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Innocuous priority

10th Feb 2017

In a series of articles over the last couple of years, I have discussed poisonous priority, its potential implications and its referral to the EPO’s Enlarged Board of Appeal in G1/15. In January 2017, I reported an order from the Enlarged Board which strongly suggested that the issue of poisonous priority was dead.

Last week, the Enlarged Board issued their full written decision which finally puts poisonous priority to bed.

The concept of poisonous priority includes the situation whereby a European (or UK) divisional application could destroy the novelty of a claim in a parent patent or application that is not entitled to priority, or vice versa. It also includes the situation where the novelty of a European (or UK) patent or patent application is compromised by the publication of its own priority application. Poisonous priority in the context of divisional applications may be illustrated as follows.

  • Application 1 – This priority patent application discloses a relatively narrow chemical formula (a) supported by representative examples.
  • Application 2 – This European patent application discloses and claims a broader chemical formula (A) which, within its scope, includes (a), and which is supported by additional examples justifying A. This application claims priority to application 1.
  • Application 3 – A divisional application is filed based on application 2, which contains the narrow chemical formula (a).

During the past few years, the concept of poisonous priority has been discussed in many articles and patent cases. It has been suggested that Application 3 is novelty-destroying for the claim of application 2 because formula (a) is entitled to the priority date (i.e. the filing date of Application 1) but formula A is not entitled to the priority date. Application 3 is novelty-only prior art against the claim of Application 2.

A potential remedy has been suggested which involves splitting the claim of Application 2 into two theoretical alternatives:

1. Formula A, excluding (a);
2. Formula (a).

The first alternative is not entitled to priority but it excludes (a) and so is not anticipated by (a) in Application 3. The second alternative is entitled to priority and so is not anticipated by (a) in Application 3.

It has been suggested that by considering the claim in this way, any issue of poisonous priority is overcome.

Acceptance of this remedy by the EPO was subject to the interpretation of Enlarged Board of Appeal decision G2/98, which concerns the situation in which a claim may have different priority dates. G2/98 held that “the use of a generic term or formula in a claim for which multiple priorities are claimed… is perfectly acceptable… provided it gives rise to claiming of a limited number of clearly defined alternative subject-matters“.

Some Board of Appeal decisions (such as T1127/00, T1443/05, T1877/08, T0476/09) have interpreted this requirement in a narrow sense, to require that the claim itself defines this limited number of clearly defined alternative subject-matters, or that the clearly defined alternative subject-matters are explicitly identified as such in the application. By interpreting G2/98 narrowly, it may not be possible to use the antidote as suggested above, because 1) formula A, excluding (a); and 2) formula (a) are not explicitly presented as alternatives in the claim, or in the application as filed.

On the other hand, some Board of Appeal decisions (notably T1222/11 and T571/10) have interpreted the requirement of “a limited number of clearly defined alternative subject-matters” in a broad sense, such that a claim can be split theoretically without requiring the clearly defined alternative subject-matters to be spelt out as such in the application.

This divergence in case law led to the referral to the Enlarged Board from the Technical Board of Appeal (T 557/13). The referral included the following question:

1. Where a claim of a European patent application or patent encompasses alternative subject-matters by virtue of one or more generic expressions or otherwise (generic “OR”-claim), may entitlement to partial priority be refused under the EPC for that claim in respect of alternative subject-matter disclosed (in an enabling manner) for the first time, directly, or at least implicitly, and unambiguously, in the priority document?

In December 2016, the Enlarged Board issued an order that gave an answer to that question:

Under the EPC, entitlement to partial priority may not be refused for a claim encompassing alternative subject-matter by virtue of one or more generic expressions or otherwise (generic “OR”-claim) provided that said alternative subject-matter has been disclosed for the first time, directly, or at least implicitly, unambiguously and in an enabling manner in the priority document. No other substantive conditions or limitations apply in this respect.

In their written decision, the Enlarged board made it clear how partial priority should be considered (my emphasis):

In assessing whether a subject-matter within a generic “OR” claim may enjoy partial priority, the first step is to determine the subject-matter disclosed in the priority document that is relevant, i.e. relevant in respect of prior art disclosed in the priority interval. This is to be done in accordance with the disclosure test laid down in the conclusion of G 2/98 and on the basis of explanations put forward by the applicant or patent proprietor to support his claim to priority, in order to show what the skilled person would have been able to derive from the priority document. The next step is to examine whether this subject-matter is encompassed by the claim of the application or patent claiming said priority. If the answer is yes, the claim is de facto conceptually divided into two parts, the first corresponding to the invention disclosed directly and unambiguously in the priority document, the second being the remaining part of the subsequent generic “OR”—claim not enjoying this priority but itself giving rise to a right to priority, as laid down in Article 88(3) EPC.

The Enlarged Board allowed the conceptual splitting of the claim, with the result that poisonous priority is dead. There is no requirement explicitly to present in the claim the alternatives that are entitled to different priority dates.

This will come as a welcome relief to most patentees and patent applicants, because it had been feared that poisonous priority could have invalidated a large number of granted patents and rendered many applications unpatentable.

This article is for general information only. Its content is not a statement of the law on any subject and does not constitute advice. Please contact Reddie & Grose LLP for advice before taking any action in reliance on it.

Andrew Carridge
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Would you like to know more? You can talk to Andrew Carridge who will be able to help. Call +44 (0)1223 360 350


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