Telomere and telomerase inventions present a distinctive patent-drafting challenge: the biological concept may be described broadly, but the patent application often depends on precise nucleotide and amino-acid sequences to establish what the invention actually encompasses. This creates a strategic tension for biotech patent applicants. A narrow disclosure of a particular telomerase sequence may be easy to characterize and examine, but it may provide limited flexibility against later-developed variants. A very broad disclosure of sequence identity, functional variants, mutations, fragments, or sequence-defined populations may provide greater potential claim scope, but can create difficult questions concerning written description, enablement, clarity, support, added matter and the sufficiency of the underlying sequence disclosure.
1. Start With the Biological Architecture of the Invention
Telomere-related inventions can involve several distinct biological components.
Depending on the invention, relevant disclosures may include:
- Telomerase reverse transcriptase (TERT)
- Telomerase RNA components
- Telomeric DNA sequences
- Telomerase-associated proteins
- Regulatory sequences
- Promoters and expression constructs
- Mutant or engineered telomerase proteins
- Nucleic acids encoding telomerase proteins
- Peptides or protein fragments
- Binding molecules directed to telomerase or telomere-associated targets
- Cells containing modified telomere or telomerase components
- Methods for increasing or decreasing telomerase activity
These categories should not automatically be treated as interchangeable for claim-drafting purposes.
For example, a disclosure directed to a particular TERT amino-acid sequence is different from a disclosure directed to:
nucleic acids encoding TERT;
which is different again from:
proteins having a specified percentage sequence identity to TERT and retaining a particular telomerase activity.
Each formulation can create different examination questions.
The specification should therefore establish the relationship between the biological entity, its sequence, its function and the claimed implementation.
2. Identify Every Sequence That May Matter Before Filing
A useful drafting exercise is to create a sequence inventory before the application is finalized.
The inventory can include:
| Sequence category | Examples of potential disclosure |
| Reference sequences | Wild-type TERT or telomerase RNA |
| Coding sequences | DNA or RNA encoding a protein |
| Protein sequences | Full-length TERT or engineered variants |
| Functional fragments | Catalytic or binding domains |
| Mutants | Substitutions, deletions, insertions |
| Variants | Sequence-identity-defined variants |
| Regulatory sequences | Promoters, UTRs, control regions |
| Telomeric sequences | Repetitive or engineered telomeric DNA |
| Construct sequences | Fusion proteins or expression cassettes |
| Control sequences | Sequences used in experimental examples |
The objective is not merely administrative completeness.
This inventory helps determine which sequences need formal sequence-listing treatment and, more importantly, which sequences may later become important for claim scope.
Under WIPO Standard ST.26, nucleotide or amino-acid sequences meeting the applicable thresholds and disclosed by enumeration generally need to be included in the sequence listing. The EPO’s current guidance, for example, states that sequences of at least 10 specifically defined nucleotides or four specifically defined amino acids that are enumerated in the application must be listed.
3. Use a Reference Sequence as an Anchor
A strong sequence-disclosure strategy commonly begins with one or more clearly identified reference sequences.
For a telomerase invention, this might involve:
- A particular TERT sequence
- A particular telomerase RNA sequence
- A defined telomeric repeat sequence
- A specific engineered construct
The reference should be assigned a consistent sequence identifier and described sufficiently to establish what it represents.
This creates an anchor for subsequent disclosures such as:
- variants;
- fragments;
- homologs;
- sequence-identity ranges;
- mutations;
- functional equivalents; and
- nucleic acids encoding the corresponding proteins.
The relationship among these categories should be explicit rather than left to inference.
4. Distinguish Exact Sequences From Functional Variants
One of the most important drafting decisions is whether the invention depends on an exact sequence or on biological function.
Consider two simplified claim concepts:
Narrow approach
A polypeptide comprising SEQ ID NO: 1.
Broader functional approach
A polypeptide having at least X% sequence identity to SEQ ID NO: 1 and retaining telomerase activity.
The second formulation potentially covers more subject matter, but it also raises more examination questions.
An examiner may ask:
- What sequences actually fall within the identity range?
- Is the claimed range adequately supported?
- Which substitutions are tolerated?
- What evidence establishes the claimed function?
- Is the entire claimed genus enabled?
- Are there meaningful structural limitations beyond sequence identity?
The specification should therefore provide a technical basis for the intended breadth rather than simply stating a desired percentage identity.
5. Treat Sequence Identity as a Claim Strategy, Not a Magic Number
Sequence identity percentages can be useful, but choosing a number such as 80%, 90%, or 95% does not automatically establish patentable scope.
A robust disclosure should explain why variants within the contemplated range are expected to retain the relevant property.
Depending on the invention, useful supporting material may include:
- Naturally occurring homologs
- Conserved-domain analysis
- Known catalytic residues
- Structure-function information
- Experimental mutants
- Functional assays
- Comparative activity data
- Sequence alignments
- Examples of tolerated substitutions
For a telomerase-related invention, the relevant function could include, for example, catalytic activity, telomere-extension activity, substrate binding, localization, complex formation, or another experimentally measurable property.
The more functional significance the claim attaches to sequence variation, the more important the supporting disclosure becomes.
6. Separate Sequence Disclosure From Functional Disclosure
A sequence listing answers an important question:
What is the sequence?
It does not necessarily answer:
What does the sequence do?
These are different disclosure functions.
A well-developed biotech specification can connect them by describing:
- the sequence;
- the encoded or corresponding molecule;
- relevant structural features;
- the biological activity;
- experimental evidence;
- variants that preserve the activity; and
- applications of the molecule.
This connection becomes especially important during examination of broad functional claims.
For example, simply providing a long TERT sequence does not necessarily establish that every sequence variant within a broad identity range performs the claimed telomerase function.
7. Pay Attention to Written-Description Issues
Sequence-heavy biotech claims can face written-description objections when the claim covers a broad class but the application identifies only a small number of specific sequences or embodiments.
The risk increases where the claim attempts to cover:
- broad sequence-identity ranges;
- large mutation sets;
- functional variants;
- broad genus claims;
- unidentified homologs;
- structurally diverse molecules sharing only a functional property.
A useful drafting strategy is to build the specification progressively:
Reference sequence → structural features → variants → functional data → broader genus
rather than jumping directly from one sequence to an expansive functional genus.
For U.S. practice, sequence-listing content is treated as part of the disclosure under the current USPTO sequence rules, which apply to applications filed on or after July 1, 2022 that contain qualifying nucleotide or amino-acid sequence disclosures.
The practical consequence is important: sequence-listing preparation should be coordinated with substantive patent drafting rather than treated as a purely formatting exercise.
8. Consider Enablement Separately
Written description and enablement are related but distinct examination issues.
A specification may identify a broad sequence genus yet still face questions about whether the skilled person can make and use the full scope without undue experimentation.
For a telomerase invention, enablement questions may become significant when the claims encompass a large number of sequence variants that are alleged to retain a biological function.
The specification can strengthen its position by describing:
- appropriate assay methods;
- representative active variants;
- methods for producing variants;
- methods for testing activity;
- relevant structural constraints;
- cellular or biochemical systems;
- expected relationships between sequence changes and function.
The more experimental or unpredictable the relevant biological property, the more important representative evidence can become.
9. Disclose Mutations Strategically
If the invention involves engineered telomerase variants, do not limit the disclosure to a single successful mutant if broader protection is commercially important.
Consider whether the specification should identify:
- individual substitutions;
- substitution positions;
- groups of substitutions;
- conservative substitutions;
- insertions;
- deletions;
- combinations of mutations;
- corresponding nucleic-acid sequences;
- functional consequences.
However, broad mutation lists should have a technical rationale.
A disclosure that simply says “the protein may contain one or more mutations” provides less useful support than a disclosure that explains which regions can be modified and what properties are expected to remain intact.
10. Decide Which Sequences Should Be Enumerated
ST.26 introduces an important drafting consideration because the formal sequence-listing obligation is tied to how sequences are disclosed.
The EPO explains that a sequence described only in prose – for example, by referring to positions within an existing sequence – does not necessarily need to be entered as a separate sequence identifier. But if the residues of that fragment are actually enumerated and meet the applicable threshold, the fragment may need its own sequence-listing entry.
This creates a practical distinction between:
Prose reference
nucleotides 90–179 of SEQ ID NO: 1
and:
Enumerated fragment
[the individual residues at positions 90–179 are expressly listed]
The latter can trigger separate sequence-listing treatment.
Drafting teams should therefore decide deliberately when to enumerate a sequence and when to refer back to an existing SEQ ID.
11. Be Careful With Ambiguous Residues
Telomerase and genomic sequences can involve uncertainty, variants, or mixtures.
ST.26 has specific rules for residues that are not specifically defined, including the use of symbols such as n for undefined nucleotide residues and X for undefined amino acids.
The treatment becomes particularly important when an enumerated sequence contains gaps or regions of undefined length. Current EPO guidance explains that different representations may be required depending on whether the number of undefined residues is known.
This is another reason sequence-listing preparation should be performed using appropriate ST.26 software and validation rather than manually assembling XML.
12. Avoid Accidental Added Matter During Sequence Conversion
One of the most serious sequence-drafting problems can occur when information is changed during conversion between sequence-listing formats or during later amendments.
The transition from ST.25 to ST.26 is particularly relevant to older applications.
WIPO states that applications filed on or after July 1, 2022 must use ST.26, while earlier applications remain subject to the applicable ST.25 transition rules.
The EPO specifically notes that ST.26 contains recommendations intended to prevent potential added or deleted subject matter when sequence listings are converted from ST.25.
For prosecution teams, this means a sequence conversion should be treated as a substantive document-control exercise, not simply as a technical file conversion.
13. Understand the Difference Between Filing Compliance and Substantive Support
A sequence listing can be formally compliant while the patent claims still have substantive problems.
For example, a sequence listing may pass an XML validation check but the application could nevertheless face an objection concerning:
- written description;
- enablement;
- clarity;
- support;
- added subject matter;
- claim construction;
- unity;
- novelty;
- inventive step or obviousness.
WIPO’s WIPO Sequence software is designed to validate sequence-listing compliance, but validation does not replace substantive patent review.
This distinction should be built into the drafting workflow.
14. Expect Sequence-Related Search Consequences
Sequence-listing compliance can directly affect patent examination and searching.
The EPO’s current guidance states that if a required ST.26 sequence listing is unavailable or non-compliant, the applicant may be invited to furnish a compliant listing and pay a late fee. If the deficiency is not remedied within the applicable period, the international search may be limited to the extent that a meaningful search can be performed.
This matters because a defective sequence listing can therefore create more than a formal inconvenience.
If the examiner cannot effectively search sequence-based subject matter, the resulting search or examination may be incomplete.
For sequence-intensive biotech applications, getting the listing correct at filing is therefore part of the substantive prosecution strategy.
15. Consider Prior-Art Sequence Identification
Another important strategy is deciding how prior-art sequences should be referenced.
Where a known sequence is already publicly available, identifying it by an appropriate database accession and version information can be useful.
The EPO provides an exception under its sequence-listing guidance for certain prior-art sequences that are publicly available in sequence databases and are identified appropriately in the application.
This can reduce unnecessary duplication while preserving a clear reference to the prior-art sequence.
However, the drafting team should distinguish between:
- a sequence that is merely background prior art;
- a sequence incorporated into the inventive disclosure;
- a sequence used as the reference for a claimed genus; and
- a sequence that must itself be searched or examined as part of the claimed subject matter.
16. Coordinate SEQ ID Numbers Across the Entire Application
SEQ ID numbers should be treated as controlled identifiers.
For every sequence, confirm that:
- the sequence is correct;
- the same SEQ ID refers to the same sequence everywhere;
- the description uses the correct identifier;
- claims use the correct identifier;
- figures use the correct identifier where applicable;
- examples correspond to the correct sequence;
- the sequence listing matches the application text.
The EPO specifically requires the sequence identification numbers used in the description to correspond to those in the sequence listing, with the same SEQ ID referring to the same sequence.
A sequence-number mismatch can create unnecessary prosecution complications and, in a serious case, uncertainty about what was actually disclosed.
17. Use a Layered Disclosure Strategy
For many telomere and telomerase inventions, a useful drafting architecture is:
Layer 1 – Exact sequences
Disclose the specific nucleotide and amino-acid sequences that are actually used.
Layer 2 – Closely related variants
Describe experimentally tested variants and their properties.
Layer 3 – Structural relationships
Identify conserved domains, catalytic regions, binding regions and other relevant structural features.
Layer 4 – Functional definitions
Explain what characteristics a variant should possess, such as a defined telomerase activity.
Layer 5 – Broader sequence relationships
Where technically justified, describe homologs, sequence-identity ranges, substitutions, fragments and related sequence classes.
Layer 6 – Implementations
Connect the sequence-defined molecules to cells, vectors, compositions, assays, therapies, or other practical embodiments relevant to the invention.
This layered structure provides the examiner with progressively more context for understanding why the claimed sequence scope is technically meaningful.
18. Common Examination Problems
Several recurring problems deserve special attention.
Problem 1: One sequence, extremely broad claim
Risk: The application provides one TERT sequence but claims an extensive genus of variants.
Drafting response: Provide technical support for the genus through structural, functional, comparative and experimental disclosures where appropriate.
Problem 2: Functional claim without sufficient sequence support
Risk: The claim defines a molecule primarily by its ability to affect telomerase or telomere biology, while the specification provides limited guidance for identifying suitable molecules.
Drafting response: Explain the relationship between sequence, structure and function and provide representative embodiments.
Problem 3: Sequence-listing error
Risk: The XML listing omits a qualifying sequence or contains incorrect sequence information.
Drafting response: Validate the listing and cross-check it against the complete application before filing.
Problem 4: Inconsistent SEQ IDs
Risk: The description, claims, examples and sequence listing use different identifiers.
Drafting response: Perform an automated and manual sequence-ID reconciliation before filing.
Problem 5: Added matter during amendment
Risk: A newly introduced sequence or sequence variant is not directly supported by the application as filed.
Drafting response: Maintain a clear disclosure map showing the source of every sequence and claimed variant.
19. Build a Sequence Disclosure Matrix
The matrix can also include:
- filing disclosure;
- priority disclosure;
- provisional application support;
- PCT disclosure;
- national-phase status;
- amendments;
- claim references; and
- experimental support.
This provides a useful audit trail when the application moves through multiple jurisdictions.
20. Use Current ST.26 Tools and Validation
For applications requiring sequence listings, applicants should use a current ST.26-compliant workflow.
WIPO provides WIPO Sequence as a tool for preparing and validating sequence listings and its current suite includes validation functionality. The latest version listed by WIPO as of July 2026 is WIPO Sequence 3.1.3.
The practical workflow should be:
Source sequences → Draft application → Generate ST.26 listing → Validate → Reconcile against application → Final legal review → File
Do not assume that a sequence listing generated early in prosecution remains correct after substantive amendments.
Any amendment affecting sequence disclosure should trigger a fresh comparison.
21. U.S., PCT and European Examination Should Not Be Treated as Identical
Although ST.26 provides international harmonization, substantive patent examination remains jurisdiction-specific.
For U.S. applications filed on or after July 1, 2022 that contain qualifying sequence disclosures, USPTO rules require a sequence listing in XML format conforming to the applicable requirements. The USPTO also states that, for U.S. applications, the content of the required sequence listing is considered part of the disclosure of the invention.
For PCT applications, ST.26 is integrated into the international sequence-listing requirements and failure to provide an appropriate listing can affect the international search.
For European applications, the EPO likewise requires ST.26-compliant sequence listings for qualifying applications filed from July 1, 2022 onward, with specific procedures for deficiencies and later-filed listings.
Accordingly, a global filing strategy should distinguish between:
sequence-format compliance and substantive patentability/support requirements.
22. A Recommended Drafting Workflow
For a new telomere or telomerase patent application, a practical workflow is:
Step 1 – Identify the invention’s biological components
Determine whether the invention concerns TERT, telomerase RNA, telomeric DNA, engineered variants, regulatory sequences, cells, constructs, or combinations.
Step 2 – Collect source sequences
Obtain verified sequence files from the experimental team and establish their provenance.
Step 3 – Assign controlled sequence identifiers
Create the initial SEQ ID inventory before drafting claims.
Step 4 – Identify commercially important variants
Determine which natural, engineered, or foreseeable variants may matter to the business.
Step 5 – Develop technical support
Connect sequence variation with structure, activity and experimental results.
Step 6 – Draft the specification around the sequence architecture
Explain exact sequences first, then supported variants and broader sequence concepts.
Step 7 – Prepare the ST.26 listing
Use appropriate software and current applicable standard requirements.
Step 8 – Validate the listing
Run formal validation and review the validation report.
Step 9 – Cross-check the application
Compare the XML sequence listing against the description, claims, examples, figures and experimental records.
Step 10 – Perform an examination-risk review
Ask whether the intended claim scope creates foreseeable issues involving written description, enablement, novelty, inventive step, clarity, support, or added matter.
Step 11 – Lock the filing version
Preserve the exact sequence files and application version used for filing.
Step 12 – Reconcile every later amendment
Any change to a sequence, SEQ ID, sequence range, mutation, or sequence-defined claim should trigger a renewed disclosure analysis.
Final Takeaway
For telomere and telomerase inventions, sequence disclosure should be treated as both a technical disclosure task and a patent-examination strategy.
The strongest applications generally do more than provide a sequence listing. They establish a traceable relationship between:
sequence → structure → function → experimental evidence → contemplated variants → claim scope.
That relationship becomes particularly important when applicants seek protection beyond an exact sequence.
At the same time, formal ST.26 compliance must be handled independently from substantive patentability analysis. A technically valid XML sequence listing does not by itself establish written-description support or enablement for broad sequence-based claims.
For patent draftsmen and counsel, the practical objective is therefore to create a sequence architecture that is complete enough for searching and formal compliance, precise enough to avoid ambiguity and sufficiently supported to withstand substantive examination.
Because sequence-listing rules and substantive examination standards vary by jurisdiction and can change, the final filing strategy should be checked against the current rules of each relevant patent office. This article is a drafting and examination overview, not legal advice.