Targeted DOK7 gene therapy for Congenital Myasthenic Syndromes

PROJECT SUMMARY Congenital Myasthenic Syndromes (CMS) are a group of genetically and phenotypically heterogeneous, neuromuscular transmission disorders characterized by muscle weakness (myasthenia) that worsens with physical exertion. DoK-7 (Downstream of tyrosine kinase 7) is a key regulator of neuromuscular junction (NMJ) formation. Homozygous loss-of or reduction of-function mutations in the human DOK7 gene underlie a limb-girdle type of CMS characterized by NMJs that are about half the normal size. DoK-7 CMS is an orphan disease estimated to affect 3,600 people worldwide. Patients with DoK-7 CMS have a decreased Quality of Life (QoL) due to exercise intolerance, dependency on intermittent respiratory support, and/or tube feeding by adulthood (2/3 of the patients). Moreover, about half of the patients will need a wheelchair for ambulation, and the other half will require walking aids. No cure nor standardized treatment has been yet developed for DoK-7 CMS. While forms of CMS are managed through the administration of acetylcholine (AChE) inhibitors, DoK-7 CMS is refractory and can deteriorate if treated with AChE inhibitors. Symptoms ameliorations for DoK-7 CMS is achieved by recurrent administration of Ephedrine and Albuterol, β2-adrenergic receptor agonists, which provide suboptimal symptom management for some patients. Moreover, prolonged exposure to β2-adrenergic receptor can cause tachycardia cardiac ischemia, heart failure, cardiomyopathy, and increased inflammatory response. Amplo Biotechnology is developing AMP-101, the first gene therapy product for DoK-7 CMS. The treatment is based on a recombinant adeno-associated virus serotype 9 (AAV9) vector carrying the human DOK7 gene. Preliminary results in a DoK-7 CMS mouse model show that AMP-101 can enlarge NMJs, improve motor function, and extend the very limited (20 days after birth) life span of DoK- 7 CMS mice to the level of WT controls. The new product will enable a shift in the current clinical practice from chronic administration of drugs to alleviate symptoms to a one-off treatment, administered through a single intravenous injection. The solution will allow physicians to treat the entire affected population, curing adult disease, and stopping disease progression in children. The goal of this SBIR Fast-Track project is to validate the efficacy and safety of using AMP-101 for DoK-7 CMS. Amplo will use Phase I activities to perform a pre-clinical dose-finding and safety study in DoK-7 CMS mice. The outcome of Phase I activities will be used to direct pivotal DMPK/ADME and toxicology studies in non-human primates (NHP) in Phase II, when manufacturing, quality, and stability procedures will also be defined. The experimental plan proposed has been validated by the FDA in a recent pre-IND query and an IND application will be submitted at the end of the project.