May 16 (Reuters) - Biogen and Ionis

Pharmaceuticals ( IONS ) said on Thursday they will terminate

the development of their experimental treatment for amyotrophic

lateral sclerosis (ALS)

after failing to show improvement in patients in

an early-to-mid stage study.

ALS, commonly known as Lou Gehrig's disease, is a rare and

fatal neurodegenerative disease that affects voluntary control

of the arms and legs and leads to breathing trouble.

The companies' drug, BIIB105, did not succeed in

significantly reducing neurodegeneration or improve functional

measures such as breathing in patients, they said.

ALS affects roughly 60,000 people in the U.S. and Europe.