The plausibility standard in UK patent law mandates that a patent application necessarily must demonstrate the achievability of the claimed invention. This is an evidential requirement, essentially developed through judicial pronouncements and precedents.
Under the principles therein, the application itself must disclose reasonably the details to establish the technical effect will occur, rather than the applicant needing to show such effect is certain. Established by the Supreme Court in Warner-Lambert v. Generics (UK) [2018][1] case and applied in Sandoz Ltd. v. Bristol-Meyers Squibb Holdings [2023][2], the plausibility standard demands that a bare assertion of a technical effect is insufficient; and, that it requires technical rationale or experimental data to be presented as evidence in the filed application.
The judgment in Generics (UK) Ltd & Ors v. AstraZeneca AB (2025)[3] reiterated the ‘plausibility’ jurisprudence; the same was further reaffirmed when the UK Supreme Court refused to hear the matter in appeal.
The case revolves around AstraZeneca’s European patent for the compound dapagliflozin, a sodium-glucose cotransporter 2, or SGLT2, inhibitor used to treat diabetes; and, related Supplementary Protection Certificates (SPCs) issued in the UK. Generics (UK) Ltd. and others challenged both the patent and SPCs on the grounds of invalidity for lack of inventive step and insufficient disclosure.
At first instance, the court ruled in its verdict the patent invalid on two primary grounds: (a) lack of sufficient disclosure (plausibility); and, (b) lack of inventive step. It was also held that the patent invalidity was further compounded by an arbitrary selection from a broad genus of related C-aryl glucosides (which included dapagliflozin) disclosed in earlier prior art.
At the priority date, the application lacked adequate support to plausibly demonstrate dapagliflozin's effectiveness as a potent SGLT2 inhibitor or its therapeutic effect in treating diabetes. Hence, the court concluded that AstraZeneca did not show any technical advantage of dapagliflozin over its close chemical neighbors in the genus.
The Court of Appeal upheld the verdict and thus reaffirmed the UK’s “ab initio plausibility” test. The court rejected AstraZeneca’s arguments that lower plausibility thresholds should apply (in particular, for a claim to the compound per se) and that more relaxed standards based on more recent European patent-law (G 2/21) developments were applicable.
The appellate forum also addressed arbitrary selection. It held that inventiveness requires a genuine technical advancement; merely extracting a compound from a known genus does not suffice. Because the original patent was declared invalid, the extended protection under the SPCs was also invalidated.
The eventual result was that the courts determined the patent claims to be unsubstantiated at the time of filing of the patent application. Post-filing information could not compensate for an inadequate original disclosure.
AstraZeneca sought leave to appeal to the Supreme Court, which was refused.
This decision removed AstraZeneca’s monopoly over dapagliflozin, thus allowing the generic companies, such as, Generics (UK) Ltd., Teva Pharmaceutical Industries Ltd., and Teva UK Ltd., to market generic versions of the drug in the United Kingdom.
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The case underscores the commitment of UK courts to rigorous plausibility standards and stringent technical-contribution requirements in pharmaceutical patents, especially for “selection” inventions, as compared to the European Patent Office.
The plausibility assessment is to be made ab initio based exclusively on the filed application; and, only considering the general knowledge commonly available at the time. Further, it is not enough to just assert mere verbal statement of a technical effect; the application must evidence a reasonable prospect of the effect being achieved.
It is pertinent to note that the plausibility standard is not a standalone ground for patentability; however, it is considered under statutory requirements, like inventive step and sufficiency of disclosure. It helps address perceived gaps in cases where a novel and non-obvious invention may not have true utilitarian value; or, where the application does not adequately disclose the details of achieving the claimed effect.
Thus, the plausibility standard is a technique used to ensure that the patent monopoly is justified by the technical contribution of the invention. It sets a higher threshold than the European Patent Office (EPO), which adheres to the G 2/21 decision that introduced the lower critical standard of ‘substantiated doubt’.
At Blaze Ventures, we have qualified professionals and elaborate processes for ensuring the patentability of pharmaceutical innovations and inventions under the ‘plausibility standard’ prevalent in the United Kingdom.
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[1] 2018 UKSC 56
[2] [2023] EWCA Civ 472
[3] [2025] EWCA Civ 903
