Biogen Idec and Elan Corporation, plc announced that the supplemental Biologics License Application (sBLA) for Tysabri (natalizumab) for the treatment of multiple sclerosis (MS) has been accepted and designated for priority review by the US Food and Drug Administration (FDA).

The FDA grants Priority Review status to products that are considered to be potentially significant therapeutic advancements over existing therapies that address an unmet medical need. Based on the FDA's designation of Priority Review for Tysabri in MS, the companies anticipate action by the Agency approximately six months from the submission date, rather than 10 months for a standard review. On September 26, 2005, the companies announced they had submitted the sBLA for the market re-entry of Tysabri for MS and requested Priority Review, a Biogen release stated.

The sBLA for Tysabri in MS includes: final two-year data from the phase III Affirm monotherapy trial and Sentinel add-on trial with Avonex (Interferon beta-1a) in MS; integrated safety assessment of patients treated with Tysabri in clinical trials; and revised label and risk management plan.

"We are pleased that Tysabri has received Priority Review designation, which we believe, reflects the unmet need in MS," said Burt Adelman, MD, executive vice president, Development, Biogen Idec. "We look forward to working with the FDA throughout the review process and are hopeful that we will be able to bring Tysabri back to people living with MS."

"We believe that the acceptance of the sBLA for Priority Review is another step in our ongoing commitment to provide Tysabri as a treatment option for MS patients in need," said Lars Ekman, MD, executive vice president and president, Research & Development, Elan. "We will continue to work closely with the FDA as they review the filing so that Tysabri can be made available with an appropriate benefit-risk profile."

On February 28, 2005, Biogen Idec and Elan announced that they voluntarily suspended Tysabri from the US market and all ongoing clinical trials based on reports of progressive multifocal leukoencephalopathy (PML), a rare and potentially fatal, demyelinating disease of the central nervous system. Biogen Idec and Elan recently completed a comprehensive safety evaluation of more than 3,000 Tysabri patients in collaboration with leading experts in PML and neurology. The results of the safety evaluation yielded no new confirmed cases of PML beyond the three previously reported.