What should pesticide companies keep in mind when seeking patent protection for pesticide compound intermediates?

Foreign originator companies implement rigorous patent strategies for their newly developed compounds to extend the life of their patent protection. Compound‑intermediate patents represent a robust form of patent protection and facilitate evidence‑gathering and enforcement in subsequent infringement proceedings.

In recent years, chlorantraniliprole, a star insecticide, has remained a focal point of industry discussion. Although the patent on the chlorantraniliprole compound has expired in China, the existence of patents on its intermediates continues to pose concerns for Chinese agrochemical companies regarding whether or not to proceed with commercial production.

Foreign originator companies place great emphasis on the intellectual property strategy for pesticide‑related intermediates, whereas Chinese agrochemical firms have yet to accord sufficient attention to patent protection for such intermediates during the R&D process. Although new intermediate compounds are frequently encountered in process development, these intermediates are typically not patented; instead, patent protection is sought for the preparation processes themselves.

Based on the author’s experience in patent examination and with service‑providing firms, it is believed that domestic companies tend to opt for protecting the preparation processes of pesticide compounds while forgoing patent protection for the corresponding intermediate compounds, for roughly two main reasons:

On the one hand, the Patent Examination Guidelines do not provide further clarification on the criteria for assessing inventiveness with respect to intermediate compounds. Since intermediate compounds are themselves compounds, companies contend that the examination standards applicable to intermediates should align with those governing compounds. However, intermediate compounds typically refer to substances that can be used directly to synthesize or isolate the final product, and they generally lack direct utility of their own. The applicant argues that, under the Patent Examination Guidelines, a compound must demonstrate a specific use or effect in order to be deemed inventive; yet, intermediate compounds have not exhibited any particular utility or effect in agrochemical applications, making it difficult to establish their inventive step.

On the other hand, there are few reports on the examination standards for the inventiveness of intermediate compounds; as a result, companies lack guidance on how to file patent applications for such compounds in compliance with the relevant examination requirements, whereas patent applications for preparation processes benefit from well-established practices that can serve as useful references.

For the reasons outlined above, domestic enterprises, when seeking to protect their pesticide‑compound synthesis processes, seldom address the simultaneous protection of novel intermediate compounds that play a critical role in those processes, thereby resulting in substantial losses of intellectual property rights over pesticide intermediates in China.

This paper examines the examination standards for intermediate compounds by reviewing the Patent Examination Guidelines and relevant case law, with the aim of providing guidance to Chinese agrochemical companies seeking patent protection for pesticide‑related intermediates.

I. Examination Standards for Intermediate Compounds

The Patent Examination Guidelines set forth only the general criteria for assessing the inventive step of compound‑related inventions:

1. For compounds that are structurally distinct from known compounds, exhibit novelty, and possess a certain utility or effect, the examiner may deem them to be inventive without requiring that they demonstrate an unexpected utility or effect.

2. For compounds whose structure is closely related to that of a known compound, they must possess an unexpected use or effect. Such an unexpected use or effect may be a use different from the known uses of the prior‑art compound; it may represent a substantial improvement or enhancement of a known effect of the prior‑art compound; or it may constitute a use or effect that cannot be readily inferred from common general knowledge.

3. Whether two compounds are structurally similar is relevant to the field in question; examiners should apply different criteria when assessing different fields.

Intermediate compounds are typically defined as substances that can be used to directly synthesize or isolate the final product, but which themselves generally lack direct utility. In patent examination practice, the inventive step of an intermediate compound is usually assessed by reference to the method for producing the downstream product or to the resulting product.

1. The inventive step of an intermediate compound may be demonstrated by its use in preparing a subsequent product that is itself inventive, and by its contribution to the structure and properties of that subsequent product. However, if the intermediate is used to prepare a subsequent product that is itself inventive solely through the use of a known compound, then the intermediate cannot be considered to have contributed to the structure or properties of the subsequent product.

2. The inventive step of an intermediate compound may also be demonstrated by its contribution to the inventive method used to produce subsequent products.

With respect to the inventive step of a novel intermediate arising in the preparation of a known pesticide compound, such inventiveness is primarily demonstrated by the intermediate’s creative contribution to the established method for synthesizing that pesticide. In the course of routine research and development, the outcomes achieved by a new process often exhibit a strong correlation with the newly identified intermediate; under these circumstances, both the method for preparing the pesticide compound and the novel intermediate can be protected simultaneously, thereby strengthening the enterprise’s intellectual property protection.

II. Typical Cases

Chlorantraniliprole is a member of the ortho‑formylaminobenzamide class of insecticides. Since its launch in 2008, it has been marketed in more than 100 countries worldwide, covering virtually all major markets. Its outstanding insecticidal efficacy has made it DuPont’s flagship product and the world’s top‑selling insecticide. On February 27, 2003, DuPont filed the original patent WO0315519; however, this patent did not provide a detailed disclosure of a synthetic method suitable for the large‑scale industrial production of chlorantraniliprole.

With respect to the preparation methods of chlorantraniliprole, DuPont has filed five patent applications, covering pyrazole intermediates, aniline intermediates, and novel process conditions. According to searches conducted in the STN and VEN databases, as of December 31, 2022, there were a total of 73 patent applications worldwide—both domestic and foreign—related to chlorantraniliprole’s synthesis. Of these, 39 were filed internationally, with five seeking protection for intermediates and three having been granted; domestically, 34 applications were filed, none of which claimed protection for intermediates. Tetrachlorantraniliprole, a similar product developed in China, received provisional registration in 2013 and full registration in 2017, and has experienced rapid growth since its market launch.

Below, in conjunction with two specific patent applications involving novel processes for chlorantraniliprole and tetrachlorantraniliprole, we analyze the protective value of intermediate compounds and the criteria for assessing their inventive step.

1. Case 1

The invention CN102285899 is a Chinese patent application that discloses a novel process for preparing o‑aminobenzamide‑type insecticides.

(1) Case Summary

In the prior art WO 03/015519 (Reference Document 1), a compound of Formula 3a is reacted with a compound of Formula 4a to afford a compound of Formula 2, which is then converted into a compound of Formula 1a according to the reaction scheme shown in Figure 1.

Figure 1 Preparation of Compound 1a in Prior Art WO03015519

In this case, the inventor has developed a novel preparation process, with the reaction scheme shown in Figure 2.

The inventor filed patent applications seeking protection for the corresponding preparation process and for the compound serving as intermediate in Formula 3b, both of which were ultimately granted. When compared with the prior art and the reaction scheme disclosed in the patent, the reaction pathways of the two are clearly distinct; therefore, the novel preparation process merits patent protection.

Although the compound serving as intermediate 3b in this process has a simple structure and is structurally similar to the intermediate 3a known in the prior art, it constitutes a novel compound that differs from the prior‑art intermediate 3a and plays a critical role in the preparation process. Accordingly, patent protection is warranted. Prior to filing, it is essential to thoroughly investigate the favorable technical effects that this intermediate imparts to the new process—such as improved yield or reduced costs—and to document these findings in the application.

Figure 2: Example 1—Preparation of the Chinese compound 1b

During the examination of this invention patent application, the National Intellectual Property Administration also questioned the inventive step of the intermediate compound, primarily on the grounds that Document 1 discloses compounds 1a and 4a. According to the reverse‑synthesis analysis commonly employed in the field, given that Documents 1 already disclose compounds of Formula 1a and Formula 4a, a person skilled in the art would readily conceive of reacting compound of Formula 4b with 2‑amino‑5‑chloro‑N,N‑dimethylbenzamide to prepare compound of Formula 1b; moreover, the reaction between an amine and a carboxylic acid to form an amide is well‑known in the art.

The National Intellectual Property Administration has recognized the inventive step of the intermediate compound primarily on the basis of the following superior technical effect: whereas the prior art requires two complex reactions to synthesize the target compound, the present invention uses the intermediate compound 3b to prepare the target compound in a single, straightforward step; thus, the method disclosed herein is more convenient, efficient, and cost‑effective.

This invention involves substantial economic interests, and a third party has initiated invalidation proceedings. The central issue in the dispute is whether the intermediate compound enhances the overall yield of the final product in the preparation process—that is, whether it contributes to an inventive method for producing downstream products.

(2) Typical Significance

The typical significance of this case lies in demonstrating that protecting intermediate compounds is of paramount importance in the preparation of pesticide compounds. Although the patent on the chlorantraniliprole compound itself has expired, the existence of a patent on its intermediate extends the overall life cycle of the compound’s patent, thereby establishing a technological barrier against competitors and generating substantial economic benefits for the company. Moreover, this case provides valuable guidance for applicants seeking to address the issue of inventive step with respect to intermediate compounds, offering clear direction and practical guidance in assessing their inventive merit.

(2) Case 2

The invention CN101747318 relates to a novel process for preparing o‑aminobenzamide‑type insecticides.

① Case Summary

The invention relates to the intermediate compound 4c shown in Figure 3. In the structural formula of 4c, R1 is selected from Br; and R2 is selected from ethyl. The process for preparing the insecticidal compound of Formula 1c, starting from the corresponding carboxylic acid compound, is illustrated in Figure 3.

Figure 3. Compound 4c and compound 1c of invention CN101747318

The patent application documents emphasize that certain final‑product compounds exhibit excellent insecticidal activity. The prior art WO 2008/010897 (Comparative Document 2) discloses the corresponding carboxylic acid compounds and a process for preparing o‑aminobenzamide‑type insecticides using these compounds as intermediates.

The inventor filed a patent application for the compound of Formula 4c; this application underwent an examination‑in‑review procedure but ultimately did not result in the grant of a patent. The National Intellectual Property Administration’s principal grounds were as follows:

1. The intermediate of the present application is not directly converted into the final product; rather, it is first transformed into the corresponding carboxylic acid—namely, the compound disclosed in Comparative Document 2—and then further converted into the corresponding acyl chloride, ultimately yielding a compound with excellent insecticidal activity. Thus, the preparation of the final product involves an intermediate derived from a known compound. Moreover, the structural moiety incorporated into the final product by this intermediate is identical to that introduced by the intermediate in Comparative Document 2. Consequently, it cannot be concluded that the intermediate of the present application contributes to the structure or properties of the inventive final product.

2. In both cases, the corresponding final products are obtained by converting the ester intermediates of this application into acyl chlorides and then reacting them with another structural moiety containing an amino group, thereby forming a final product bearing an amide bond. Since the method of converting a carboxylic acid into an acyl chloride and subsequently reacting it with an amino-containing fragment to yield an amide‑containing product has already been disclosed in Comparative Document 2, and given the fundamental knowledge of carboxylic acids commonly acquired in the field of organic synthesis, it is readily apparent that one would choose a low‑molecular‑weight aliphatic carboxylic acid ester—such as an ethyl ester—that is both typical in this field and easily hydrolyzable, and hydrolyze it to obtain the corresponding carboxylic acid. Thus, hydrolysis of the carboxylic acid ester of Formula 4c in this application represents the most widely used approach for preparing carboxylic acids in the art.

The present application does not disclose any technical content demonstrating that the method of obtaining a carboxylic acid intermediate via hydrolysis of the compound of general formula 4c, followed by the production of the final product, yields any superior technical effects. Accordingly, it fails to establish that the invention contributes to the development of an inventive method for producing downstream products.

②Typical Significance

The typical significance of this case lies in further clarifying the criteria for assessing the inventive step of intermediate compounds. If, during the research and development process, the applicant had paid attention to the technical effects that the intermediate compound imparts to the preparation method and emphasized these effects in the specification, or if they had investigated and developed alternative synthetic routes or final products that demonstrate the intermediate’s contribution to the prior art, then the inventive step of that intermediate compound would be more likely to be recognized and to result in grant of patent protection.

III. Summary

New intermediate compounds that emerge during the preparation of pesticide compounds make significant contributions to the manufacturing process, and protecting these intermediates can make it difficult for competitors to circumvent them. Moreover, since the structures of these intermediates are well-defined, they are easy to compare in subsequent infringement analyses, facilitating evidence collection and exerting a strong deterrent effect on rivals. Therefore, when new intermediate compounds arise in the course of researching pesticide‑compound synthesis processes, priority should be given to securing protection through patent applications. Patent applications should emphasize the remarkable technical advantages that these intermediates confer in the preparation of the target pesticide compounds; only such filings stand a better chance of being granted.

Source: Pesticide, Issue 8, 2023; Authors: Han Tao, Xu Yan, Wang Xian.