US Judge Rules Japan’s Duchenne Drug Patent Invalid

(the article has been updated to make it concise and cohesive)

In a landmark decision, a district court judge in Delaware ruled that Nippon Shinyaku’s patent for Viltepso (viltolarsen), an exon-skipping oligonucleotide drug for Duchenne Muscular Dystrophy (DMD), is invalid. The ruling favors Sarepta Therapeutics (NASDAQ: SRPT), which holds the patent for a similar exon-skipping drug, golodirsen, used for DMD patients with a 53-exon mutation.

Viltepso, marketed in the U.S. by NS Pharma, Nippon Shinyaku’s U.S. subsidiary, was challenged in court by Sarepta, which argued that its own patent, licensed from the University of Western Australia, should take precedence. The court validated Sarepta's patent and awarded the company $115.2 million.

This decision marks a significant win for Sarepta, which already markets three antisense oligonucleotide drugs for DMD in the U.S. targeting exon 51, 45, and 53. The ruling also dealt a blow to Nippon Shinyaku, whose shares fell nearly 8% on December 23, 2024.

In 2021, NS Pharma filed a lawsuit against Sarepta over the exon 53 patent, prompting a counter-suit. The ruling on December 23 is the first in this ongoing legal battle. Nippon Shinyaku is evaluating all options, including a potential post-jury appeal, but noted that the ruling does not impact the current sales of Viltepso or its ongoing development of other oligonucleotide treatments.