Shares of Acorda Therapeutics fell more than 20% on Friday after a federal judge in Delaware invalidated patents held by Acorda related to its multiple sclerosis drug Ampyra.
The ruling by US District Judge Leonard Stark could pave the way for generic versions of the drug by companies including Roxane Laboratories and Mylan.
According to Reuters data, sales of Ampyra made up almost 90% of Acorda’s 2016 revenue of $519 million.
The judge invalidated four Acorda patents on methods of delivering the drug which were not set to expire until between 2025 and 2027.
The judge upheld one Acorda patent on the extended-release formulation of Ampyra which is due to expire in 2018.
Acorda said it would appeal the ruling on the four patents invalidated.
“We are disappointed by the court’s decision and are preparing our appeal,” said Acorda CEO Ron Cohen.
“Medical innovation depends on the recognition of valid intellectual property claims.
“We believe that we demonstrated novel and unexpected findings in our AMPYRA development program that led to the issuance of valid patents.”
Acorda said: “The company has developed contingency plans to address its business needs and objectives in the event of a loss of AMPYRA exclusivity, and will provide an update after finalizing the implementation timeline.”