Background

EP2513134B1 claimed “A method of producing a purified antibody”, which included a step of washing with a wash solution comprising a number of ranges. During opposition, Novartis AG (the patentee) filed a main request that further defined a range for the pH of the wash solution.

In its decision, the Opposition Division rejected the arguments of the opponents in relation to added matter, sufficiency and inventive step, and allowed the claims of the main request. Appeals were filed against the decision of the Opposition Division, which included the successful attacks relating to added subject matter that led to the revocation of the patent.

Disclosure of the application as filed

Focusing on the disclosure relating to the wash solution, claim 1 of the main request required a combination of selections including:

1. the concentration of arginine or arginine derivative in the wash solution.
2. the concentration of the non-buffering salt in the wash solution.
3. the pH of the wash solution being greater than 8.0.

For feature (1), the application as filed disclosed a concentration of “between 0.05 M and 2.0 M [...] more preferably between 0.05 and 0.85 M [...] most preferably between 0.1 and 0.5 M” (emphasis added). Claim 1 of the main request recited the intermediate preferred range (“more preferably”) of these three originally disclosed levels of preference.

For feature (2), the application as filed disclosed a concentration “typically is between 0.1 and 2.0 M…, or between 0.5 M and 1.5 M,… or between 1 M and 2 M”. Hence, the application as filed disclosed a broad range and two sub ranges, with claim 1 of the main request reciting the broad range.

For feature (3), the application as filed disclosed “the pH of the one or more wash solutions is greater than 8.0, preferably at least 8.1, more preferably at least 8.5 and even more preferably at least 8.9” (emphasis added). Claim 1 of the main request recited the broadest preferred range (“is greater than 8.0”) of the multiple levels of preference for the pH value.

Decision of the Board of Appeal

The Board of Appeal identified that feature (1) “unmistakably” related to an intermediate level of preference, while features (2) and (3) related to the selection of the broadest disclosed ranges. The Board of Appeal then concluded that the main request was not allowable because “the combination of the features… is based on multiple selections at different levels of preference without any pointer being present in the application as filed for these selections”.

For the auxiliary request, the claimed wash solution defined a combination of the most preferable range of feature (1), one of the sub-ranges of feature (2), and a pH range for feature (3) having a lower limit corresponding to the intermediate level of preference described as more preferable.

The proprietor argued that basis for the combination was provided by examples disclosed in the application as filed. The Board of Appeal agreed for features (1) and (3) because the examples disclosed values representative of the limits of these claimed ranges, but not for feature (2), because the relevant values in the examples fell within both the broader and more specific ranges, and hence could not be used to distinguish between these ranges.

Conclusion

This case demonstrates that the amendments relating to features disclosed with increasing levels of preference should be treated with a degree of caution, and reinforces the importance of clear and unambiguous pointers for combinations for the assessment of Article 123(2) of the European Patent Convention (EPC).

In line with this decision, the use of preferable language is not sufficient in and of itself to provide a pointer to every permutation of described features, and importantly it is not possible to simply amend down each separate list in order of preference until a novel and inventive claim is arrived at.

This creates a problem in that suitable basis in an application may require the explicit linking of different features with multiple levels of preference, which leads to a significant burden when drafting and the potential ballooning of specifications if all permutations are described. Furthermore, this could create potential issues in which all permutations are equally pointed to, and hence the skilled person is not pointed to any particular combination over any other.

A pragmatic approach may therefore be needed in which advantageous synergistic combinations of related features are identified and defined at the drafting stage to provide suitable fall-back positions.