The Court of Appeal highlights frontloaded nature of proceedings

In its decision of 29 December 2025 (UPC_CoA_71/2025), the UPC Court of Appeal ruled on the extent to which new allegations and new evidence may be introduced when a request for limitation of a patent has been filed.

While the CoA reiterates that the front-loaded procedural system of the UPC requires submitting all arguments as early as possible, it also confirms that the principle of fairness and an adversarial process can allow a party to introduce new evidence and facts in response to the other party in particular to rebut (counter-)evidence or support a challenged point already made previously.

Background and First Instance Decision

The dispute concerns a revocation action brought before the Paris Central Division concerning a patent related to tobacco vaporizers. The patent proprietor and defendant, in addition to requesting dismissal of the action, sought to defend its patent by introducing different auxiliary requests.

In response, in accordance with Rule 43.3 RoP, the claimant filed a reply brief (the so‑called Defence to the application to amend the patent). In this brief the claimant added new evidence and invalidity arguments challenging the validity of the amendments as well as the patent as granted. The Court of First instance rejected these submissions and arguments to the extent that they related to the patent as granted only but allowed them insofar as they included a response to certain arguments made by the defendant regarding the common general knowledge and claim construction.

On this basis the Court declared the patent invalid in its entirety for lack of inventive step.

Court of Appeal Decision

In its appeal against the first instance decision, the patent proprietor and defendant focused mainly on the alleged inadmissibility of the new arguments and evidence only introduced by the claimant in response to the statement of defense and auxiliary requests. In particular, the proprietor argued that the first instance court had misapplied the principle of the front‑loaded procedure, in allowing submissions that should have and could have been made by the claimant in its statement for revocation.

While the Court of Appeal held the principle that the response to auxiliary requests cannot become an opportunity to introduce new grounds for invalidity against the patent as granted, it clarified the need to distinguish between the grounds, facts and evidence submitted in relation to the patent as granted and those specifically pertaining to the newly introduced auxiliary requests and defensive arguments filed by the patent proprietor.

In this context the CoA reaffirmed the general principles governing proceedings before the UPC. In particular, the system being structured so as to require parties to present the facts comprehensively from the outset and in a timely manner, as clearly indicated in the Preamble to the Rules of Procedure. Nonetheless, the CoA notes that this principle should not be applied rigidly and without regard to the specific context of the dispute. Referring to the Orthoapnea case law (UPC_CoA_456/2024), the Luxembourg judges recalled that specific new arguments may indeed be admitted at a later point when justified by the circumstances of the case.

Thus, provided that the principles of proportionality, fairness and the right to be heard are respected, new facts or new evidence may be introduced in the Defence to the Application to amend the patent, in reply to the arguments of the patent proprietor. This is particularly the case when such elements serve to reinforce an argument already submitted and any counterarguments submitted by the patent proprietor, for example concerning the common general knowledge of the skilled person, or to rebut certain evidence.

On the basis of these considerations, the Court of Appeal confirmed the admissibility of the additional submissions by the claimant and upheld the first‑instance decision declaring the patent invalid.