New requirements for sequence listings


On 1 July 2022, the new WIPO ST.26 sequence listing standard came into effect in all WIPO-contracting states. New PCT, national and regional applications, with a filing date (not the priority date) after 1 July 2022 must comply with the ST.26 standard.  This does not apply to PCT applications with a filing date before 1 July 2022 with a national/regional phase entry date after 1 July 2022.

For UK divisional applications, the UK IPO has confirmed that they will not require an ST.26 compliant sequence listing if the parent application has a filing date before 1 July 2022. In this case only, the ST.25- compliant sequence listing filed on the parent application can be used. However, this is not the case for UK and European priority-claiming applications and European divisional applications all of which require an ST.26 compliant sequence listing.

What is a sequence listing?

A sequence listing contains nucleotide or amino acid sequences disclosed in a patent application and forms part of the description. The purpose of a sequence listing is to allow sequence data of the application to be searchable by IP offices and the public databases (INSDC: International Nucleotide Sequence Database Collaboration).

What has changed?

The new ST.26 standard introduced many new aspects to sequence listings. Most notably, adopting an .XML format over .TXT format used in ST.25 and the, now mandatory, use of feature keys and qualifiers. Moreover, nucleotide analogues (e.g., PNA or GNA), D-amino acids and linear portions of branched sequences must now be included in the sequence listing.

Perceived issues

The requirement to include more information related to nucleotide and amino acid sequences in ST.26 compared to ST.25 could present potential issues in light of the EPO’s strict basis requirements. For example, any new information included in the ST.26 compliant sequence listing that is not disclosed in the earlier application (e.g. priority or parent application) could be deemed to add subject matter potentially resulting in added subject matter and/or lack of priority objections.

For new filings, issues may also arise due to the increased features that must be included in the sequence listing, e.g., D-amino acids etc, which increases the amount of time and effort involved in creating the ST.26 compliant sequence listing.


The WIPO ST.26 standard provides information on how we may avoid potential added matter issues and maintain a valid priority claim. We are adapting this information in line with European practice and have the below advice:

  • For UK and European priority-claiming applications and European divisional applications, where the sequence listing forms part of the priority or parent application as filed, the ST.25 sequence listing filed with the priority or parent application should be included in the description to ensure that no subject matter is lost. This will increase the number of pages in the application and, as a consequence, the number of additional pages fees due. Where possible, we advise providing instructions concerning filing these applications at least two weeks in advance of the respective deadline. This will ensure that we have sufficient time to prepare the ST.26 compliant sequence listing, if required.
  • For first-filings, we suggest reciting the sequences in the description and providing as much information about the sequence as possible (for example, molecule type and organism) so that the ST.26 sequence listing can be formulated without adding subject-matter.


What can we do to help?

Forresters’ Life Sciences team is well versed in the new ST.26 sequence listing requirements. If you have any questions, please reach out to your usual Forresters attorney who will be happy to assist. In particular, we are happy to assist in preparing ST.26 sequence listings as well as reviewing any ST.26 sequence listings prepared by external providers.

Lara Weaver
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