May 2026 Sequence Identity Claims After T 0137/24
The recent Board of Appeal decision in T 0137/24 provides useful guidance on how sequence identity claims are assessed under the EPC, particularly in relation to added matter and sufficiency.
Biotech sequence-related claims are often drafted using percentage identity language, for example “[…] a polypeptide having at least 90% sequence identity to SEQ ID NO: XX.” Such wording allows protection to extend beyond a single disclosed sequence to include closely related variants.
The question in T 0137/24 was how far such claims can extend while remaining legally valid.
Convergent Identity Ranges
The application in question disclosed a series of identity thresholds, including 65%, 70%, 80%, 90%, and 100%. The Board treated these not as separate alternatives, but as a convergent series of progressively narrower limitations.
This was significant for added matter. Selecting a higher threshold during prosecution (for example moving from 65% to 90% identity) was viewed simply as narrowing the original disclosure rather than introducing new subject matter. The decision therefore confirms that carefully drafted identity ranges can provide valuable fallback positions during examination.
Functional Definitions Matter
A key factor in the Board’s reasoning was that the claims were not based on sequence identity alone. The claimed polypeptides also had to exhibit a defined biological function.
The Board considered this functional limitation important because it excludes non-working variants that may technically fall within the identity threshold. In effect, the functional feature acts as a filter, ensuring that the claim remains tied to the technical contribution of the invention.
The decision therefore reinforces an important drafting principle: sequence identity claims are considerably stronger when coupled with clear functional language.
Sufficiency and Routine Screening
On sufficiency, the Board accepted that generating variants and testing them for activity is routine work in biotechnology. Although some variants within the claimed range might not function, the skilled person could identify operative embodiments using standard screening methods without undue burden.
Importantly, the Board did not require experimental support for every possible variant within the claim scope. It was enough that the patent provided a credible basis enabling the skilled person to perform the invention across the claimed range.
Practical Takeaways
T 0137/24 supports the continued use of broad sequence identity claims, particularly where applications include structured fallback identity ranges and clear functional limitations. The decision also confirms a relatively permissive approach to routine screening and experimental verification.
However, the case involved relatively high identity thresholds (>90%), and the Board did not define how far the same reasoning can be extended to lower levels of sequence similarity. As identity decreases, the number of non-functional variants is likely to increase, potentially raising sufficiency concerns.
Thus, at least for now, higher identity thresholds combined with functional definitions remain the safest drafting approach.
