assignment of priority right

Practice points

The entitlement of the intended Convention applicant to the priority rights of all the priority applicants should always be checked before filing the Convention application.

Where necessary, ensure that assignments of the priority rights, that are valid assignments under the relevant national law, have been executed by all the priority applicants in favour of the intended Convention applicant before filing the Convention application.

We recommend that these assignments should at least be in writing, preferably signed by both parties (see T62/05) unless this is clearly not required under relevant national law, and preferably should expressly assign the right to claim priority (in addition to any rights in the invention and the priority application).

If suitable assignments have not been put in place, it may still be possible to establish the Convention applicant’s title as successor through relevant applicable national law e.g. rights may have vested by operation of law or contract or the existence of rights in equity may suffice.

Where there is any doubt, assignments should be completed

If not all the relevant assignments are in place or there is any doubt as to the intended Convention applicant’s entitlement, the applicants for the Convention filing should include those priority applicants (or successors in title through valid assignments, etc.) who have not assigned their rights to the intended Convention applicant.

If the Convention applicant was not the successor in title to all the priority applicants at the Convention filing date, correction may be possible. Correction should be considered at an early stage as it may be more convenient to deal with this under the PCT rather than regionally/nationally. However, correction needs to be approached with caution as it could make public a possible priority problem.

Retroactive assignments may be an alternative route to establishing succession under relevant national law, if these would be treated, as between the parties and in relation to third parties, as entered into prior to the Convention filing date. However these may well not be acceptable to cure a priority problem in the EPO and the UK in light of the approach in T62/05 and the comments in Edwards v Cook.

Relevant provisions

Article 4A(1) Paris Convention (Stockholm Revision):

Any person who has duly filed an application for a patent, or for the registration of a utility model, or of an industrial design, or of a trademark, in one of the countries of the Union, or his successor in title, shall enjoy, for the purpose of filing in the other countries, a right of priority during the periods hereinafter fixed.

Article 87(1) European Patent Convention:

Any person who has duly filed, in or for (a) any State party to the Paris Convention for the Protection of Industrial Property or (b) any Member of the World Trade Organization, an application for a patent, a utility model or a utility certificate, or his successor in title, shall enjoy, for the purpose of filing a European patent application in respect of the same invention, a right of priority during a period of twelve months from the date of filing of the first application.

In the UK, the priority date of an invention is dealt with by section 5 Patents Act which, by section 130(7), is to be construed in conformity with the corresponding provisions of the EPC (including Article 87).

Relevant case law – UK

KCI Licensing Inc & Others v Smith & Nephew Plc – UK Patents Court: Arnold J – 23rd June 2010

One of the issues in this infringement action was the validity of the priority claim to European patents (UK).

The US priority applicant was Mr Lina.  The PCT applicants were Mr Lina and Mr Heaton for the US, Kinetic Concepts Inc (Mr Lina’s employer) for all designated states except the US and Mediscus Products Ltd (Mr Heaton’s employer and a wholly-owned subsidiary of KC Inc) for GB only.

Arnold J found that KC Inc was the sole applicant for the PCT application in so far as it related to the European patents; Mediscus was only a co-applicant in relation to the GB national which was not in issue – see further comments below.

The principal question to be addressed was therefore whether KC Inc was a successor in title for the purpose of validly claiming priority.

Arnold J said that it was common ground that “successor in title” means successor in title to the invention, which was also common ground in Edwards v Cook, referred to below.

A Confidentiality Agreement between Mr Lina and KC Inc contained an express assignment of all his rights in inventions conceived or developed by him during his employment and a further assurance to enable the company to file patent applications for the inventions. Although the Agreement was governed by Texas law, no evidence as to Texas law was put forward and it was therefore common ground that it should be assumed to be the same as English law.

Arnold J held that an assignment of rights in a future invention was effective, under English law, to assign legal title to the invention to KC Inc and that therefore KC Inc was Mr Lina’s successor in title at the date of the PCT Application. Alternatively, if an assignment of a future invention could not convey the legal title, the Agreement had transferred the beneficial interest in the invention, including the right to file patent applications: this was sufficient to make KC Inc the successor in title to Mr Lina for the purposes of claiming priority, even if KC Inc had not acquired the bare legal title; he referred to J19/87 in support, which is discussed below.

He commented that the operation of Article 4A Paris Convention and Article 87(1) EPC, being provisions of international treaties, could not depend upon the distinction drawn by English law, but not by most other laws, between legal and equitable title.

Thus,“when determining whether a person is a “successor in title” for the purposes of the provisions, it must be the substantive rights of that person, and not his compliance with legal formalities, that matter”.

This appears to be a more relaxed approach than that adopted by the EPO Board of Appeal in T62/05, discussed below.

There was an issue over whether Mediscus was named as an applicant for the EP(UK) or just the GB national (which was not the subject of the proceedings) and whether Mediscus was entitled to rely upon the priority claim.  The case was contrasted with Edwards v Cook (see below) where there had been 3 priority applicants and one PCT applicant which was the successor in title to the rights of only one of the priority applicants. Having found that Mediscus was not a co-applicant of the EP(UK), Arnold J nevertheless went on to consider whether, if he were wrong, this would adversely affect the priority claim.  KCI argued that KC Inc had agreed by conduct to transfer part of its interest in the invention to its subsidiary Mediscus and that this was sufficient to make Mediscus a successor in title for the purposes of claiming priority and that no greater degree of formality was required.  Arnold J accepted this submission and held that the priority claim would therefore not be adversely affected if Mediscus was held to be a co-applicant. Arnold J’s decision appears to be based on the premise that all the PCT applicants had to be successors in title to the priority applicant for the purpose of validly claiming priority.

However, it was accepted that the PCT application disclosed the same invention as that disclosed in the priority application. Mr Heaton had not in fact contributed to the invention and Mediscus, his employer, was named purely as a device for filing the PCT application through the UK-IPO.

Arnold J’s decision does not therefore deal with the situation where the Convention application contains added inventive matter. Since the added inventive matter cannot in any event benefit from the priority, it is reasonable to argue that the addition of a non-successor co-applicant for the Convention filing should not adversely affect the validity of the priority claim for the invention described in both the Convention filing and the priority application.

Edwards Lifesciences AG v Cook Biotech Incorporated – UK Patents Court: Kitchin J – 12th June 2009

The validity of the priority claim was also in issue in this revocation and infringement action. (The subsequent appeal was decided on 28th June 2010 on the issue of obviousness and so it was not necessary to review Kitchin J’s findings on the priority issue.)

The US priority application was filed in the names of 3 inventors: Obermiller, Osse and Thorpe. The applicant for the PCT application, from which the UK patent in suit derived, was Cook Biotech Incorporated.

For the purposes of Article 4A(1) Paris Convention, Kitchin J decided that “successor in title” must mean successor in title to the invention, as the parties before him had agreed. He added that “a person who files a patent application for an invention is afforded the privilege of claiming priority only if he himself filed the earlier application from which the priority is claimed or if he is the successor in title to the person who filed that earlier application”.

It was accepted that Cook was entitled to Obermiller’s rights via his contract of employment. Osse and Thorpe were not employees of Cook; they assigned their rights to Cook after the PCT filing date and before grant of the patent in suit.

The transcript of the hearing shows that the assignments were expressed to be effective from the priority date i.e. they were expressly retroactive. During the hearing, Kitchin J referred to the existence of case law to the effect that retrospective assignments “might be good between the two parties to the assignment but cannot properly affect the interest of third parties”. In the event, Cook appears not to have relied upon the assignments being retroactive but focused on the argument that assignment before grant was sufficient.

Kitchin J held that the priority claim was invalid because, at the filing date of the Convention application, Cook was neither the applicant for the priority application nor the successor in title from all the applicants for the priority application.

The assignment of the rights of Osse and Thorpe to Cook after the Convention application was filed (albeit that the assignments were worded to have retroactive effect) did not help because it remained the case that Cook was not entitled to claim the priority at the Convention filing date.

In his decision, Kitchin J stated that “any other interpretation would introduce uncertainty and the risk of unfairness to third parties”.

Kitchin J considered that his decision was consistent with EPO case law, in particular referring to T62/05 and J19/87 which are summarised below.

Relevant case law – EPO

T62/05 – Technical Board of Appeal – 14th November 2006

In this EPO case, the priority document was a Japanese filing in the name of Nihon GE Plastics KK, a Japanese company. The Convention filing was a PCT application in the name of a US company, GE Company, which owned a majority share in the Japanese priority applicant.

Under opposition, the validity of the priority claim was questioned.  GE Company then assigned the European patent to Nihon GE (without any retroactive wording or choice of law clause) in an attempt to save the priority claim.

The Board of Appeal said that this assignment was not relevant to the question of whether GE Company was entitled to claim priority from the Japanese priority application as at the Convention filing date. GE Company could only be considered as the owner of the right to claim priority provided it was established that the succession in title from Nihon GE to GE Company occurred before the end of the 12 month period starting from the filing date of the priority application.

Although the assignment did not state that it was retroactive (i.e. nunc pro tunc), this would probably not have made a difference to the outcome in light of the Board’s finding that entitlement to claim priority must be established at the date of the Convention filing or at least within 12 months of the priority date.

It was also argued that there was an understanding that GE Company was entitled to file for European protection and claim priority, with some inconclusive documents said to evidence this. No evidence was put forward asto how this understanding and the documents should be construed under any relevant national law and as to what law would be applicable.

The Board of Appeal said that priority rights are assignable independently of the corresponding patent application and may be restricted to specific countries. It then went on to consider the requirements for assignment of the priority rights in relation to the filing of a European patent application. It decided that the transfer of priority rights must be proven in a formal way and that it was reasonable to apply an equally high standard of proof as required for an assignment of a European patent application by Article 72 EPC i.e. in writing and signed by or for both parties.

The Board of Appeal decided that, even if an intention to transfer priority rights (i.e. before the PCT filing) might have been discerned from the various documents relied upon, this intention had not been finalised in a form that would indubitably establish that the transfer of the priority rights for the filing of a European patent application on the basis of the Japanese priority application had taken place before the end of the 12 months Convention period.

Of interest here is the fact that the Board did not consider whether any relevant national law might be applicable in determining the question of entitlement to the priority rights, by contrast with J19/87 and T1008/96, summarised below. No evidence on the relevant national law having been submitted, the Board considered the matter under the EPC. As the EPC makes no provision for the assignment of the right to claim priority, the Board applied the same standards for the valid transfer of such rights as apply under Article 72 for the valid transfer of a European patent application: in writing and signed by both parties.

J19/87 – Legal Board of Appeal – 21st March 1988

In this case, national law was considered in evaluating the validity of the priority claim.

The priority document was a UK filing by the inventor, Mr Belcher, who then assigned his rights in the invention, the UK application, the right to file further applications and the right to claim priority to National Research Development Corporation (a UK entity). NRDC later signed an assignment back to the inventor of the rights in the invention and the application but this document was not signed by the assignee, as was required at the time for a valid legal assignment of a UK patent application. The inventor subsequently filed the EP Convention application in his own name and then assigned both applications to Burr-Brown Corporation.

The validity of the priority claim became an issue when Burr-Brown sought to correct the EP Convention applicants ab initio to NRDC and Mr Belcher, arguing that the assignment from NRDC to Belcher was not effective as it was only signed by NRDC and that the European application contained additional inventive matter over the UK application for which Mr Belcher was the inventor.

In this case, Burr-Brown was invited to file a legal opinion as to the effect under English law of the assignment from NRDC to Mr Belcher that had only been signed by the assignor. The subsequently filed opinion of Nicholas Pumfrey (then, a UK barrister) was to the effect that the assignment was a valid legal assignment of the rights in the invention (making the assignee a successor in title of the inventor to the invention) and gave the assignee an equitable interest in the UK priority application.

Mr Pumfrey also said that, as an owner in equity of the priority application, the assignee was entitled to claim priority from that application as a successor in title (making the assignee a successor in title to the priority application under Article 87).

The Board relied on this in finding that there was a valid priority claim.

T1008/96 – Technical Board of Appeal –  25th June 2003

Again the Convention applicant differed from the priority applicant and the validity of the priority claim was raised in opposition proceedings. Both applicants were Italian and the priority documents were two Italian utility model applications. The Board stated that the question of entitlement should be answered in accordance with national law. Because of a conflict of evidence as to whether the Convention applicant was indeed the successor in title under Italian law, the priority claim failed.

This information provides a summary of the subject matter only. It should not be acted on without first seeking professional advice.

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• 27. October 2023

EPO on the assignment of priority rights

In its decision on the merged proceedings G 1/22 and G 2/22, the Enlarged Board of Appeal recently confirmed that the EPO has competence to assess whether a party has a priority claim based on the EPC.  This also applies if the priority right has been assigned to a legal successor. The formal requirements for such an assignment are set very low by the Enlarged Board of Appeal, which confirms the possibility of an implicit assignment.

The legal succession of priority rights, in particular the validity of assignments of priority rights, frequently raises questions in practice due to their international character. This is because transfers of private rights – such as priority rights – and underlying agreements are generally subject to national civil law. Since the origin, existence and effects of priority rights are governed only by the EPC (and by the Paris Convention in its relationship to the EPC), the Enlarged Board of Appeal is of the opinion that priority rights according to Article 87(1) EPC are autonomous rights under the EPC and should also be judged only in the context of the EPC, i.e. independently of national laws. In this context, according to the Enlarged Board of Appeal, it is justified to consider an agreement implied by the joint filing of a subsequent application as an agreement subject only to the autonomous law of the EPC. In this respect, the EPO is competent to assess whether a party is entitled to priority according to Article 87(1) EPC.

In principle, according to the autonomous law of the EPC, there is a rebuttable presumption that the applicant claiming priority is entitled to claim priority. Nothing else applies in the case where the priority right has been assigned to a legal successor. It was questionable to what extent a joint filing of a subsequent application constitutes an informal or silent (implicit) and effective agreement between two parties, if only one of the parties was an applicant of the earlier priority application. In this respect, the Enlarged Board of Appeal is of the opinion that if national laws already do not provide for any or only minor formal requirements for the assignment of priority rights, the autonomous law of the EPC should also not provide for any formal requirements higher than the national laws which may be relevant in connection with a European application. Rather, the EPO should be guided by the lowest standards of national law and accept implied assignments of priority rights in almost all circumstances. For example, the autonomous law of the EPC should not require that the assignment of priority rights be in writing or signed by the parties, as this would be a high threshold in view of national law. The Enlarged Board of Appeal concludes, based on the low formal requirements, that in the absence of unambiguous indications to the contrary, a joint subsequent application is sufficient evidence that the parties have entered into an implied agreement allowing one party to rely on the priority right established by the filing of another party’s priority application.

Almost incidentally, the Enlarged Board of Appeal also commented on the requirement that the assignment of the priority right must be completed prior to the filing of a subsequent European patent application. Even this requirement was questionable. If there are national legal systems that allow a subsequent (“nunc pro tunc”) assignment of priority rights, the EPO should not apply higher standards here either.

In summary, the assessment of whether a party is entitled to priority according to Article 87(1) EPC is, in the view of the Enlarged Board of Appeal, a question of autonomous law of the EPC, i.e. independent of national laws, and the EPO is competent in this respect. The formal requirements for the assignment of priority rights are set very low by the Enlarged Board of Appeal, which should be a great convenience for patent applicants in practice. Thus, in the future, it should generally be presumed that a priority claim exists in favor of the later applicant of a European patent application, even if the latter is not identical with the applicant of the earlier priority application.

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Latest news, shape matters – the epo’s new and fundamentally broader definition of „substance or composition” for medical use claims as per decision t 1252/20, t 2790/17: application of article 83 epc for second medical use claims in view of g 2/21, t 1076/21 – epo on a shift of the burden of proof when asserting insufficient disclosure, feel free to contact us.

European Patent Office Makes Major Changes in Priority Entitlement

The Enlarged Board of Appeal of the European Patent Office (EPO) has issued a new dual decision – G1/22 and G2/22 – dealing with the assessment of priority rights at the EPO. The decision represents a significant break from the previous practice of the EPO and seems to adopt a much more ‘pro-applicant/patentee’ approach when assessing these rights and their effects on European patents and patent applications. In particular, the onus on the applicant to demonstrate their right to claim priority has been greatly reduced, with the threshold for opponents attacking this right in opposition proceedings now significantly higher.

The two key questions answered by the Enlarged Board of Appeal are:

• Is the EPO competent to assess whether a party is entitled to claim priority under Article 87(1) of the European Patent Convention (EPC)?
• If question 1 is answered in the affirmative, can party B validly rely on the priority right claimed in a Patent Cooperation Treaty (PCT) application for the purpose of claiming priority rights under Article 87(1) EPC in a case where:
• A PCT application designates party A as applicant for the US only and party B as applicant for other designated states, including regional European patent protections.
• The PCT application claims priority from an earlier patent application that designates party A as the applicant.
• The priority claimed in the PCT application is in compliance with Article 4 of the Paris Convention.

In summary, the board’s answer to both questions is an emphatic yes .

In more detail, referring to the first question, the board drew a clear distinction between competency to ‘decide a dispute as to whether a particular applicant is legally entitled to apply for and be granted a European patent in respect of the subject-matter of a particular application’, where national courts are competent, and priority rights, where the board held that ‘no national laws are involved when a priority right is created or claimed for a subsequent application’. The board further reasoned that if the EPO was not competent to assess priority rights under its own law (i.e., not applying national law), then ‘situations could arise in which the EPO has evidence potentially affecting the patentability of an invention but cannot use such evidence in its decision on patentability’. This stems from the effect a valid priority right has on the assessment of prior art and is, evidently, a situation which is desirable to avoid. This scenario also is clearly distinct from entitlement proceedings, where the EPO is not competent, as the EPO’s assessment of patentability of the invention, and the prior art, should not be affected by the identity of the applicant (in part because the EPO does not provide carte blanche grace periods).

Accordingly, the board has decided that the EPO is competent to determine whether a priority right is validly claimed – i.e., whether a party is the successor in title required by the EPC – and that this assessment should be made using its own law and not the national law of the relevant member states. Furthermore, the board has decided that ‘the autonomous law of the EPC should not establish higher formal requirements than those established under national laws that may be relevant in the context of a European application’, and moreover that ‘the EPO should adapt itself to the lowest standards established under national laws and accept informal or tacit transfers of priority rights under almost any circumstances’. That the transfer of a priority right should not need to meet the same threshold as the EPO requires for the assignment of a European application (i.e., in writing and signed by both parties) is directly stated: ‘[T]he autonomous law of the EPC should not require that the assignment of priority rights has to be in writing and/or has to be signed by or on behalf of the parties to the transaction’.

Indeed, the board’s decision even implies another change from the practice, to date, that the transfer of priority rights must have occurred prior to the filing date of the European application, providing the rationale that ‘[i]f there are jurisdictions that allow an ex post (“nunc pro tunc”) transfer of priority rights … the EPO should not apply higher standards’. It is cautioned, however, that ‘the allowability of a retroactive transfer of priority rights may have limited practical relevance if priority entitlement is presumed to exist on the date on which priority is claimed for the subsequent European application’. That said, it is possible to add a priority claim to a European patent application 16 months from the earliest priority date, so there is – theoretically – a situation where an ex post transfer could be applied, though we expect the first cases to do so to be brought under significant scrutiny by third parties, although their ability to do so has been curtailed.

In line with the board’s new permissive approach to the transfer of priority rights, this ‘rebuttable presumption’ that the priority claim is valid ‘involves the reversal of the burden of proof, i.e. the party challenging the subsequent applicant’s entitlement to priority has to prove that this entitlement is missing’. This means that – for example, in opposition proceedings – an opponent cannot ‘just raise speculative doubts but must demonstrate that specific facts support serious doubts about the subsequent applicant’s entitlement to priority’. This higher burden on opponents, along with the more relaxed stance of the EPO, seems likely to reduce EPO proceedings – such as oppositions – where the validity of a priority claim on the basis of the patentee’s entitlement to claim priority is put to issue. It is important to note, however, that national courts will still have jurisdiction over granted European patents and are not beholden to the EPO’s approach or decisions. Thus, third parties are not necessarily prevented from raising this issue in national proceedings where a more stringent test might be applied.

Referring to the second question, it is perhaps unsurprising that the application of the answer to the first question has led to the board agreeing with the referring decision that ‘the mutual filing demonstrates – absent indications to the contrary – the existence of an implicit agreement between party A and party B, conferring party B the right to benefit from the priority for the EPC territory’. In order for this implied agreement to be questioned, the board considered that ‘evidence would be needed that an agreement on the use of the priority right has not been reached or is fundamentally flawed’. Situations such as those seen with pre-America Invents Act (AIA), US-originating PCT applications – where the US provisional priority filing is filed in the names of the inventors and the resulting PCT application designates the inventors as applicants for the US where, for example, their employer is the applicant elsewhere – appear to be officially resolved at the EPO for now.

Ultimately, the position adopted by the Enlarged Board of Appeal in response to the two questions at issue represents a significant softening of the EPO’s historically strict position on the assessment of priority. Whether this change in attitudes will be reflected in the courts of the EPO’s member states in the future – or whether applicants will potentially remain beholden to the EPO’s previous approach if they wish to enforce patent rights nationally – remains to be seen.

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Chapter II – Priority

Article 87 81 , 82 priority right.

(1) Any person who has duly filed, in or for 

(a) any State party to the Paris Convention for the Protection of Industrial Property or 

(b) any Member of the World Trade Organization,  

an application for a patent, a utility model or a utility certificate, or his successor in title, shall enjoy, for the purpose of filing a European patent application in respect of the same invention, a right of priority during a period of twelve months from the date of filing of the first application. 

(2) Every filing that is equivalent to a regular national filing under the national law of the State where it was made or under bilateral or multilateral agreements, including this Convention, shall be recognised as giving rise to a right of priority. 

(3) A regular national filing shall mean any filing that is sufficient to establish the date on which the application was filed, whatever the outcome of the application may be. 

(4) A subsequent application in respect of the same subject-matter as a previous first application and filed in or for the same State shall be considered as the first application for the purposes of determining priority, provided that, at the date of filing the subsequent application, the previous application has been withdrawn, abandoned or refused, without being open to public inspection and without leaving any rights outstanding, and has not served as a basis for claiming a right of priority. The previous application may not thereafter serve as a basis for claiming a right of priority. 

(5) If the first filing has been made with an industrial property authority which is not subject to the Paris Convention for the Protection of Industrial Property or the Agreement Establishing the World Trade Organization, paragraphs 1 to  4 shall apply if that authority, according to a communication issued by the President of the European Patent Office, recognises that a first filing made with the European Patent Office gives rise to a right of priority under conditions and with effects equivalent to those laid down in the Paris Convention.

81 Amended by the Act revising the European Patent Convention of 29.11.2000.

82 See decisions/opinions of the Enlarged Board of Appeal G 3/93 , G 2/95 , G 2/98 , G 1/03 , G 2/03 , G 1/16 (Annex I).

• Art. 66 , 122 R. 52 , 57 - 59 , 136

Priority right - prove it or lose it

25 February 2021

In a recent appeal decision (T 407/15), an application was refused as obvious after the applicant failed to prove it had the right to claim priority.

The University of Western Ontario appealed against the EPO’s decision to refuse its application, EP2252901A. The application claimed priority from two US provisional applications, filed by applicant-inventors who were not applicants of the subsequent PCT application.

During the appeal proceedings, the Board of Appeal identified an article published by the inventors between the priority dates and the filing date. The article was considered to be particularly relevant to the claimed subject matter. As a result, the validity of the priority claims became pertinent to the application’s patentability.

Article 87(1) EPC states that “Any person who has duly filed […] an application for a patent, […] or his successor in title, shall enjoy, for the purpose of filing a European patent application in respect of the same invention, a right of priority”.

According to established EPO practice, all applicants of a priority application, or their successors in title, must be applicants of the subsequent application for a valid claim to priority.

CRISPR patent appeal decision: EPO maintains “all applicants” approach to priority

The EPO’s “all applicants” approach to priority was recently confirmed in the widely reported appeal decision T 844/18 (see our summary article: “CRISPR patent appeal decision: EPO maintains “all applicants” approach to priority”, 21 December 2020: https://dycip.com/all-applicants-priority).

In addition, any transfer of the right to claim priority must have occurred in advance of the filing date of the subsequent application. Although other jurisdictions allow retroactive transfers of priority rights, they are not accepted by the EPO.

In the present case, each of the US provisional applications specified that the University of Western Ontario was an assignee on their respective filing dates (and therefore in advance of the PCT filing date). However, no further detail of the assignment was included. The Board of Appeal decided that this was not sufficient evidence to establish a valid transfer of the right to claim priority from the earlier applications. In particular, the Board of Appeal reasoned: “This is a consequence of the fact that the filing of a first application gives rise to two different and independent rights, namely the right to the application in question, and the right of priority. While… the priority documents... appear to provide evidence of a transfer of the right to a patent, it is silent as to any right of priority based on said filings.”

The EPC and the Paris Convention do not specify formal requirements for a valid transfer of priority rights. However, it is established EPO practice that an applicant/proprietor bears the burden of proving succession in title when the validity of a priority claim is called into question. Therefore, the University of Western Ontario was asked to provide evidence that it was entitled to claim priority from the earlier US provisional applications. However, it failed to do so. Consequently, the Board of Appeal decided that the application was not entitled to priority, and the claims were found to be obvious in light of the intervening disclosure.

According to established EPO case law, the independence of a priority right and the right to an application does not mean that a valid transfer of a priority right inevitably requires a separate and express assignment declaration. As such, the explicit transfer of a priority right may not be essential, when other evidence is sufficient. For example, in T 205/14 and T 517/14, an expert witness attesting to the applicant’s inherent right to claim priority from an application based on its employees’ service inventions, under Israeli law (the law of the country of employment and place of business), was considered adequate evidence of a right to claim priority. In addition, in the interlocutory decision of the opposition division relating to EP2203462B, an assignment of “the entire right, title and interest in and to any and all Letters Patent which may be granted therefor” was considered to implicitly include the right to claim priority, under US law (the law of the country of the priority filing, and the law governing the legal relationship between the parties).

It is clear from T 407/15 that merely indicating the transfer of the right to a priority application may not be sufficient to prove that the priority right had also been transferred.

Given that an applicant’s/proprietor’s right to claim priority in advance of the filing date may need to be proven for patentability, where not all of the applicants of a priority application are listed on the subsequent application, we recommend that an assignment is executed that specifically mentions the transfer of the right to claim priority.

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