Which prior art is the closest?

Case Law Patents

In this opposition appeal the respondent (patentee) argued that a prior art D12 is less close than D1 and therefore should not be considered for an alternative problem solution approach. D1 and D12 were both in the same field and concerned the same problem, but differed in the distinguishing features. The Board did not go along and deemed that if two prima facie relevant prior arts are available, two problem solutions approaches are appropriate. In case one of these arts takes away inventive step this art is the closest. For the current case the claims were deemed inventive over both D1 and D12.

We consider it purposeful to take account of documents D1 and D12 as alternative starting points in the prior art...

Board of Appeal -

The invention related to microspheres of risperidone, a medicament for schizophrenia. The encapsulate comprised a blend of a low and a high molecular weight polylactide-co-glycolide (PLGA) polymer which were both ‘uncapped’. According to the patent the claimed release system provided for low and high drug loading without a lag phase or burst-release and good storage properties.

The selection of the closest art was the central discussion point in this appeal; the respondent (patentee) argued that D12, as being a more remote prior art should be ignored and only a problem solution approach starting from D1 should be considered.

D1 concerned a similar release system as the claims of the patent comprising two different PLGA polymers with different molecular weights. The release system of D1 differed in that the high molecular weight PLGA of D1 was ‘capped’ has a different lactide-glycolide ratio compared to the claims of the patent.

D12 was also concerned with a PLGA release system and concerned several uncapped PLGA polymers falling within the lactide-glycolide ratio and molecular weights of the claims of the patent. However D12 did not mention blends.

In the decision the Board took both D1 and D12 into account as closest prior art. In its motivation in reason 2.2 the Board referred to established case law of the Boards of Appeal (section I.D.3.1 to I.D.3.4 of the 9th edition of the Case Law book). The Board first elaborated on the situation that a prior art is present that is convincingly the closest. When a single closest prior art can convincingly be selected and inventiveness is established, attempts to argue a lack of inventive step starting from less promising starting points are bound to fail. Therefore arguments that such less promising prior art should be considered is generally not persuasive.

However, for the current case the Board saw two prior arts that did not appear prima facie unsuitable to deny the claimed subject-matter an inventive step. Therefore the Board ‘considered it purposeful to take account of documents D1 and D12 as alternative starting points in the prior art without attempting to determine from the outset which of documents D1 and D12 would effectively represent the closer prior art.’

Unfortunately for the appellant both alternative problem solution analyses lead to the conclusion that the claims were inventive, both D1 and D12 did not take away inventive step.

EPO Case Law

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