An experimental Alzheimer’s drug being developed by a US biotech group has offered hope that scientists may be closer to a breakthrough for the devastating disease, after early trials showed the treatment slowed the rate of cognitive decline.

Biogen’s Aducanumab is one of several drugs under development by big pharmaceutical groups that aim to reduce so-called “amyloid plaque”, a sticky build-up in the brain that many believe is responsible for Alzheimer’s disease.

A year-long study of 166 patients with a mild form of the disease showed that Biogen’s drug significantly reduced the build-up of plaque and delayed the onset of cognitive decline, according to data published yesterday at a medical conference in Nice, France.

Shares in Biogen, which have risen about 28 per cent this year in anticipation of the data, jumped by 7 per cent in New York trading, while other companies with similar drugs also gained, including Eli Lilly, up 2.4 per cent, and Sanofi, which added 1.6 per cent.

Biogen’s market value has risen by $45 billion to nearly $110 billion in a little over a year.

However, analysts and doctors voiced concerns over the drug’s safety, with a quarter of patients on the highest dose discontinuing treatment due to adverse effects, including swelling on the brain. Drug companies have trialled similar drugs for years with disappointing results, but the industry has pressed ahead because the commercial opportunity is huge: there are more than 25 million Alzheimer’s sufferers globally and five million in the US, the majority of whom do not respond to existing treatments.

Biogen and its partner Neurimmune developed the drug by cloning the memory cells of people in their 90s who had “super cognitive function” despite their age, as well as people who had Alzheimer’s that was progressing at an unusually slow rate.

– Copyright The Financial Times Limited 2015