Sequence Identities and Functional Definitions - Where Is the Limit? (T 0137/24)

Key Takeaways

• Convergent sequence‑identity lists narrow scope, not added matter
• Functional definition of enzymes excludes non‑working variants from claim coverage
• Higher identity thresholds (e.g., 90%) can be claimed without new disclosure
• Board’s ruling eases biotech patent prosecution, supporting broader sequence ranges

Pulse Analysis

Biotech patent drafting often hinges on how sequence identity is framed. The European Patent Office treats lists of increasing identity percentages as "convergent" when each level simply narrows the same functional feature. This contrasts with non‑convergent lists, where each element represents a distinct alternative that can trigger added‑matter objections under Article 123(2) EPC. By recognizing convergent lists, examiners and applicants gain flexibility to define proteins or nucleic acids by a range—say 65 % to 100 %—without risking disallowed cherry‑picking.

In the recent T 0137/24 appeal concerning a genetically modified yeast that produces cannabinoids, the Board applied this principle to reject the opponent’s added‑matter claim. The patent originally disclosed a list of identity thresholds from at least 65 % up to 100 % for two SEQ ID numbers. When the claim was narrowed to a 90 % threshold, the Board held that the selection merely refined the scope, not introduced a new invention. Moreover, the claim’s functional definition—requiring enzymatic activity—ensured that non‑functional variants fell outside protection, satisfying the sufficiency requirement despite the lack of experimental data for every identity level.

The decision sends a clear signal to biotech firms and patent practitioners: functional definitions paired with convergent identity lists can safeguard broader claim coverage while meeting disclosure standards. Drafting strategies should therefore emphasize clear functional criteria—such as catalytic activity or binding affinity—and reference convergent identity ranges to pre‑empt added‑matter objections. As the EPO Guidelines already note for antibodies, "less than 100 % identity" is permissible when coupled with a functional feature, and T 0137/24 confirms that this approach extends to enzyme‑based inventions. Companies can now pursue more ambitious sequence‑identity scopes, reducing the need for multiple narrow claims and streamlining prosecution.