种模型中的视锥细胞免于退化，并且实际上部分恢复了用于光接收的功能细胞器（视锥细胞外节）。这表明了上述人类和CNGB3狗视锥细胞功能恢复的可能的解剖学基础。使用 CNGB3 色盲小鼠模型将使我们能够探索视锥细胞救援的潜在机制以及增强和延长这种影响的条件。 临床方案： 用于治疗 CNGB3 色盲的 CNTF 植入物 ClinicalTrials.gov 标识符：NCT01648452 目的：本研究的目的是评估眼部 NT-501 装置的安全性，其中封装的 NT-201 细胞向 CNGB3 色盲患者的视网膜释放睫状神经营养因子 (CNTF)。 研究人群：招募了 5 名患有 CNGB3 色盲的参与者，每名参与者一只眼睛接受治疗。 设计：这是一项 I/II 期、前瞻性、单中心研究。每个参与者的一只眼睛接受了释放 CNTF 的玻璃体 NT-501 装置植入物。一旦最终参与者接受三年的随访，研究将完成。 结果测量：主要结果是植入后六个月不良事件以及全身和眼部毒性的数量和严重程度。 CNGB3色盲患者眼部CNTF植入物的额外安全性将通过对所有时间点的视网膜功能、眼部结构和不良事件发生情况的评估来确定。次要结果包括视觉功能的变化，包括视敏度和色觉、视网膜电图（ERG）反应以及光学相干断层扫描（OCT）视网膜成像。