Oct 25 (Reuters) - Biogen Inc (BIIB.O) on Tuesday said the Alzheimer's disease drug it is developing with Japan's Eisai Co Ltd (4523.T) would be used by doctors in a competitive market as investors wait for data from rival therapies made by Eli Lilly and Co (LLY.N) and Roche (ROG.S). The drug, lecanemab was shown to slow the progress of the disease by 27% in a trial last month, and additional data is expected next month. "The data needs to be seen from the other anti-amyloid therapies before we decide what is going to be meaningful," said Biogen interim research chief Priya Singhal. Its costs were about halved as the company significantly cut back on commercial infrastructure around the launch of Aduhelm, its previous Alzheimer's drug that has sputtered amid controversy over efficacy and lack of coverage by health insurers. read moreInvestors have been pinning hopes on the Alzheimer's drug as cheaper generics of Biogen's multiple sclerosis treatment Tecfidera have entered the market, hurting sales.

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