The EPO favours the problem-solution approach in the assessment of inventive step. This involves identifying the closest prior art, as the prior art document that provides the most promising starting point for an obviousness attack. However, the step of identification of the closest prior art in the problem-solution approach creates a potential tension with one of the most fundamental aspects of inventive step analysis: the avoidance of hindsight.

Recent EPO Board of Appeal case T 0605/20 provides a reminder any tendency to hindsight based on knowledge of a drug’s success in the clinic or otherwise should be avoided.

On appeal against the maintenance of EP1687019 during opposition proceedings, the Appellants argued that the claims lacked inventive step. The key difference between the claimed invention and the closest prior art document was the use of a different isotonic agent (propylene glycol instead of mannitol).

The Appellants argued that the skilled person would recognise the instability issues associated with use of the prior art formulations resulted in the formation of undesirable deposits. The Appellants further argued that it would have been obvious to the skilled person to replace the prior art isotonic agents with propylene glycol in order to solve the problem.

The Board of Appeal found that there was a lack of any indication in the prior art that the formulations could or should be tested for their propensity to form deposits. As such, the Board of Appeal found that the undesired phenomena forming the basis of the objective technical problem to be solved by the claimed invention would not have been inevitably manifest upon the practical implementation of the teaching of the prior art. Recognition of the problem to be solved was therefore identified as part of the inventive contribution of the claim. The Board of Appeal therefore dismissed the Appellant’s obviousness attack for being based on hindsight.