By Jan Wolfe

(Reuters) – A U.S. federal appeals court on Wednesday upheld a ruling that Biogen Inc’s patents on its blockbuster multiple sclerosis drug Tecfidera are valid, rejecting a challenge by Danish drugmaker Forward Pharma A/S.

The U.S. Court of Appeals for the Federal Circuit said it agreed with a March 2017 ruling by the Patent Trial and Appeal Board that freed Biogen <BIIB.O> from future royalty payments to Forward.

Forward said in a statement it was disappointed with the ruling and considering its options. Biogen did not immediately respond to a request for comment.

The companies had been locked in a dispute over patents for dimethyl fumarate, the key active ingredient in Tecfidera, the leading oral MS treatment. Tecfidera had sales of about $4.2 billion in 2017.

Biogen’s Tecfidera exclusivity in the United States is secured through 2028 under the ruling.

In January 2017, Biogen took out an insurance policy against a potential defeat in the patent dispute, agreeing to pay Forward $1.25 billion to license the company’s patents covering MS drugs and gain a share of Forward’s intellectual property.

The 2017 agreement would have allowed Forward to receive additional royalty payments if it had won the Federal Circuit appeal.

(Reporting by Jan Wolfe; Editing by Chizu Nomiyama and Paul Simao)