Gene Transfer Therapy for Treating Children and Adults With Limb Girdle Muscular Dystrophy Type 2D (LGMD2D)

Muscular Dystrophies

limb girdle muscular dystrophy type 2D, alpha-sarcoglycanopathy, LGMD, LGMD2D, gene therapy, gene transfer, muscular dystrophy, SGCA, sarcoglycan, limb girdle, adeno-associated virus, AAV, AAV1

Limb girdle muscular dystrophy type 2D (LGMD2D) is a genetic disease that affects skeletal muscle. Insufficient levels of the protein alpha-sarcoglycan result in muscle weakness that worsens over time. The purpose of this study is to evaluate the safety and effectiveness of gene therapy in treating children and adults with LGMD2D.

The primary objective of this study is the assessment of the safety of intramuscular administration to alpha-sarcoglycan deficient subjects of recombinant adeno-associated virus serotype 1 (rAAV1)-human alpha-sarcoglycan gene (hαSG) vector under control of a skeletal muscle creatine kinase promoter. The secondary objective is to determine the dose of rAAV1.tMCK.hαSG vector required to achieve a detectable level of alpha-sarcoglycan in muscle of subjects with this disorder. A recombinant virus vector constructed from AAV1 has been altered to carry the human alpha-sarcoglycan gene expressed from a tMCK promoter. The construct has been shown to initiate the production of a functional alpha-sarcoglycan protein in laboratory animals. This construct can reverse the dystrophic phenotype in the alpha-sarcoglycan knock out mouse, a laboratory animal model for the clinical disorder. Intramuscular injection of rAAV1 restores muscle histology to normal and increases muscle strength to levels exceeding control knock out mice but not to the same degree as wild-type mice. The proposed human clinical trial is a phase I, double-blind randomized protocol with injection of rAAV1.tMCK.hαSG gene vector into muscle. Two cohorts of subjects with LGMD2D(alpha-sarcoglycan deficiency), each with proven mutations will undergo gene transfer. A minimum of three subjects will be enrolled into each cohort. The first cohort will receive a total of 1.5 ml volume of study agent in two to six separate injections into the selected muscle (extensor digitorum brevis) or other muscle if more appropriate considering the individual patient) with a dose of 3.25 X 10 to the 11 vg in 1.5 ml. The anatomical midline point of the muscle will be identified on the skin and 2 to 6 vector injections will be distributed in the direction of an X. The second cohort will receive the same dose delivered to muscle according to the same paradigm. In each cohort, only one extremity will receive vector with transgene while the opposite extremity will be injected with placebo. On the day of the vector infusion, 4 hours before gene transfer, patients will receive intravenous methylprednisolone 2.0 mg/kg (not to exceed 1 gm total), with repeat doses on two consecutive mornings. The methylprednisolone is specifically given to diminish the immediate inflammation from the needle injection, which is known to arouse an inflammatory reaction and could contribute to bringing antigen presenting cells to the site of vector delivery. We have previously demonstrated that this treatment enhances gene expression by at least 2-fold (Included as part of BB-IND-12936 for minidystrophin gene transfer). Safety endpoints to be assessed include inflammatory reaction to the vector, as evaluated by muscle biopsy, and changes in hematology, serum chemistry, urinalysis, immunologic responses to rAAV1 and alpha-sarcoglycan, and reported history and observations of symptoms. The patient will have 10 to 12 follow-up visits for the next 2 years after the initial infusion.

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