GTx Therapy Increases Survival, Improves Functioning, of Mice with Duchenne MD, Study Shows

One of a class of compounds that GTx is developing increased the survival of mice with Duchenne Muscular Dystrophy (DMD), and improved their muscle, heart and lung function, according to a pre-clinical trial study.

The therapies are known as selective androgen receptor modulators, or SARMs.

The study, “Androgen Receptor Agonists Increase Lean Mass, Improve Cardiopulmonary Functions, and Extend Survival in Preclinical Models of Duchenne Muscular Dystrophy,” was published in the journal Human Molecular Genetics.

DMD is a genetic disorder characterized by progressive muscle weakness and degeneration that mostly affects boys. The typical age of onset is 3 to 5 years.

About 18,000 American boys have DMD, according to estimates. Until recently, patients seldom survived beyond their teens or 20s, but progress in cardiac and respiratory care has made survival into the early 30s more common.

GTx treats DMD by targeting hormone receptors, proteins in cells that can bind with a specific molecule, or ligand.

SARMs are compounds that bind to an androgen receptor. Upon binding, they are able to control gene expression, either blocking or stimulating the hormone receptor, depending on the conditions.

Genetic mouse models of DMD who were treated with SARM GTx-026 survived 50% to 70% longer than control mice, researchers discovered. In addition, the treatment increased the mice’s weight and lean mass, and improved their grip strength, cardiac and pulmonary functions.

Other SARMs that GTx has developed – Ostarine (GTx-024, enobosarm) and GTx-027 – increase body mass and improved muscle function and tissue characteristics, research has indicated.

Ostarine has also been shown to increase muscle mass in patients with non-small cell lung cancer — the most common type of lung cancer. And it’s being studied as a treatment for urinary incontinence in post-menopausal women.

Altogether, the compound has been investigated in 24 completed or ongoing clinical trials involving more than 1,700 subjects.

“DMD typically afflicts boys around 3 to 5 years of age, followed by declining physical functions before attaining puberty. Current treatment options for DMD rely on corticosteroids to reduce inflammation, but unfortunately the prolonged use of corticosteroids results in hyperglycemia, osteoporosis, and muscle wasting, which are all counterproductive in this disease,” Dr. Ramesh Narayanan, director of the Center for Cancer Research and associate professor at the University of Tennessee’s College of Medicine, said in a press release. Narayanan is also a consultant for GTx.

“We hypothesize that an androgen receptor agonist may reverse musculoskeletal complications and extend survival in these boys, and in preclinical models, GTx-026 increased muscle mass, function, and survival, therefore supporting the concept of a SARM to treat DMD-affected boys,” he added.

GTx is seeking a collaboration with biopharma companies experienced in developing therapies for rare diseases with the goal of establishing a SARM as a treatment for DMD.