Novel Immunotoxin and IGF Therapy for Strabismus

描述（由申请人提供）：斜视是一种常见的眼科问题，影响美国学龄前儿童人口的2-5%。斜视表现为眼睛不对准，未经治疗导致弱视和永久性视力缺陷。许多这样的孩子需要外科手术来矫正他们的双眼对准。这项研究的目的是开发既能增强肌肉又能削弱肌肉的药物治疗方法。目前的选择包括切口手术和肉毒杆菌毒素。切口手术可能受到诱导瘢痕、改变肌球动力学和破坏眼外肌与软组织滑轮关系的限制。这些变化影响眼外肌功能，并可能影响手术结果。肉毒杆菌毒素注射避免了大多数这些并发症，并已有效地用于儿童和成人斜视。然而，用肉毒杆菌毒素治疗先天性斜视往往产生不一致的结果，特别是在初始偏差较大的情况下。肉毒毒素注射的主要限制是作用时间相对较短。理想情况下，注射的药物应该允许可滴定调节眼外肌力的产生，以便在异常的传出运动信号存在时，可以实现双眼对齐。这些影响必须持续足够长的时间，以便感觉和运动适应能够发生，从而造成地球旋转位置的永久变化。免疫毒素是生物毒素，如蓖麻毒素，与抗体结合，针对表达选定抗原的特定细胞和组织的毒素。本研究旨在验证针对眼外肌的免疫毒素可以通过产生长期肌肉无力来治疗斜视的主要假设。我们将继续测试蓖麻-单抗35和我们正在开发的一种新的免疫毒素DR-iTox，一种由蓖麻毒素a链和白喉a链结合到烟碱乙酰胆碱受体单克隆抗体上的融合蛋白。这两种免疫毒素都是肌毒性的，并针对成熟的肌纤维；它们不需要卫星细胞和成肌细胞，从而允许肌肉再生。我们将确定与蓖麻毒素- mab35治疗相比，DR-iTox增加的肌毒性是否会延长肌肉衰弱的持续时间。我们也将尝试通过直接注射胰岛素生长因子I或II来加强选定的眼外肌。增加拮抗剂的动力可以增强免疫毒素在眼外肌中的长期削弱作用，这是斜视治疗的一种独特方法。这些新颖的治疗方法可以在不需要切口手术的情况下，实现斜视手术的目标，即眼球旋转位置的可滴定和持续变化。

DESCRIPTION (provided by applicant): Strabismus is a common ophthalmologic problem, affecting between 2-5% of the population of preschool aged children in the U.S. It is manifested by a misalignment of the eyes and untreated results in amblyopia and permanent visual deficits. Many of these children require a surgical procedure for correction of their binocular alignment. The goal of this study is to develop pharmacologic treatments that will result in both muscle strengthening and muscle weakening. Current options include incisional surgery and botulinum toxin. Incisional surgery may be limited by induced scarring, altered muscle-globe dynamics, and disruption of extraocular muscle relationships with soft-tissue pulleys. These changes affect extraocular muscle function and may influence surgical outcomes. Botulinum toxin injection avoids most of these complications and has been used effectively for both childhood and adult strabismus. However, the treatment of congenital strabismus with botulinum toxin often yields inconsistent results, particularly where the initial deviation is large. The principle limitation of botulinum toxin injection is its relatively short duration of action. Ideally, injected agents should allow titratable adjustment of extraocular muscle force generation so that, in the presence of abnormal efferent motor signals, binocular alignment can be achieved. These effects must last sufficiently long so that sensory and motor adaptation can occur to create a permanent change in the rotational position of the globe. Immunotoxins are biological toxins, such as ricin, conjugated to antibodies that target the toxin against specific cells and tissues that express the selected antigen. This study is designed to test the primary hypothesis that immunotoxins, targeted against extraocular muscle, can be used in the treatment of strabismus by producing long-term muscle weakness. We will continue to test ricin-mAb 35 and a new immunotoxin we are developing, DR-iTox, a fusion protein composed of the ricin A chain and the diphtheria A chain conjugated to a monoclonal antibody to the nicotinic acetylcholine receptor. Both immunotoxins are myotoxic and targeted to mature myofibers; they spare satellite cells and myoblasts, permitting muscle regeneration. We will determine if the increased myotoxicity of the DR-iTox will extend the duration of muscle weakening compared to treatment with ricin-mAb35. We will also attempt to strengthen selected extraocular muscles by direct injection of insulin growth factor I or II. Increasing the motive force of the antagonist could augment the long-term weakening effect of an immunotoxin in an extraocular muscle, and this represents a unique approach to strabismus treatment. These novel treatments may allow titratable and sustained changes in the rotational position of the globe, the goal of strabismus surgery, without requiring an incisional procedure.