This matter concerns levocetirizine, which is an enantiomer of cetirizine. The Court held that, at the priority date, it would have been obvious to the skilled person to check whether levocetirizine (which had been individually disclosed before the priority date) had improved pharmacological characteristics compared to the racemic mixture (i.e. cetirizine).
As a rule, resolving a racemic mixture into its individual enantiomers and examining the resulting biological activity is an obvious and predictable first step when researching improvements to a drug with a chiral center, except under certain circumstances. The Court found that Sepracor had not sufficiently shown that one of the exceptions to this rule applies in the present case. The skilled person would thus have acted in the same manner since there was a reasonable expectation of success. The Court therefore invalidated the Belgian part of the patent and, consequently, revoked the Belgian SPC.