The EPO’s Enlarged Board of Appeal (EBA), i.e. the EPO’s body of highest instance, has now rendered a milestone decision acknowledging the possibility of claiming priority from an earlier application even when the earlier application discloses only a part of the subject-matter claimed in the later European application.

This follows a conflicting trend in the EPO Board of Appeal (BoA) case law.

In fact, some recent BoA decisions had acknowledged that, where the priority application discloses only a part of the subject-matter claimed in the later European application (e.g. the priority application only discloses embodiment A, while the European application claims embodiments A and B as alternatives to one another), the claims – or part of the claims – of the European application which relate to the subject-matter already disclosed in the earlier application are entitled to the priority date. On the other hand, some other BoA decisions had instead held that, under those same circumstances, the European claims are not entitled to the priority date at all.

This conflicting trend derived from the statement, contained in an earlier EBA decision, whereby “[t]he use of a generic term or formula in a claim for which multiple priorities are claimed … is perfectly acceptable… provided that it gives rise to the claiming of a limited number of clearly defined alternative subject-matters [emphasis added].

The EBA thus set out to determine whether the European Patent Convention (EPC) provisions relating to the priority right should be interpreted so as to include, in addition to any conditions set out therein, also the additional condition that the European claim relate to “a limited number of clearly defined alternative subject-matters”.

The EBA first reviewed the EPC provision establishing the right of priority, emphasizing that
(a) this is a right of the applicant, and
(b) its sole substantive condition is that the invention claimed in the later European application be the same as the one disclosed in the priority application.

The EBA then reviewed the stated purpose of that EPC provision, noting that the legislative history clearly shows that the goal of the priority right is to prevent invalidation of a later claim claiming priority from an earlier application by reasons of any acts accomplished during the priority interval, be they acts accomplished by a third party or by the applicant itself.

Based on these considerations, the EBA concluded that if a claim in the later European application is broader than an embodiment disclosed in the priority document (i.e. if the later European claims covers the earlier embodiment of the priority document and also protects additional embodiments that are alternative to such earlier embodiment), then priority may not be claimed for all other embodiments encompassed by the claim, but it may be validly claimed for such earlier embodiment, regardless of how the European claim is worded (i.e. be it a list of embodiments, a Markush formula, a range, etc.).

The EBA therefore establishes that:

“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 to this respect.”

Given that applicants very frequently develop the invention further during the priority year by identifying additional embodiments that solve the same problem addressed in the priority application, the acknowledgement by the EBA of the possibility of claiming a partial priority under such circumstances is certainly very good news for all users of the European patent system.

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