EPO oppositions & appeals

Commercially-focused advocacy for EPO oppositions and appeals

Most patents are never opposed. It's the commercially significant patents—the ones that threaten to shift market dynamics—that get opposed. For nine months after a European patent is granted, competitors have a critical window to challenge the patent centrally at the European Patent Office (EPO). Whether defending your own innovations or challenging a competitor's rights, EPO contentious proceedings are a powerful strategic tool. Our experts are here to ensure you achieve your commercial objectives.

We defend your market share

If your patent is opposed, it’s a sign you are on the right track. Your innovation is making competitors nervous and your patent portfolio is on track to deliver real business value. This has strong implications for market position, investment, and monetisation. But first, your patent must survive the opposition and any subsequent appeal – and that’s where our expertise comes in.

Contentious proceedings can turn on the finest details where there is no room for error. We combine deep technical expertise with procedural savvy to navigate the complexities of the EPO opposition procedure. We listen to your commercial priorities and steer the proceedings, through first instance and appeal, to ensure your patent retains the maximum value for your business. An opposition can even enhance the value of your patent, once it has been successfully defended.

We clear your path to market

You’ve identified a competitor’s patent that blocks your commercial path. With only a nine-month window to act, there is no time to lose. We are here to help clear that path.

Our forensic approach and sharp oral advocacy routinely tip the balance in opposition and appeal proceedings. We dissect patents with precision, uncovering vulnerabilities that range from subtle technical arguments to fatal formal errors. With deep expertise in EPO procedure and a close eye on evolving case law, we hold the other side to the strict requirements of the rules – narrowing their room for manoeuvre and maximising your chances of success.

Turn to us for complex, high-stakes cases

We are the firm of choice for businesses with significant value riding on the outcome of EPO contentious proceedings. As veterans of major patent disputes, we frequently lead strategies that form a key part of broader, multi-jurisdictional litigation. We excel at coordinating attacks on complex and interrelated patent families, where every argument is carefully chosen to avoid unintended consequences.

Our strength lies in our collaborative approach. We build the perfect team for your case, integrating seamlessly with your in-house and external legal counsel to achieve high-impact commercial outcomes.

Strategic & contentious IP

Strategic IP enforcement: UPC

Their team consistently demonstrated strategic insight, deep legal expertise, and a practical, business-oriented approach. Their handling of complex opposition matters has been instrumental in protecting our key IP assets. It’s always a pleasure to work with such a responsive and reliable team.

- Client quote

Our approach includes:

A best-in-class hearing environment

Our state-of-the-art office features a dedicated suite of video conferencing rooms, purpose-built for the intensity of virtual and hybrid EPO hearings, ensuring a seamless and professional experience.

Uncompromising preparation

For pivotal cases where no stone can be left unturned, we arrange comprehensive mock hearings, stress-testing arguments and preparing the team for every eventuality at the EPO oral proceedings. Our creativity and curiosity are applied to each case to create a strategy tailored to the circumstances, rather than assuming that a single formula works every time.

Appeal strategy

Our strength in appeal proceedings matches that at first instance, backed by extensive experience before the EPO Boards of Appeal. This means we have a deep working knowledge of the procedural complexities that can often prove decisive on appeal. Equally, we know how to structure our opposition case at first instance with the appeal process in mind, ensuring we stay on the front foot if the decision is appealed.

Unmatched technical depth

With over 80 professionals across technical groups, we have specialists in a range of fields – many of whom have advanced degrees and relevant hands-on laboratory experience.

Our Life Sciences & Chemistry team has extensive experience across all areas of pharmaceutical technology, from small molecules to biologics, antibodies to vaccines, formulation technologies to clinical trial-based applications. They have equally significant expertise in high-value chemicals and materials, notably next-generation chemicals and processes, products in highly regulated fields and materials for sustainable energy.

Our Tech & Engineering team has in-depth technical knowledge across MedTech, AI, automotive and aeronautical engineering, telecoms, semiconductors, optics, and beyond. Whatever the technology, we have the right technical expertise at the ready – ensuring that we speak your language and no technical nuance passes us by.

On the attack when lawsuits land: revoking competitors’ patents leveraged against our clients

Our clients look to us to defend them when they’re taken to court. We work for a billion-dollar international consumer goods group who is active in the highly contested field of personal hygiene products.

When they were sued for alleged infringement of a competitor’s patent in a national European court, they came to us to attack the patent as invalid at the EPO. We worked tirelessly to invalidate not only the patent as granted, but all of the competitor’s fall-back positions. We used technical arguments developed in close collaboration with our client to have the patent and many of the fallback positions declared invalid, and used our extensive knowledge of the EPO’s rules of procedure to have the remaining fallback positions declared inadmissible. We were therefore successful in fully revoking the patent, wiping it out in its entirety across Europe.

Defending a ground-breaking anti-cancer immunotherapy patent in opposition proceedings

Our clients trust us to protect their most valuable assets.

We secured grant of a European patent protecting a first-in-class bifunctional fusion protein immunotherapy that was in clinical development with potential in several difficult-to-treat cancers. The drug was the subject of a multi-billion-pound development deal between two pharma giants.

Multiple third parties attacked the patent at the EPO after grant. By working closely with our client and technical experts on detailed submissions to rebut the third-party challenges, we successfully demonstrated that the patent was valid in opposition proceedings and preserved our client’s protection for this groundbreaking new therapy.

Reversing the trend when the stakes are sky-high

We were brought in to turn the tables in a head-to-head battle between two of the world's largest aircraft manufacturers. Taking on a portfolio of over 50 oppositions, we reversed a trend of losses to successfully defend critical patents for a world-leading passenger jet.

In a landmark case for a different client, we successfully opposed a major airline’s business class seating patent, which had been upheld by the UK Court of Appeal. Our success at the EPO was pivotal in the UK Supreme Court's decision to overturn an award of £49 million in damages.

Turning IP value into financial value

We successfully defended a client's patent against an opposition from a consortium representing the major players in the Swiss watch industry, with the patent maintained as granted and ultimately sold to the opponents.

We also defended a pioneering portfolio of Radio-Frequency cooking patents against concerted attacks from major white goods manufacturers. Our robust defence cleared the way for a significant licensing agreement for our client.

Get in touch

Alexander Korenberg

Tech & Engineering | Contact Alex akorenberg@kilburnstrode.com

Tom leonard

Life Sciences | Contact Tom tleonard@kilburnstrode.com

Elizabeth Crooks

Chemistry | Contact Elizabeth ecrooks@kilburnstrode.com

Recommended reading

The Pre-Launch Patent Playbook: Tactical Responses to Patent Obstacles

On 1 July 2025, Emer Bollinghaus, Nick Shipp, and Alexander Korenberg discussed tactical responses to patent obstacles in the finale of our three-part series on IP risk analysis.

Opposition Hotspots: Which medical technology sectors face the highest rate of EPO opposition?

Which MedTech sectors see the most oppositions at the EPO? Which MedTech patents are safer from being revoked or limited via EPO opposition?

G1/24: Claim Interpretation Score Card - who wins: Patentees or Opponents? 

The EPO Enlarged Board of Appeal (EBA) has issued its much-anticipated decision in G1/24, confirming a foundational principle of European patent law: the claims must always be interpreted in light of the description and drawings. The decision definitively sets aside a divergent line of case law which held that the description should only be consulted when the claims are ambiguous.

G1/24: EPO Enlarged Board’s decision extinguishes uncertainty on patent claim interpretation

Yesterday, the Enlarged Board of Appeal issued their decision on case G1/24 regarding how patent claims must be interpreted when assessing patentability.

8 July 2025 - Fast response webinar: EPO Enlarged Board of Appeal Decision G1/23

Today, the EPO Enlarged Board of Appeal handed down decision G1/23, dealing with the treatment of complex commercially available products as prior art. G1/23 asked the EPO to answer several key questions.

R 12/21: Petition for review succeeds after EPO Board of Appeal found to violate right to be heard

The petition for review procedure under Article 112a EPC allows parties adversely affected by a decision of the Board of Appeal (BoA) to request a review by the Enlarged Board of Appeal (EBoA). The bar for an admissible request is high; only fundamental procedural violations may form the basis for a review.

Can “public prior use” be relied upon to invalidate European patents?

The “state of the art” for assessing novelty and inventive step at the European Patent Office includes “…everything made available to the public by means of a written or oral description, by use, or in any other way…”.

24 March 2025 - Latest lessons from the EPO - 2024 case law review

We would love you to join us for a virtual event on Monday 24 March as Kilburn & Strode’s patent experts reflect on some of the most influential case law that emerged from the EPO last year while identifying some key take-away practice points.

A cautionary tale for medical use claims in Europe

A recent, first-instance decision from an Opposition Division (OD) suggests that the European Patent Office (EPO) could tighten their assessment of medical use claims under Article 123(2) EPC (the requirement that a patent or application does not extend beyond the content of the application as originally filed). Here, the OD decided that a medical use claim is “directly and unambiguously” disclosed only if the application as filed provides a “certainty of success” that the therapeutic effect is actually attained for the specifically claimed embodiment.

Prior use ''pitfalls'' – three key tips for success in EPO oppositions

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