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  • Loveleen Kaur

High Court dismisses injunction against NATCO PHARMA in patent infringement action by FMC Corp.


The High Court in the case of FMC Corporation & Ors. vs Natco Pharma Limited has dismissed the application by FMC Corporation seeking a decree of permanent injunction against Natco Pharma Limited, to stop them from directly or indirectly infringing the methods of manufacturing ‘Chlorantraniliprole’ (CTPR) covered by FMC Corporation’s patent.

The case of the Plaintiffs was primarily predicated on the Doctrine of Equivalents and the contention of Natco was that element-to- element test must be applied and the impugned process used by the Natco must be tested on that anvil.

The Court laid down tests to evaluate infringement in process patents thus concluding that NATCO’s process and the suit patent are distinct and different and NATO’s process prima facie does not come under the rigors of Doctrine of Equivalents.


Plaintiffs had an injunction in their favour in respect of the product patent 1IN201307 and its process patent [1]IN213332 with respect to CTPR, however, both patents had expired on 13.08.2022.

The present suit however was instituted by the FMC Corporation & Ors. (hereinafter referred to as the “Plaintiffs”) seeking permanent injunction for infringement of the method of the suit patent 298645 [hereinafter referred as the ‘suit patent’] by Natco Pharma Limited (hereinafter referred to as the “Defendant”).

The Plaintiff asserted that it is engaged in the production and sale of chemicals including agrochemicals and provides cost-effective solutions for enhancement of crop yield and in non-agricultural markets as well.

The suit patent relates to a novel method for preparing anthranilic diamide insecticide compounds and a total of 12 claims have been granted in the suit patent. The said method involves combining (1) a carboxylic acid compound, (2) an aniline compound and (3) a sulfonyl chloride, to prepare or manufacture CTPR. Thus, in the patented method, a pyrazole carboxylic acid of Formula 2, and aniline of Formula 3 and a sulfonyl chloride are combined (contacted) to prepare CTPR.

The Plaintiff learnt of the process adopted by the Defendant for synthesis of CTPR through a document titled ‘Environmental Management Plan for obtaining consent for establishment (CEF)- Expansion’, submitted by the Defendant to A.P. State Pollution Control Board. As per the Plaintiff, the Defendant is employing a method claimed in the suit patent to prepare identical CTPR and thus, constituting infringement of the patent.

The Plaintiff claimed that both the processes of preparing CTPR, describe an amide bond formation and rely on activation of carboxylic acid moiety to facilitate the amide formation, to yield CTPR, in substantially the same way, i.e., coupling of carboxylic acid with aniline and thus, are equivalent.

The Plaintiff contended that ‘all essential elements’ of the suit patent are present in the infringing process and the only variation in the Defendant's process is use of a different chloride i.e. thionyl chloride is used in instead of the sulphonyl chloride, which are equivalent reagents and cannot shield the Defendant from infringement being such a minor variation. It was alleged by the Plaintiff that sulfonyl chloride is ‘preferred’ because of its commercial availability and the process can use both organic and inorganic chloride, as mentioned in the specification and hence include both the chlorides.

The Plaintiff further placed reliance on the concept of “Doctrine of Equivalence” and exhibited various judgements which determine the relevance of the doctrine. ‘Doctrine of Equivalents’ propounds that despite an absence of literal infringement of a patent claim, infringement can be proven if an element of the accused product or service and a claimed element of patented invention are found to be substantially equivalent.

The Plaintiff stated that thionyl chloride used by the Defendant is equivalent to sulfonyl chloride since both are Reagents and have the same function. They emphasised that as the starting materials are the same i.e. the acid and amide intermediates, the end result is the same i.e. CTPR and the Reagents are equivalent, it is a prima facie case of infringement.

The Plaintiff also repudiated the Defendant's contentions regarding sequence of combining the reactants and stated that there is no such limitation and change of sequence of combining the reactants would have no impact.

The Defendant, contrary to the Plaintiff’s submissions, argued that the process disclosed in the suit patent involves using a specific organic chloride viz. sulfonyl chloride reagent for coupling carboxylic acid intermediate with aniline intermediate in a single step. The scope of protection vide claim 1 is expressly limited to this coupling using sulfonyl chloride, and the suit patent does not identify/refer/disclose any other organic or inorganic chloride, which could be used as a reagent.

The Defendants asserted that the reagent used in the Defendant’s process is inorganic thionyl chloride which is different from organic sulfonyl chloride. Further, the sequence of reaction used in the Defendant’s process is also different, which makes the process completely outside the scope of claims of suit patent.

The Defendant further relied on [2]Warner-Jenkinson Co., Inc v. Hilton Davies Chemical Co. and contended that for a process patent, the relevant test is ‘all elements’ test i.e. not only the starting materials and the end product, but all reagents and each step must be equivalent between the patented and the impugned process. Further, reliance was placed on the findings of Scientific Advisors in support of their arguments

Findings of the Court:

The Court went on to conduct a prima facie comparison of the two processes and observed that the settled law for determining the question of infringement is that it has to be kept in mind that non-essential or trifling variations in the allegedly infringing process would not be germane, so long as the substance of the suit patent is copied.

Doctrine of Equivalents should be applied to examine if the substituted element(s) in the infringing product does the same work, in substantially the same way, to accomplish the same result. Seen in this light, it is now required to be considered, if the use of thionyl chloride in the Natco process is a minor/trivial change from use of sulfonyl chloride, which as a reagent is critical to the novelty and functionality of the suit patent, so as to infringe the suit patent, applying the Doctrine of Equivalents.

The Court clarified that “in a process claim, the monopoly is restricted to the method by which the product is manufactured and if the same product is manufactured through a different process/method, the patentee cannot extend its monopoly to the different process.

Upon referring to the reports of the Advisors and reviewing their submissions the Court concluded that “(1) sulfonyl chloride is an essential element of the suit patent and (2) thionyl chloride used as a reagent in the Natco process, differs from sulfonyl chloride in its physical and chemical properties”.

The Court upon analysing the contentions made, the categorical findings of both the Scientific Advisors and applying the principles enunciated in the Judgements relied by both the parties, upheld that the suit patent process and the Natco process are distinct and different. Sulphonyl chloride is an essential element of suit patent and use of thionyl chloride as a reagent coupled with a different sequence of the reaction, as brought forth by the Scientific Advisors, cannot be termed as an insignificant or trivial or insubstantial change in the Natco process and thus the process prima facie does not come under the rigors of Doctrine of Equivalents.”

Based on the Court’s analysis, the application for seeking an injunction was dismissed, and the Defendant was permitted to launch its product, CTPR, with a caveat that the process claimed in suit patent shall not be used.


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