Neurim Pharmaceuticals (1991) Limited & Anor. v Generics (UK) Limited & Anor.

For a second medical use patent, plausibility is assessed from the patent’s disclosure read with the common general knowledge. The skilled reader may presume that reported clinical trials were competently conducted and that an apparently general questionnaire was administered in a way capable of producing meaningful data, unless the patent gives reason to think otherwise. That presumption does not reduce plausibility to good faith: the claimed therapeutic effect must still be supported by reported results and reasonable scientific grounds, rather than bare assertion or mere possibility. An apparent inconsistency in the specification requires expert evidence to resolve, and a party cannot rely on a technical point not advanced or tested at trial.

Neurim Pharmaceuticals and Flynn Pharma alleged infringement of a second medical use patent concerning prolonged-release melatonin for improving restorative sleep in older patients with primary insomnia characterised by non-restorative sleep. Mylan challenged the patent’s validity for insufficiency, specifically lack of plausibility. Marcus Smith J rejected the challenge in the December Judgment, [2020] EWHC 3270 (Pat), as supplemented by the March Judgment, [2022] EWHC 519 (Pat). Mylan appealed, arguing that the trial data came from lay patients answering a question about quality of sleep which did not necessarily identify non-restorative sleep. The central issue was whether the patent plausibly disclosed the claimed therapeutic effect.

1. Appeal dismissed unanimously. Arnold LJ gave the principal judgment, with Birss LJ and Newey LJ agreeing. The assessment of plausibility was evaluative, so Mylan had to establish an error of principle.
2. The applicable standard, stated in Warner-Lambert Co LLC v Generics (UK) Ltd [2018] UKSC 56, was that a second medical use patent must disclose more than a bare assertion or abstract possibility. It must provide reasonable scientific grounds giving the skilled person a reasonable prospect that the claimed therapeutic effect will prove true. Definitive proof is unnecessary. The effect may be supported by experimental data or a priori reasoning, and common general knowledge may supplement, but not replace, the patent’s teaching. The same standard applies under EPC Articles 83 and 84 and section 14 of the Patents Act.
3. The lay-patient argument failed. The skilled reader would read the reported studies in the context of the specification as a whole. That context made clear that the studies were directed to improving restorative sleep, namely treating non-restorative sleep. Although the patients were laypeople, the skilled reader could understand the reported question as a suitable measure of the claimed effect. The reasoning was consistent with the observations in Conor Medsystems Inc v Angiotech Pharmaceuticals Inc [2008] 4 All ER 621 and the plausibility discussion referring to Salk T-609/02.
4. Absent a reason to think otherwise, the skilled reader could presume that the trials were competently conducted. Meaningful data could have resulted from administering the established questionnaire in full chronological sequence, or from giving appropriate instructions even if the relevant questions were administered in isolation. No finding of common practice was required. This did not assume that the results supported the patent’s conclusions or reduce plausibility to good faith.
5. The apparent tension in the final sentence of paragraph [0039] required expert evidence about the skilled reader’s technical understanding. Mylan had neither adduced the necessary evidence nor put the point to the opposing expert. It was therefore not open to Mylan to rely on it. The judge was entitled to reject Professor Morgan’s evidence and prefer Professor Roth’s evidence. Example 2 alone rendered the claimed effect plausible, and the judge’s conclusion disclosed no error of principle.

1. Court of Appeal (Civil Division): In [2022] EWCA Civ 699, the court unanimously dismissed Mylan’s appeal.
2. High Court, Patents Court: Marcus Smith J rejected the validity challenge in [2020] EWHC 3270 (Pat) and supplemented his reasoning in [2022] EWHC 519 (Pat).