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Godemeyer Blum Lenze   werkpatent

Interesting facts


Validy of European patents in danger: anticipation by filing divisional applications ("poisonous" or "toxic" patent applications)

In recent years new problems for the validity of European patents arose from the case law of the Boards of Appeal (T 1496/11) of the European Patent Office: so-called poisonous or toxic divisional applications may anticipate their respective parent application and vice versa.

Applicants face a new problem when seeking protection for their inventions. European patent applications may be refused or patents be revoked because a European patent application of the same patent family and claiming the same priority becomes anticipatory state of art for the patent application or patent under examination. What is the reason for this?

Most patent filing strategies involve one or more national first filing(s) and a subsequent direct EP application or PCT application designating EP, of which the subsequent application claims priority of the first filing. Applicants and patent practitioners are used to amend the subsequent application to some extent in view of further new developments carried out and data obtained during the priority year. In some cases, the subsequent application is amended by features being generalized, limited or new features being introduced. Such re-drafting of the subsequent application may, however, implant the first element causing invalidity of the EP application or patent at a later stage:

Namely, if the claims of the European patent application in question are amended during the examination procedure in that way that features are introduced, which are not directly and unambiguously derivable from the prior application, such claim will not be entitled to the priority. This is because under such circumstances the EPO will not recognize that the subject-matter of the claim under examination refers the same invention as described in the prior application. Consequently, the priority is lost.

In the absence of any further relevant prior art, the claim (not entitled to priority) will be valid. However, filing a divisional application may create prior art which may destroy the novelty of the parent application: According to Article 54 (3) EPC the content of a European patent application having its filing date prior to the filing date of the patent application under examination, and which is published later, represents prior art for the assessment of novelty.

If the divisional EP application discloses examples or embodiments, which have already been disclosed in the prior application, then such disclosure will be entitled to the priority claimed in the divisional application. If such examples or embodiments fall within the scope of the claim of the parent application or patent, then novelty of such claim is destroyed. The disturbing aspect of the recent ruling of the case law is that validity of the parent application or patent completely depends on a procedural action of the applicant long after filing the parent application: namely to file or not to file a divisional application with the same text as the parent application!

Strategies to overcome or to avoid the problem

There are several – but not really satisfying – options how to avoid problems. The following options reflect the situation that a divisional application may anticipate a parent application not entitled to the priority. It should be kept in mind that the toxic anticipatory effects may also occur vice versa and among several divisional applications: 

  1. filing a PCT application as first filing designating EP, while avoiding first filing;

  2. no re-drafting of subsequent EP or PCT application versus first filing;

  3. not filing divisional application; or withdrawing divisional application before publication;

  4. removing from the text for the intended divisional application any matter which may anticipate the claimed subject-matter of the parent application;

  5. not claiming priority when filing the divisional application; or removing priority claim before publication of divisional application.

  6. introducing disclaimer into claim (not entitled to priority) of parent application disclaiming subject-matter (entitled to priority), which is intended to become part of divisional application.

It is self-evident that the options listed may be disadvantageous in respect to other aspects or even may form the reason for other objections: For example option IV may pose a problem in respect to enablement, while option V may have the result that further relevant prior art may be cited against the divisional application.

In order to estimate the likelihood of problems the patent practitioner representing the European patent application(s) needs to know if and which amendments were made in the subsequent PCT application versus the first filing.

We at werkpatent® will keep on watching the case law and further developments in respect to possible legal initiatives relating to this issue and will report about the outcome.


© Dr. Erwin Blum

Patent attorneys   European patent trademark and design attorneys