The ability of a party filing a patent application to “claim priority” from the filing of an earlier application is enshrined in Article 4 of the Paris Convention of 1883. At first sight it appears a simple matter for the applicant for the original application, or their successor in title, to claim the benefit of the earlier filing date for the same invention. However, over the years a number of questions have arisen as to the conditions which must be fulfilled for the priority claim to be validly made. In light of the recent high-profile European Board of Appeal hearing involving priority issues in a CRISPR gene editing case (T 844/18), which members of our team attended as observers, we provide some practical suggestions of how to avoid potential problems. 

Introduction

Intact priority claims are often of vital importance to patent validity in jurisdictions without a prior art grace period. An invalid priority claim often equates to an invalid patent due to an intervening publication of relevant prior art, be it by third parties or by the applicant themselves.

For a claim to priority to be valid, the priority-claiming application must be filed by the “same applicant” or the successor in title as the applicant of the original priority application. The recent decision T 844/18 has reinforced how the term “same applicant” is interpreted by the European Patent Office (EPO). Although the full written decision is not yet available, the case emphasises that, where a priority application is filed by a plurality of applicants (“co-applicants”), for the applicant of the subsequent priority-claiming application to be considered the “same applicant”, all co-applicants (or their successor(s) in title) must be included. This means that for any subsequent priority-claiming application, applicants can be added, but not removed, unless their share of the priority right is validly transferred to one of the other parties continuing as an applicant.

This serves as a timely reminder to applicants and their advisers to examine carefully the question of which party holds the right to priority, prior to the filing of any subsequent priority-claiming applications.

It is also important to remember that, if the subject matter is broadened when filing the priority-claiming application, compared to the disclosure of the priority application, a claim may be entitled to different priority dates for the different subject matter. Ideally, such broadening should be avoided, or handled carefully if it is unavoidable.

Current best practice when drafting and filing

Most priority issues can be avoided easily by following good practice at the drafting and filing stages. Our main recommendations are as follows:

• Always file a later priority-claiming application in the same party name(s) as the priority application, or ensure that an assignment document is executed prior to filing the later application in the name of the assignee.
• If the priority application was filed jointly in the name of more than one party, file the later priority-claiming application naming all of those parties, or ensure that an assignment document is executed prior to filing, to transfer the priority right to at least one of the other co-applicants.
• Any assignment should be executed by assignor and assignee and explicitly mention assignment of the right to claim priority.
• Where a person signs on behalf of a company, take care to ensure they have the necessary authority.
• If it is necessary to broaden or change the definition of the invention as claimed in the priority-claiming application, compared to the priority application, do so carefully. If possible, the scope of the priority-claiming application should be altered in a way that finds basis in the disclosure of the priority application.
• If the priority application does not provide the required basis for alterations, and particularly if the scope of the definition of the invention is to be broadened, text should be included in the specification which explicitly delineates the subject matter which was disclosed in the priority application from the subject matter which is covered by the broader definition. Unless changes are unavoidable, the original text of the priority application should be retained and added to, rather than altered or deleted.
• If a claim in the priority-claiming application is to be broadened in scope, as compared to the priority application, use of a generic definition covering original and added subject matter is acceptable, but it is advisable to include in the text a definition of the generic term which explicitly delineates, as clearly defined alternative subject matters, the original and the added matter. For example, if a range is broadened from “3-5” to the range “1-8”, include a definition that this means “1-2 or 3-5 or 6-8”.

If you are preparing revisions to a specification prior to claiming priority, at Greaves Brewster we are always happy to advise on the suitability, under European practice, of the changes to be made. We can also make suggestions as to the most appropriate practice in order to mitigate the likelihood of challenges to the validity of the priority claim in Europe.

Recognising priority problems in existing filings and finding solutions

There are two main ways in which a claim to priority can be found invalid, according to case law developed over the last few years at the European Patent Office (EPO) and in the UK Courts.

• The party named as applicant on the priority-claiming application is not entitled to the right to claim priority from the original priority application

How does this arise?

The party which is the applicant for the later application may believe that it is the effective owner of the priority application and the associated right to claim priority from it, for example if it is the employer of an inventor who was the applicant for the priority application, or if the invention has been made under some other contract. That is, the party considers itself to be the “successor in title” of the inventor.

However, legal title may not have been transferred unless an assignment document has been completed before the priority-claiming application has been filed. Such a failure to transfer the legal title with an assignment, pre-dating the later application, can lead to a loss of priority. This cannot be avoided by a subsequent completion of an assignment document including a statement that the assignment has retroactive effect.

An alternative possibility is a co-applicant of a priority application believing that as one of the applicants of the priority application, they are entitled to file subsequent priority-claiming applications without the other co-applicants. For example, a priority application may have been filed by co-applicants A and B. Yet the subsequent priority-claiming application was filed by co-applicant B alone. This situation may arise in the USA, where a priority application and subsequent application need only have one overlapping inventor in common (inventors often being named as co-applicants).

However, under the European Patent Convention, all co-applicants of a priority application must be named on the subsequent priority-claiming application for the priority to be claimed validly. The only exception to this is when the right (and associated right to claim priority from) to the priority application is transferred to the remaining co-applicants, or to another party named as an applicant. Again, any necessary assignment document must have been completed before the priority-claiming application is been filed.

An assignment document was not completed before filing – what can be done?

Depending on the law which applies to the relationship between the priority applicant and the later applicant, it may be that the equitable right to claim priority was transferred in time. If this is the case, it may be sufficient to rely on this. The notion of equity does not exist under all legal systems, however, so this approach may not be effective for all countries.

If legal title has not been transferred but the transfer may have occurred in equity, care should still be taken as to which party name to use when filing the priority-claiming application. If a party holding the legal title makes a claim to priority when the equitable title has been transferred away from them, the claim may be invalid.

If neither legal nor equitable title has been transferred to the party which claimed priority, for applications pending at the EPO it may be possible to request a correction of the applicant to the party which filed the priority application. This can be successful in restoring the effectiveness of the priority claim, but can only be done before grant. At Greaves Brewster, we have successfully acted for a number of clients to arrange such corrections, though we would caution that this should not be relied upon, as EPO practice may change in this area.

If you are concerned that there may be a problem with the entitlement to claim priority, please consult one of us at Greaves Brewster. We can propose the best course of action, on the basis of the particular facts of the case.

• The invention claimed in the priority-claiming application is not the “same invention” as the invention disclosed in the priority application

How does this arise?

A later application may claim priority from an earlier application if it relates to the “same invention” as that earlier application. Under EPO case law, the “same invention” is the subject-matter which a skilled person might directly and unambiguously derive from the disclosure of the priority application. At least very strong implicit, ideally literal, basis for a claimed combination of features is required in the priority document in order for a priority claim to be valid for that combination.

If the definition of the invention is altered in the text of the priority claiming application, compared to the text of the priority application, this may lead to a loss of entitlement to priority in the following situations:

• The priority application disclosed feature A but the later application claims “A and B”. Since the combination “A and B” was not disclosed in the priority application, the claim in the later application is not entitled to claim priority.
• The priority application disclosed feature “A” but the later application claims “A or B”. In this case, the part of the claim covering “A” is entitled to claim priority, whilst the part of the claim covering “B” is not, instead taking the filing date of the later application as its priority date. The claim has more than one priority date.

There are some situations where an “OR” claim is not presented as including explicit alternatives, but rather covers broader alternatives in a generic fashion. For example, this might be achieved by broadening a claimed range, or by broadening the definition of a class of chemical compounds. Such a so-called “generic ‘OR’ claim” is also capable of having multiple priority dates, provided that the generic term gives rise to the claiming of a limited number of clearly defined alternative subject-matters.

It looks like a pending claim may not be entitled to priority – what can be done?

Available options to restore priority to a pending claim depend on the content of the priority document and the priority-claiming application as filed. In some cases amendments can be made such that the claim finds basis in the priority document in its entirety. In other situations, a small amendment may transform a claim from being an AND claim (see (i) above) into an OR claim (see (ii) above), such that it is at least partly entitled to priority. Even partial entitlement to priority can make all the difference to which prior art becomes relevant.

Often the approach to amending such claims has to balance commercial requirements, prior art issues and priority considerations. Of course, in some circumstances, it may be the preferred option to accept a loss of priority. However, such a loss of priority should be a conscious decision, such that vulnerabilities in validity are managed as well as possible and do not come as a surprise post-grant.

Once again, if you are concerned that there may be a problem with the entitlement to claim priority, please consult one of us at Greaves Brewster. We can propose the best course of action, on the basis of the particular facts of the case.

This update is for general information and does not constitute legal advice. If you have any questions regarding the issues discussed in this update, please contact your usual Greaves Brewster attorney, or Rhiannon Turner.

Sources of case law

The party claiming priority

Relevant EPO cases

T62/05 – deciding that a formal assignment document is required for the right to claim priority to be transferred. (https://www.epo.org/law-practice/case-law-appeals/pdf/t050062eu1.pdf)

T517/14 and T205/14 – deciding that the right to claim priority may have been transferred in equity (according to the law determining the relationship between the parties), even if the ownership of the priority application has not been transferred (https://www.epo.org/law-practice/case-law-appeals/pdf/t140517eu1.pdf and https://www.epo.org/law-practice/case-law-appeals/pdf/t140205eu1.pdf)

J19/87 – the equitable title of the priority right may have been transferred, according to the evidence of the intention of the parties, even though the formal legal title had not. (https://www.epo.org/law-practice/case-law-appeals/pdf/j870019eu1.pdf)

T577/11 – for priority to be claimed validly, the transfer of title must have been completed before the priority-claiming application is filed. A subsequent assignment, stating that the assignment has retroactive effect, does not provide the required transfer. (http://www.epo.org/law-practice/case-law-appeals/pdf/t110577eu1.pdf)

T844/18 – in circumstances where a priority application is filed by a number of co-applicants, for priority to be validly claimed by a subsequent priority-claiming application, all of the co-applicants must be named, or valid transfers to the continuing applicants executed prior to filing. (https://www.epo.org/law-practice/case-law-appeals/communications/2020/20200117.html and https://www.greavesbrewster.co.uk/breaking-news-european-priority-law-maintained-at-epo-board-of-appeal-crispr-hearing/)

Relevant UK Court cases

Edwards Life Sciences AG v Cook Biotech Inc.– the applicant had no contractual relationship with one of the priority applicants and the right to claim priority was not assigned before priority was claimed. (http://www.bailii.org/ew/cases/EWHC/Patents/2009/1304.html)

KCI Licensing Inc v Smith and Nephew plc – the right to claim priority had been transferred, both legally and in equity, by a confidentiality agreement between the inventor and KCI, completed between the filing of the priority application and of the subsequent application claiming priority. (http://www.bailii.org/ew/cases/EWHC/Patents/2010/1487.html)

Idenix Pharmaceuticals Inc v Gilead Sciences Inc. –  the wording of agreements between the parties was effective to transfer the legal title to the invention and associated right to claim priority. Even if legal title had not been transferred, due to the intention of the parties equitable title had been transferred. This would have been sufficient for the priority claim to be valid. (https://www.bailii.org/ew/cases/EWCA/Civ/2016/1089.html)

Fujifilm & Others v Abbvie –provided equitable interest in the title of the priority right has been transferred, according to the evidence available, it does not matter if legal title has not also been transferred. If equitable interest has been transferred, a priority claim by the party holding the formal legal title may be invalid. (https://www.bailii.org/ew/cases/EWHC/Patents/2017/395.html)

The subject matter to be claimed

Relevant EPO cases

G2/98 – defining the meaning of “the same invention” for the purposes of claiming priority. (https://www.epo.org/law-practice/case-law-appeals/pdf/g980002ex1.pdf)

G1/15 – setting out the question to be answered when determining whether or not a claim is entitled to the priority date and the meaning of “clearly defined alternative subject-matters”. (https://www.epo.org/law-practice/case-law-appeals/pdf/g150001ex1.pdf)

T 557/13 – the Board of Appeal which provided the referral to the Enlarged Board of Appeal in G1/15; contains a detailed analysis of preceding conflicting case law. (https://www.epo.org/law-practice/case-law-appeals/pdf/t130557ex1.pdf)

T1519/15 – the Board of Appeal applied G1/15 to decide that the absence of a feature in a claim of a subsequent application, when the claim of the priority application contained the feature, can be seen as a broadening of scope to which partial priority can be applied, so that different subject matter covered by claim 1 had different priority dates. (https://www.epo.org/law-practice/case-law-appeals/pdf/t151519eu1.pdf)

Relevant UK Court cases

Nestec S.A., Nestlé Nespresso S.A. et al. v. Dualit et al. – conclusion that the use of a generic definition in a claim meant that there was no “clearly defined alternative subject matter”, so it was not possible to allocate different priority dates to different parts of the claim. Therefore, the whole claim was not entitled to the priority date. (https://www.bailii.org/ew/cases/EWHC/Patents/2013/923.html)

Nicocigs v. Fontem Holdings & Fontem Ventures – it was found that, for priority to be claimed, the priority disclosure must support the claim across the whole breadth; because this was not the case, the claim was not entitled to claim priority. (https://www.bailii.org/ew/cases/EWHC/Patents/2016/2161.html)