Balancing Disclosure and Protection: Plausibility after G 2/21

Abstract This article examines the evolving doctrine of plausibility in European patent law following the Enlarged Board of Appeal’s decision in G 2/21 (Reliance on a purported technical effect for inventive step (plausibility)). Plausibility, an implicit requirement ensuring that a patent’s technical contribution is commensurate with the scope of protection granted, originates from Technical Boards of Appeal (TBA) decisions to curb speculative claims, particularly in pharmaceuticals. G 2/21 emphasises free evaluation of evidence and a context-dependent assessment: a technical effect must be encompassed by the application’s technical teaching and embody the original invention. For product patents, it tilts toward ab initio implausibility, easing reliance on post-published data and potentially enabling earlier or less developed filings. In contrast, second medical use claims demand that the technical effect be made plausible at filing (ab initio plausibility), with limited post-published support to prevent overbroad protections for known compounds. Drawing on European litigation, the article analyses national courts’ interpretations, revealing divergences, and evaluates the implications of G 2/21 for the fundamental balance between disclosure and protection in patent law.