Knowledge & News

Selecting from lists at the EPO – the “two-lists principle”

21 October 2015

This article first appeared in the AIPLA’s Chemical Practice Chronicles newsletter.

The European Patent Office (EPO) has a reputation for applying a strict approach to assessment of basis for amendment under added matter (Article 123(2) EPC). EPO law dictates that there must be “direct and unambiguous basis” for amendments in the application as filed and the bar for meeting that standard is high.  Much of the EPO case law around this provision has focussed on what constitutes direct and unambiguous basis, and from within this developing legal framework has emerged some useful rules of thumb that can provide guidance for both European and overseas patent practitioners alike.

Selecting subject matter from lists has direct relevance to the examination of added matter and novelty. This is because creating a new combination by selecting features from one or more lists will either mean: a) the amendment will add matter where the lists in question are in the patent application as filed; or b) the amendment will impart novelty where the lists in question are in a prior art document. The underlying reasoning in the cases presented below can therefore be applied to assessment of added matter or novelty in this regard, depending on whether the lists reside in the prior art or the application as filed.

Mono-dimensional restriction of a list

The EPO Guidelines for Examination (Chapter H-V, 3.3) indicate that it is permissible to delete parts of the claimed subject-matter if the corresponding embodiments were originally described as alternative embodiments in the application. The following example of an allowable amendment is provided in the EPO Guidelines:

Original application:
"A polymer blend XY ... containing, as a filler, graphite, talc, asbestos or silica”

Prior art:
"A polymer blend XY ... containing asbestos".

Limited claim:
"A polymer blend XY ... containing, as a filler, graphite, talc, asbestos or silica ".

Indeed, it is now well established EPO law that this mono-dimensional limitation of a list is generally allowable and thus would not add matter or impart novelty. This can therefore be a useful guiding principle when considering whether a possible amendment would add matter or impart novelty in Europe. There are, however, exceptions to this rule, which should always be borne in mind. These exceptions generally relate to the “disclosure status” of the options in the lists concerned and, particularly, to whether the listed options are indeed mere “alternative embodiments”.

For instance, EPO Technical Boards of Appeal Decision T 948/02 concluded that mono‑dimensional restrictions are allowable and thus would not add matter, provided the resulting list differs from the original list only by its smaller size and not because the remaining compounds show improvements or additional effects not otherwise disclosed in the application as filed. In other words, the singling out of a smaller sub-list should not shift the core focus of the invention.

In the more recent decision T1799/12, the patent in suit was a divisional patent and the amendment concerned the restriction of a list to an option that was deemed to have inferior properties to the other listed options. It was decided that each of the individualised alternatives in the list was not an equally viable alternative having the “same quality”. Whilst it remains to be seen how closely this case will be followed by other EPO Technical Boards of Appeal, this case clearly has potential implications for applicants seeking to claim remaining, but inferior, subject matter in divisional applications where the preferred subject matter has already been pursued in a parent case.

The two-lists principle

Whilst the mono-dimensional restriction of a list is typically allowable in Europe, amending a claim by deleting features from two or more lists is not normally allowable.

An early landmark decision was EPO Technical Boards of Appeal Decision T12/81 (Diastereomers).  In that case, it was decided that

If […] two classes of starting substances are required to prepare the end products and examples of individual entities in each class are given in two lists of some length, then a substance resulting from the reaction of a specific pair from the two lists can nevertheless be regarded for patent purposes as a selection and hence as new.

In short, this case established that the combination of two specific features (starting materials in this case), each selected from different lists “of some length” may, when combined, form a newly individualized combination (and thus add matter or impart novelty).

Whilst T12/81 applied this reasoning in the context of the selection of starting materials in a chemical reaction, other cases later followed that applied the underlying two-lists principle to many other types of combinations, eg: 

  • Decision T 7/86 (Xanthines) concluded that this principle applies to polysubstituted chemical compounds resulting from selection of individual substituents from two or more lists of some length (see 5.1 of the reasons).
  • Decision T 401/94 applied this rationale to mixtures of chemical entities. It was decided that a chemical mixture resulting from a selection of individual entities, where each entity had been selected from a relatively long list, is new (see 4.4 of the reasons).

Given the lack of precision of the terms “of some length” and “relatively long list”, decisions in this area have left room for European patent practitioners to argue either way as to whether a given list is long enough for the two-lists principle to apply. Certainly, where there are multiple lists that are clearly very long, there is a good chance that selecting from those lists would be deemed by EPO Examiners to single-out a new combination of features not previously disclosed. T 7/86 (Xanthines), however, showed that lists as short as 2+5 may be considered by the EPO to be “two or more lists of some length”. At the extreme, T 686/99 (Lubricant for refrigerating apparatus/Hitachi) decided that selecting a particular refrigerant from a list of only two, and a lubricant-base oil from a list of only three singled-out a new combination not derivable from the application as filed. This sort of case law may therefore be useful when attacking third party patents under added matter where selections have been made, or when arguing that a particular selection is novel over a prior art document.

When is selecting from two lists acceptable?

Selecting from two-lists can be acceptable in Europe, in certain circumstances. It is important to note that a true singling-out of subject matter would not be allowed by the EPO. Nonetheless, there are instances where selections from more than one list may not be deemed to result in the singling-out of new combinations, and thus would not add matter or impart novelty.

Decision T 783/09 (Antidiabetic combinations/ Novartis) related to a combination made by selecting a specific DPP-IV inhibitor from two equally preferred possibilities, and simultaneously selecting any one of three alternative anti-diabetic compounds from a list of 22 alternative possibilities. In this case, the level of preference of the specific DPP-IV inhibitor was a key factor in the decision. It was concluded that the disclosure should be considered to be a list of 44 distinctly preferred alternatives, i.e. each of the two preferred DPP-IV inhibitors with each of the 22 anti-diabetic compounds. The claimed combination of one of the preferred DPP-IV inhibitors with any one of three anti-diabetic compounds was, therefore, considered to be a selection of three equally preferred alternative options from a single list of 44. Whilst the pros and cons of referring to “preferred” features when drafting patent applications should always be carefully considered, this case highlights an advantage of identifying, in the application as filed, when an option is indeed truly preferred.

Decision T 1733/06 concerned a chemistry case where two lists of 18 and 15 in length were allowed to be limited to marginally shorter lists of 16 and 13, respectively. In this case, an important factor was the extent of the restriction. In particular, the relatively small scale of restriction of these relatively long lists was deemed to be “far from creating a new invention by singling out a hitherto not specifically mentioned individual compound or group of compounds”.  This thread of EPO case law is still not well developed, and outcomes will tend to depend on the facts, but there is a suggestion that deletion of a few components from long lists may (rather counter-intuitively) be more allowable than deletion of a few components from a shorter list, as the overall change in list length is less significant. It remains to be seen, however, where the line of allowability is to be drawn.

In view of the development of EPO case law in this area, amending a claim based on a selection from one or more lists should always be carefully considered against other amendment options. The safest approach in Europe for claiming a specific combination of features is still to base an amendment on an explicit disclosure of that specific combination in the application as filed. The importance of reciting important combinations explicitly when drafting new applications, to avoid recourse to selection from lists case law in Europe, cannot therefore be overstated.


Jonathan Stafford

Jonathan Stafford Partner Manchester (UK) Chartered (UK) and European Patent Attorney

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