Patenting pharma inventions in Europe: evidence considerations for sufficiency of disclosure

A key patentability requirement for European patents relating to pharmaceutical inventions is sufficiency of disclosure. Whether a European patent complies with this requirement is fact dependent, and patentability and validity decisions regarding this requirement often turn on the available evidence in the common general knowledge, prior art, patent application as originally filed, and published after the filing date of the application (so-called post-published evidence). Further, the case law relating to the ability of patentees to rely on post-published evidence under sufficiency at the European Patent Office (EPO) has evolved in recent years.

We explore the EPO’s and the UK’s current approach to assessing whether the requirements of sufficiency are met by European pharmaceutical patents, outline considerations for relying on post-published evidence under sufficiency, and provide practical advice on best practice when preparing a patent application that will be filed with the EPO.

Evidence required to establish sufficiency of disclosure

To meet the requirement of sufficiency of disclosure at the EPO, the patent application as originally filed together with the common general knowledge must enable a person skilled in the art to carry out the invention. Further, the priority document must enable a person skilled in the art to carry out the invention for a subsequent European patent to claim priority validly (T 883/23). The level of disclosure required in the application depends on the invention being claimed. In the technical field of pharmaceuticals, there is a general split between claims directed to products, such as new chemical entities and formulations, and those directed to medical uses (methods of treatment in the European claim format).

Claims directed to pharmaceutical products must be supported by disclosure in the application which allows a person skilled in the art to produce the product, and there should be no substantiated doubts that the product could be used in therapy (T 1616/09).

On the other hand, claims directed to medical uses must be supported by proof of the claimed therapeutic effect in the application, particularly if, in the absence of experimental data in the application, it would not be credible to the skilled person that the therapeutic effect is achieved (G 2/21). Proof of the therapeutic effect in terms of concrete experimental data in the application might not be necessary if the therapeutic effect is rendered credible by the application as filed (T 1210/20). However, European patents claiming a medical use must provide some information, usually experimental tests, that prove the claimed compound has a direct effect on a metabolic mechanism specifically involved in the disease claimed, this mechanism being either known from the prior art or demonstrated in the application (T 294/20 citing T 609/02). A simple verbal statement that the therapeutic effect is achieved by the invention is unlikely to provide a sufficient disclosure. Clinical or animal data may not be necessary; showing a therapeutic effect in vitro may be sufficient if for the skilled person this observed effect directly and unambiguously reflects the claimed therapeutic application (T 609/02). Medical use claims limited to a particular dosage regime or a specific patient group must be supported by proof of the therapeutic effect for the claimed dosage regime (T 1592/12) or patient group (T 166/22).

At a national court level, the concept of plausibility is relevant to sufficiency of UK patents claiming either a chemical compound per se or a medical use. The majority view of the UK Supreme Court in Warner-Lambert Company LLC v Generics (UK) Ltd (t/a Mylan) & Anor [2018] UKSC 56 (“Warner-Lambert”) confirmed that medical use patents, when read together with the common general knowledge, must make it plausible that the invention will achieve the claimed therapeutic effect in order to sufficiently disclose the use.

The England and Wales Court of Appeal in Sandoz v Bristol-Myers Squibb held that the plausibility standard adopted by the majority in Warner-Lambert was not altered by G 2/21, and that the underlying principles are also applicable to claims to single chemical compounds. It follows that, in order for a claim to a single chemical compound to be patentable, the application must make it plausible, when read in the light of the skilled person’s common general knowledge, that the compound has the asserted utility. The applicability of the same plausibility standard to claims to single chemical compounds, as in Sandoz v Bristol-Myers Squibb, was confirmed by the England and Wales Court of Appeal in Generics v AstraZeneca. In both Sandoz v Bristol-Myers Squibb and Generics v AstraZeneca, EP(UK) patents which included claims to a single chemical compound (apixaban and dapagliflozin, respectively) were revoked due to lack of plausibility.

Other national courts of EPC Contracting States have taken more “patentee-friendly” approaches to sufficiency of pharmaceutical inventions.

Sufficiency and post-published evidence at the EPO

The ability of patentees to rely on post-published evidence under sufficiency at the EPO is relatively narrow. Sufficiency must be satisfied at the filing date of the patent application and cannot be remedied by post-published evidence. However, post-published documents may be used as evidence that the disclosure is reproducible without undue burden under certain circumstances.

For medical use claims, post-published evidence may be taken into account to back up the findings in the patent application, but not to establish sufficiency on their own (T 609/02). A lack of proof of a claimed therapeutic effect in the application as originally filed, if it would not be credible to the skilled person that the therapeutic effect is achieved, cannot be remedied by post-published evidence (G 2/21).

Conversely, the ability of opponents to cite post-published evidence when attacking the sufficiency of a European patent at the EPO is relatively broad. When objecting under sufficiency, opponents must establish that a person skilled in the art would have serious doubts, substantiated by verifiable facts, that the invention could be carried out. Evidence to substantiate those serious doubts can be obtained after the filing date of the patent. So, for a medical use claim, post-published evidence of a failed late-stage clinical trial relevant to the claimed medical use can undermine the initial sufficiency provided by the patent application (T 816/22).

Sufficiency and best practice when preparing European patent applications

Sufficiency must be satisfied at the filing date of the Europeanpatent application and cannot be remedied by post-published evidence. Therefore, a lack of sufficient disclosure in the application as filed can be fatal to the validity of the patent. Further, a lack of sufficient disclosure in the priority document can result in invalid priority. This means that public disclosures between the priority date and filing date may pose a greater threat to patentability. Therefore, both the priority application and patent application as originally filed should enable a person skilled in the art to carry out the invention.

European patents claiming pharmaceutical products must be supported by disclosure in the application as originally filed which allows a person skilled in the art to produce the product, and they should include data demonstrating therapeutic utility of the product, if not already known in the prior art.

European patents claiming a medical use must include proof of the claimed therapeutic effect if, in the absence of experimental data in the application as originally filed, it would not be credible to the skilled person that the therapeutic effect is achieved. While the credibility of the therapeutic effect can be established by reference to prior art, the application as originally filed should provide a technical contribution to the art to mitigate the risk of the claimed invention from being found to be either insufficiently disclosed or lack an inventive step over the prior art (a sufficiency-inventive step trap). Therefore, best practice is to include experimental evidence of the therapeutic effect in the application as originally filed. While in vitro data may be enough to support a medical use claim sufficiently in a European patent, depending on the circumstances, it may be advantageous to defer filing a medical use patent until in vivo data, particularly clinical data, proving therapeutic efficacy is obtained, but before such data is published. Adopting this deferred filing strategy can optimise term of patent protection and sufficiency prospects, and allow the patent application to be prepared with a better understanding of what particulars may eventually be included in the prescribing information if the product candidate receives regulatory approval. On the other hand, this deferred filing strategy needs to be balanced against the risk of clinical trial disclosures affecting the assessment of inventive step.

If you would like to discuss evidence requirements for European patents relating to pharmaceutical inventions, please contact your usual GJE attorney, or email us: gje@gje.com.