The U.S. Food and Drug Administration approved Biogen Inc and partner Alkermes Plc's oral drug to treat multiple sclerosis, the companies said on Wednesday.

The approval is good news for Biogen as its top-selling drug Tecfidera, also a multiple sclerosis treatment, is facing patent challenges and increased competition from newer treatments such as Roche AG's Ocrevus.

The new drug, Vumerity, was approved to treat relapsing forms of multiple sclerosis, a disabling autoimmune disease that damages the central nervous system and can lead to fatigue, pain, vision loss and impaired coordination and motor skills.

Biogen said it would make the drug available in the United States in the near future.

Earlier this month, Alkermes disclosed that the drug had received tentative approval. At the time, brokerage Wedbush estimated Vumerity to bring sales of about $800 million at its peak. Tecfidera brought Biogen sales of $4.27 billion last year.

Wednesday's approval was based on data comparing Vumerity and Tecfidera, the companies said in a statement. 

Under the terms of a license agreement between the two companies, Biogen will pay Alkermes $150 million and royalties from the worldwide commercial sales of the drug.

(Reporting by Tamara Mathias and Trisha Roy in Bengaluru Editing by Supriya Kurane) ((Tamara.Mathias@thomsonreuters.com; within U.S. +1 646 223 8780, outside U.S. +91 806749 1208;))