Biogen isn't worried about competing with Eli Lilly as they both attempt to bring an Alzheimer's drug to the market, Biogen's CEO said Tuesday. "I think it will be good if there are other players in the market, but I don't think we are too concerned about competing with donanemab," Christopher Viehbacher, the chief executive, said during the company's first quarter earnings call, referring to one of Eli Lilly's potential Alzheimer's treatments.