In late January, Biogen announced that the Food and Drug Administration moved the Prescription Drug User Fee Act (PDUFA) action date for its Alzheimer’s drug aducanamab from March 7th to June 7th. On that date, the FDA will make a decision whether to approve or reject the Biologics License Application (BLA) for aducanamab. A BLA approval would allow Biogen to make aducanamab commercially available.

According to Biogen, the extended review period is a result of additional data they provided at the request of the FDA. In November, an FDA advisory committee ruled against approving aducanamab, citing insufficient evidence of the drug’s efficacy. It is unclear whether this additional data addresses the concerns of the advisory committee.

The path to approval for aducanamab has not been straightforward; study of the drug was initially abandoned before a reanalysis of the data convinced Biogen that one of the trials had in fact yielded positive results. Consumer advocacy group Public Citizen has also criticized the close relationship between Biogen and the FDA throughout the approval process.

Pharmaceutical industry insiders believe that the delay improves the chances of aducanamab’s ultimate approval; shares in Biogen rose 9% the day the prolonged review was announced.