Yu BAI
Attorney-at-Law
Chinese Patent Attorney
Beijing Wei Chixue Law Firm

 
In patent confirmation proceedings, whether the claim to priority right establishes can have dominant influence on the heading direction of the case. Losing the priority right can be fatal—once the priority right is rendered void, a greater range of prejudicial documents can be cited in rejection to the novelty or inventiveness of the subject patent. For example, in that case, a reference document published on a date between the priority date and the actual date of filing of the subject patent will become the prior art and form a critical piece of evidence supporting the invalidation of the subject patent. Hence, the validity of the priority claim is crucial for either an applicant aiming to establish the priority right or an opposing party seeking to invalidate a patent.

As prescribed by the Guidelines for Patent Examination, an invention for the same subject matter as referred to in Article 29 means an invention of which the technical field, technical problem to be solved, technical solution, and prospective effect are the same as those of the first application. The determination result as to the “invention for the same subject matter” plays a key role in determining whether the priority claim is valid. The related practice in specialized fields such as medicinal chemistry is highly complex. To address this, three typical cases from the field of medicinal chemistry are introduced below to help clarify the logic for verifying priority right, which may serve as a reference for practitioners.

CASE 1: Can a priority claim be verified when the earlier application lacks data on compound activity?

Case Briefing

The CNIPA made the Examination Decision No. 580173 on Request for Invalidation Declaration to maintain the subject patent, having accepted the priority right as valid.

The subject patent provides three pharmaceutically acceptable salts of ruxolitinib.

The subject patent provides Example A of In vitro JAK Kinase Assay (specific steps omitted herein) and draws the conclusion that “both the phosphoric acid salt of the invention, and the corresponding free base compound, were found to have IC₅₀ values of less than 50 nM for each of JAK1, JAK2, and JAK3.” (see Para. [0092]-[0094] of the specification)

Comparing the texts, the priority document differs from the specification of the subject patent merely in lacking the afore-said Example A and the corresponding conclusion.

In addition, the subject patent and the priority document both cite a US Patent Application No. 11/637,545 (hereinafter referred to as the cited document) in the section “Background” of the specification.

The cited document intends to provide a compound having a JAK inhibitory activity. Referring to Example 67 of the cited document, in Step 2, a racemic mixture was obtained and separated by HPLC to afford the enantiomer in the R-configuration (ruxolitinib) and the corresponding S-enantiomer; in Step 3, the enantiomers were both reacted with TFA to generate their respective final product, i.e., R- and S-enantiomers of trifluoroacetic acid salts. The two trifluoroacetic acid salts were both tested for inhibitory activity of JAK and both found to be active JAK inhibitors, with one being more active than its enantiomer.

The cited document employs substantially the same method for testing JAK activity as the subject patent. However, it does not disclose the specific test result for any compound. The cited document merely indicates the standard for determining the JAK activity, i.e., IC₅₀≤10 μM.

In light of the above findings, the panel opined that:

In the field of medicinal chemistry, due to the high unpredictability of technical effects, it is usually necessary to include in the specification sufficient qualitative or quantitative experimental data to demonstrate that the purported use and/or expected effect has been achieved, so as to convince a person skilled in the art that the invention can indeed achieve the stated use or effect. Accordingly, the determination of an invention for the same subject matter in this field—specifically, whether the earlier application and the later application share the same technical effect—heavily on experimental data.

The cited document discloses ruxolitinib and the use thereof as a JAK inhibitor. The subject patent seeks to improve upon the disclosed art, providing three pharmaceutically acceptable salts of ruxolitinib to obtain more effective pharmaceutical preparations. In light of the cited document in combination with the common general knowledge in the art that salt formation generally does not result in the loss of activity of a pharmaceutical compound, a person skilled in the art would directly and unambiguously recognize that the claimed three pharmaceutically acceptable salts have the function of a JAK inhibitor verifiable by the test method described in the cited document. Regarding the specific test result of the increased JAK inhibitory activity as compared to the priority document, it constitutes an enhanced technical effect rather than a new added matter, and is therefore not deemed as violation of the first-to-file principle.

Therefore, even though the priority document does not state the test method or result of the JAK inhibitory activity (IC₅₀) as described in the specification of the subject patent, a person skilled in the art can correctly understand the technical field, the technical problem to be solved, the technical solution, and the expected technical effect of the earlier application based on the disclosure of the cited document. The technical solution according to claim 1 of the subject patent is consistent with the earlier application in these aspects and is therefore an invention for the same subject.

Case Summary

This case, as one of the 2024 Top Ten Patent Re-examination and Invalidation Cases, provides an example of how to examine the technical effect of the subject patent in comparison with that of the earlier application to which priority is claimed, in order to make a determination on “an invention for the same subject matter” in the field of medicinal chemistry.

In determining whether the subject patent is an invention for the same subject matter, the panel decided that the earlier application and the subject patent expect technical effect, because it can be determined from the priority document and the cited document that the claimed compound has the function as a JAK inhibitor. That is, in the context of this case, disclosure of the test data for JAK inhibitory activity (IC₅₀) is not necessarily required in the priority document or the cited document.

Nonetheless, it can still be inferred that in the determination on “an invention for the same subject matter,” all four factors—namely, the technical field, the technical problem to be solved, the technical solution, and the expected technical effect—are taken into account to reach a comprehensive conclusion. Therefore, to mitigate the risk of losing the priority right, it is advisable in practice to draft the earlier application, which serves as the priority document, with sufficient disclosure of the technical effect and other relevant information.

CASE 2: When the later application defines a feature of administered dose that is absent from the earlier application, can the earlier application still serve as the first application for the same subject matter, noting that such a dose feature is generally not considered limiting in the novelty assessment of a pharmaceutical use claim?

Case Briefing

The subject patent is a patent for invention entitled “Dipeptidyl peptidase inhibitors for treating diabetes.”

Claim 1 of the subject patent reads as follows: Use of compound I in preparing a pharmaceutical composition for treating Type II diabetes by administering a daily dose between 5 mg and 250 mg of Compound I through oral administration, wherein Compound I has the formula (omitted herein).

The two earlier applications to which priority is claimed are directed to the subject matter of claims 1 to 17 of the subject patent.

The petitioner submitted Evidence 4, which is the published specification of the patentee’s another earlier application, filed on December 15, 2004, earlier than the earliest priority date claimed by the subject patent. Evidence 4 does not mention “a daily dose between 5 mg and 250 mg” as recited in claim 1 of the subject patent. This daily cannot be directly and unambiguously determined from Evidence 4, either.

The CNIPA made the Examination Decision No. 38952 on Request for Invalidation Declaration and opined as follows.

Although claim 1 of the subject patent defines a daily dose of Compound I by oral administration of between 5 mg and 250 mg, this feature defines the administration and reflects the choice of the physician in prescription, and is therefore not limiting to the claim scope. Evidence 4 has disclosed an invention for the same subject matter with claims 1 to 17 of the subject application, which means that neither of the two earlier applications to which the subject patent claims priority is the first application. Hence, claims 1 to 17 cannot enjoy the priority right. Since the priority right is lost, Evidence 4 constitutes prior art for the subject patent. In that case, claims 1 to 17 are not novel in view of Evidence 4, as Evidence 4 has disclosed the same subject matter. Accordingly, claims 1 to 17 are declared invalid fully.

The patentee, dissatisfied with this decision, filed an appeal. The court of first instance rendered a judgment rejecting the patentee’s claims. The patentee then appealed to the Supreme People’s Court. Ultimately, the Supreme People’s Court ruled in favor the patentee, reversing the judgment of first instance and the appealed Decision No. 38952 on Request for Invalidation Declaration.

The ruling of the Supreme People’s Court is excerpted as follows.

“In the determination of novelty and inventiveness, certain claim limitations may be deemed not substantively limiting and are therefore excluded from consideration. However, this approach should not apply to the verification of a priority claim, for the following reasons.

Claim limitations that are not substantively limiting are disregarded in novelty and inventiveness determinations because such limitations cannot serve as a basis for finding novelty or inventiveness—whether due to their lack of technical relevance to the invention or as required by applicable special legal provisions. In other words, the substantive limiting effect of these limitations is taken into account in the assessment of patentability. On the other hand, the verification of priority right merely serves only to determine whether, under the conditions prescribed by law, the filing date of the earlier application may be accorded as the priority date and thus be recognized as the effective filing date of the subject patent. The verification of a priority right does not concern patentability. Accordingly, the factors considered in patentability assessments do not apply.

Once the standard for examining whether a feature is substantively limiting is applied to the verification of a priority right, any priority claim would be deemed valid as long as the added contents do not affect the novelty or inventiveness determination. This would contravene the purpose of the priority system and could result in unjustified benefits for patent applicants.

It has been prescribed in Section 4.6.2 of Chapter 8, Part 2 of the Guidelines for Examination that if a person skilled in the art cannot directly and unambiguously derive the technical solution from the earlier application, the earlier application cannot serve as the basis for claiming the right of priority. Furthermore, Section 4.1.2 of Chapter 3, Part 2 of the Guidelines for Examination prescribes that an invention or utility model for the same subject matter as referred to in Article 29 means an invention or utility model of which the technical field, technical problem to be solved, technical solution, and prospective effect are the same as those of the first application respectively. This standard is different from the standard for novelty assessment provided in the Guidelines for Examination.

Evidence 4 does not mention ‘a daily dose between 5 mg and 250 mg’ as defined in claim 1. Moreover, this feature cannot be directly and unambiguously derived from Evidence 4. Accordingly, the two earlier applications, rather than Evidence 4, should be recognized as the first applications for the same subject matter. On this basis, the priority claim of claim 1 is valid, as are the priority claims of claims 2 to 27.”

Case Summary

The ruling in this case makes clear that the standard for verifying the validity of a priority claim differs from the novelty examination standard under the Guidelines for Examination. Building on this ruling, the determination of whether a claimed priority date should be accorded as the effective filing date of a patent application under the conditions prescribed by law does not involve an assessment of patentability. Accordingly, the factors considered in patentability examinations cannot be applied in the verification of priority claims. Although claim limitations deemed not substantively limiting are disregarded in the examination for novelty and inventiveness, they should not be excluded from consideration in the verification of priority claims.

CASE 3: When the earlier application discloses a compound defined by a Markush formula and the later application claims a specific compound within the scope of the Markush formula but not explicitly disclosed, can the specific compound enjoy the right of priority?

Case Briefing

During the invalidation proceedings, the patentee amended the claims of the subject patent, removing the compound defined by a Markush formula and a part of specific compounds, remaining only the compound 104 and Macitentan.

The invalidation decision was made relying on the priority document of the subject patent, submitted as Evidence 2. The priority document discloses Formula I compound and provided 14 preparation examples, recording IC₅₀ values of 11 specific compounds for ETA and ETB acceptors. However, the priority document does not mention the names and structures or the preparation of the compound 104 and Macitentan, and does not provide corresponding experimental data of tests of the technical effect.

The panel opined that the amended claims should lose the priority right to the earlier application because the compound 104 and Macitentan were not disclosed in Evidence 2.

The Examination Decision No. 48183 on Request for Invalidation Declaration made by the CNIPA in this case is excerpted as follows.

“As an initial matter, the Markush compound of the earlier application and the specific compound of the later application do not belong to one common technical solution, and are therefore not considered as ‘invention-creations for the same subject matter.’ Further, recognizing the right of priority solely on the basis that the specific compound of the later application falls in the scope of the Markush compound of the earlier application would undermine the fundamental requirements of the priority system. The Markush compound, as a special form of compound expression, is generally regarded as an integrated whole formed by the various substituents and their different selections. Patent applications for the inventor’s compounds of analogous structures in the form of a Markush compound based on the summerized structural commonalities are frequently seen in the practice of patent examination in the chemical field and are not prohibited by law. However, when the compounds in an earlier application are drafted in Markush form, recognizing the priority claim of a later application for any specific compound falling within the scope of that Markush compound would effectively turn the earlier application into a boundless reservoir. This would enable the applicant, through further research, to generate new specific compounds—or any narrower generic formula—and still avail themselves of the earlier priority date. This is obviously inconsistent with the rationale underlying the priority system. Therefore, the determination to validate the priority claim of a later application for a specific compound or narrower generic formula should be premised on explicit or implied disclosure of said specific compound or narrower sub-generic formulae in the earlier application. Otherwise, rights and obligations of the applicant would become unbalanced.”

Case Summary

According to the Decision on this case, if the earlier application does not disclose the specific compound claimed by the later application while a person skilled in the art cannot derive an implied disclosure of the specific compound from the whole of the earlier application, the claims seeking protection for said specific compound will lose the right of priority to the earlier application. The same applies to a narrower generic formula. This case reminds us to be more foresighted in the layout of our patent portfolio in the field of medicinal chemistry. The first application is the cornerstone of the entire rights fortress. In preparing the earlier application that will function as the priority document, it is advisable to provide a detailed and reliable description of specific compounds, alongside a well-defined Markush formula and thoughtfully established tiers of protection.

Conclusion

The Guidelines for Examination puts forward a relatively clear standard for verifying the validity of a priority claim. However, some complex circumstances may emerge in practice, causing confusions and controversies. The cases introduced in this article provide some guidance on determining whether the priority claim can be established in certain specific circumstances.