In a recent decision (Warner-Lambert Company LLC v Generics Ltd t/a Mylan and Actavis Group), the Supreme Court has rejected an appeal by Warner-Lambert against a High Court and subsequent Court of Appeal decision regarding the invalidity and infringement of their patent. The patent at issue (EP 0934061) relates to the use of pregabalin for treating pain and the particular claims at issue relate to the use of pregabalin for the preparation of a medicament for treating pain (claim 1), inflammatory pain (claim 2) and neuropathic pain (claim 3). The claims were drafted in “Swiss form”, a claim format previously allowed by the EPO for obtaining protection for second (and further) medical uses of known compounds.
In the initial High Court Decision, it was held that claims 1 and 3 were invalid on the basis of insufficiency. In particular, Justice Arnold found that there was sufficient disclosure to support the use of pregabalin in the treatment of inflammatory and peripheral neuropathic pain, but not central neuropathic pain, which was encompassed by claims 1 and 3. The Court of Appeal agreed with these findings and upheld the decision. Regarding infringement of the claims by the respondent, Justice Arnold and the Court of Appeal differed in their opinion regarding the test which should be applied when the patent claims relate to the manufacture of a product for a particular medical use.
On appeal to the Supreme Court, Warner-Lambert asserted that all the claims of the patent were valid. However, their primary concern appeared to be establishing the validity of claim 3 which recites the use of pregabalin for treating neuropathic pain – the most commercially important indication which Warner-Lambert wanted to protect. There were a number of issues to be decided on by the Supreme Court which included: (i) how the claims should be construed, particularly claim 3 which referred to neuropathic pain; (ii) whether the subject matter of the claims was sufficiently disclosed in the application as filed, particularly the use of pregabalin for treating neuropathic pain; and (iii) what the test for infringement should be when considering claims directed towards manufacturing a product for a particular limited use (i.e. Swiss type claims).
In relation to construction of the claims, the Supreme Court unsurprisingly agreed with the view of the High Court and Court of Appeal, namely that the phrase “neuropathic pain” includes all neuropathic pain, including central and peripheral neuropathic pain.
Regarding validity, the Supreme Court decided by a majority (rather than unanimously) that the specification of the patent provides sufficient disclosure to support the claims to inflammatory pain, but not to all kinds of neuropathic pain, therefore upholding the decisions of the High Court and the Court of Appeal that claims 1 and 3 were invalid for insufficiency. The Supreme Court reasoned that for such second medical use claims to fulfill the requirement for a sufficient disclosure, the patentee is required to disclose a “plausible” reason why the claimed compound would work to the skilled person at the filing date claimed indication, in order to prevent such second medical use patents “to be obtained on a wholly speculative basis”. In the patent in suit, no such plausible reason for pregabalin being effective in central neuropathic pain (a significant sub-category of pain covered by the generally claimed “neuropathic pain”) was disclosed, despite it actually being effective.
The Supreme Court commented that this concept of “plausibility” at the filing date originated in EPO case law as a response to overly broad claims and is “not a distinct condition of validity…but a standard against which validity must be demonstrated”. The plausibility test was described as “relatively undemanding” but it must be able to prevent speculative claims. For example, the mere assertion that a compound might be efficacious for a particular treatment would not render the claim plausible. However, if “reasonable scientific grounds” for that assertion were provided then this may provide the required plausibility. Such reasoning could theoretically distinguish between a non-plausible speculation and a plausible “contribution to the art”. These “reasonable scientific grounds” may be provided by direct experimental evidence, but could alternatively be provided by scientific reasoning, reference to specific properties of the compounds or the disclosure of some unifying principle that relates to the proposed use. Therefore, experimental proof that the compound works in the claimed second medical use is not always necessary to meet the requirement of plausibility but there must be a plausible scientific reason in such a case.
In the present case, the Supreme Court considered that the experimental data in the specification was predictive of efficacy in the treatment of inflammatory pain, but did not make it plausible that pregabalin would be effective for all kinds of neuropathic pain. They also considered that the patent lacked a disclosure of a unifying principle which made it plausible that pregabalin would also work with neuropathic pain, based on its effectiveness in inflammatory pain. Warner-Lambert tried to argue that the “central sensitization” mechanism provided such a “unifying principle”, but the Supreme Court decided that neither the patent specification nor the common general knowledge in the art at the filing date suggested that this was the case. Lord Briggs further commented that later filed data can “reinforce” the plausibility of the invention but could not on its own render the claimed therapeutic effect plausible.
Regarding infringement, the Supreme Court unanimously held that even if claims 1 and 3 had been valid, they would not have been infringed by Actavis. However, the reasoning behind the decision from the different Law Lords varied, in particular whether the intent of the alleged infringer should be considered. The test outlined in the majority decision was termed the “outward presentation test” and aims to determine what indication the allegedly infringing medicines are being supplied for. This outward presentation test considers the “physical characteristics of the product as it emerges from the relevant process, including its formulation and dosage, packaging and labelling and the patient information leaflet”. Crucially, this test does not involve an assessment of the supplier’s intent or knowledge of potentially infringing uses of the medicine.
An application to amend claims was not allowed as an abuse of process as it was only made after handing down of the judgement at first instance, when it could have been made before or during trial and it would require a further trial. Accordingly, if the case raised against the patent may require amendment this should be made before trial, if possibly conditionally.
This decision provides further guidance regarding the often asked question about how much data should be obtained at least before filing for second medical uses. In general, we would suggest including as much data as possible which supports the invention over the whole scope of the claims rather than relying only on scientific reasoning or speculation. However, the recent Supreme Court decision indicates that if significant experimental data is not available, detailed reasoning regarding how the compound is proposed to function (for example, referring to the effect of the compound on a signaling pathway known to be implicated in a particular indication) may sometimes be sufficient to render the technical effect plausible.