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    灼华资讯︱黄斑病变可以基因治疗了,你造吗?
    发布:筱岩 发布时间:2017-06-21 新闻来源: 沈阳 浏览量:911

    Gene therapy in age-related macular degeneration 


    In a small and preliminary clinicaltrial, Johns Hopkins researchers and their collaborators have shown that anexperimental gene therapy that uses viruses to introduce a therapeutic geneinto the eye is safe and that it may be effective in preserving the vision ofpeople with wet age-related macular degeneration (AMD). AMD is a leading causeof vision loss in the U.S., affecting an estimated 1.6 million Americans. Thedisease is marked by growth of abnormal blood vessels that leak fluid into thecentral portion of the retina called the macula, which we use for reading,driving and recognizing faces.

     

    The study published on May 16in The Lancet, reports an exciting new approach in which a virus, similarto the common cold, but altered in the lab so that it is unable to causedisease, is used as a carrier for a gene and is injected into the eye. Thevirus penetrates retinal cells and deposits a gene, which turns the cells intofactories for productions of a therapeutic protein, called sFLT01. 

     

    The abnormal blood vessels that causewet AMD grow because patients have increased production of vascular endothelialgrowth factor (VEGF) in their retinas. Current treatments require injections ofproteins directly into the eye that bind and inactivate VEGF, reducing fluid inthe macula and improving vision. However, the therapeutic proteins exit the eyeover the course of a month, so patients with wet AMD usually need to return tothe clinic for more injections every six to eight weeks in order to stave offvision loss. Eye specialists say the burden and discomfort of the regimen isresponsible for many patients not getting injections as frequently as theyneed, causing vision loss.

     

    Because viruses naturally penetratecells and leave behind genetic material, the investigators designed their virusto target retinal cells and provide them with a gene that produces sFLT01.Thus, retinal cells become factories that produce the therapeutic protein — potentially eliminating the need to repeatedly injectit.

     

    “This preliminary study is a smallbut promising step towards a new approach that will not only reduce doctorvisits and the anxiety and discomfort associated with repeated injections inthe eye, but may improve long-term outcomes because prolonged suppression ofVEGF is needed to preserve vision, and that is difficult to achieve withrepeated injections because life often gets in the way,” says Peter Campochiaro, M.D., the George S. and Dolores D.Eccles Professor of Ophthalmology at the Johns Hopkins University School ofMedicine.

     

    The phase 1 clinical trial involved 19men and women, 50 years old or older with advanced wet AMD.   

     

    Participants were divided into fivedifferent groups that received increasing doses from 2X10^8 to 2X10^10 viralparticles containing the therapeutic gene in 0.05 mL of fluid. Each group wasexamined by investigators for signs of adverse reactions for at least 4 weeksbefore administering a higher dose to the next group.

     

    After the virus deposited the gene, thecells began secreting sFLT01 which bound to VEGF and prevented it fromstimulating leakage and growth of abnormal blood vessels. The goal is for theretinal cells infected by the virus to produce enough sFLT01 to permanentlystop the progression of AMD.

     

    After monitoring the first three groupsand finding no dose-limiting toxicity, the researchers administered the maximumdose to a group of ten participants and observed no serious side effects. “Even at the highest dose, the treatment was quite safe.We found there were almost no adverse reactions in our patients,” Campochiaro says.

     

    For safety and ethical reasons, thestudy group was composed of people for whom standard approved treatments werehighly unlikely to regain vision, meaning in part that only 11 of the 19 hadthe potential for fluid reduction. Of those eleven patients, four showeddramatic improvements. The amount of fluid in their eyes dropped from severe toalmost nothing, just like what is observed with optimal standard treatment,Campochiaro says. In addition, two other participants showed a partialreduction in the amount of fluid in their eyes.

     

    Five participants showed no reductionin fluid levels. Surprisingly, the researchers say, they found that all of thepatients who did not show improvement had pre-existing antibodies to the AAV2virus.

     

    From that result, the researchersconclude that even if further studies affirm the safety and value of their genetherapy, it may have limitations for broad use. That’s because an estimated sixty percent of the U.S.population has been infection with adeno-associated virus, the family ofviruses that AAV2 belongs to, and have built an immunity to it. The researchersbelieve that in these patients, the immune system destroyed the virus before itcould insert the therapeutic gene. Campochiaro explains, “The numbers are small and simply show a correlation, so we don’t know if serum antibodies are definitely an impediment, but morework is needed to determine this.”


    年龄相关性黄斑病变的基因治疗

    约翰霍普金斯大学医学院的研究者以及相关合作人员在一个小规模的初步临床试验中发现,利用病毒将基因引入眼内试验性基因治疗是安全的,并且这种方法会有效保护湿性年龄相关性黄斑病变(AMD)患者的视力。老年性黄斑病变在美国成为导致视力减退的主导因素,大约有160万人受影响。这种疾病的特点是异常血管的生长导致液体渗漏到视网膜的中心点处,这个点就是黄斑,黄斑是我们用来阅读、开车和识别人脸结构的。

     

    这份研究发布在5月16日的《柳叶刀》杂志上,上报了一个令人兴奋的新观点:利用一种经过实验室改造后不能致病,而且类似与流感的病毒作为基因载体,并将其注射入眼睛中。这种病毒可以透入视网膜细胞储存一段基因,使细胞转化为一个能够生产出具有治疗作用的蛋白质的工厂,这种蛋白质称为 sFLT01。

     

    由于患者在视网膜上的血管内皮生长因子(VEGF)的增加导致了湿性AMD的血管异常生长。目前的治疗方法要直接将蛋白质注射到眼睛中,使之结合并灭活VEGF,减少黄斑区的液体渗漏并改善视力。因为这种治疗性的蛋白会在一个月后离开眼睛,所以患有湿性AMD的病人通常需要每六到八周回到医院接受多次注射来避免视力下降。眼科专家指出,这种治疗手段所带来的负担和令人不适的规律是导致许多患者拒绝接受频繁注射导致视力下降的原因。

    由于病毒能够自然穿透细胞并留下遗传物质,研究人员将病毒设计成能够标记并锁定视网膜细胞的种类,同时向其提供能够翻译出 sFLT01 蛋白的基因序列,使其变成生产治疗性蛋白的工厂,这将有望消除反复注射蛋白质的繁琐过程。

     

    美国约翰霍普金斯大学的眼科教授、医学博士 PeterCampochiaro 指出:“这虽然是一个初步的小规模研究,但未来将有望成为一种新的治疗方法。这种方法不仅仅能够减少看望医生的次数和反复给眼睛注射药物带来的焦虑与不安,还有望长期地保持这种治疗效果,因为需要长期地抑制VEGF才能保护视力。生活还得继续,这使得反复注射药物显得不实际且难以实现”。

     

    第一阶段临床试验涉及19名男性和女性,年龄皆为50岁以上,患有湿性AMD。

     

    参与实验的人员被分成5个不同的组,分别接受从2×108到2×1010 带有治疗基因0.05mL的颗粒注射,研究人员在对下一组注入更高剂量之前会对每个小组进行至少4周不良反应的监测。

     

    在病毒寄存该治疗基因后,细胞将翻译出sFLT01蛋白来与VEGF因子结合,阻止其刺激异常血管的生长和渗出。目的是使得被病毒感染的视网膜细胞能够产生足够的sFLT01蛋白来永久地防止AMD病情的发展。

     

    在监测了前三组后发现没有需要药物毒性限制剂量,研究人员对其中一组的10名参与者进行了最大剂量的实验,结果并没有发现严重的副作用。Campochiaro 说:“即使在最高剂量的情况下,治疗也相当安全,我们发现病人几乎没有任何不良反应。”

     

    出于安全和伦理方面的原因,该研究小组是由一些通过标准治疗手段后不太可能恢复视力的患者参与。所以19名中有11名有望减少眼睛中渗出的液体,而且这11名中有4名患者出现了戏剧性的改善。Campochiaro说他们的眼睛里的液体量从严重的多量到几乎完全没有,正如最初的理想治疗效果一样。此外,另外两名参与者在他们的眼睛中显示出液体的明显减少。

     

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