The issue of “double patenting” arises in the EPO when one applicant files two European patent applications with closely related claims and the same effective filing date. A situation where double patenting commonly needs to be considered is when the claims of a divisional application overlap with the claims of its parent application. Under such circumstances it is necessary to determine how much overlap between the claims of the two applications should be permitted. The case law has developed such that the EPO will generally allow substantial overlap between the claims.
Double patenting considerations may also arise when a first European patent application claims priority from a second European patent application. Questions concerning double patenting in this situation were referred to the Enlarged Board of Appeal in February 2019. This referral should result in further clarification of EPO practice in relation to double patenting.
The European Patent Convention (EPC) contains no explicit statutory prohibition against double patenting. However, the Guidelines for Examination in the EPO indicate that "it is an accepted principle in most patent systems that two patents cannot be granted to the same applicant for one invention" (Guidelines, section G-IV-5.4).
Our day-to-day experience of prosecution in the EPO is that substantial overlap between the claims is permitted. If we obtain grant of claims to a narrow species in a parent application, the EPO is very likely to allow claims to a broader genus that encompasses the species in a divisional application (and vice versa). For example, a parent application could contain a claim specifying copper, and a divisional application could contain a broader claim specifying any metal. We find that objections of double patenting are generally upheld only where there is no practical difference between the subject-matter of the claims.
Consistent with our experience, the Guidelines for Examination in the EPO state that:
"… in the rare case in which there are two or more European applications from the same applicant … and the claims of those applications … relate to the same invention, the applicant should be told that he must either amend one or more of the applications in such a manner that the subject-matter of the claims of the applications is not identical, or choose which one of those applications he wishes to proceed to grant."
"If the claims ... are merely partially overlapping, no objection should be raised."
This approach is supported by the case law of the EPO’s Boards of Appeal, as summarised below.
T0318/14 is an appeal against an examining division decision to reject a European patent application. The examining division rejected the European patent application on the basis that it claimed "100% identical" subject-matter to its already-granted European priority application, and referred to earlier Enlarged Board of Appeal decisions G1/05 and G1/06 in its reasoning.
The appellant argued that it did indeed have a legitimate interest, namely an additional year of patent term, in accordance with the reasoning of T1423/07 discussed above. The Board of Appeal considered that there was conflicting case law on this issue, and so referred the following questions to the Enlarged Board of Appeal.
1. Can a European patent application be refused under Article 97(2) EPC if it claims the same subject-matter as a European patent granted to the same applicant which does not form part of the state of the art pursuant to Article 54(2) and (3) EPC?
2.1 If the answer to the first question is yes, what are the conditions for such a refusal and are different conditions to be applied where the European patent application under examination was filed
a) on the same date as, or
b) as a European divisional application (Article 76(1) EPC) in respect of, or
c) claiming the priority (Article 88 EPC) in respect of a European patent application on the basis of which a European patent was granted to the same applicant?
2.2 In particular, in the latter case, does an applicant have a legitimate interest in the grant of the (subsequent) European patent application in view of the fact that the filing date and not the priority date is the relevant date for calculating the term of the European patent under Article 63(1) EPC?
Although the Enlarged Board of Appeal may decide to confine its decision to answering question 2.2 above, it may additionally decide to address the issues of what constitutes a "legitimate interest" more generally and/or what is meant by "the same subject-matter". A decision is expected in 2020.
The EPO's case law suggests that double patenting objections are unlikely to arise provided that the claims in question can be shown to have non-identical scope. A mere difference in wording of claims is unlikely to suffice. However, a double patenting objection should be avoided where one of the claim sets contains a meaningful feature that is not present in the other claim set.
Please do not hesitate to contact us should you have any questions or require any advice about the issues raised in this briefing.
 The claim form "use of X for the manufacture of a medicament for therapeutic application Y" was approved by the Enlarged Board of Appeal in its decision G 5/83 (EISAI) and until December 2007 was the only means of claiming second and further medical indications of a known substance or composition having a previously known medical utility. Such claims remain available for European applications that have a priority date of earlier 29 January 2011 (for later applications only the purpose-limited product claim form is permitted).