Submitting experimental examples at the European Patent Office (EPO) after filing

A common question asked by our colleagues outside Europe is whether the EPO allows applicants to submit new experimental examples, which are not disclosed in the specification, during prosecution to support the claims.  This note was written to answer that question.

In general, there are two ways in which experimental examples in a European patent application support a claimed invention:

  • Examples are often required to provide an enabling disclosure of a claimed invention, as required by Article 83 EPC.
  • Examples can establish that a claimed invention provides a particular technical effect, which can be crucial for supporting an inventive step.

In very broad terms, at the point of filing, an application must include enough information to meet the requirement of Article 83 EPC and to establish any technical effect forming the basis for an inventive step.  Additional examples can be placed on the record later to confirm the effect of the invention.  However, late-filed examples cannot be incorporated into the specification and cannot be used to meet the enablement requirement of Article 83 EPC.

The standard for an invention being enabled

Article 83 EPC stipulates that the European patent application shall disclose the invention in a manner sufficiently clear and complete for it to be carried out by a person skilled in the art.

In accordance with the case law of the Boards of Appeal, Article 83 EPC has been interpreted as meaning that the whole subject matter which is defined in the claim should be enabled, without undue burden, by the teaching of the patent specification.  The patent monopoly should not be extended to subject matter which, after reading the patent specification, would still not be at the disposal of the skilled person (EPO Board of Appeal decision T435/91).

Experimental examples in the application at the time of filing

EPO case law states that an invention is in principle sufficiently disclosed if at least one way of carrying out the invention is clearly indicated enabling the skilled person to carry out the invention (T292/85).

The EPO Guidelines for Examination state (at F-III, 1) that a single example may suffice, but where the claims cover a broad field, the application should not usually be regarded as satisfying the requirements of Article 83 EPC unless the description gives a number of examples or describes alternative embodiments or variations extending over the area protected by the claims.

In practice, the number of examples required to meet the requirement of sufficiency / enablement will depend on the facts and evidence of the particular case.  There can be situations where even a broad field is sufficiently exemplified by a limited number of examples or even one example, but in such cases the application must contain, in addition to the examples, sufficient information to allow the person skilled in the art, using his common general knowledge, to perform the invention over the whole area claimed without undue burden and without needing inventive skill (T727/95).

If the claims define the invention, or a feature thereof, in terms of parameters, the application as filed must include a clear description of the methods used to determine the parameter values, unless a person skilled in the art would know what method to use or unless all methods would yield the same result (EPO Guidelines for Examination at F-III, 2).

It is a requirement that the technical teaching disclosed in the application under Article 83 EPC is reproducible (EPO Guidelines for Examination at I-E, 2).  A reasonable amount of trial and error is permissible, e.g. in an unexplored field or where there are many technical difficulties, but the skilled person has to have at his disposal, either in the specification or on the basis of common general knowledge, adequate information leading necessarily and directly towards success through the evaluation of initial failures (T226/85). Where the skilled person can only establish by trial and error whether or not his particular choice of numerous parameters will provide a satisfactory result, this amounts to an undue burden (T32/85).

For therapeutic applications, attaining the claimed therapeutic effect is a functional technical feature of the claim, and as a consequence, unless this is already known to the skilled person at the priority date, under Article 83 EPC the application must disclose the suitability of the product for the claimed therapeutic application.  It may be sufficient to show a pharmaceutical effect in vitro, if for the skilled person this observed effect directly and unambiguously reflects such a therapeutic application (T609/02).  A claimed therapeutic effect may be proven by any kind of data as long as they clearly and unambiguously reflect the therapeutic effect (T801/06).

Opportunities for presenting new experimental examples after filing

The EPO takes a very strict approach to added matter.  Article 123(2) EPC states that the European patent application or European patent may not be amended in such a way that it contains subject-matter which extends beyond the content of the application as filed.  The requirement of sufficiency of disclosure under Article 83 EPC therefore must be complied with as from the day of filing.  If the disclosure is insufficient, such a deficiency cannot be cured subsequently by adding further examples without offending against Article 123(2) EPC.  There is, therefore, no opportunity for adding new examples to the specification.

If the disclosure is insufficient only in respect of some embodiments of the invention and not others, it could be remedied by restricting the claims to correspond to the sufficiently described embodiments only (EPO Guidelines for Examination at F-III, 2).

It may be possible to file new experimental examples during prosecution to support an inventive step argument.  This can be done in the form of a declaration or affidavit, or simply as an ‘experimental report’.  Case law states that such post-published evidence can only be used to back up the teaching derivable from the application (T716/08); it may not serve as the sole basis to establish that a technical problem is solved (T1329/04).

One common reason to submit new experimental examples in support of an inventive step argument can be to convince the EPO that an inventive step is present for a broader scope of claim than the EPO may be willing to grant initially.  For example, in chemical patent applications it is relatively common for EPO examiners to accept that examples in the application show a technical effect for the particular compound which is exemplified in the application, but to object that it cannot be expected that all compounds covered by a broad claim would have that same technical effect.  They could therefore object that the technical problem is not solved over the whole range claimed and hence the claim lacks an inventive step.

Such an objection can often be overcome by filing further experimental examples, if such further examples show that the technical effect is also observed for different compounds falling within the broader scope claimed.  It can then be argued that, based on the available experimental examples, it is reasonable to predict that the desired technical effect would be present over the whole range claimed, and that the broader claim therefore has an inventive step.

This update is for general information and does not constitute legal advice. For further information, please contact Freija Glansdorp on +44 1934 745 880, or at, or your usual contact at Greaves Brewster LLP.