On Friday August 15, the US FDA approved use of a drug called Plegridy for treatment of multiple sclerosis. The drug is produced by Biogen Idec, the company that also produces an MS drug called Avonex. The company hopes that Plegridy sales will outpace Avonex sales.

European health officials approved the drug on July 23 for use in MS patients.

Multiple sclerosis is an auto-immune disease that attacks the body's nervous system, causing disabling symptoms that can affect patients' ability to talk, make fine motor movements, or even walk in extreme cases. MS is a lifelong disease that still has no cure. The disease currently affects about 400,000 people in the United States. Over 2.3 million people around the world suffer from MS. The drugs Plegridy and Avonex can help patients manage the illness by lowering the risk of relapse, and slowing progression.

Plegridy needs to be used every two weeks, as opposed to Avonex, which must be taken weekly. Avonex needs to be injected into the skin intramuscularly, with a larger needle. Plegridy can be injected subcutaneously, or anywhere beneath the skin. It can be used with a smaller needle than Avonex.

For the time being, Biogen will continue to make Avonex for patients who are happy with using it and don't want to make the switch to Plegridy. Avonex has sold more than $1.5 billion worldwide so far this year, Biogen said. The company thinks that Plegridy sales will surpass that, taking a share of sales currently going to Avonex as well as other interferon drugs on the market right now that are sold by other companies. Other interferon drugs used to treat MS need to be taken more frequently than once every two weeks.

"We believe Plegridy has the potential to be the leading interferon on the market," Tony Kingsley, Biogen's head of global commercial operations, said. "As the class shrinks, we will be in a position gain share within that class. The most convenient product wins over time."

Plegridy will be ready for market soon, Kingsley said. This drug marks Biogen's fourth MS drug approved by the FDA.

Pharmaceutical companies have been making advancements in treatment of MS recently. Earlier this month, a study was done suggesting that drugs used to prevent HIV could also prevent multiple sclerosis effectively.

Biogen also recently got FDA approval for use of two new drugs, Alprolix and Eloctate, used for long-term treatment of hemophilia.