The US pharmaceutical company Eli Lilly is facing a potential delay in the approval of its Alzheimer's drug Donanemab in the United States. The US Food and Drug Administration (FDA) has announced a consultation with external experts to discuss the results of the pivotal Phase III study in terms of the safety and efficacy of the therapy. The FDA's decision to conduct additional consultation came as a surprise to Lilly, as a decision on approval was expected by the end of the first quarter.

The Lilly stock reacted to the news with a slight decline in pre-market trading. Donanemab, an antibody targeting the amyloid plaques in the brains of Alzheimer's patients, has shown side effects such as brain swelling and cerebral hemorrhage in studies. Such side effects require careful monitoring of patients. These risks are not uncommon for drugs in this class, as evidenced by the Alzheimer's medication developed by Eisai and Biogen, which also has similar side effects.

While news of a potential delay affected Lilly, Biogen's shares benefitted from the development and recorded pre-market gains. Eli Lilly remains confident in the potential of Donanemab despite the upcoming FDA evaluation and external advisors' review, and has announced it will work closely with the agency to resolve any outstanding issues. An exact date for the consultation with external experts has not yet been determined.