By Ana Herrera Arroyo, head of Patents, Technological Development and Innovation at PONS IP
In modern biotechnology, few issues generate as much debate during patent prosecution and validity proceedings as claims directed to biological sequences defined by percentage identity. For any applicant, claiming only a specific sequence is often commercially inadequate: competitors may introduce minor modifications to the nucleotide or amino acid sequence and develop products with very similar properties. Consequently, it is common practice to seek broader protection through claim formulations such as “a sequence having at least 90%, 95% or 99% identity to SEQ ID NO: 1”.
At first glance, such claims appear entirely reasonable, since, from a biological perspective, small variations in a sequence do not necessarily alter its function. However, from the standpoint of patent offices, a fundamental question immediately arises: is it truly justified to extend protection to all sequences falling within that percentage identity threshold?
From a clarity perspective, such claims are, in principle, entirely admissible in Europe, although they are subject to particularly rigorous scrutiny. The EPO Guidelines for Examination expressly recognise that amino acid and nucleotide sequences may be defined by percentage identity, provided that the method or algorithm used to determine such identity is clearly specified in the patent application. In the absence of a specific definition, the claim may be interpreted using any reasonable method known at the filing date, which may give rise to clarity issues.
In European practice, however, the real challenge generally lies in the requirements of sufficiency of disclosure and inventive step. The EPO frequently assesses whether the application provides sufficient information to enable the skilled person to identify, obtain (the “reproducibility” requirement), and reliably use (the “plausibility” requirement, which becomes more critical than ever in drafting of this nature) the numerous variants encompassed by the claimed percentage identity. As a general rule, the lower the percentage identity, the greater the level of justification required. Recent decisions of the EPO Boards of Appeal demonstrate that combining percentage identity thresholds with clearly defined functional features may support relatively broad claims. Nevertheless, each case depends heavily on the technical evidence disclosed in the original application and on the extent to which those results can reasonably be extrapolated.
In the United States, the approach differs, although the practical outcome is often similar. Claims based on percentage identity are common and generally acceptable, provided that the specification satisfies the requirements of written description and enablement. The key issue is demonstrating that, at the filing date, the inventor was genuinely in possession of the full claimed scope. US examiners and courts are particularly sensitive to broad claims seeking to cover extensive families of variants without providing sufficient examples, which must be representative of the entire claimed genus, or without identifying essential structural elements within the sequences that must remain unchanged and that enable the skilled person to determine which sequences will retain the desired function and technical effect. Recent developments in US biotechnology case law reflect an increasingly stringent assessment of broad genus claims.
Japan, for its part, adopts what might be described as a balanced position. Identity-defined claims are admissible, but examiners generally pay particular attention to issues of clarity and sufficiency of disclosure. Japanese practice shares with Europe and the United States the concern that a percentage identity threshold, by itself, does not necessarily define a homogeneous group of molecules. Indeed, the JPO itself recognises the importance of adequately specifying the methodology used to determine sequence identity and of providing technical support for the claimed variants.
The practical consequence for applicants is clear. Claims based on percentage identity remain a fundamental tool for obtaining commercially meaningful protection in the biotechnology sector, but it is not enough simply to include a long list of progressively decreasing identity thresholds in the specification. Major patent offices expect to see experimental data, functional characteristics, selection criteria, identification of key structural elements (regions within the sequences that must remain unchanged to ensure achievement of the intended technical effect), and technical arguments demonstrating why the variants falling within the claimed scope should be regarded as forming part of the same technical contribution made by the invention over the prior art, particularly in terms of inventive step and sufficiency of disclosure.
In many respects, the evolution of international practice reflects a continuing tension within biotechnology patent law: applicants seek to protect not only the exact sequence they have discovered, but also the surrounding technological space to which that discovery reasonably extends, while patent offices legitimately aim to prevent scientific evidence of inherently limited scope from conferring excessively broad rights over variants that the inventor never characterised or experimentally validated. Striking the right balance between these competing interests remains one of the central challenges of protecting biotechnological inventions and will, in all likelihood, continue to be the subject of debate for many years to come
