Plausibility and post-filed data at the EPO part I – a practical guide

Plausibility and post-filed data at the EPO part I – a practical guide

The EPO is currently wrestling with (arguably) one of the most significant legal challenges of the last few decades. This is the saga that is Enlarged Board of Appeal referral G 2/21 (see our previous articles here and here for an introduction) and how should the EPO deal with admissibility of post-filed data and the overall patentability concept of “plausibility”.
This is an article in three parts. Here, we provide a five-minute summary of what you need to know (in a hurry), followed by practical tips for attorneys and applicants to help ensure applications are (plausibly) fit-for-filing and prosecution before the EPO. Part II is an analysis of the technical/legal facts of the appeal behind G 2/21 and provides a digest of post-filed data/plausibility issues in practice. Part III is a deep-dive into the case law for those looking for the detail, and includes insights that can be gleaned from historical decisions on this area of law.

Five-minute summary

In G 2/21, the Enlarged Board of Appeal (EBA) has been referred fundamental questions on plausibility and the admissibility of post-filed data (also known as post-published data). The EBA is the EPO’s highest judicial body, tasked with ensuring the uniform application of European patent law. 
These questions essentially ask the EBA to determine what technical teaching and data must be included in a patent application on filing and what can be added afterwards. The outcome therefore will have broad implications in patent filing strategies, particularly in the pharmaceutical field and other sectors where the race to file is often most acute.
We’ll illustrate the issues by referring to the following hypothetical scenario: an EPO patent Examiner cites prior art and raises an inventive step objection. You believe your invention has a technical effect/advantage which the prior art does not. You file new data to support this – should the EPO admit these data and consider your (arguably “new”) technical effect/advantage? 
Three scenarios are outlined in the table below (left column). G 2/21 will consider three options (right three columns) and hopefully will tell us which will set the standard at the EPO going forward.


Can post-filed data be taken into consideration, if the application as filed:

G 2/21 outcome: what’s the standard?

No plausibility standard

[Low bar]

Ab initio implausibility”
(or “plausibility is assumed” at filing)

[Medium bar]

Ab initio plausibility”
(or “plausibility to be proven” at filing)

[High bar]

- showed the technical effect/advantage was at least plausible (without the data)
- (regardless of suggestions in the prior art); 

✔️ ✔️ ✔️

- did not show the technical effect/advantage was plausible and
- there was nothing at the time of filing (e.g. in the prior art) to suggest it was implausible; or

✔️ ✔️

- did not show the technical effect/advantage was plausible and
- there was something at the time of filing (e.g. in the prior art) to suggest it was implausible?


On 13 October 2022, the EBA issued a preliminary, non-binding, opinion (see our previous article covering this here) indicating that it believes the medium bar “ab initio implausibility” standard should be applied. If this is indeed the outcome of the referral, the EPO would not admit post-filed data in the situation above if there were reasons (at the time of filing) to doubt the “new” technical effect/advantage. However, since this is a non-binding opinion, the legal standard to be adopted is still open for debate at the upcoming oral proceedings.
If the EBA in fact decides that the outcome is the low bar, no plausibility standard, the burden for applicants to include data and explanation of technical effects/advantages achieved by the invention could be reduced. However, if the EBA takes a strict view and applies the high bar “ab initio plausibility” standard, it may not be possible to rely upon post-filed data to support a technical effect/advantage that isn’t already made plausible (e.g. with preliminary evidence, technical explanation) in the application as filed. This means that applicants should carefully consider whether their applications include enough supporting information prior to filing.

Clearly, the outcome could greatly affect filing strategies in Europe, particularly in terms of timing. 

Practical implications for attorneys and applicants

When can we expect a decision?

Although the preliminary, non-binding opinion was issued by the EBA on 13 October 2022, the oral hearing for G 2/21 is not scheduled until 24 November 2022. We’ll follow this closely to see what is discussed on the day and what can be gleaned from the hearing. The written decision will follow afterwards (expected ~Q1-Q2 2023) and we look forward to reporting on this. It is likely that the decision will hinge on specific legal tests and their wording, which may not be announced during the oral hearing, so the written decision will be crucial for us to determine the impact of G 2/21 on this area of law. 

What will be in the decision?

The EBA has been asked to give input on three questions. Essentially, these ask whether the low, medium or high bar mentioned above should apply. The EBA has many options: they may reframe the questions (e.g. determine that a different plausibility standard is needed altogether), answer different questions and/or decide/opine on additional matters relating to plausibility and post-filed data. 
The EBA’s preliminary opinion indicates that the questions will not be reframed, and that they will decide upon one of the three proposed standards. As noted in the summary above, the preliminary opinion suggests that the EBA is in favour of the “ab initio implausibility” standard, but this is non-binding and the final decision may deviate from this.
The decision could have broad precedential applicability to numerous circumstances or could be confined closely to the facts (technical and legal) at hand. The decision will be binding on EPO Boards of Appeal and Examiners dealing with patent applications alike. We hope that the EBA will use this opportunity to at least partially clarify and harmonise this tricky area of law.

What to include on filing an original application to maximise your chances at the EPO

It’s important to bear in mind that European patent law includes numerous safeguards which aim to deter filing of speculative applications for so-called “armchair inventions”. For example, European patent law requires that an invention must be industrially applicable. These and other provisions are oftentimes cited to prevent purely speculative patent applications – see part III of this article for more details. As a result, even if a low bar “plausibility” standard is adopted, it would still be important to include as much information supporting technical effects/advantages as possible in the application as originally-filed.
Top tips – useful information for including in the original application (e.g. to gather during the invention capture process):

  • wet data (actually demonstrating the technical effect/advantage, e.g. in vitro, in vivo, pre-clinical, clinical etc.);

  • in silico or other modelled data1;

  • prophetic (future tense) examples for experiments to be conducted; and/or

  • technical explanations of rationale and theories understood to be underpinning a technical effect/advantage and/or how any of the above information can be extrapolated to a technical effect/advantage.

Other top tips that arise from the case law in this field:

  • consider the unpredictability of your technical effect/advantage – the more unpredictable the effect, the more likely it is that you’ll need comprehensive data or information supporting technical effects/advantages across the scope of the claims2;

  • aim for a set of examples which represents a reasonable generalisation of the claimed subject-matter3;

  • assertions regarding biological/chemical activity may be enough to establish plausibility, though this will be highly fact-specific4.

What could each standard mean for attorneys and applicants?

  • No plausibility standard: low bar

Our advice: the burden for applicants to include information supporting technical effects/advantages achieved by the invention in the original application could be reduced. However, as mentioned above, European patent law includes other safeguards against entirely speculative patent applications. As a result, including information supporting technical effects/advantages in the original application would still be important, even under this low bar standard. We therefore still advise following the top-tips above when drafting original patent applications.
Nonetheless, in strongly competitive fields, where early filing is important to get your flag in the ground before others, this low bar may give applicants more comfort since the burden to provide technical information on filing is arguably lower. Even then, applicants should be prepared to produce data or information supporting technical effects/advantages after filing, e.g. if they are presented with inventive step objections and need to demonstrate that the invention provides an advantageous technical effect. 

  • Ab initio implausibility” standard (plausibility is assumed on filing): medium bar

Our advice: if your invention achieves technical effects/advantages which a skilled person would have legitimate reasons to doubt/consider implausible, then you must ensure these are backed up by technical information supporting those technical effects/advantages in the original application. Here, “legitimate reasons” might include a general belief within the technical field that such a technical effect/advantage is not achievable, and/or a conflict between the conclusions drawn in the application as filed and the conclusions drawn from the post-filed data. Under these circumstances, we should take care to enhance the technical information supporting these technical effects/advantages when drafting original patent applications.
Otherwise, as with the low bar approach, the burden for applicants could be reduced. 
It is worth noting that the referring Technical Board of Appeal (TBA) in G 2/21 had identified several past decisions which they believe applied the ab initio implausibility standard. In all cases, they noted that this standard was deemed to have been passed – the patent application as originally filed did include enough technical information and there was no issue in adding post-filed data to support technical effects/advantages relied upon for patentability. If history is anything to go by, this indicates that the “medium” bar would still be quite generous to patentees.

  • Ab initio plausibility” standard (plausibility to be proven on filing): high bar

Our advice: it will be vital to ensure all key technical effects/advantages are well-supported by technical information in the original application, as anything not originally disclosed could be disregarded by the EPO entirely. Particular attention should be given to enhance disclosure around technical effects/advantages expected to be relied upon for patentability (e.g. for inventive step). It will also be vital to ensure that any explicitly claimed technical effects or advantages themselves are well-supported (this commonly arises where a claim includes a functional feature or method step). For example, if a claim is directed to the treatment of a specific medical condition, then it is vital to ensure that this technical effect is well-supported.
This is a rather high bar – in all decisions identified by the referring TBA as applying the ab initio plausibility standard, the standard was deemed to have not been passed. This suggests that the “high” bar could be quite challenging to patentees and the top tips above should be followed closely.
We’re closely monitoring developments: we’ll report further as G 2/21 progresses and the legal landscape becomes clearer. For more information please contact Nick Lee, James Snaith, Joseph Etherington, or your usual Kilburn & Strode advisor.


1 See T 898/05, Reasons 22: “[in silico data] can often allow plausible conclusions to be made regarding the function of a product before it is actually tested”.
2 See T 939/92 (AgrEvo, discussed in pt. III of this article), Reasons 2.6.2, where a technical effect (herbicidal activity) was considered unpredictable and plausibility was not established.
3 In the AgrEvo example above, the TBA concluded that the examples and data included on filing did not represent a reasonable generalisation of the claimed compounds.
4 See T 2015/20, Reasons 2.7, for an example of an assertion regarding activity which did establish plausibility.

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