Indian patent claims: when prosecution history leads the infringement analysis

The grant of every patent is subjected to an examination by the examiner in the Indian Patent Office. It is normal to restrict certain claims or concede a certain claim limitation in view of cited prior art. The applicant’s submission in relation to the first examination report forms part of the prosecution history of the application. Prima facie, this amounts to a tacit admission of certain facts relating to understanding the subject matter of the invention. These submissions are in-fact pointers regarding the difference between the prior art and the claimed invention.

The admissions and limitations imputed in the claims during the prosecution of the patent application are considered by the courts during the infringement analysis to decide the reach of the claimed invention in infringement disputes. The primary reason for adopting this is that no party can be permitted to approbate and reprobate at the same time.

There is no dearth of judicial precedents, both in India and abroad, where prosecution history estoppel has been a well-recognised parameter to adjudicate issues pertaining to patents. For instance, in Pharma Tech Solutions, Inc., Decision IT Corp. v LifeScan, Inc., LifeScan Scotland, Ltd. (decided on November 22 2019), the United States Court of Appeals for the Federal Circuit emphasised the importance of prosecution history in the context of infringement analysis.

If the defendant seeks prosecution history estoppel in a patent dispute, the courts invariably draw on the relevant prosecution history. For example, in Astrazeneca AB and Ors. v Intas Pharmaceuticals Ltd. and Ors. (2021), the High Court of Delhi devolved to the prosecution history estoppel to determine if coverage of dapagliflozin in the IN 205147 (genus) patent extends to the related IN 235625 (species) patent.

In Vifor and Others v Virchow Biotech and Others (decision dated July 24 2023) (the Vifor case), the High Court of Delhi asserted that the prosecution history estoppel became pronounced on account of the fact that the patent was obtained by representing that the novel properties in the product were attributable to characteristic features of the process mentioned therein. The Vifor suit patent, IN 221536, is titled ‘Water Soluble Iron Carbohydrate Complex and A Process For Producing Water Soluble Iron Carbohydrate Complex’ (IN’536), relating to ferric carboxymaltose (FCM).

Prosecution history estoppel can occur in two ways:

• By making a narrowing amendment to the claim (‘amendment-based estoppel’); or

• By surrendering claim scope through argument to the patent examiner (‘argument-based estoppel’).

However, in both cases the applicant accepts in principle that it will restrict the original claims. When this is done, the applicant is estopped from retracting from the conceded position during infringement disputes before the court. The US court in VLSI Tech. v Intel Corp. held that a "patentee's decision to narrow his claims through amendment may be presumed to be a general disclaimer of the territory between the original claim and the amended claim".

In Almirall, LLC v Torrent Pharm., Ltd., argument-based prosecution history estoppel was held by the court to bar a patent owner from asserting equivalents for a claim. In Trading Techs. Int’l, Inc. v Open E Cry, LLC (2013), the United States Federal Court of Appeals held that “prosecution history estoppel applies as part of an infringement analysis to prevent a patentee from using the doctrine of equivalents to recapture subject matter surrendered from the literal scope of a claim during prosecution.”

In India again, the courts recognise the prosecution history estoppel in the decision-making process to adjudicate issues pertaining to patents, particularly at the stage of granting interim injunctions. This principle was well recognised by Indian courts in Astrazeneca AB and Ors. v Intas Pharmaceuticals Ltd. and Ors. (2021) and FMC Corporation and Others v GSP Crop Science Private Limited (2022).

In the Vifor case, the High Court of Delhi went to the extent of stating that “there is [a] wealth of judicial precedents, both in India and abroad, where prosecution history estoppel has been a well-recognized parameter to adjudicate issues pertaining to patents, particularly, at the stage of grant of interim injunctions, which is a discretionary relief and one of the factors that goes into the decision-making process is the conduct of the party seeking equitable relief.”

In this context, the High Court of Delhi in the Vifor case observed that “no party can be permitted to approbate and reprobate at the same time and the prosecution history estoppel becomes pronounced on account of the fact that the patent was obtained by representing that the novel properties in the product were attributable to characteristic features of the process mentioned therein.

“Additionally, in a response filed by Vifor in the EP Application 03769422.1, granted as EP’315, it was expressly stated that invention of Claim 1 of EP’315 is different from the cited prior arts which taught oxidation of dextrin and dextran on the ground that EP’315 uses alkali material, i.e., aqueous hypochlorite. These facts are pointers of the inconsistency of Vifor’s stand in different matters and applications. Prima facie, this amounts to a tacit admission that the step of oxidation of maltodextrins using aqueous hypochlorite in alkaline pH range is essential and critical to determination of the scope of Claim 1 of EP’315 and IN’536 and is the distinguishing feature [emphases added].”

In the Vifor case, the court further asserted that the United States Court of Appeals for the Federal Circuit in Pharma Tech Solutions, Inc., Decision IT Corp. v LifeScan, Inc., LifeScan Scotland, Ltd., decided on November 22 2019, emphasised the importance of prosecution history in the context of infringement analysis and the principle was well recognised by the court in Astrazeneca AB and Ors. v Intas and FMC Corporation and Others v GSP Crop Science Private Limited. These assertions by the courts in India and other jurisdictions point towards the importance of prosecution history in the context of infringement matters.

In fact, in this case the court considered prosecution history as a decisive factor to prove that the alleged claims were product-by-process claims and this ruling supported the contention of the defendant that the different process to arrive at the FMC is not an infringement of the amended claims.

Analysis of the prosecution history by the court states that “The stand now taken by Vifor claiming that Claim 1 is a product claim, though ingenious, is further dented by a close look at the prosecution history of IN’536. During these proceedings, the Assistant Controller of Patents and Designs had in the First Examination Report (‘FER’) dated 10.12.2007 raised an objection to the Patent application of Vifor on the ground that the claimed invention was not novel under […] Section 2(1)(j) of the 1970 Act, citing 5 prior art documents. In response to the FER vide letter dated 19.12.2007, Vifor had limited the invention to iron (III) complexes, having an average molecular weight of 80 kDa to 400 kDa and stated that the essence of invention resided in appropriately selecting suitable maltodextrins, having specific Dextrose Equivalent as defined in the claims and oxidizing them stereoselectively and regioselectively at the terminal aldehyde group and then by reacting them with iron (III) salts, as a result of which iron (III)-oxidized maltodextrin complexes are obtained, which are polynuclear complexes, having a specific high average molecular weight. The maltodextrins and the oxidation process are known, but the new feature of the present invention is that the obtained iron complexes are very stable to heat, have a very low toxicity, a low risk of anaphylactic shock and thus can be sterilized by heating and used for injection in very high doses. With this in the backdrop, it cannot be argued by Vifor, at this stage, that Claim 1 for preparation of ‘water-soluble iron carbohydrate complexes’ was not limited by the process defined therein [emphases added].”

When the patentee chooses to limit the scope of the claim through amendments, the court asserted that “it cannot be argued by Vifor, at this stage, that Claim 1 for preparation of ‘water-soluble iron carbohydrate complexes’ was not limited by the process defined therein.”

The court further observed that “the maltodextrins and the oxidation process are known, but the new feature of the present invention is that the obtained iron complexes are very stable to heat, have a very low toxicity, a low risk of anaphylactic shock and thus can be sterilized by heating and used for injection in very high doses.”

Against this backdrop of prosecution history, the court held that the claimed invention in IN’536 is a product-by-process claim and the infringement analysis would be guided by this fact. Therefore, there is merit in the contention of the defendants that if they are able to successfully establish that their product FCM is made by a different process, the defendants cannot be accused of infringement.

Hence, the court held that “in view of the aforesaid, in my prima facie view, Defendants have succeeded at this stage in establishing that the process adopted by them to obtain FCM is outside the limits of the scope of IN’536 and it is held that the impugned process of CRPL [Corona Remedies Private Limited] and VBPL [Virchow Biotech Private Limited] is non-infringing.”

As stated, there is a wealth of judicial precedents, in India and abroad, where prosecution history estoppel has been a well-recognised parameter to adjudicate issues pertaining to patents. This is particularly the case at the stage of grant of interim injunctions, which is a discretionary relief, and one of the factors that goes into the decision-making process is the conduct of the party seeking equitable relief.

The Vifor case highlights how the prosecution history can affect the reach of any claim. The patentee should be more vigilant during the prosecution of the application before the patent examiner. Amendments in claims during the examination of the application are invariably viewed by the court as a narrowing of the claims.

The patentee should be extra careful when any admissions and limitations are imputed in the claims during the prosecution of the patent application.

The courts in India favour the prosecution history estoppel if contended by the defendant in a patent dispute. This is particularly true as prosecution history is also considered by the courts during the infringement analysis to decide the reach of claimed invention, as was done by the High Court of Delhi in the Vifor case discussed above. In the US, courts put a bar on the application of the doctrine of equivalents based on prosecution history and prevent a patentee from using the doctrine of equivalents to recapture subject matter surrendered from the literal scope of a claim during prosecution of the application. This situation can happen in India as well, as Indian courts are not averse to following important principles laid down by foreign courts.

Expert advice can save the patentee and help to guard its asserted claims. Furthermore, extra caution and care in making amendments to claims at the prosecution stage can help the patentee to enforce infringement action more diligently.