12.  Legal Proceedings

 

From time to time, we are involved in legal proceedings arising in the ordinary course of our business. Periodically, we evaluate the status of each legal matter and assess our potential financial exposure. If we consider the potential loss from any legal proceeding to be probable and we can reasonably estimate the amount, we accrue a liability for the estimated loss. The outcome of any proceeding is not determinable in advance. Therefore, we are required to use significant judgment to determine the probability of a loss and whether the amount of the loss is reasonably estimable. Our assessment of a potential liability and the amount of accruals we recorded are based only on the information available to us at the time. As additional information becomes available, we reassess the potential liability related to the legal proceeding and may revise our estimates.

 

On September 11, 2025, we sued Arrowhead Pharmaceuticals, Inc., in the Central District of California asserting that Arrowhead's announced intention to commercialize plozasiran in November 2025 would infringe our patent US9,593,333. Arrowhead is now commercializing plozasiran and the lawsuit is ongoing. Arrowhead has filed its Answer to our Complaint and Counterclaims asserting that our patent US9,593,333 is invalid or not infringed by use of plozasiran.

 

On June 1, 2026, Biogen received notice that Somerset Therapeutics, LLC had filed an Abbreviated New Drug Application, or ANDA, seeking approval to commercialize a generic version of SPINRAZA intrathecal injection, 12 mg/5 ml. The ANDA alleged that certain patents that cover SPINRAZA and its use are invalid or would not be infringed by Somerset. On June 22, 2026, Biogen, Cold Springs Harbor Laboratory and Ionis filed a lawsuit together in the District Court of Delaware asserting patent infringement. This lawsuit is ongoing.