Delhi High Court’s Decision Discussing Doctrine of Equivalents: An Exhaustive but Blinkered Exercise?

Logo of FMC
Logo of FMC (Image from here)

Concluding Round 2 of the FMC- Natco CTPR litigation saga, a Division Bench of the Delhi High Court refused to interfere with the Single Judge’s order which had allowed Natco to launch its variant of CTPR. In doing so the court discussed ‘doctrine of equivalents’, relying extensively on foreign precedents. The doctrine is a contribution of American IP jurisprudence, which states that minor, colorable changes to a product, to avoid “literal” infringement, will still amount to an infringement if the product performs the same function as the patented product, in the same way, and yields the same result. The order holds that the application of this doctrine is not limited to product patents and it will apply to process patent cases as well. 

Brief Background 

FMC and Natco have a history of Chlorantraniliprole (CTPR) patent litigation with each other. Previously there have been multiple suits alleging that Natco infringed FMC’s patent IN’207307 (IN’307), Process Patent IN’213332 (IN’332), now expired IN’204978 (IN’978) and IN’215218 (IN’218). (Nikhil has previously covered the interim injunction granted by the Delhi High Court in litigation pertaining to IN’ 307 and IN’ 332, here.) The present order concerns another one of FMC’s CTPR patent- IN’298645 (IN’ 645). 

The Dispute– Natco (Defendant) stated that considering the history of litigation between the parties, it sent a notice under Section 105, to FMC asserting that the process employed by them does not infringe the suit patent IN’ 645. Regardless, FMC sued Natco alleging that it was using its patented method, as claimed by Claim nos. 1, 5-8, and 11 to prepare an identical product. FMC alleged that since both the competing methods, describe an amide bond formation reaction to yield CTPR, they are ‘equivalent’ and on the basis of the doctrine of equivalents, Natco has infringed FMC’s suit patent. During the hearing for this suit, Natco stated that it shall not launch its variant of CTPR till the subsistence of IN’ 307 and IN’ 332 (which were due to expire in August 2022) and that its variant will not infringe IN’ 645. Thus, the bone of contention was whether Natco’s method infringed IN’ 645. 

The Patent– The suit patent (IN’ 645) is a 12-claim process regarding ‘Method For Preparing N- Phenylpyrazole-1- Carboxamides’ and is used to prepare anthranilic diamide insecticide. The method functions as a combination of three ingredients- (l) a carboxylic acid compound, (2) an aniline compound and (3) a sulfonyl chloride to prepare or manufacture CTPR.  The suit patent is valid till December 2025. 

The Single Judge Decision- Considering the technical issues involved, the court-appointed scientific experts and relying on their findings/ response the court ruled that the two competing processes were not similar. The court understood the FMC’s process patent as mixing of a carboxylic acid (Formula 2) and an aniline (Formula 3) whether with the base or a solvent and thereafter, adding sulfonyl chloride to the said mixture, and noted that while reactants could be combined in various orders, the method necessarily entailed the use of sulfonyl chloride with the mixture. However, the process used by Natco did not use sulfonyl chloride and instead uses thionyl chloride and employs a different sequence of reaction. Accordingly, the Court, prima facie, found that the difference between the suit patent and the Natco’s process was not minor or insubstantial.

The Division Bench Order

 FMC appealed against the above understanding and argued that though Natco’s process is not identical to FMC’s process, by applying doctrine of equivalents, Natco has infringed the suit patent. It argued the “Natco process and the suit patent entail stoichiometric activation of the carboxylic acid intermediate, leading to a coupling reaction between the activated acid intermediate and the aniline intermediate.” FMC claimed this to be an essential feature of the suit patent IN’645. It argued that the use of thionyl chloride instead of sulfonyl chloride as a reagent is an insubstantial variation as sulfonyl chloride was not essential to the suit patent IN’645. Conversely, Natco argued that its process to manufacture CTPR is a two-step process requiring two reactors. As the outcome, though the yield of CTPR by Natco’s process is lower than Appellant’s process, it also does not produce any toxic by-products. Lastly, it argued that doctrine of equivalents has limited application in a method patent.

Doctrine of Equivalents

Simply put, the doctrine of equivalents comes into the picture when there is an apprehension of a patent’s infringement via ‘colorable or slight variations’ to fall out of the reach of the patent. As mentioned above, the doctrine is an outcome of US IP jurisprudence where the SCOTUS in Graver Tank & Mfg. Co.v Linde Air Products, looked beyond the literal scope of the claims to accord protection against something which though falls outside the claims of the patent, still performs the same function in the same way to yield the same result. This was seen as a departure from the UK’s “pith and marrow” approach, where the courts had refused to go beyond the technical understanding of the claim. (However, post-Actavis v. Eli Lilly, the UK Supreme Court seems to have injected doctrine of equivalents in the UK law as well.)  Professor Basheer had previously discussed this doctrine on the blog here

Coming back to the present case,  the court explained that the doctrine will be applicable in cases where the variation between product/ process and the patented claim is insignificant, insubstantial and not essential. And that for such a comparison, the scope and essence of the patent must be looked at. 

However,  the court then assessed the application of the doctrine on process patent infringement suits and accordingly modified the three-step test [competing products i) performs the same function; ii) in the same manner; iii) to yield the same result.] The court held that achieving the same result will not be material in determining infringement. But rather first, the essential elements of the process need to be identified, and then the manner in which these elements interact with each other at each step needs to be observed. And, if this interaction of essential elements is similar in the competing methods, then only can the claim of infringement be sustained. Applying its version of the doctrine, the court held that use of sulfonyl chloride was an essential part of the suit patent and since Natco’s process varies with the patented process by using thionyl chloride instead, it was prima facie held to be different. 

Looking at this part of the court’s overall approach, it seems like it has adopted a US-like model, where the court will be willing to look past the literal constructs of the claims in order to make an assessment of the infringement. However, by shifting the focus to a step-by-step interaction of the essential elements of the process, the order has set a herculean task for the courts that shall apply this doctrine in the time to come. For instance, in this case, the court called out FMC’s argument that the essential feature of its patent is stoichiometric activation leading to a coupling action. The court denied it, holding that neither its claims nor its detailed description indicates the above to be the novel inventive feature of the suit patent. Conversely, this raises the question of what shall happen to the assessment of the Defendant’s process, which is not expanded in such an elaborate manner always? As Eashan Ghosh has also highlighted in his piece, culling out ‘essential’ features for comparison at every step might not be so easy, and the order offers little to no help. 

Another thing that merits attention in this regard is the existence of expert submissions in the present case. Considering the technical nature of most process patents, undertaking such a nuanced comparison between competing processes should attract frequent appointments of scientific experts. Hopefully, this understanding resonates with the future benches that will consider utilizing this doctrine in similar cases.     

Lastly, while this may perhaps be one of the most detailed orders on the doctrine of equivalents in India, I cannot help but think about the associated social costs with such an approach. Long-time readers will recollect this guest post by Prof. Josh Sarnoff, who briefly touched upon this and warned against applying this doctrine, in his post here. While this doctrine is here now, I think it’s time that we should also think about its impact along these lines as well. 


The author would like to thank Sandeep Rathod and Swaraj Barooah for their comments on this issue.

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