The question whether or not the subject matter of a claim is inventive, is routinely determined by the so-called "problem-and-solution approach" (PSA) before the European Patent Office. European case law further teaches that the discovery of an unrecognized problem may give rise to patentable subject matter even in the case where the claimed solution is retrospectively trivial and in itself obvious (see T 2/83). However, the absence of a hint that there might be a problem does not provide proof for the existence of an unrecognized problem (T 252/10).

Presence or absence of an inventive step was, inter alia, the subject of lawsuits between Sandoz and Leo Pharmaceutical in several European states including the Netherlands regarding Leo Pharmaceuticals’ patent EP679154 directed to calcipotriol monohydrate. Calcipotriol is a vitamin D derivative that is effective against psoriasis, a hyperproliferative skin disease. An earlier patent of Leo Pharmaceuticals, EP227826, described an anhydrous form of calcipotriol. EP679154 is directed to the monohydrate of calcipotriol, a crystalline form which was not known and would have superior properties compared to anhydrous calcipotriol.

The Dutch entry of EP679154 was maintained in first Instance, but was rejected by the Court of Appeal in 2013. Using PSA, the Court decided that a skilled person would have been motivated to study other forms of calcipotriol for therapeutic applications. In addition, several documents would have indicated that monohydrous forms of vitamin D analogues might have improved properties, compared to anhydrous forms.

Leo Pharmaceuticals filed a cassation appeal to the Supreme Court. The main argument was that by taking the objective technical problem as a "starting point" in PSA, the Court of Appeal had not grasped that the skilled artisan might not have recognized the problem that was solved by the invention. Hence, the discovery of the unrecognized problem would be indicative of the presence of an inventive step.

The Supreme Court decided on 3 October 2014 that it is not relevant whether the objective technical problem to which the invention offers a solution, would have been recognized by the skilled artisan. What is relevant is whether the invention does not result from the state of the art in an obvious manner. With this remark, the Supreme Court dismissed Leo Pharmaceutical’s cassation appeal and endorsed the decision of the Appeal Court in which EP679154 is deemed to lack inventive step.