Co-pending applications: Collision course

It is a well-established legal concept in Europe that ‘co-pending’ patent applications are available for the purpose of assessing the novelty of a European patent application that
has been filed between the priority/filing date (the effective date) and publication date of an earlier application. Normally, both a parent application and its related divisional application possess the same effective date for the assessment of patentability and so cannot be cited against one another.

However, the European Patent Office’s (EPO) boards of appeal held, in T1496/11, that a divisional application may, in certain circumstances, be considered to be a co-pending patent application for the purpose of assessing novelty of its own parent application (or vice versa). These applications can be described as ‘self-colliding’ (also commonly referred to as ‘poisonous divisionals’).

How does self-collision occur?

The concept of self-collision occurs when a broad (generic) claim in the parent application is found not to have a valid priority, but a related divisional application describes a specific (narrower) embodiment that does possess a valid priority. The invalid priority of the parent application in this situation means the effective date for the assessment of patentability of the parent application is no longer the priority date, but instead changes to the later filing date.

In parallel to this, the divisional application describes narrower subject matter that retains a valid priority date, thereby resulting in the divisional application in effect being ‘filed earlier’ than its own parent and, consequently, available as a co-pending application for the assessment of novelty.

The damage due to the self-collision then occurs because the narrower subject matter of the divisional is a wholly encompassed specific example of the broader embodiment of the parent and, as a result, destroys the novelty of the broader claim in the parent application.

Self-collision can also apply to a first priority-forming application being novelty-destroying to a later application that claims priority from the first application. However, that is provided that the later filed application is found to have an invalid (or partially invalid) priority claim and seeks to protect a broader claim scope than a specific example disclosed in the priority application. It is worth noting that this concept applies to priority-forming and priority-claiming applications only to the extent that they are both filed in the same territory (eg, both are European applications).

A typical example of self-collision would include a disclosure of a single antibody to a specific target (and which has a valid priority) in a divisional, whereas the claim of the parent that loses priority is directed more generally to binding molecules to the same specific target. Applying the logic of T1496/11 would lead to the binding molecules of the parent lacking novelty over the antibody of its own divisional.

New practice

Before T1496/11, and despite some academic consideration of the hypothetical possibility of self-collision occurring, it had never been seriously contemplated that a patent office would apply the concept. Therefore, the outcome of T1496/11 had, at least initially, worried many European practitioners because it placed a significant number of European applications in the potentially impossible-to-overcome situation of becoming prior art against a related application that had no possibility of a valid priority claim.

However, European practitioners have, relatively quickly, adapted their patenting strategies to limit the potential impact of self-collision. For example, preventing publication of a same-country priority application will prevent a priority-forming application destroying the novelty of the priority-claiming application; and ensuring that all commercially-significant claims filed at the EPO have a valid priority claim will prevent self-collision between parent and divisional.

"Ensuring that all commercially-significant claims filed at the EPO have a vaild priority claim will prevent self-collison between parent and divisional"

Furthermore, the potential tidal wave of objections based on T1496/11 from the EPO itself has not come to pass. EPO examiners, whether intentionally or not, do not appear to have latched on to this decision as a means of objecting to one or more related patent applications in a family. Attacks using self-collision have, however, rapidly become popular in opposition practice, with opponents using self-collision as an effective way of revoking or forcing significant amendments with relatively little effort.

Formal review

The issue of priority validity and its impact on availability of prior art, including self-colliding applications, was, in December 2014, the subject of further EPO boards of appeal proceedings. In T557/13, the issue in question has arisen based on arguments regarding the validity of the priority itself. Ultimately, however, it relates to a self-collision scenario with novelty of the divisional patent in question hinging on whether the claimed broader embodiment can validly claim priority to a narrower embodiment that is also disclosed (and has a valid priority) in the immediate parent patent application.

The prevailing case law applicable to whether the priority claim in T557/13 includes a divergence of opinion on whether a small number of narrow embodiments can give rise to any level of valid priority (including what is referred to as a partial priority) for a generic embodiment encompassing them.

The concept of partial priority has long been acknowledged to exist in relation to a claim covering a broader range of embodiments than the priority document, such that a selection of embodiments of the claim may be entitled to priority whereas other embodiments are not. However, this has previously been specifically where the claim in question lists each embodiment separately, so it is possible to clearly identify which of that list was also listed in the priority document and therefore entitled to priority.

The situation in T557/13 (and other self-collision cases) is different, as there is no easily identifiable list of embodiments that are listed in the priority application. Instead, to acknowledge partial priority for a generic claim, it must be accepted that a notional (and not explicitly disclosed) narrower embodiment exists alongside the narrower explicitly disclosed embodiment of the priority.

This can be exemplified by referring back to the antibody-binding molecule example discussed above, whereby a claim to binding molecules would possess a valid partial priority for antibodies, but no valid partial priority for the notional part of “binding molecules excluding antibodies”.

If such partial priorities are allowable then self-collision cannot occur because (a) the partial priority for the narrower embodiment portion of the claim is valid and so the parent is not prior art for that portion; and (b) the partial priority for the notional remainder of the claim is not valid for both the claim of the divisional and the parent such that both the parent and divisional change their effective date to the filing date for the notional embodiment, therefore meaning the parent is not novelty-destroying.

Going to the highest level

The idea of notional undisclosed embodiments has not been legislated for or considered at the highest level at the EPO, so over the last few years the boards of appeal have come to differing conclusions regarding whether partial priority claims in this situation are possible. The board in T557/13 therefore decided that due to these conflicting boards of appeal decisions and their importance in assessing novelty, the issue of priority self-collision should be referred to the Enlarged Board of the EPO.

At the time of writing, the exact questions to be referred to the Enlarged Board have not been published. However, based on the proceedings in T557/13 to date, it is reasonable to suppose that the questions should, at least, cover the following areas:

May a generic embodiment claim a valid priority to one or more specific embodiments wholly encompassed by the generic embodiment?

If not, how should priority be assigned to the generic embodiment in respect of the narrower (but not specifically claimed) embodiments that individually possess a valid priority? Can the generic embodiment claim therefore possess different priority dates (partial priorities) for each embodiment within a generically claimed embodiment?

Does the European Patent Convention (EPC) prevent the generic embodiment of the divisional and the narrower embodiments of the parent being given different effective dates?

If not, does the EPC allow for co-pending applications to include a parent application so that the divisional lacks novelty over its parent?

The answers to these (or similar) questions will provide a better understanding about whether self-collision is a real threat in European practice. In cases where this issue is currently live and critical to validity, the EPO will likely stay proceedings until the Enlarged Board’s decision is handed down.

The decision, when issued, will have a considerable impact on the future of claim drafting and divisional filing strategies in Europe. However, as it may be many months until the decision is issued, applicants should continue to ensure that they minimise their risk of falling into the self-collision trap.

Jane Wainwright is a partner at  Potter Clarkson. She can be contacted at: jane.wainwright@potterclarkson.com.