As outlined in our recent news article of October 13, 2023, the burden of proof when asserting insufficient disclosure under Article 83 EPC can become a highly relevant but sometimes tricky issue for both parties in opposition proceedings.
This is also true for so-called second medical use claims having the usual structure “substance/composition X for use in the treatment of disease Y”, where the advantageous therapeutic effect is considered to be a technical feature of the claim. Importantly, said therapeutic effect must have been credible demonstrated in the application as filed. A lack in this respect cannot be remedied by post-published evidence, as confirmed in recent decision G 2/21 of March 23, 2023 on the admissibility of post-published evidence in support of inventive step and sufficiency of disclosure in item 77 of the reasons copied below:
… the scope of reliance on post published evidence is much narrower under sufficiency of disclosure (Article 83 EPC) compared to the situation under inventive step (Article 56 EPC). In order to meet the requirement that the disclosure of the invention be sufficiently clear and complete for it to be carried out by the person skilled in the art, the proof of a claimed therapeutic effect has to be provided in the application as filed, in particular if, in the absence of experimental data in the application as filed, it would not be credible to the skilled person that the therapeutic effect is achieved. A lack in this respect cannot be remedied by post-published evidence.
The outcome of G 2/21 was decisive to a number of pending applications and opposition proceedings at the EPO, which were suspended in expectation of said landmark decision and where the therapeutic effect in the case of second medical use claims has been credible shown only by post-published evidence, as e.g. in the opposition proceedings of recently published decision T 2790/17 of November 6, 2023.
In T 2790/17, the Board of Appeal had to consider whether a granted second medical use claim was sufficiently disclosed to meet the disclosure requirement of Article 83 EPC. Even though the application as filed comprised experimental data, i.e. everything appeared to be fine at a first glance, the Board thoroughly studied said data and came to the conclusion that said original data did not show the therapeutic effect. Referring to G 2/21, post-published documents relied upon for evidence of the therapeutic effect could not be considered either.
T 2790/17 shows once again that applicants prior filing the application should check that the experimental data in the application to be filed are consistent with the claims, including the presence of the alleged therapeutic effect required for second medical use claims. Opponents, on the other hand, should also carefully review the experimental data in the patent in the opposite direction in order to identify data in the examples which may not provide support for the alleged therapeutic effect and sometimes even disclose “kamikaze” data that was overlooked by the applicant, paving the way for a successful insufficient disclosure objection under Article 83 EPC.