Court of Appeal strengthens patent plausibility standards in AstraZeneca dapagliflozin ruling
Court of Appeal reinforces plausibility requirements for pharmaceutical patent validity claims
The Court of Appeal's decision in Generics (UK) Limited & Others v AstraZeneca AB represents a significant development in UK patent law, particularly regarding plausibility standards and inventive step requirements. The judgement, delivered on 16 July 2025, upheld the High Court's April 2025 ruling that declared AstraZeneca's dapagliflozin patent invalid for lack of inventive step and insufficiency.
Patent plausibility under scrutiny
The central issue concerned whether AstraZeneca's patent adequately demonstrated the plausibility of dapagliflozin's efficacy as an SGLT2 inhibitor for diabetes treatment. The Court of Appeal determined that the patent failed to provide a plausible basis for the claimed therapeutic benefits, emphasising that mere assertions of effectiveness without supporting experimental data or sound theoretical foundation are insufficient for patent validity.
Lord Justice Arnold reinforced the plausibility standard established in Warner-Lambert Co LLC v Generics (UK) Ltd, stating that patents must disclose sufficient information to make the claimed invention plausible at the filing date. The court rejected AstraZeneca's argument that dapagliflozin represented a distinct advancement over prior art, specifically International Patent Application WO 01/27128 A1.
Inventive step assessment
The claimants successfully argued that AstraZeneca's patent merely presented an arbitrary selection from known compounds without demonstrating genuine technical contribution. Despite AstraZeneca's contention that dapagliflozin offered unique benefits in diabetes treatment, the court concluded that the patent failed to adequately distinguish the compound as possessing superior properties compared to previously disclosed compounds.
The judgement reaffirmed the critical role of the skilled person standard in evaluating disclosure sufficiency. Patent applications must be interpreted with the assumption that the reader possesses the technical expertise necessary to understand and assess the invention's practical implications based on the information provided.
Implications for pharmaceutical patents
This ruling establishes important precedent for pharmaceutical patent drafting and prosecution. The decision reinforces that patent applications must ground efficacy claims in substantial evidence rather than speculative assertions. The heightened plausibility requirements will likely influence patent strategies, requiring more comprehensive disclosure of experimental data and theoretical justification at the filing stage.
The judgement also highlights the court's increasingly rigorous approach to evaluating inventive step in pharmaceutical patents, particularly where claims involve selections from known compound classes. Patent applicants must demonstrate clear technical advantages and provide convincing evidence of unexpected benefits to survive validity challenges.
Broader legal significance
The Court of Appeal's decision strengthens the governance framework surrounding patent plausibility and inventive step requirements in the UK. The ruling provides clarity on the evidential standards required for pharmaceutical patents, particularly in highly competitive therapeutic areas where incremental improvements are common.
This precedent will likely influence future patent litigation strategies and may encourage more robust pre-filing experimental programmes to support patent applications. The decision also reinforces the UK's alignment with European Patent Office practice regarding plausibility requirements, ensuring consistency in patent examination and enforcement standards.
The AstraZeneca ruling serves as a reminder that patent validity depends not merely on technical novelty but on demonstrable plausibility supported by adequate disclosure. This approach maintains the balance between rewarding genuine innovation and preventing the grant of patents for speculative or inadequately supported claims, ultimately strengthening the integrity of the pharmaceutical patent system.