biogen inc’s stock biib rose about 2 before paring those gains premarket friday after the us food and drug administration on thursday granted full approval to leqembi the company’s alzheimer’s disease treatment codeveloped with eisai co ltd esalf  the step secures medicare reimbursement for the first drug shown to slow the progress of the disease rather than just treating its symptoms the drug’s label will have a boxed warning about amyloidrelated imaging abnormalities or aria which usually have no symptoms but in some rare cases cause lifethreatening brain swelling the fda said thursday oppenheimer reiterated its outperform rating on the stock and said the boxed warning may mean that greater scrutiny will be given to donanemab a rival product from eli lilly  co lly “we look forward to more details on donanemab efficacy and safety stratified by apoe4 status expected at aaic” analysts wrote in a note referring to the alzheimer’s association international conference scheduled for july 16 to 20 wedbush took a more subdued tone reiterating its neutral rating on biogen stock “for our part we continue to anticipate logistics may weigh on uptake” analyst laura chico wrote in a note to clients “no changes to our leqembi estimates following the update this marks an important transition period for biib as many of its flagship products face increasing competition and new ceo chris viehbacher attempts to change both the cost structure and risk profile of the product portfolio” biogen’s stock was last down 12 but has gained 3 in the year through thursday’s close while the sp 500 spx has gained 15