Biogen Idec Inc. said the Food and Drug Administration (FDA) has extended by three months the date for its final review of the company’s new multiple sclerosis drug, Plegridy. The FDA has not asked for additional studies, but indicated the extra time, which is within the range of a standard extension period, is necessary for review. The FDA as well as regulatory authorities in the European Union originally accepted the application for Plegridy to be used for relapsing forms of multiple sclerosis (RMS) in July 2013.

A new molecular entity, Plegridy is a subcutaneous pegylated interferon drug that has an extended half-life and therefore prolonged exposure in the body. Interferons are produced in small amounts by immune system cells as a way to communicate with each other; they are usually made in response to a pathogen, including viruses, bacteria, parasites, or tumor cells. The interferons attach to other immune cells, activating them to help the body fight infections and tumors. Synthetic versions of interferons are sometimes used as a form of immunotherapy — they boost the body's immune system to help it fight diseases, including MS and cancer.

“We expect that interferons will remain an important and widely used option for patients with MS,” said Dr. Douglas E. Williams, Biogen Idec’s executive vice president of research and development. Biogen was expecting to launch the drug Plegridy by mid-2014. Most people taking interferon drugs experience flu-like symptoms. Common side effects include fever, malaise, headache, and muscle and joint pains. High levels of interferons can even cause kidney, liver, bone marrow and heart toxicity. Reuters reported that analysts believe the market for interferon-based treatments will shrink over the next decade with the entry of newer products.

Williams noted that if approved, Plegridy “could offer a less frequent dosing schedule, a favorable safety profile, and the potential to become the preferred interferon treatment.” Since March 2013, Biogen, which focuses its drug development efforts on neurodegenerative diseases, hemophilia, and autoimmune disorders, has marketed another new MS product, Tecfidera, in the U.S. The company reported that after just six months Tecfidera had become the number one prescribed oral therapy for relapsing forms of MS.

Affecting women more than men, MS is an autoimmune disease that affects the brain and spinal cord. MS is caused by damage to the myelin sheath, the protective covering that surrounds nerve cells. When this nerve covering is damaged, nerve signals slow down or stop. The disorder can appear at any age, but is most commonly diagnosed between the ages of 20 and 40. Current treatments include 10 FDA-approved drugs, which reduce disease activity and disease progression in many people with relapsing forms of MS.