Preclinical studies to validate the efficacy of novel mechanism-of-action small molecule inhibitors to treat Duchenne muscular dystrophy

进行性肌肉无力和退化是Duchenne肌营养不良症(DMD)的特征。在……里面 DMD患者，肌营养不良蛋白的缺乏降低了肌肉纤维结构的完整性，使肌肉容易受到 持续的伤害和损坏。修复这些受损的肌肉需要肌肉的持续激活 干细胞(MUSC)，导致MUSC功能障碍和衰老，最终导致肌肉变性 在DMD患者中观察到虚弱表型。不幸的是，现有的FDA批准的药物(eteplirsen， 并不能充分改善肌肉再生，而且似乎只能提供微不足道的改善。 对DMD患者肌肉功能和生活质量的影响。脊线治疗公司开发了新的口服- LY生物可用小分子NNMT(烟酰胺N-甲基转移酶)抑制剂(例如，rtl-72484) 重新激活功能失调和衰老的MUSC。虽然最初是作为一种治疗药物来逆转与年龄相关的 肌肉退行性变，最近的体内研究表明，NNMT抑制剂rtl-72484可以改善肌肉再生。 DMD患者的遗传和功能。该项目将在我们的初步研究的基础上扩展并完成 概念验证研究，以严格测试rtl-72484两种互补的dmd小鼠模型的疗效。 NNMT过表达干扰NAD挽救途径、MUSC再生功能和细胞- 大代谢(包括线粒体生物能量学)。DMD患者的骨骼肌有很大的损伤。 NNMT的表达增加，提示NNMT可能是MUSC功能障碍和 DMD患者中观察到代谢紊乱。作为一种潜在的治疗DMD的药物，RLT-72484通过Se-Se-1发挥作用。 选择性抑制NNMT，导致MUSC活性增加，增强线粒体功能，最终 改善肌肉力量和功能。这些独特的作用机制使RLT-72484(和其他 NNMT抑制剂)有别于少数获得FDA批准或处于早期阶段的DMD疗法- 阶段性临床试验。这个第一阶段的STTR项目将建立在我们令人鼓舞的体内DMD疗效研究的基础上 并在更先进和与翻译相关的DMD小鼠模型上测试RLT-72484的有效性。 将完成以下两个目标，以评估RLT-72484作为口服DMD药物的潜力。 目标1将完成一项口服食物混合药代动力学(PK)研究，以评估RLT- 72484，并与通过口服给药观察到的全身暴露进行比较。这项PK研究 将验证在DMD小鼠身上进行纵向疗效研究的最佳给药路线。目标2将于年内完成 使用DMD的B10/MDX和D2/MDX小鼠模型进行体内剂量范围疗效研究，评估MUSC的活性， 线粒体功能、横隔膜收缩功能与体外纤维化和体内功能终点 (例如，肌肉力量、耐力和握力)。在成功演示了治疗方法之后 Rtl-72484在动物模型中的作用，Ridgeline将作为一种潜力迅速推进rtl-72484进入临床试验 DMD治疗，因为RLT-72484正在进行GMP扩大和GLP安全性研究，以获得单独的临床适应症。

Progressive muscle weakness and degeneration is a hallmark of Duchenne muscular dystrophy (DMD). In DMD patients, the lack of dystrophin reduces muscle fiber structural integrity, making muscles vulnerable to persistent injury and damage. Repairing these damaged muscles requires the continual activation of muscle stem cells (muSC), which leads to muSC dysfunction and senescence, and ultimately the muscle degeneration and weakness phenotype observed in DMD patients. Unfortunately, existing FDA approved drugs (eteplirsen, deflazacort) do not sufficiently improve muscle regeneration, and appear to provide only marginal improve- ments in muscle function and quality of life for DMD patients. Ridgeline Therapeutics has developed novel oral- ly-bioavailable small molecule NNMT (nicotinamide N-methyltransferase) inhibitors (e.g., RTL-72484) that reactivate dysfunctional and senescent muSC. While initially developed as a therapeutic to reverse age-related muscle degeneration, recent in vivo studies suggest the NNMT inhibitor RTL-72484 could improve muscle re- generation and function in DMD patients. This project will expand on our preliminary research and complete proof-of-concept studies to rigorously test the efficacy of RTL-72484 two complementary DMD mouse models. Overexpression of NNMT interferes with the NAD salvage pathway, muSC regenerative function, and cellu- lar metabolism (including mitochondrial bioenergetics). Skeletal muscles of DMD patients have greatly in- creased expression of NNMT, suggesting NNMT could be a vital contributing factor to muSC dysfunction and metabolic dysregulation observed in DMD patients. As a potential DMD treatment, RLT-72484 functions by se- lectively inhibiting NNMT, resulting in increased muSC activity, enhanced mitochondrial function, and ultimately improved muscle strength and function. These unique mechanisms-of-action makes RLT-72484 (and other NNMT inhibitors in our pipeline) distinct from the few DMD therapeutics that are FDA-approved or in early- stage clinical trials. This Phase I STTR project will build upon our encouraging in vivo DMD efficacy studies and test the effectiveness of RLT-72484 in more advanced and translationally-relevant murine models of DMD. The following two Aims will be completed to assess the potential of RLT-72484 to serve as an oral DMD drug. Aim 1 will complete an oral chow-admixed pharmacokinetic (PK) study to assess plasma profiles of RLT- 72484 and compare to systemic exposures observed via oral gavage administration of the drug. This PK study will validate the optimal drug delivery route for longitudinal efficacy studies in DMD mice. Aim 2 will complete in vivo dose-ranging efficacy studies using B10/mdx and D2/mdx mice models of DMD, evaluating muSC activity, mitochondrial function, diaphragm contractile function, and fibrosis ex-vivo, and in vivo functional endpoints (e.g., muscle strength, endurance, and grip strength). Following successful demonstration of the therapeutic effects of RTL-72484 in animal models, Ridgeline will rapidly advance RTL-72484 to clinical trials as a potential DMD treatment, since RLT-72484 is in GMP scale-up and GLP safety studies for a separate clinical indication.