g) Level of proof required in case of a serious disease

The board in T 979/23 referred in its communication (Art. 15(1) RPBA) to parent case T 1779/21 and the reasoning therein, both cases dealing with Dravet syndrome. Although the skilled person could conclude, from the data in the patent or the application as filed, that fenfluramine in combination with valproate alleviated some symptoms of Dravet syndrome, it was not clear whether this also applied in the case of a monotherapy. In view of the serious nature of the disease, additional circumstances had to be borne in mind when deciding whether "proof of a claimed therapeutic effect" was provided in the application as filed. In this particular case, where an incorrect therapeutic decision could lead to irreversible damage, the level of proof required had to be at least such that the skilled person had reason to assume that the standard valproate treatment could be discontinued and replaced by fenfluramine without worsening the patient's condition. In T 979/23, the respondents (patent proprietors) alleged that T 1779/21 incorrectly took the severity of the disease into account, which implied a higher standard. The board did not agree because what was assessed in T 1779/21 was whether it was credible that fenfluramine monotherapy could achieve a therapeutic effect in Dravet syndrome. Achieving a therapeutic effect would mean that the therapeutic treatment resulted in at least an amelioration of the patient's condition in some way. This was in particular the case if not treating the disease would have irreversible consequences. If, however, it was not credible that fenfluramine monotherapy lowered the number of epileptic seizures in comparison to other established treatments, a relative worsening of the patient's condition had to be expected, since monotherapy means that no additional treatment is permitted. The board in T 979/23 did not identify any legal or technical errors in decision T 1779/21.