In the landmark case "Sorafenib-Tosylat" decided 28 November 2023 (X ZR 83/21), the German Federal Court of Justice (FCJ) concurred with decisions G1/22 and G2/22 of the Enlarged Board of Appeal of the European Patent Office (EPO). In addition, the FCJ upheld novelty despite a disclosure in a specific example, implicitly applying the EPO's two-lists principle without adopting it per se.
Sorafenib tosylate is used for the treatment of cancer. It is relatively poorly soluble in water, but it has sufficiently high oral bioavailability. Its low water solubility is compensated by a high dissolution rate.
In the present case, only patent claim 12 of the German part of European patent 2 305 255 was challenged in an action for revocation. The challenged claim was directed to the compound sorafenib tosylate as such.
In the opinion of the FCJ, the subject matter of the main request was novel. The nullity plaintiffs had argued that the compound sorafenib tosylate was disclosed in the prior art and was therefore not novel. However, the FCJ stated in its judgment that the prior art does not contain a direct and unambiguous disclosure of said compound. In order to arrive at sorafenib tosylate, sorafenib must first be selected from a list of over 100 compounds of a similar type and then combined with tosylate from a further list of several anions. The FCJ therefore implicitly applied the two-lists principle of the European Patent Office, but without adopting it per se.
Despite acknowledging novelty, the FCJ considered sorafenib tosylate as a compound to be obvious, i.e. not inventive. It was known that the free base sorafenib had an inhibitory effect on the growth of cancer cells. However, the relevant prior art did not contain additional information on the specific formulation of the active ingredient sorafenib. The FCJ stated that the skilled person therefore had reason to search for suitable chemical variants of sorafenib as part of a preformulation study. According to the FCJ, the skilled person would have easily come across the tosylate salt of the sorafenib base, namely the claimed sorafenib tosylate.
The same applied to the subject matter of auxiliary request 1, which differed from the subject matter of the main request only by the non-limiting indication of the purpose "for oral administration".
Deviating from this, the FCJ confirmed that the subject matter of auxiliary request 2 involves an inventive step. The skilled person would have come across sorafenib tosylate, but would not have readily provided it in an oral dosage form (for example as a tablet).
The fact that the tosylate salt in particular has sufficient bioavailability would not have been apparent from an ordinary preformulation study. The skilled person would have been able to determine through further investigations that sorafenib tosylate has a surprisingly high dissolution rate despite its relatively low water solubility. However, this would have required investigations which, in the opinion of the FCJ, would have gone beyond the scope of an ordinary preformulation study and which the skilled person did not feel compelled to carry out.
Furthermore, the Federal Court of Justice expressly endorses the decision G1/22 and G2/22 of the Enlarged Board of Appeal of the EPO by reference (see para. 111 of the decision). As such, a transfer of the priority right is subject to the rebuttable presumption that the transfer of rights has taken place correctly. Thus, according to this principle, the burden of proof of an incorrect transfer of rights falls to the nullity plaintiff.
In this context, however, the FCJ outlined a way in which the nullity action could nevertheless prove an ineffective claim to the right of priority. Namely, if it is possible to obtain information from the applicant of the priority application that they did not consent to the transfer of the priority right, the burden of proof can pass to the patent proprietor. This seems to clarify that, despite the changed burden of proof (at least at the EPO) in priority matters, well-known recent cases (e.g., CRISPR) may not have been decided differently.
The concept of selection inventions had not been generally recognized in German patent practice. Nevertheless, in German proceedings in which novelty is disputed, applicants and patent proprietors nevertheless should consider presenting arguments based on the two-lists principle given the FCJ approach described above.
The blog has been co-authored with Sebastian Greding.