Sanofi Pasteur (Paris) has formally withdrawn its application to the European Medicines Agency (EMA) for a centralized marketing authorization for its pandemic influenza vaccine Emerflu. The vaccine was intended to help prevent influenza during an officially declared pandemic. A core pandemic dossier was submitted in the context of preventing influenza in an officially declared pandemic, according to the mock-up vaccine procedure. Sanofi Pasteur withdrew the application because the EMA’s Committee for Medicinal Products for Human Use (CHMP) said that the data did not allow the committee to conclude a positive benefit–risk balance, according to the EMA.

Sanofi submitted the application for marketing authorization in April 2007. However, the CHMP issued a negative opinion for the drug in March 2009 because of concerns about the vaccine’s ability to trigger the production of enough antibodies against the flu virus.

“According to criteria laid down by the CHMP, a mock-up vaccine needs to bring about protective levels of antibodies in at least 70% of people for it to be considered suitable,” stated a Q&A from the EMA concerning Emerflu. “Because antibody production following Emerflu administration was below this level in the main studies (less than 40% in participants aged below 60 years), the CHMP was concerned that Emerflu was not suitable for use as a mock-up vaccine.”

Similar results were also seen in people who received the drug containing a different strain of flu virus, and studies looking at the effects of a third dose produced contradictory results, thus raising concerns about the vaccine’s low immunogenicity, regardless of the strain of virus included.

More information about the withdrawal, including the withdrawal letter from the company, will be published on the EMA website after the next CHMP meeting on December 13–16, 2010.