UPC Raises the Bar for Staying PI Cases During EPO Oppositions

On 29 August 2026, the Unified Patent Court Court of Appeal set out a stricter approach to requests to pause preliminary-injunction proceedings when an EPO opposition is running in parallel. The existence of an opposition, even one moving on an accelerated timetable, is not enough on its own. A defendant seeking a stay must put forward an invalidity case strong enough to show a very high likelihood that the patent will be revoked at the EPO.

The ruling narrows the tactical value of using EPO opposition proceedings to slow urgent UPC relief. Patent owners gain more confidence that a PI application will continue on its own timetable, while defendants will need to front-load their best prior-art attacks and, where appropriate, seek accelerated EPO handling rather than rely on procedural overlap alone.

Parallel opposition does not itself justify a stay

The procedural point is important because it keeps the stay analysis focused on the quality of the invalidity case, not simply on the existence of another forum examining the patent. A pending EPO opposition may remain relevant, but it does not automatically displace the UPC's interest in deciding urgent provisional relief quickly.

Acceleration at the EPO becomes more strategically important

The EPO already allows opposition proceedings to be accelerated when related UPC litigation is pending. After this ruling, defendants have a stronger reason to coordinate the two tracks: they need persuasive prior art before the UPC while also trying to obtain an early EPO view that may carry practical weight in the stay analysis.

Invalidity arguments need to be ready earlier

For defendants, a general assertion that the EPO may ultimately revoke the patent is unlikely to carry much weight. The better approach is to identify the strongest prior art, map it clearly to the asserted claims and explain why revocation is genuinely probable. Patent owners, in turn, should stress-test the same vulnerabilities before filing for a PI; speed at the UPC should not be treated as a substitute for a robust validity position.