Keeping up with Belgian Patent Litigation – mid-2025 - mid-2026

The BelgianKats are back with a mid-year review
of Belgian patent litigation 

The emerging case law of the UPC has understandably drawn most of the attention in European patent litigation over the last years.  National courts, however, remain central to the system. They continue to hear cases that fall outside the UPC’s jurisdiction, to develop areas of substantive and procedural law, and to provide litigants with strategic options besides the UPC.  As in previous years, the Stibbe IP team  (in the form of  
Philippe Campolini, Louis Bidaine, Vince Van der Wangen, Anya Murphy, Mari Muzashvili, Nathan Thys, and Kate Criel)
has therefore prepared a selection of decisions rendered between mid-2025 and mid-2026, to keep up with the latest developments on the Belgian patent litigation scene. 

Over to the Stibbe team:  

"The decisions covered in this edition touch on a broad range of issues, namely the availability of unjust enrichment claims following the enforcement of a patent later found to be invalid, the Bolar exemption, the strict disclosure obligations that apply in ex parte saisie proceedings, the cross-border reach of saisie orders in the face of diverging national infringement regimes, the minimum content required for a valid SPC manufacturing waiver notification, the autonomy of national court proceedings vis-à-vis pending EPO proceedings, unregistered licences, exhaustion, the geographic scope of information orders and, rounding out the year, the relation between biosimilarity and technical equivalence.

Liability for enforcing a provisional injunction based on a patent subsequently found invalid

Belgian Supreme Court, 11 September 2025, Viatris v. Novartis

In our 2023 chronicle (see here), we reported on the Brussels Court of Appeal’s decision in Mylan v. Novartis, concerning the well-known question of the patentee’s liability for enforcing a provisional injunction based on a patent subsequently found to be invalid. The Court held that the Court of Justice of the European Union (CJEU)’s decision in Bayer v. Richter (C-688/17) left no room for objective liability, that is, liability arising solely from the patent’s invalidity. It further held that the doctrine of unjust enrichment could not apply in such circumstances, as doing so would amount to objective liability by another name. Under Belgian law, the revocation of a patent, despite its retroactive effect, does not affect final, enforced infringement decisions, without prejudice to claims for damages arising from the patentee’s negligence or bad faith, or for unjust enrichment. On that basis, the Court of Appeal held that the party subject to the provisional injunction must establish that the patentee knew or ought to have known, when seeking, maintaining, or enforcing the provisional injunction, that the patent was invalid, and that its conduct was unlawful or amounted to an abuse of rights.

Mylan appealed to the Belgian Supreme Court, though solely on the issue of unjust enrichment. The question of objective liability was not directly raised. During the Supreme Court proceedings, the CJEU issued its decision in Mylan v. Gilead (C-473/22), holding that Article 9(7) of the Enforcement Directive does not preclude national legislation establishing a strict liability mechanism for compensation of injury caused by a provisional measure, provided the court may adjust damages in light of the circumstances, including the defendant’s contribution to the harm.

The Supreme Court dismissed the appeal on 11 September 2025. It confirmed that the retroactive annulment of the patent does not strip the provisional injunction decision of its res judicata, which continues to constitute a valid legal cause for the transfer of wealth, and that the legislator did not intend to alter the conditions for unjust enrichment by ignoring the final character of an infringement decision. Interestingly, the Court did not consider it necessary to make a distinction between decisions on the merits and decisions in summary proceedings. As a consequence, the Court considered that the provisional injunction decision itself must be considered as a lawful basis for the enrichment.

Given the limited scope of the appeal, the Supreme Court did not expressly exclude objective liability under Belgian law, leaving the question open. Since the Enforcement Directive does not harmonise this area, liability regimes continue to diverge across jurisdictions.

Brussels Court of Appeal overturns saisie order: the Bolar exemption and duty to disclose in ex parte saisie requests

Brussels Court of Appeal, 17 July 2025, Samsung Bioepis v. Amgen

The Brussels Court of Appeal set aside a previously granted saisie order in a patent dispute between Amgen and Samsung Bioepis, concerning the active ingredient denosumab.

The Court held that shipments of denosumab made for the purposes of obtaining regulatory authorisation fell prima facie within the Bolar exemption and could not, as such, be considered as indications of infringement capable of justifying a saisie order. It further confirmed that an applicant seeking ex parte measures bears a strict duty of disclosure, and that failing to provide material information or clarification in relation to submitted documents is incompatible with that duty.

Samsung Bioepis was developing a biosimilar version of denosumab, the active ingredient in Prolia® and XGEVA®. Amgen held several IP rights over denosumab, including European patent EP 016 in force in Belgium, supplementary protection certificate ABC 039, and its US counterpart patent US 736. After Samsung Bioepis notified Amgen and the Belgian IP Office of its intention to have denosumab-containing products manufactured in Belgium for export, invoking the manufacturing waiver under Article 5(2)(b) of the SPC Regulation, Amgen filed an ex parte application for descriptive measures at the premisses of the manufacturer, Catalent Belgium. The application was initially dismissed but then granted on appeal, and the description was carried out in February 2025. Samsung Bioepis then brought opposition proceedings before the Court of Appeal.

The heart of the case was whether there were sufficient indications of infringement to justify the description order. The Court found there were not, for two distinct but related reasons. Amgen’s primary evidence consisted of FDA database records showing shipments of denosumab from Belgium to the United States in late 2021 and early 2022, with Catalent Belgium identified as manufacturer, as well as a further shipment in October 2022. Crucially, the October 2022 shipment was described in those same FDA records as a “Patient Kit Denosumab for IND #141802” (“IND” standing for Investigational New Drug) indicating it had been dispatched in the context of a regulatory authorisation procedure and was therefore in all likelihood covered by the US Bolar exemption under 35 U.S.C. § 271(e)(1). Amgen failed to draw that designation to the court’s attention or explain its significance. The Court was therefore unequivocal: the mere presence of the “IND” label in the submitted documents did not discharge Amgen from its duty of disclosure, and the omitted information was directly material to the assessment of whether indications of infringement existed. As for the earlier shipments in late 2021 and early 2022, the Court found no indication that they differed in nature or scale from the “IND” shipment.

The Court also rejected Amgen’s position that the Belgian Bolar exemption did not apply because the products were destined for the United States. According to the Court, clinical trials conducted there may equally serve the purpose of obtaining a marketing authorisation (MA) in the EU, something Amgen could reasonably have been expected to appreciate. Samsung Bioepis confirmed that its EU MA did indeed rely on the results of the very trials referred to in Amgen’s documents, conducted in both the United States and France. The Court considered that the Belgian shipments were therefore at least prima facie also covered by the Belgian Bolar exemption. On that basis, the Court set aside the descriptive measures and ordered the return of all information gathered in the course of the saisie.

The ruling carries several important lessons. First, it confirms a broad reading of the Bolar exemption: acts carried out in Belgium in connection with clinical trials in third countries may fall within its scope where the data generated also serve the purpose of obtaining an AM in the EU. Second, it reiterates the strict disclosure obligation in ex parte proceedings: the applicant must proactively draw attention to all elements material to the assessment, including information that could point away from infringement. Third, it confirms Belgium’s potential as a forum for cross-border evidence gathering, even in support of non-EU patent rights.

This approach closely mirrors the standard applied by the UPC Court of Appeal in its Ecovacs v. Roborock decision (UPC_CoA_3/2026), where the Court held that Rule 192.3 RoP imposes a heightened requirement whereby the applicant must disclose, and not leave out, any material facts that might be relevant for the assessment of the request, and that omissions and distorted accounts of material facts which might be of central importance for the assessment of whether to allow the request at all cannot be compensated or circumvented by later submissions made in response to a request for review.

Foreign patent law in cross-border saisie proceedings

Brussels Court of Appeal, 16 December 2025, Huntsman v. BASF

In a decision of 16 December 2025, the Brussels Court of Appeal addressed two questions that arise regularly in cross-border saisie proceedings but have rarely been examined with this degree of analytical rigour: how far does the prima facie assessment go, and what must the applicant show in its request when seeking to collect evidence of infringement of foreign patents?

BASF held a European patent that was valid in 19 countries. Suspecting indirect patent infringement by Huntsman on a global scale, BASF filed an ex parte saisie request on 16 July 2024 covering both the Belgian part and the 18 foreign national parts of its European patent. The saisie was granted and enforced in the following days. Huntsman filed an opposition, which was rejected in first instance, and subsequently appealed.

During the opposition proceedings, Huntsman contested the methodology by which BASF had determined the density of Huntsman’s product, arguing that deriving density from specific gravity rather than direct measurement was unreliable and that water and additives had not been properly accounted for. The Court rejected this defence, considering that such technical arguments exceed the prima facie assessment applicable in saisie proceedings. According to the Court, it suffices that indications of infringement are present and full proof is not required. The Court recalled that the saisie aims precisely at gathering evidence with the assistance of an independent expert. The Court found that the offering of Huntsman’s product was prima facie an indirect patent infringement in Belgium and confirmed the saisie for the Belgian part of EP 720.

BASF relied on the pan-European availability of Huntsman’s product and Huntsman’s presence across multiple European countries to also seek descriptive measures covering indirect infringement in Bulgaria, Germany, France, Italy, Austria, Portugal, Romania, Slovenia, Greece, the United Kingdom, Hungary, Poland, Slovakia, Spain, the Czech Republic, Turkey, Sweden and Switzerland. Because Huntsman argued that indirect patent infringement is not recognised in each of these countries and that the conditions for indirect patent infringement vary from one country to another, the Court found that it needed to be better informed about the content of the various applicable national laws. It therefore reopened the debates after the oral hearing to allow the parties to inform the Court of the national law applicable in each of the countries concerned, and to take a position on the conditions applicable to indirect patent infringement under these various national regimes.

It will be instructive to see how, based on the information provided by the parties, the Court will balance the need to take into account the fact that there are indeed variations in the various applicable legal regimes with the need to remain within the limits of a prima facie assessment, which is inherent to a saisie that only requires indications of infringement.

Too soon for Bolar?

Brussels French-speaking Enterprise Court, 26 June 2025, Sterigenics & Amgen v. Regeneron

The Brussels French-speaking Enterprise Court confirmed an ex parte descriptive seizure order obtained by Regeneron on the basis of its Belgian SPC 029, which protects the use of aflibercept (the active substance of its pharmaceutical product EYLEA®).

Regeneron suspected Sterigenics of being involved in the manufacturing chain of several aflibercept biosimilars and obtained an order authorising a saisie, which was ultimately conducted at Sterigenics’ Leuven and Petit-Rechain sites. Sterigenics and Amgen jointly opposed the order through opposition proceedings.

The decision is interesting, firstly, for its treatment of the requesting party’s duty of disclosure in unilateral requests. The Court reiterated that the applicant owes a duty of procedural loyalty, which forbids it to remain silent on determinative facts or to present the facts in a tendentious way. It found that, by relying on the commercialisation of biosimilars in the United States and South Korea without explaining that its corresponding rights in those territories had expired and without flagging pending parallel proceedings, Regeneron had unnecessarily drawn the judge’s attention to factors that, prima facie, were irrelevant because unrelated to the title invoked. However, that flaw was held not to invalidate the order insofar as that information did not have a significant incidence on the descriptive seizure order, a conclusion confirmed by the wording of the experts’ mission (which was centred on the activities carried out in Belgium before the expiry of SPC 029).

Secondly, and most notably, the Court declined to engage with the Bolar defence at the saisie stage. Sterigenics and Amgen relied heavily on the argument that the sterilisation activities formed part of regulatory-phase work in view of obtaining a European MA and therefore benefited from the Bolar exemption. The Court held that requiring the saisie judge to take the full measure of an exception (particularly when, as was the case here, its application depends on a concrete examination of the circumstances) would exceed the prima facie scope of the saisie proceedings, the function of which is evidentiary. It is noteworthy that this decision was rendered a few weeks before the decision of the Brussels Court of appeal cited above, which took a different view on this question.

The case prompts a forward-looking observation in light of the EU Pharma Package. The compromise text for the revised Bolar exemption explicitly extends the personal scope of the exemption to third-party suppliers and service providers. Applied to the facts as presented, the sterilisation activities carried out in Belgium exclusively to validate the sterilisation procedure for the SPC’s EU MA dossier, with no commercial use of the sterilised batches, would appear to fall squarely within that expanded safe harbour.

Whether it would have altered the outcome at the saisie stage is, however, a different question: the Court’s refusal to engage with that defence rested not on uncertainty about the exemption’s scope, but on the structural logic that applying any exception requires a fact-intensive examination that exceeds the prima facie remit of saisie proceedings. It also remains to be seen whether, in the future, the Brussels French-speaking Enterprise Court will adapt its approach in line with the Brussel Court of appeal’s more recent case law commented above.

No waiting game: national revocation action and the limits of EPO influence

Brussels Dutch-speaking Enterprise Court, 2 September 2025, Devan Chemicals v. Heiq Christal

The Brussels Dutch-speaking Enterprise Court’s decision of 2 September 2025 offers a noteworthy reaffirmation of the principle of independence between Belgian national proceedings and parallel EPO proceedings. The Court expressly declined to stay the nullity action that had been brought against a Belgian patent, notwithstanding the ongoing examination of the corresponding European application before the European Patent Office (EPO). It thereby confirmed that the validity of a national patent must be assessed autonomously, without awaiting the outcome of the corresponding European grant procedure.

This approach is grounded in the well-established Belgian case law, according to which a Belgian patent constitutes a distinct legal title, legally and procedurally independent from any corresponding European patent or patent application. The Court emphasized that the coexistence of both rights, even in respect of the same invention, does not inherently create a risk of conflicting decisions, particularly where claim sets diverge or evolve separately over time. This reasoning reflects a pragmatic position: deferring national proceedings would not necessarily enhance consistency, but could instead unduly delay access to judicial resolution, especially where the EPO proceedings are protracted. Parties therefore cannot assume that ongoing EPO proceedings will shield them from immediate national invalidity challenges, even where the underlying invention is the subject of parallel examination at the European level.

Notification without authorization

President of the Brussels French-speaking Enterprise Court, 12 November 2025, Regeneron v. Sandoz

A few months after the aforementioned Sterigenics decision, Regeneron was at the heart of another aflibercept dispute concerning the same SPC, where it sought an injunction against Sandoz before the Brussels French-speaking Enterprise Court. Sandoz had notified its intention to manufacture aflibercept biosimilars in Belgium under the SPC manufacturing waiver introduced by Regulation (EU) 2019/933. The decision addresses the conditions for the fabrication-for-export derogation, and in particular whether the manufacturer must already hold a MA in the third country at the time of its notification.

By a notification dated 19 February 2024, Sandoz informed Regeneron of its intention to have aflibercept biosimilars manufactured in Belgium for export and stockpiling, indicating that the MA reference number for the third country of export was “not yet available”. Sandoz subsequently sent two updates: one on 16 August 2024 communicating the US MA reference number, and another on 28 January 2025 communicating the UK MA reference number. Regeneron argued that the initial notification was void on the grounds that a MA must already exist at notification stage, and that any subsequent manufacture on that basis would infringe its SPC.

The Court rejected that reading. It started from the text of Article 5(5)(e) of the amended SPC Regulation, which requires the manufacturer to communicate "for medicinal products to be exported to third countries, the reference number of the marketing authorisation, or the equivalent of such authorisation, in each third country of export, as soon as it is publicly available" (emphasis added). The Court noted that the mention "as soon as it is publicly available" expressly contemplates that the MA may not yet be available at notification stage, in which case the information is to be supplied later by update. The Court further situated its analysis in the emerging European jurisprudence on the manufacturing waiver and aligned itself with the decision of the Brussels Dutch-speaking Enterprise Court of 23 December 2024 (commented in our previous case law review) and the judgment of the Hague Court of Appeal of 11 February 2025.

Having validated the February 2024 notification and its subsequent updates, the Court turned to the actual injunction request. Although Sandoz’ notification indicated an intention to rely on the manufacturing waiver, at the close of the hearings, Regeneron’s counsel had acknowledged that they did not know whether any aflibercept biosimilar was actually being manufactured by Sandoz in Belgium, and Sandoz declined to provide information in this regard. In line with established case-law, the Court held that a serious and concrete threat, and not a mere abstract possibility, is required for a preventive action. As the alleged threat of unlawful stockpiling or export remained purely hypothetical (as no evidence of such acts had been brought forward), Regeneron’s claims were declared inadmissible. The Court’s reasoning is particularly stringent on this point, as it treated Sandoz’s own notification of an intention to manufacture under the waiver as insufficient, on its own, to establish a serious and concrete threat.

The decision is significant on at least two counts. Substantively, the Brussels French-speaking Enterprise Court adopted a reading of the manufacturing waiver that confirms the stance already taken by its Dutch-speaking counterpart. Procedurally, it is also a useful reminder that Belgian courts can take a demanding approach towards an action ad futurum, requiring more than the prospect that a defendant could eventually act unlawfully.

Belgian court weighs in on unregistered licences, exhaustion and cross-border information orders

Brussels Dutch-speaking Enterprise Court, 9 December 2025, W.S. & Hoy Geokunststoffe v. Hye & Voets Gewapende Grondconstructies

In its judgment of 9 December 2025, the Brussels Dutch-speaking Enterprise Court addressed three questions of practical importance for patent litigators: the opposability of an unregistered licence against alleged infringers, the conditions under which the doctrine of exhaustion can extinguish a patentee’s rights, and the territorial scope of information orders.

The dispute concerned a European patent in force in, inter alia, Belgium, but not in the Netherlands, which protects welded wire mesh for gabions with a zinc-aluminium mixture of a specific composition. Gabions are wire mesh cages or baskets filled with rocks, pebbles or concrete, widely used in civil engineering. The dispute arose in the context of a public tender for the construction of a road bridge over the Albert Canal in Wijnegem, where a Belgian construction company engaged a Dutch subcontractor which in turn ordered welded wire mesh panels from a supplier sourcing steel wire from Bekaert NV, an acknowledged licensee under the patent. When the patent proprietor and its exclusive licensee, Hoy Geokunststoffe GmbH, discovered that gabions were being installed on site that seem to infringe the patent, they carried out a descriptive seizure. The defendants’ own documents confirmed that the panels had been made using Bekaert’s Bezinal 5000 wire, falling within the scope of claim 1.

The first question addressed by the Court concerned the opposability of Hoy’s unregistered licence. Belgian law requires patent licences to be registered in order to be opposable against third parties, and both defendants relied on that requirement to challenge Hoy’s standing to sue. The Court rejected the argument. Drawing by analogy on the CJEU’s reasoning in the Thomas Philipps decision (C-419/15) concerning design rights and the Hassan decision (C-163/15) concerning trademark rights, it held that the protection afforded by the registration requirement is reserved for third parties acting in good faith. The Court drew a clear distinction between a party that transacts in reliance of the patent register and an (alleged) infringer who has not taken, or even attempted to take, any licence of its own and who therefore has, in principle, no legitimate interest in knowing who the licensee is or what the terms of the licence are. The Court held that an (alleged) infringer cannot invoke the registration requirement as a basis for deciding, on its own assessment, whether to take the risk of infringement, based on whether a licence has been granted or to whom it has been granted.

On the question of exhaustion, the defendants argued that the patentee’s rights had been exhausted when Bekaert placed the steel wire on the market. The Court rejected this on two independent grounds. First, Bekaert’s licence did not concern the sale of steel wire “as such”, but of welded steel wire mesh for use in gabions. Accordingly, as Bekaert’s sale concerned steel wire for use in applications other than gabions, no product falling within the scope of the patent had been placed on the market with the patentee’s consent. Second, the wire had been placed on the market in the Netherlands, a jurisdiction in which the patent has no effect, without any indication, at the time of that marketing, that the product would subsequently be used in Belgium. Since a European patent confers independent national rights in each validated state, marketing a product in a non-validated jurisdiction cannot exhaust rights where the patent does have effect.

Finally, the claimants sought an information order requiring the Dutch subcontractor to disclose information regarding the origin and distribution channels of the infringing goods, not only in respect of Belgium, but also in respect of all other countries in which the patent is in force (namely Switzerland, the Czech Republic, Germany, Denmark, Finland, France, Ireland, Luxembourg, Poland, Sweden and Slovakia). The Court granted this request subject to a limitation of its scope, and ordered the subcontractor to confirm that no other infringing gabions had been installed across all of those jurisdictions during the five years preceding the judgment or, if such confirmation could not be given, to provide details of the relevant locations, quantities, suppliers and clients. The cross-border scope of this information order is noteworthy, as the information order extended to all jurisdictions in which the patent is in force, despite acts of infringement having been found only for the Belgian territory.

Biosimilarity and technical equivalence

President of the Brussels Dutch-speaking Enterprise Court, 8 January 2026, Regeneron v. Celltrion

In its judgment of 8 January 2026, the President of the Brussels Dutch-speaking Enterprise Court dismissed Regeneron’s preliminary injunction request against the Belgian launch of Celltrion’s aflibercept biosimilar Eydenzelt®. Regeneron relied on a formulation patent covering VEGF-antagonist (vascular endothelial growth factor-antagonist) formulations for intravitreal administration. There was no dispute that Eydenzelt® literally reproduced several features of claim 1, but Celltrion argued that its product did not reproduce the buffer system (feature 1.4, requiring sodium phosphate), the tonicity agent (feature 1.3) and the stabilising agent (feature 1.5). Regeneron argued, among other things, that Eydenzelt®’s use of histidine as a buffer constituted infringement by equivalence.

The Court rejected Regeneron’s position, for two notable reasons.

First, the Court held that bioequivalence under pharmaceutical law must not be confused with technical equivalence under patent law. Bioequivalence does not preclude differences between the composition of a generic medicine and that of the reference product as regards pharmaceutical form, chemical form of the active substance, or excipients. In the same vein, substantial technical differences between the formulation of a biosimilar and that of the reference product do not exclude bioequivalence within the meaning of pharmaceutical law. The fact that Eylea® was used as the reference product for Eydenzelt® was considered insufficient to conclude that there is an apparent infringement by equivalence.

Second, applying the function-way-result test, the Court found that Regeneron had not shown that histidine and sodium phosphate perform their buffering function in substantially the same way and with substantially the same result, noting that formulation stability is the product of a highly specific combination of excipients whose interactions produce results that are often unpredictable. The fact that the equivalent effect of the buffer had not been contested in the parallel German proceedings was insufficient to convince the Court of the prima facie equivalence. In addition, the Court referred to the fact that in the English proceedings, by contrast, it was undisputed that histidine and sodium phosphate buffer in substantially the same way (by taking up and releasing hydrogen ions), but the English court found that this did not establish substantially the same result, since expert evidence showed that the choice of buffer also mattered for the stability of the formulation. The Court considered that Regeneron had failed to demonstrate that the English court’s finding was technically wrong.

Finally, the Court also found that the balance of interests favoured Celltrion, considering that Regeneron had already recouped its investment through years of monopoly protection, that the alleged losses were quantifiable and recoverable in main proceedings, and that the public interest in an affordable biosimilar weighed against an injunction.

The previous editions of this year case law review are available here (2020), here (2021), here (2022), here (2023) and here (2024-mid 2025). "