Priority: Shield and Sword (of Damocles) – Decision T844/18 («CRISPR/Cas9»)

| Moritz Hönig | Alfred Köpf

The priority concept is one of the cornerstones of the Paris Convention for the Protection of Industrial Property and is implemented in one form or another in virtually every patent system in the world. Especially in fast-moving and disruptive technical fields, the priority right is an essential element in any patent prosecution strategy.

In order to beat competitors in the race for an early priority date, applicants struggle with the tradeoff between a perfectly finished application and a fast filing. The latter often makes amendments and revisions necessary within the priority year which poses a first threat to the priority claim. In particular, the strict requirement of «the same invention» established by the EPO’s Enlarged Board of Appeal can lead to lost or partial priorities. In case of the latter, decision G1/15 delivered an «antidote to poisonous priority». However, change of control situations, collaborations, additional inventors and other common dynamics in disruptive fields present further pitfalls faced by applicants, which have to be avoided.

The present article focuses on the above-mentioned issues regarding the applicants, for which the EPO has established the so-called «all applicants» approach. This approach requires that all applicants of a priority application, or their successors in title, must be named as applicants on the subsequent application in order to validly claim its priority.

The «all applicants» approach has been the subject of intense controversy for years and has been widely criticized for being unduly restrictive for patent applicants and for effectively transforming the priority right from an enabling right available to patent proprietors into a weapon that may be used against them. The controversy reached a dramatic climax early in 2020, when an EPO Board of Appeal held four-day long oral proceedings in deciding about a European patent relating to the revolutionary CRISPR/Cas9 technology, for which the Nobel Prize in Chemistry would be awarded later that year.

Originally discovered in the context of the adaptive immune system of bacteria, the CRISPR/Cas9 system has been developed into a biotechnological tool that has revolutionized numerous fields, from agriculture to medicine, from basic research to applied biotechnology. In essence, the CRISPR/Cas9 technology provides a highly versatile and | cost-effective biotechnological tool for selectively manipulating DNA at a specific position. This allows researchers, among various other applications, to control which genes are expressed in an organism.

The following example illustrates how the CRISPR-Cas9 technology may be used to selectively modify a target DNA at a specific target position (Figure 1). Knowing the sequence of this target DNA, a guide RNA molecule can be produced using standard RNA synthesis techniques. The guide RNA includes a sequence which is designed to be complementary to the target DNA and therefore binds to it with high precision. The guide RNA is also bound to the Cas9 protein (gRNA/Cas9 complex). This ensures that the Cas9 protein is brought into close proximity of the target DNA and that it cuts the target DNA exactly at the right position. The CRISPR/Cas9 system is therefore frequently described as highly specific genetic scissors.

Figure 1: Schematic illustration of CRISPR/Cas9 gene editing.

The freshly cut DNA may now undergo two different pathways, depending on the desired overall outcome. If gene deactivation is envisioned, the damaged target DNA is repaired using the cell’s non-homologous end joining repair machinery. Although this machinery successfully reanneals the target DNA, it is prone to errors and thus leads to mutations at the break site. Alternatively, a new synthetic DNA sequence may be added at or to the position of scission using homologous recombination. This results in a new DNA molecule in which the new DNA fragment has been inserted at the position of scission.

The CRISPR/Cas9 system originates from the adaptive immune response of bacteria and archaea. Key insights into the exact mechanism by which the CRISPRS/Cas9 system operates were reported by Emmanuelle Charpentier (then Umeå University, Sweden; now Max Planck Institute for Infection Biology in Berlin) in 2011. She subsequently began a collaboration with Jennifer A. Doudna (University of California, Berkeley) and the two researchers showed that the Cas9 protein could be used in conjunction with a single engineered RNA (to induce DNA double-strand breaks), suggesting application of the system in other organisms and as a biotechnological tool. This finding was immediately recognized as a major breakthrough and sparked the interest of various researchers. Soon after, the scientists Feng Zhang (Broad Institute, Boston) and George Church (Harvard University) reported that the system could also be used in eukaryotic cells, such as mouse cells or human cells. Since then, the use of CRISPR/Cas9 genetic scissors has skyrocketed. According to Fyodor Urnov, a gene-editing scientist at the University of California, Berkeley, the number of discoveries in biomedicine that have had the impact of Emmanuelle Charpentier’s and Jennifer A. Doudna’s discovery «can be counted on the fingers of one hand: recombinant DNA, PCR [polymerase chain reaction], DNA sequencing and now CRISPR».

The value of the respective contributions of each of the major players in the field has also been the subject of controversies, which has resulted in a number of legal battles relating to scope and ownership of relevant patents on different aspects of CRISPR/Cas9 gene editing. As some of the earliest patent applications were still filed before the America Invents Act came into effect, the entitlement to these patent applications and the resulting patents is assessed in interference proceedings under the «first-to-invent» regime. Another legal battle relating to the validity of a priority claim of a European patent was recently decided by the EPO in the decision at hand (T 0844/18).

As far as academic merit is concerned, Emmanuelle Charpentier and Jennifer A. Doudna were awarded the Nobel Prize in Chemistry last year «for the development of a method for genome editing». Among the various benefits of the revolutionary CRISPR/Cas9 technology that the two Nobel Prize winners pioneered are its operational simplicity, high fidelity, low cost and broad applicability. Or, to put it in other words: «any idiot can do it»!

Decision T 0788/05 is frequently cited as the origin of the EPO’s «all applicants» approach. In it, a Technical Board of Appeal was faced with the question of whether or not a document D1 is to be considered the «first application» in the sense of Art. 87(1) European Patent Convention (EPC) for the patent in suit. This question was relevant for the assessment of novelty and inventive step as it impacted which documents would constitute prior art according to Art. 54(2) and (3) EPC.

Document D1 had been filed by Terumo and Tokin as co-applicants, while the subsequent application, on the basis of which the patent in suit was granted, had been filed by Terumo as sole applicant. No evidence of a transfer of the priority right from Tokin to Terumo was presented to the Board.

In answering the question whether D1 constitutes the «first application», the Board assessed the meaning of Art. 87(1) EPC as follows:

«The term ‹a person› in Article 87(1) EPC (or ‹an applicant› in Article 88(1) EPC) implies that the applicant be the same for ‹the first application› (or ‹previous application› in Article 88(1) EPC) and for the later application for which a priority right is claimed.» (Reason 2)

In the case of co-applicants, this would mean that «the priority right belongs simultaneously and jointly to the two applicants, who thus constitute a legal unity unless one of them decides to transfer his right to the other applicant» (Reason 2). In the case at hand, therefore, D1 could not represent the «first application» within the meaning of Art. 87(1) EPC.

It is notable that the decision at hand does not seem to cite earlier case law relating to the interpretation of the term «a person» in Art. 87(1) EPC, which is perhaps due to a lack of relevant prior case law. Nevertheless, the decision is widely regarded as a crucial early milestone for the increasingly rigorous application of the strict requirement of identity of applicants (or their successors in title) that came to be known as the infamous «all applicants» approach.

This approach has since been readily adopted in various decisions by the Boards of Appeal of the EPO and has also impacted national case law. While a comprehensive discussion of subsequent decisions would go beyond the scope of this article, we would like to present one example of a recent national decision relating to the «all applicants» approach issued by the Swiss Federal Patent Court.

The case O2015_009 focused on a dispute over legal ownership of two European patent applications, EP 2 and EP 3, as well as two subsequent international patent applications, WO 2 and WO 3, claiming priority from the respective European patent applications. The defendant had filed all four patent applications as sole applicant, while the claimant was named as sole inventor on the two European patent applications and as one of three inventors on the two subsequent PCT applications.

The claimant requested, among other things, that the defendant be obliged to withdraw the claim to priority to EP 2 and EP 3 in all national patent applications stemming from WO 2 and WO 3, respectively. While the court did find the claimant to be jointly entitled to the European patents EP 2 and EP 3 with the defendant, this would not mean that the priority to EP 2 and EP 3 had been invalidly claimed under Art. 87(1) EPC by the defendant when filing WO 2 and WO 3. Rather, the Swiss Federal Patent Court held that the formal designation as applicant rather than the material entitlement to the priority application would guide the assessment of Art. 87(1) regarding whether the priority application had been filed by the same person or her successor in title. This assessment should further be based on the legal circumstances at the time of filing of the subsequent application. Since the defendant was formally the applicant of EP 2 and EP 3 at the time of filing of WO 2 and WO 3, respectively, the «same person» requirement of Art. 87(1) was met.

It seems to the authors of this paper that the reasoning outlined above would have been sufficient in deciding the question at hand. However, the Court went one step further and provided supplementary reasoning for the hypothetical case that the material entitlement to priority rather than the formal designation as applicant would guide the «same person» assessment of Art. 87(1). Even in this hypothetical case, and assuming that the claimant and the defendant were to be viewed as co-applicants of EP 2 and EP 3, the court would still consider the priority to be valid for two reasons:

First, the Swiss Federal Patent Court noted that if the underlying premise that the claimant was entitled to EP 2 and EP 3 was accepted, then this entitlement should equally apply to WO 2 and WO 3, so that the formal and material identity of applicants would be given. In outlining the second reason, the court challenged the case law generated by the EPO Boards of Appeal by stating that it would suffice if at least one of the applicants of the priority application and one of the applicants of the subsequent application would be identical in order to validly claim a priority under Art. 87(1) EPC. The Swiss Federal Patent Court further noted that neither the EPC nor the Paris Convention provide sufficient legal basis to prohibit a sub-group of the applicants of a priority application from validly claiming its priority in a subsequent application. The Court’s view would correspond to US practice under the Paris Convention.

| The decision of the Swiss Federal Patent Court illustrates that the widespread application of the «all applicants» approach is not without criticism. Some critics argue that the approach places an inappropriate focus on the bureaucratic efficiency of the EPO to the detriment of patent proprietors. The approach is further criticized as simply lacking legal basis in either the EPC or the Paris Convention. On a more fundamental level, it is argued that the EPO’s strict practice effectively transforms the priority right into a weapon that may be used by third parties against patent proprietors, which would contravene the very nature of the priority right as protecting patent applicants from interim disclosures. This controversy has been pointedly described by the metaphor that the priority right is meant to be a «shield rather than a sword».

The controversial debate over the «all applicants» approach has been ongoing for years and has recently been affirmed in a high-profile case relating to the CRISPR/Cas9 technology (T 0844/18).

Decision T 0844/18 concerns European patent EP 2 771 468, which was based on a PCT application filed on 12 December 2013. The PCT application and its corresponding European application (hereinafter «subsequent application») claim priority from 12 US provisional patent applications (hereinafter «priority application»).

Following grant of the European patent in 2015, the patent was subject to opposition proceedings before the EPO with no less than nine opponents. In applying the previously described «all applicants» approach, the opposition division found that the priority claim from certain US provisional applications was invalid. As a consequence, prior art documents D3 and D4 were found to be novelty-destroying and the patent was revoked. The appellants subsequently filed an appeal against this decision.

The significance of the case at hand is evidenced by the fact that auxiliary requests 1–64 were maintained by the patent proprietors from the opposition proceedings and documents D1 to D315 were admitted by the Board of Appeal. The submissions made by the parties amounted to several thousand pages, and the appeal proceedings involved oral proceedings of a spectacular length of four days. The case was closely followed in the patent community, with some practitioners hoping for a referral to the Enlarged Board of Appeal.

Indeed, the Board of Appeal’s preliminary comments during the written proceedings and the course of days one and two of the oral proceedings suggested that the Board considered a referral. However, in what was described as «a dramatic turn of events», the Board changed its view and dismissed the appeal.

In essence, the core issue underlying the case at hand may be stated in the following form:

«A and B are applicants for the priority application. A alone is the applicant for the subsequent application. Is a priority claim valid even without any assignment of priority right from B to A?» (p. 3 of T 0844/18)

In answering this core issue, the arguments were set out in the form of the following three questions:

Question I: Should entitlement to priority be assessed by the EPO?

Question II: How is the expression «any person» in Art. 87(1) EPC to be interpreted?

Question III: Does national law (in this case US law) govern the determination of (any person) who has «duly filed» according to Art. 87(1) EPC?

Should entitlement to priority be assessed by the EPO?

In answering this question, the Board began by noting that Art. 87(1) EPC clearly defines four distinct requirements that need to be met in order to validly claim a priority right, which relate to the following questions:

• 1)
  Who filed the previous application?
• 2)
  Where was the priority application filed?
• 3)
  What kind of application was the priority application (i.e. an application for a patent, utility model or utility certificate)?
• 4)
  When was the priority application filed?

Given that the EPO’s obligation to assess the last three requirements is undisputed, the Board argued that there would be no reason why the EPO would not be equally obligated to assess the first requirement as well.

While the appellants did not dispute that the entitlement to priority should be assessed by someone, they questioned the EPO’s jurisdiction or competence to make this assessment. Instead, the appellants argued that any challenges regarding entitlement to priority should be decided in entitlement actions before national courts, as is already the case for challenges over ownership of a patent under Art. 60(3) EPC. In addition to a lack of jurisdiction or competence, the appellants noted that the EPO’s current practice has unintended legal implications which contravene fundamental principles in property law: Since the priority right is a property right, the appellants argued that the EPO’s «all | applicants» approach would effectively allow non-owners of the property right to raise issues over entitlement, which may lead to destruction of the underlying property itself.

The Board dismissed the appellants› questioning of the EPO’s jurisdiction by noting that there is no analogous provision to Art. 60(3) EPC for entitlement to priority. The lack of a legal provision would not mean that there is a gap to be filled. Instead, the Board maintained the express obligation of the EPO to assess the «any person» requirement present in Art. 87(1) EPC. The Board further noted that, strictly speaking, Art. 87(1) EPC would not require a profound assessment of the legal entitlement to priority but instead would only require a formal check of the names of the applicants. Accordingly, the EPO did not actually carry out the legal assessment for which it was criticized by the appellants, but only assessed a formal requirement. This would, in principle, be no different from the several other formal requirements present in patent law.

How is the expression «any person» in Art. 87(1) EPC to be interpreted?

The wording of Art. 87(1) EPC is largely identical to the wording of Art. 4A of the Paris Convention, which laid out the fundamental principles of the concept of priority in patent law as early as 1883. In answering the question how this «any person» phrase is to be interpreted, the Board stressed that the «all applicants» approach is supported by over 100 years of consistent case law and practice, which constitutes an aspect of legal certainty by itself. As a consequence, the bar to changing the approach should therefore be very high.

The appellants contested the EPO’s viewpoint by arguing that the «all applicants» approach had been originally adopted in T 0788/05 almost without reasoning (vide infra) and had been readily applied in subsequent national and European case law without any critical evaluation of its legal basis. Given the lack of legal basis for the approach, it would be necessary to abandon the approach regardless of the established case law. Indeed, the decision G 1/15 would show that an established practice can – and should – be changed if it were wrong.

In assessing the legal basis for the «all applicants» approach, the appellants argued that the «any person» in Art. 87(1) EPC is to be understood more broadly as simply requiring that at least one of the persons of the priority application or their successors in title is to be named on the subsequent application claiming priority. According to the appellants, this follows directly from the meaning of the respective terms in the English and German version of Art. 87(1) EPC, namely «any person» and «jedermann». The open, permissive meaning of these terms would also be in conjunction with the general objective of the priority right, which is supposed to enable rather than restrict the filing of subsequent applications for applicants without being accorded a new filing date.

The choice of rather permissive German and English terms in Art. 87(1), however, contrasts starkly with the narrower French term used, «celui qui», which is also the authentic wording of the Paris Convention. According to the Board, the French term tends to require strict identity of applicants and thus support the «all applicants» approach. However, the Board admitted that the different terms in English, German and French would be too ambiguous to unequivocally discern the exact will of the legislator of the EPC. Accordingly, the Board next considered the purpose and object of the Paris Convention in order to explore the legislator’s will. The purpose and object of the Paris Convention was adopted literally from decision T 0015/01 to be to: «safeguard, for a limited period, the interests of a patent applicant in his endeavour to obtain international protection for his invention» and to «assist the applicant in obtaining international protection for his invention» (paras. 32 and 34 of T 0015/01).

According to the appellants, the EPO’s restrictive understanding of «any person» would contravene the above-mentioned purpose of the Paris Convention by essentially introducing an additional requirement according to which all applicants (or their successors in title) of the priority application must be designated as applicants on the subsequent application.

The Board, however, rejected the appellants› argument as being inherently flawed because, following their reasoning, any formal requirement relating to priority would contravene the Paris Convention. In other words, while the general object and purpose of the Paris Convention are important guidelines in construing the meaning of specific legal provisions relating to priority, they cannot be artificially pitted against clearly articulated formal requirements for claiming priority. The Board further noted that patent law abounds with formal requirements, and that it is widely known and commonly accepted that negligence of even minor formal requirements may lead to a loss of rights.

In a further argument to dispute the EPO’s interpretation of «any person» in Art. 87(1) EPC, the appellants considered that the act of filing a priority application would result in a priority right, which is co-owned by all applicants (or their successors in title). By analogy to property law, it would follow that each one of them would be able to exercise their right individually and separately of each other. The immaterial nature of the priority right would also ensure that it cannot be exhausted, but rather that it may be exploited multiple times. While the appellants acknowledged that the possibility of multiple exploitation of a single priority right may encourage double patenting, they noted that this consideration should be subordinate given that the priority right was never intended as a mechanism | to address double patenting. Rather, protection of the interests and rights of the co-owning applicants would be its superior object.

Regarding the exact legal nature of the priority right, the Board argued that the EPC and the Paris Convention would leave unclear whether joint ownership applies or not. It is equally unclear in the Board’s view whether the legal distinction between disposal and exploitation of a property right, which derives from the law of real property, would apply to the immaterial priority right. However, even if the appellants› arguments regarding the legal nature of the priority right were accepted, the Board still found that the consequences of classifying the right to priority as a «right of exploitation» should not be fully applied in view of sufficiently strong countervailing policy concerns.

The Board concluded that the EPO’s «all applicants» approach does not contravene Art. 87(1) EPC or the purpose of the Paris Convention. Since the appellants› arguments and public policy considerations would be insufficient to overturn the «many decades of EPO and national practice supporting the ‹all applicants approach›» (para. 85 of the present decision), the Board maintained the EPO’s interpretation of «any person» as requiring that all applicants for the priority application, or their successors in title, must be designated as applicants for the subsequent application.

Does national law (in this case US law) govern the determination of «any person» who has «duly filed» in Art. 87(1) EPC?

Even if the EPO’s restrictive «all applicants» approach and the empowerment and obligation of the EPO to assess the validity of a priority right claim were accepted, it still needs to be discerned which law governs this assessment. In controversial previous cases, the EPO has famously overridden national law in adjudicating on whether or not a transfer of a priority right performed under national law was legally valid. This assertive practice has been criticized by several practitioners, among other things for a lack of legal basis for this significant curtailment of national legal jurisdiction.

Drawing on this previous criticism, the appellants argued that the priority right arises before filing of the subsequent application. Accordingly, the only law that could possibly be applicable would be the law governing the filing of the priority application, which in many cases, including this one, is national law. The appellants› interpretation would be supported by Art. 87(1) EPC, which expressly requires that the application whose priority is claimed was «duly filed»: whether or not the priority application was in fact «duly filed» could only possibly be assessed under the law applicable to the filing of the priority application.

In countering the appellants› reference to the competence of national law, the Board once again rejected the premise that the EPO would in fact perform an assessment of the legal entitlement to priority under Art. 87(1) EPC or the corresponding provision of the Paris Convention. Rather, the Board confirmed its previous interpretation according to which Art. 87(1) EPC merely constitutes a formal requirement which the EPO is obliged and competent to assess. Indeed, the wording of Art. 4A(1) and (2) of the Paris Convention would make it clear that «person» refers to a «person who has carried out an act, that of filing a patent application» (para. 108 of the present decision). In other words, Art. 4A(1) and (2) would not in fact require an assessment of whether that person was the inventor or whether that person was actually entitled to be the applicant. As a consequence, it would be immediately determinable upon filing who the «person» of Art. 4A(1) and (2) is.

Indeed, this formalistic interpretation would be in accordance with the intention of the drafters of the Paris Convention, as evident from its Travaux Préparatoires, specifically from the discussions at the Fourth Session on 9 November 1880. During an exchange of arguments on the question of whether or not the «any person» would be required to be legally entitled to make the filing, it was concluded that:

«Il s’agit de la priorité du dépôt, mais non pas du droit définitif de propriété».

In other words, as stated in the decision at hand, the determination who «any person» is under the Paris Convention «does not require that the ‹any person› is actually legally entitled to make the filing, but merely that they did so» (para. 110 of the present decision).

Beyond the general question of which law governs the determination of «any person», the present case is rendered more complex due to intricacies of the US patent system relating to provisional patent applications and the tie between inventorship and applicant status. As opposed to regular patent applications, US provisional patent applications do not lead to grant of a patent but instead solely serve to obtain a filing date at a low cost. Provisional applications are frequently filed using preliminary data and often include several different inventions. Additionally, the reader is well aware that unlike under European patent law, where a legal entity employing the inventor is typically named as applicant, under US patent law, the applicant status is tied with inventorship.

As an example of the implications of these provisions, it would be possible under US patent law to disclose, in a single provisional patent application (US1), invention X made by inventor A and invention Y made by inventor B (see Figure 2). In this scenario, both inventors A and B would be designated as applicants and inventors on the application, even though A did not contribute to invention Y and B did not contribute to invention X. If applicant A would like to file a subsequent European patent application | (EP1) claiming the priority of her earlier provisional patent application, then the EPO’s «all applicants» approach would require that A and B both be named on the subsequent application, or that A would be the legal successor in title of B.

Figure 2: Exemplary depiction of the implications of the «all applicants» approach in cases where a priority founding application discloses two or more inventions which were made separately by different inventors who are designated as applicants.

Following this logic, the appellants argued that in the case of US provisional patent applications serving as priority applications, it would be necessary to discern who exactly was the inventor of the invention for which protection is sought in the subsequent application. In other words, if inventor A of the example above was to file a subsequent application with claims directed only to her own invention X but not to the invention Y made by inventor B, then it should be possible for A to file the subsequent application as sole applicant.

It should be noted that the complication outlined above is not restricted to US provisional patent applications. In fact, other national and European patent applications are frequently objected to on the basis of a prima facie lack of unity between two distinct inventions (or groups of inventions). If, for example, the two distinct inventions had been made separately by two inventors employed by two different companies and both companies were designated as applicants on the priority founding application, then a similar problem would arise if one of the two companies were to file a subsequent application as sole applicant. The fundamental reason for this is that the claim to priority refers to an application and not to the invention disclosed in that application. It follows that any legal assignment of the priority right relating to specific inventions disclosed in a priority founding application among other inventions is a tricky undertaking.

According to the appellants, national law (in this case US law) would therefore be the only possible law suitable for proper assessment of the «any person» of Art. 87(1) EPC. By contrast, the EPO’s «all applicants» approach would not duly consider the complexities arising from priority claims involving provisional patent applications. This would amount to a violation of the national treatment rule of the EPC, which would prescribe that the EPO must give foreign nationals access to the EPO patent system on an equal footing as nationals of EPC member states. The appellants did not eschew accusing the EPO of discriminating against US inventors as a consequence of its «all applicants» approach.

The Board rejected the accusation of discrimination against US inventors by pointing out that the US is a party of the Paris Convention, in which the «all applicants» approach is rooted. While the EPO would be required to accept US provisional applications as founding a priority right, this would not mean that US provisional applications are exempt from proper application of the Paris Convention.

The Board further clarified that the principle of the «national treatment» rule of the EPO would be that foreigners are treated in the same way as nationals are treated. As nationals would be subject to the same formal requirements regarding priority claims as the appellants, the EPO would not violate the «national treatment rule». Instead, the Board rebuked the appellants by pointing out that the «appellants are mistaken when they consider this principle [of national treatment] requires the EPO to treat applicants and patentees from non-member states in the same way as they would have been treated in their home country» (para. 115 of the decision).

As a consequence, the Board answered question III by noting that the «national law» determining who «any person» is, would in this case be the Paris Convention.

The present decision has important practical implications for practitioners in prosecution and litigation alike. For those seeking patent protection, the decision serves as a timely reminder of the EPO’s strict formal practice that all applicants of a priority application, or their successors in title, are required to be designated as applicants on the subsequent application. In cases of an imminent filing of a subsequent application and where a written assignment could not be concluded prior to filing, it is advisable to designate all applicants named on the priority application as applicants on the subsequent application upon filing and to take care of the assignment later.

More generally, exceptional caution is required in the assignment of a priority right relating to a priority application with two or more designated applicants, which discloses two or more distinct inventions made separately by two or more different inventors. Given the obvious difficulty in outlining such an assignment, it may be advisable to postpone the assignment until after filing of the subsequent application and to designate all applicants of the | priority founding application on the subsequent applications.

The present decision also adds further weight to the increasing body of case law documenting that the EPO’s strict interpretation of Art. 87(1) EPC may be used as a potent and often lethal weapon against patent proprietors in contentious proceedings. Future case law will show whether this offensive use of the priority right, which many argue contravenes the very purpose of the priority right as a protective right, can be attenuated under the «all applicants» approach.