Biogen Idec and Elan may be feeling slightly trepidacious after receiving a date from the US Food and Drug Administration’s peripheral and central nervous system drugs advisory committee to review the multiple sclerosis drug, Tysabri (natalizumab), and determine whether it should be permitted back onto the market.

Tysabri was withdrawn last year, just three months following launch, after a small number of patients died from a rare brain infection known as progressive multifocal leukoencephalopathy.

However, since that time, Biogen Idec and Elan have gone to extraordinary lengths to uncover the true safety profile of Tysabri and, in October last year, it was given a clean bill of health when the companies found no further evidence of PML – either amongst multiple sclerosis patients, or in trials of the drug for rheumatoid arthritis or Crohn’s disease.

Elan and Biogen Idec, which suffered significant financial losses from the withdrawal of Tysabri, re-filed for approval of the drug in the USA in September followed by a submission to the European drug regulator, the European Medicines Agency.

On March 7, Tysabri will come up against the FDA panel, which will consider two-year data from the AFFIRM monotherapy trial and SENTINEL add-on trial with Biogen Idec’s Avonex (interferon beta-1a), as well as a revised label and risk management plan.

A decision on approvability is expected by the end of March after the FDA granted Tysabri priority review status, which is awarded to drugs considered to address an unmet medical need, and means regulatory action within six months from submission date.