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FDA Approves Intramuscular Plegridy for Relapsing MS

March 11, 2021

The U.S. Food and Drug Administration has approved an additional version of Plegridy® (peginterferon beta-1a, Biogen) that is injected into thigh muscles (intramuscular injection - IM) every two weeks. Plegridy is a disease-modifying therapy that was approved for treating relapsing forms of MS in 2014 as a biweekly under-the-skin (subcutaneous – SC) injection, after it was shown to delay the progression of MS disability and reduce relapses.
  • Relapsing forms of MS  include people with clinically isolated syndrome (an initial episode of neurological symptoms), relapsing-remitting MS, and active secondary progressive MS. People with active secondary progressive MS have had progression of disability but still experience acute relapses or new MRI activity.
  • Plegridy is a “pegylated” form of interferon that enables interferon molecules to maintain biologic effects in the body for longer periods of time and allows for less frequent dosing than traditional interferon therapies.
  • This FDA approval was based on data evaluating bioequivalence and adverse reactions associated with IM injections compared to SC injections in healthy volunteers. Participants receiving IM Plegridy experienced fewer injection-site reactions compared to those receiving it by SC. (14.4 percent vs. 32.1 percent).
  • In Plegridy clinical trials involving people with MS, the most common adverse events were injection site reactions and flu-like symptoms. Side effects reported include liver problems, including liver failure and increases in liver enzymes; depression or suicidal thoughts; serious allergic reactions; cardiac problems, including congestive heart failure; blood problems, such as decreases in white blood cell or platelet counts; autoimmune disorders; and seizures.
  • IM Plegridy is now available for prescription. According to the company, the price of IM Plegridy will be comparable to the price for SC Plegridy.
Read the Plegridy prescribing information for healthcare providers (.pdf)
Read the Plegridy Medication Guide for patients (.pdf)
Learn more about Biogen-sponsored support and financial assistance programs:
1-800-456-2255; or visit the Plegridy website
Note on starting a disease-modifying therapy during the COVID-19 pandemic: Many experts believe it is safe to start a disease-modifying therapy during the COVID-19 pandemic. Interferons (Avonex, Betaseron, Extavia, Plegridy, Rebif) are unlikely to impact negatively on COVID-19 severity. There is some preliminary evidence that interferons may reduce the need for hospitalization due to COVID-19. Taking a disease-modifying therapy is currently the best way to reduce MS disease activity and future deterioration. Selecting any therapy should be done by people with MS in collaboration with their MS healthcare providers, taking into account a variety of factors, including the effectiveness of any therapy they are currently using, and weighing potential risks and benefits, costs and lifestyle factors.

Plegridy is a registered trademark of Biogen

About Multiple Sclerosis

Multiple sclerosis is an unpredictable, often disabling disease of the central nervous system. Symptoms range from numbness and tingling to blindness and paralysis, and there is currently no cure for MS. The progress, severity and specific symptoms of MS in any one person cannot yet be predicted, but advances in research and treatment are leading to better understanding and moving us closer to a world free of MS. An estimated 1 million people live with MS in the United States. Most people with MS are diagnosed between the ages of 20 and 50, and it affects women three times more than men.


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