Inter partes review (IPR) proceedings before the Patent Trial and Appeal Board (PTAB) frequently involve patents in biotechnology, pharmaceuticals, diagnostics and other life-sciences fields. In these matters, patent claims may depend on precise nucleotide or amino-acid sequences, sequence identities, mutations, alignments, or other biological relationships.
Because even a small sequence difference can affect the scope or validity of a claim, sequence listings can become important evidence in an IPR. Properly identifying, presenting and supporting sequence information can help petitioners and patent owners establish – or challenge – the technical basis for their arguments.
What Is a Patent Sequence Listing?
A patent sequence listing is a standardized electronic representation of nucleotide and/or amino-acid sequences disclosed in a patent application.
Modern U.S. patent practice uses ST.26, the World Intellectual Property Organization (WIPO) standard for the presentation of nucleotide and amino-acid sequence listings. Sequence information can include individual sequences, sequence identifiers, annotations and related biological information.
For an IPR involving sequence-based claims, the sequence listing may provide a structured source for identifying exactly what sequences were disclosed in the challenged patent.
However, the sequence listing should not automatically be treated as establishing the meaning or legal scope of a claim. The significance of particular sequence information depends on the claims, specification, prosecution history, prior art and the evidence presented in the proceeding.
Why Sequence Evidence Matters in IPRs
A central issue in many IPRs is whether the challenged claims are unpatentable over the asserted prior art.
For sequence-based claims, that inquiry may require highly precise comparisons. A petitioner may need to demonstrate that a prior-art reference discloses a particular sequence, or that a skilled artisan would have understood a disclosed sequence to correspond to the claimed sequence.
For example, a claim may require:
- A specific nucleotide or amino-acid sequence.
- A sequence having a specified percentage identity to another sequence.
- A protein containing particular substitutions.
- A nucleic acid encoding a specified protein.
- A sequence with a defined functional characteristic.
- A biological molecule containing one or more mutations.
In each situation, the exact sequence evidence can affect whether the prior art meets the claim limitations.
Sequence Listings as Evidence
A sequence listing can be useful because it provides a structured representation of sequence information appearing in the patent record.
Attorneys may use sequence listings to:
- Identify the sequence corresponding to a claim limitation.
- Verify sequence identifiers referenced in the specification or claims.
- Compare claimed sequences with sequences disclosed in prior-art references.
- Support expert analysis concerning sequence identity or similarity.
- Help establish relationships between nucleotide and amino-acid sequences.
- Detect discrepancies between sequence references in different documents.
The evidentiary value, however, depends on how the sequence information is connected to the legal arguments in the IPR.
Simply submitting a large collection of sequences may not establish that a particular claim limitation is satisfied.
Connecting Sequence Evidence to the Challenged Claims
One of the most important considerations is claim-by-claim mapping.
Suppose a challenged claim requires a polypeptide having at least a specified percentage sequence identity to SEQ ID NO: 7. The relevant analysis may involve several distinct questions:
- What is SEQ ID NO: 7?
- What sequence does the prior-art reference disclose?
- What sequence-comparison methodology should be used?
- Which sequence regions should be compared?
- Does the relevant identity threshold apply to the full sequence or a specified region?
- Does the prior art expressly or inherently disclose the claimed sequence?
- Would a skilled artisan have had a reason to make any required modifications?
The sequence listing can help answer the first question, but additional documentary and expert evidence may be necessary to address the others.
Sequence Comparison Requires Methodological Precision
Sequence identity arguments can become complicated because different comparison methods can produce different results.
For example, sequence comparisons may differ based on:
- Global versus local alignment.
- Alignment algorithms.
- Gap penalties.
- Treatment of insertions and deletions.
- Sequence regions included in the calculation.
- Whether nucleotide or amino-acid sequences are being compared.
- Whether the relevant sequence is full-length or truncated.
Accordingly, an IPR expert should explain not only the numerical result but also how that result was obtained and why the methodology is appropriate to the relevant claim or prior art.
An unexplained statement that two sequences are “90% identical,” for example, may be less persuasive than a reproducible analysis identifying the sequences, alignment method, comparison region and resulting calculation.
Expert Testimony Can Be Critical
Sequence-related disputes often involve technical questions that are beyond ordinary knowledge. Expert testimony can therefore play an important role.
A qualified expert may explain:
- The biological significance of the sequences.
- How a skilled artisan would interpret sequence disclosures.
- Whether two sequences are identical or sufficiently similar.
- How sequence identity should be calculated.
- Whether a reference discloses a claimed sequence expressly or inherently.
- Whether a particular sequence variation would have been expected.
- Whether a skilled artisan would have had reason to select or modify a particular sequence.
The expert should connect technical conclusions to the evidence of record rather than simply providing unsupported conclusions.
Avoiding “Black Box” Sequence Analysis
A common risk in sequence-heavy IPRs is presenting computational results without sufficient explanation.
A spreadsheet or software output may show that two sequences have a particular identity percentage, but the Board may need to understand the underlying methodology and assumptions.
For that reason, attorneys should consider preserving:
- The source sequences.
- Sequence identifiers.
- The software or algorithm used.
- Relevant software settings.
- Alignment parameters.
- The portion of each sequence analyzed.
- The resulting alignment.
- Calculations supporting the stated identity percentage.
Maintaining this underlying evidence makes the analysis more transparent and can make it easier to respond to challenges from the opposing party.
Prior-Art Sequence Listings
Sequence listings in prior-art patents and patent applications can also be important.
A petitioner may identify a sequence in an earlier patent document and argue that the sequence anticipates a claim limitation or forms part of an obviousness analysis.
The attorney should carefully establish what the prior-art document actually discloses. A sequence identifier in one document should not automatically be assumed to correspond to the same identifier in another document.
Sequence numbers are document-specific unless the record establishes the relationship.
For this reason, attorneys should identify the actual sequence associated with each relevant identifier and provide an appropriate comparison when relying on sequence-number correspondence.
Anticipation and Sequence Evidence
For anticipation, the petitioner generally must establish that the prior art discloses every limitation of the challenged claim, arranged as required by the claim.
In a sequence-based claim, this can make precise sequence evidence particularly important.
If a claim requires a specific sequence, the relevant prior-art disclosure must be carefully analyzed to determine whether that sequence is actually disclosed. If the claim instead permits a range of sequence identities, the analysis may focus on whether the prior-art sequence falls within the claimed range.
Where the argument depends on inherency, additional evidence may be required to establish that the claimed feature necessarily follows from the prior-art disclosure rather than merely being a possible result.
Obviousness and Sequence Evidence
Sequence listings can also support obviousness arguments, but the analysis is different.
An obviousness challenge may involve a combination of references, routine optimization, known variants, or a motivation to modify a disclosed sequence.
Here, the evidence may need to address why a skilled artisan would have selected the relevant sequence or modification and why the expected result would have been predictable.
Evidence concerning:
- Known sequence variants
- Conserved regions
- Structure-function relationships
- Mutation studies
- Biological activity
- Sequence databases
- Published research
- Prior successful modifications
may therefore become relevant.
The mere existence of a sequence variant in a large universe of possibilities does not necessarily establish that selecting that particular variant would have been obvious.
Sequence Databases and External Evidence
Sequence databases and other scientific resources may provide useful background or corroborating evidence in an IPR.
However, attorneys should distinguish between using a database to explain the state of the art and relying on it as substantive evidence for a particular proposition.
When database information is important to the argument, the record should establish what the database contained, when the information was publicly available and how the information relates to the relevant patent or prior-art reference.
This is especially important when the proceeding involves an asserted publication date or other timing requirement.
Maintaining an Evidence Trail
Because sequence analysis can involve numerous files and iterations, maintaining a clear evidence trail is essential.
A well-organized sequence evidence package might include:
- The challenged patent.
- Relevant patent sequence listing files.
- Prior-art sequence listings.
- Sequence extraction records.
- Sequence-alignment files.
- Comparison tables.
- Software outputs.
- Expert declarations.
- Supporting scientific literature.
- Exhibits identifying the source of each sequence.
Each sequence should ideally have an unambiguous identifier that can be traced back to its source document.
This approach can save substantial time when preparing declarations, deposition exhibits, demonstratives and hearing presentations.
Common Problems in Sequence-Based IPRs
Several recurring problems can weaken sequence-related arguments.
Ambiguous Sequence Identification
Referring to “SEQ ID NO: 10” without clearly identifying the document in which that sequence appears can cause confusion.
Unsupported Identity Percentages
A numerical identity percentage without an explanation of the comparison methodology may be difficult to evaluate.
Inconsistent Sequence Versions
Even a small difference between sequence files can produce different results. Attorneys should verify that the sequence analyzed is the same sequence disclosed in the relevant evidence.
Overreliance on Software
Software can perform calculations, but the legal significance of the result still requires technical and evidentiary explanation.
Failure to Connect the Analysis to the Claim
A technically accurate sequence comparison may have little value if the analysis does not establish how it satisfies a specific claim limitation.
Best Practices for Attorneys
Patent attorneys handling sequence-heavy IPRs can improve efficiency and evidentiary clarity by adopting several practices.
- First, identify the critical sequences early. Determine which sequences actually matter to the challenged claims rather than attempting to analyze every sequence in every reference.
- Second, preserve the original evidence. Keep the source sequence listing and document from which each sequence was obtained.
- Third, document the methodology. Record the software, parameters, alignment method and comparison region used in sequence analysis.
- Fourth, involve technical experts early. Early expert review can identify weaknesses in sequence interpretation before substantial briefing is completed.
- Fifth, create claim-focused comparison tables. Tables can help attorneys and experts connect individual sequence findings to specific claim limitations.
- Finally, distinguish technical evidence from legal conclusions. The sequence data may establish a technical relationship, but the ultimate question of patentability requires applying the governing legal standards to the complete evidentiary record.
Conclusion
Sequence listings can be powerful evidence in Inter Partes Review proceedings involving biotechnology and other sequence-based inventions. They provide a structured way to identify and analyze nucleotide and amino-acid sequences, but their usefulness depends on how carefully they are authenticated, compared, explained and connected to the challenged claims.
For petitioners and patent owners alike, successful sequence-based advocacy requires more than producing sequence files or reporting identity percentages. The strongest approach combines accurate source identification, transparent computational analysis, qualified expert testimony, claim-specific mapping and a well-organized evidentiary record.
As sequence-based patent disputes become increasingly sophisticated, attorneys who establish a disciplined process for managing sequence evidence can make their IPR arguments clearer, more reproducible and more persuasive.