DMF - the story continues as the Danish High Court finds the presumption of validity rebutted despite a positive OD decision

On 18 July 2025, the Danish High Court (Eastern Division) rendered its decision on a matter concerning the medicinal product Dimethyl Fumarate (“DMF”) “Hexal” used in the treatment of multiple sclerosis. The ruling constitutes a very important contribution to the set of related cases regarding Biogen’s enforcement of patent DK/EP 2 653 873 (the “patent in suit”), as well as an important contribution to the general understanding of the requirements for rebutting the presumption of validity under Danish patent law.

The DMF “Hexal” case was initially decided by the Maritime and Commercial High Court on 25 February 2025. While the claimant (Biogen) requested that the Court issue a preliminary injunction based on infringement of the patent in suit, the defendants (Sandoz and Glenmark) argued that the patent-in-suit lacked inventive step and that the presumption of validity was therefore rebutted.

At the time of the Maritime and Commercial High Court’s decision, the Opposition Division (the “OD”) had rendered its final decision, holding the patent-in-suit as granted invalid. However, the OD upheld the patent in an amended and limited version based on Auxiliary Request 12 (“AR12”) (contrary to its preliminary opinion). Biogen argued that a preliminary injunction should be granted on the basis of the amended claims in AR12. The defendants, on the other hand, argued that AR12 also lacked inventive step and that the OD’s final decision contained serious errors in the application of law, e.g., in conflict with the Enlarged Board of Appeal’s decision in G 2/21.

The Maritime and Commercial High Court held that the presumption of validity had been rebutted for the patent-in-suit as granted. However, as the defendants had not demonstrated “clear errors and omissions” in the OD’s decision on the amended AR12, the Court granted a preliminary injunction against Sandoz and Glenmark. This decision was subsequently appealed to the Eastern High Court.

In its decision, the Eastern High Court initially held – in line with the Maritime and Commercial High Court’s decision - that the presumption of validity for the patent-in-suit as granted had been rebutted. The subsequent question before the Court was therefore whether a preliminary injunction could be based on the amended set of claims in AR12.

The defendants argued, inter alia, that AR12 lacked inventive step and was therefore invalid. According to the assessments conducted by the OD, AR12 could only be considered to solve the technical problem if post-published phase III clinical trials were admitted as evidence of the alleged technical effect at the patented dosage regimen. In line with the defendants’ arguments, the Court found it reasonable to assume that the Technical Board of Appeal (“TBA”) would regard the OD’s reliance on post-published data in its final decision as an error in the application of law. The TBA would therefore presumably declare the amended claims in AR12 invalid. The Court further noted that, should the TBA conclude that AR12 did not lack inventive step, it would (presumably) find that AR12 lacked sufficient basis.

Consequently, the High Court held that the burden of proof for rebutting the presumption of validity had been liftedd - both for the patent-in-suit and for the amended claims in AR12. The High Court therefore revoked the preliminary injunction granted by the Maritime and Commercial High Court.

The High Court’s decision constitutes an important contribution to Danish patent case law, preventing the enforcement of so-called “armchair inventions”, i.e., where the invention is effectively made after the priority date of the patent. The decision is a rare example in Danish patent litigation, and it will be exciting to see how it may influence future court assessments of the presumption of validity.

In a parallel action, the Danish Supreme Court is expected to rule on many of the same issues, which have not previously been heard by the Danish Supreme Court.

BUGGE VALENTIN represented Sandoz.