LIFE SCIENCES | EPO Board of Appeal on sufficiency and priority in therapeutic inventions

On 26 September 2025, the EPO Technical Board of Appeal (Technical BoA) issued its decision in case T 0883/23 (Ipsen Biopharm v Sandoz & Generics UK), clarifying the relationship between sufficiency of disclosure in therapeutic inventions and the “same invention” requirement for claiming priority under Article 87(1) of the European Patent Convention (EPC).

The patent at issue concerned the use of liposomal irinotecan in a method for treating metastatic pancreatic cancer. The key question before the Technical BoA was whether the claimed dose combination was entitled to priority.

The Technical BoA found that the priority application did not disclose any information concerning the tolerability of the claimed dose combination. According to the Technical BoA the “same invention” requirement is satisfied only if the subject matter is directly and unambiguously derivable and sufficiently disclosed in the priority document. For therapeutic inventions, dose tolerability is a functional technical feature and a precondition for therapeutic efficacy. Since the critical tolerability information was disclosed only in the later patent and not in the priority application, the claimed invention could not benefit from the latter. In addition, the decision clarified that study protocols alone cannot secure priority for therapeutic effect inventions, as experimental data remain essential to establish both sufficiency and “same invention” under the EPC.

Newsletter n. 112 – November 2025