(Bloomberg) -- Eisai Co.’s shares had the biggest gain on record after partner Biogen Idec Inc.’s experimental drug for Alzheimer’s slowed progression of the disease in an early-stage study.
The Japanese drugmaker’s shares climbed as much as 21 percent to 8,748 yen in Tokyo trading today, headed for the largest gain since Bloomberg started tracking the data in 1974. The benchmark Topix Index rose 0.7 percent.
Biogen’s drug BIIB037 reduced beta amyloid, a protein fragment, in the brains of Alzheimer’s patients. It also cut cognitive decline, with higher doses and longer treatment resulting in more improvement in an early-stage trial of 166 patients announced on March 20.
Eisai has an option to co-develop and co-promote BIIB037 with Biogen.
Eisai and Biogen are likely to equally split profits if the drug is successful in the last-stage trial as part of their Alzheimer’s disease collaboration, Thomas Wei, an equities analyst at Jefferies Group LLC, said in a note to clients.
To contact the reporter on this story: Kanoko Matsuyama in Tokyo at kmatsuyama2@bloomberg.net
To contact the editors responsible for this story: Anjali Cordeiro at acordeiro2@bloomberg.net Terje Langeland