T 1870/21 (Crenolanib for treating flt3 mutated proliferative disorders / AROG) 23-05-2024

1. Procedural violation

1.1 During the first instance proceedings, the respondent filed annex 3 and D46-D56 (i.e. E36-E46 in the respondent's original numbering) on 13 March 2020, i.e. on the last date for making submissions set by the opposition division under Rule 116 EPC in the summons dated 10 September 2019.

Following a postponement, the oral proceedings before the opposition division eventually took place on 29 March 2021. The appellant raised an objection against the admittance of annex 3 and documents D46-D56 (see the minutes, page 1, 4**(th) paragraph). It is established that, during the oral proceedings, neither the admittance of these documents, including D50, nor their contents, were discussed.

1.2 According to the appealed decision (see §6.2), annex 3 and D46-D56 were not relevant for the reasons of the decision, so that the appellant's request not to admit them was not discussed. This is however contradicted by the fact that the inventive step reasoning set out later in the decision relies on "E40", which corresponds in fact to D50 in the respondent's original numbering (see §8.4.3.1).

1.3 The relevant question is thus whether the opposition division committed a substantial procedural violation justifying a reimbursement of the appeal fee under Rule 103(1)(a) EPC.

1.3.1 The sole fact that, at the oral proceedings, the parties did not refer to D50 does not as such mean that the opposition division's reliance on this document in the decision infringes the appellant's right to be heard under Article 113(1) EPC. This is because D50 and the line of argumentation based thereon had been submitted in writing by the respondent in their letter dated 13 March 2020 (see page 4) and had been notified to the appellant. Accordingly, the appellant had an opportunity to present their comments on D50.

1.3.2 However, it remains that the opposition division took D50 into account in the appealed decision without first hearing the parties on the appellant's request not to admit D50. By deciding to reject the opposition without hearing the appellant on a request relevant to that decision, the opposition division infringed Article 113(1) EPC and committed a procedural violation. Considering that, during the oral proceedings before the opposition division, neither the admittance nor the content of D50 were discussed, and no decision as to its admittance was announced, it could not be expected from the appellant that they would present their arguments at the oral proceedings with regard to D50.

1.4 Under Rule 103(1)(a) EPC, for the appeal fee to be reimbursed, the procedural violation must be substantial (see the Case Law of the Boards of Appeal, 10**(th) edition, 2022, II.B.2.2.2).

1.4.1 According to the respondent, D50 is not the underlying reason for the opposition division's finding of non-obviousness, which was rather motivated by the case law (T385/07 and T715/03) acknowledging inventive step over prior art referencing ongoing clinical phase I and II trials. The opposition division's conclusion at the end of section 8.4.2 would already address the question of 8.4.3 regarding whether there was a reasonable expectation of success in view of the promising results, such that the same conclusion would have been reached even without section 8.4.3.1.

1.4.2 The Board is not convinced that, considering the reasoning set out in the appealed decision, the same outcome would have been reached if D50 had not been admitted, for the following reasons.

In the contested decision, the opposition division examines first the disclosure in the prior art starting points. According to §8.1, document D3, and the corresponding abstract D2 (considered together by the opposition division), teach in particular that crenolanib was assessed for its suitability in the treatment of FLT3 mutant AML and has shown very promising results in in vitro experiments on human cell lines and in an animal in vivo model (mouse). D2/D3 would further refer to ongoing clinical trials.

The section relying on D50 (i.e. §8.4.3.1) is the only passage of the decision explaining why, in the opposition division's view, and contrary to the appellant's position, there was no reasonable expectation of success despite these promising results disclosed in the prior art D2/D3.

In sections §8.4.1 and 8.4.2, the opposition division explains that phase II clinical trials were known (from D4) to be ongoing, but that this neither meant that phase I trials of crenolanib in AML had been performed, nor did it allow the skilled person to expect crenolanib to be active on AML patients, because clinical trials are known to regularly fail. These passages address the question of reasonable expectations in view of the known ongoing clinical trials, but not in view of the promising results reported in D2/D3. Despite the broader wording of the last paragraph of section §8.4.2 ("the OD has come to the conclusion that the mere fact that phase II clinical trials are ongoing and that in vitro and in vivo experiments were considered promising is not enough to render it obvious to administer crenolanib to human patients with FTL3 mutated AML and expect it to work", emphasis added by the Board), there is in fact up until this point of the decision no explanation why the promising results do not as such provide this expectation.

In section §8.4.4, the opposition division differentiates the case at hand from decisions T 2506/12, T 725/11 and T 239/16, and concludes that the knowledge that clinical trials were ongoing would not have given the skilled person a reasonable expectation of success. This passage does not address either the issue of expectations in view of the promising experimental in vitro and in vivo results reported in D2/D3, which the appellant had raised in the first instance proceedings (see the third paragraph on page 4 of the minutes).

Accordingly, it cannot be concluded that the argumentation based on D50 is to be seen as a merely supererogatory and incidental argument in the appeal decision.

1.5 The Board therefore concludes that the appealed decision is tainted by a substantial procedural violation.

2. Remittal and reimbursement of the appeal fee

Under Article 11 RPBA, the Board shall not remit a case to the department whose decision was appealed for further prosecution, unless special reasons present themselves for doing so. As a rule, fundamental deficiencies which are apparent in the proceedings before that department constitute such special reasons.

In the case at hand, the above substantial procedural violation is a fundamental deficiency in the sense of Article 11 RPBA justifying that the case be remitted to the opposition division for further prosecution. In addition, as a result of this substantial procedural violation, the appeal decision must be set aside and a reimbursement of the appeal fee is equitable under Rule 103(1)(a) EPC.

Considering that the parties' agreement that the issues of remittal and reimbursement of the appeal fee be addressed without oral proceedings, the present decision can be issued in writing without holding oral proceedings.