|AUDENTES THERAPEUTICS, INC. filed this Form 10-K on 03/13/2017|
Our AAV Product Candidates
AT132 for the Treatment of X-Linked Myotubular Myopathy
Overview of XLMTM
XLMTM is a rare, severe, congenital muscle disease with an estimated incidence of one in 50,000 male births. The disease is caused by mutations in the MTM1 gene, which encodes a protein called myotubularin. Myotubularin is an enzyme involved in the development, maturation, maintenance and function of skeletal muscle cells. Mutations in the MTM1 gene result in production of too little or no functional protein. Importantly, we believe that even a modest increase of functional protein may have a significant therapeutic benefit for XLMTM patients.
Infants with XLMTM are typically born with severe muscle weakness and the majority require chronic mechanical ventilation from birth. Approximately 50% of patients die in the first 18 months of life. There is no approved treatment for XLMTM and disease management is primarily supportive. Of the patients that survive the infantile period, most are severely incapacitated, require ventilator support and do not have a life expectancy beyond early adolescence. Diagnosis of XLMTM is generally based on recognition of clinical symptoms at birth, typically followed by muscle biopsy and confirmation with genetic testing. Like many rare diseases, we believe XLMTM is under diagnosed and that approval of treatment would increase disease awareness, screening and diagnosis.
AT132 is an AAV8 vector that delivers an MTM1 gene expression cassette containing a desmin promoter, which is a regulatory element that drives gene transcription in muscle tissue. The MTM1 cassette is capable of increasing myotubularin expression in targeted tissues. AT132 was designed with these elements because AAV8 is known to effectively penetrate skeletal muscle and the desmin promoter is primarily active in muscle. We believe AT132 has the potential to provide long-term clinical benefit to XLMTM patients through persistent expression of the functional protein following a single intravenous administration.
Preclinical Proof-of-Concept for AT132
We have two robust animal models of XLMTM, a murine model consisting of mice engineered to knock out the functional MTM1 gene, or MTM1 KO mice, and a naturally occurring canine model. Preclinical studies in these models have used an AT132 construct engineered to include the species-specific MTM1 transgene. Both models present with disease symptoms similar to that of humans including severe muscle weakness, respiratory failure and early death. We believe that in this indication the canine model, as with many large animal models, is particularly valuable given similarities to humans with XLMTM in size, weight and physiology.