Gene therapy strengthens muscles in monkeys

WASHINGTON (Reuters) - A gene therapy treatment that stops the breakdown of muscle appeared safe in monkeys and may build up muscle, too, researchers reported on Wednesday.

The approach is being developed in the hope of treating severe muscle weakness caused by multiple sclerosis, muscular dystrophy and neurodegenerative diseases, but progress is slow in part because of fears about its safety.

Janaiah Kota of the Center for Gene Therapy at Nationwide Children’s Hospital in Columbus, Ohio, and colleagues used an engineered virus called an adeno-associated virus to carry a gene into the leg muscles of healthy monkeys.

The gene causes cells to produce human follistatin, which interferes with another compound called myostatin. Myostatin breaks down muscle, so in theory adding follistatin should encourage muscles to grow.

The new gene therapy went safely into the muscles of the monkeys and within three months, the monkeys’ muscles were growing bigger, the researchers reported in the journal Science Translational Medicine.

The effects lasted for at least 15 months, they said. This is important for treating lifelong diseases such as MS and muscular dystrophy.

No other organs appeared to be affected, they said.

“Our results, together with the findings in mice, suggest that therapy with AAV1-FS344 may improve muscle mass and function in patients with certain degenerative muscle disorders,” they wrote.

But they noted the animals are experimental models only.

“Despite the beneficial effects of follistatin gene therapy that we demonstrated in macaques, these animals did not have a degenerative muscle disease, and so our findings may not translate successfully to clinically effective treatments for such diseases,” they wrote.

Gene therapy is a promising field that has been dogged by failure. In 1999, an 18-year-old volunteer in a gene therapy trial died and later two French boys developed leukemia, both cases a direct result of the gene therapy.

However, this year U.S. gene therapy researchers restored partial sight in 12 patients with a rare inherited disease called Leber congenital amaurosis and French researchers stopped a rare and fatal illness called X-linked adrenoleukodystrophy or ALD in two boys.

Editing by Vicki Allen