Patent Plausibility Uncertainty Persists, EPO Petition Shows

• Published date: 02 April 2024
• Subject Matter: Intellectual Property, Patent
• Law Firm: Finnegan, Henderson, Farabow, Garrett & Dunner, LLP
• Author: Ms Yelena Morozova, Craig Slater, Ph.D., Jamie Barcombe, Maeve O'Flynn, James G. Bell and Ali Badreddine

Patent applicants may face a plausibility challenge at the European Patent Office, or EPO, even though the concept of plausibility is nowhere to be found in the European Patent Convention. This concept generally concerns the idea that a purported effect of the claimed invention, e.g., a treatment of a particular disease, must have been credible to the skilled person at the time of filing of the application based on the disclosure in the application as filed.

The March 23, 2023, decision in the Enlarged Board of Appeal referral, known as G2/21, was expected to provide guidance on the application of the plausibility concept. However, a petition for review filed by the appellant/opponent on Jan. 17, 2024, in the appeal proceedings¹ that led to G2/21 referral shows that the uncertainty remains.

In the G2/21 referral, the Enlarged Board of Appeal was asked to provide guidance on the degree to which a technical effect relied upon for patentability must be rendered "plausible" from the application as filed. This issue can be of critical importance, especially in the life sciences field where patent applications are often filed before full clinical trials commence, meaning that the evidence available at the filing date to render the technical effects of the invention plausible is typically limited.

The case law of the Boards of Appeal was inconsistent on the standard to which plausibility was to be assessed, resulting in much uncertainty for applicants.

It was hoped that the Enlarged Board of Appeal would provide clear guidance on this point in G2/21. However, the Enlarged Board of Appeal rejected the notion of plausibility as a distinct concept, and set out a new framework for assessing whether a technical effect may be relied upon. By doing so, rather than clarifying the situation, the Enlarged Board of Appeal added to the uncertainty due to the need to interpret the new framework.

The recent petition for review shines a light on the uncertainty that still surrounds the issue of plausibility at the EPO, and the outcome could provide useful guidance on how the Enlarged Board of Appeal's orders in G2/21 should be interpreted.

What is plausibility?

Plausibility is not a formal requirement for patentability at the EPO. Instead, it is a concept that the Boards of Appeal have developed through case law for the assessment of both sufficiency of disclosure and the inventive step.

In relation to sufficiency of disclosure ' where a technical effect or purpose is claimed, e.g., a therapeutic application ' for an invention to be accepted as being sufficiently disclosed, the application, in combination with the common general knowledge, has to render it technically plausible that the invention does indeed provide the claimed technical effect or is suitable for the claimed purpose.²

In relation to the inventive step, plausibility is...