The Delhi High Court, in the case of FMC Corporation & Ors. vs Natco Pharma Limited [CS(COMM) 607/2024], decided an interim injunction application filed by FMC seeking to restrain the alleged infringement of its patented Compound of Formula 3, as claimed in Claim 12 of patent number 298645 (IN’645), entitled “Method for Preparing N-Phenylpyrazole-1-Carboxamides”. Claims 1 to 11 of the patent relate to a process for preparing the insecticidal active ingredient “Cyantraniliprole” and Claim 12 discloses a Compound of Formula 3, which is an intermediate compound used in that process. FMC’s case centred on proviso (d) of Claim 12, which discloses the intermediate compound (2-amino-5-cyano-N,3-dimethylbenzamide) alleged to have been used by Natco.

The decision was pronounced nineteen days before the expiry of the suit patent.

The suit was instituted as a quia timet action, seeking a permanent injunction restraining Natco from manufacturing or preparing the impugned product, ‘Cyantraniliprole 10.26% OD (Oil Dispersion)’, or product containing Cyantraniliprole using FMC’s patented Compound of Formula 3 as a specific intermediate compound.

Natco had launched its product during the pendency of the proceedings and submitted before the Court that it had “cleared the way” prior to the launch. Pursuant to the directions of the Court, Natco filed an affidavit placing on record details of the stocks manufactured and sold, as well as the revenue earned from the sale of its product. Natco admitted that it was engaged in making and using the intermediate compound (2-amino-5-cyano-N, 3-dimethylbenzamide), to make the impugned product. It challenged the validity of the suit patent on multiple grounds, including prior claiming by IN 269104 (double patenting), lack of novelty, obviousness, insufficiency of disclosure, and patent ineligibility under Sections 3(d) and 3(e) of the Patents Act. Natco also raised the Gillette defence of non-infringement, contending that the impugned product was based on expired prior art and therefore did not infringe the suit patent. In such a case, the defendant is not required toassail the validity of the suit patent itself; it is sufficient to demonstrate that its activities fall entirely within the scope of prior disclosures.

Notably, the parties have been engaged in multiple litigations concerning the Chlorantraniliprole and Cyantraniliprole patent families since 2022, including suits in which FMC was denied the grant of interim injunctions in respect of the process claims (Claims 1-11) of the same patent. Natco also instituted a declaratory suit seeking a declaration of non-infringement of FMC’s patent IN 277358 in relation to Cyantraniliprole 10.26% OD. Thereafter, Natco filed a revocation petition challenging Claim 12 of the suit patent and subsequently obtained regulatory approvals and commenced commercial manufacture of the impugned product in April 2025. In parallel, FMC instituted three additional suits before the District Court at Chandigarh alleging infringement of Claim 12, which were later transferred to the Delhi High Court.

In opposing the grant of interim injunction, Natco contended that FMC had constructed a patent thicket comprising more than 40 patents around Cyantraniliprole and analogous products. According to Natco, Claim 12 of the suit patent (a genus patent) fell within the scope of FMC’s earlier species patent IN 269104, having a priority date of January 22, 2002, substantially preceding the priority date of the suit patent. Natco specifically countered FMC’s submission that the priority date of IN’104 stood deferred to 2008 on account of amendments, pointing out that the records of the Indian Patent Office reflected January 22, 2002, as the priority date of IN’104. Thus, it was stressed that the suit patent was liable to be revoked on the ground of prior claiming under Section 64 (1)(a) of the Act.

Natco further relied upon WO 03/062226, the PCT application corresponding to IN’104, to contend that the same class of intermediates stood anticipated by prior publication under Section 64(1)(e). It was argued that the disclosure in WO’226 was enabling and that the intermediate could be derived without any inventive effort or hindsight reconstruction.

Addressing equities, Natco submitted that it had “cleared the way” by filing a revocation petition challenging Claim 12 before commercialisation. Natco further pointed out that it had obtained all necessary regulatory approvals and had made substantial investments in setting up manufacture of Cyantraniliprole 10.26% OD. Given that the suit patent was close to expiry, Natco argued that granting an interim injunction at this stage would cause disproportionate and irreversible harm, while any alleged loss to FMC could be adequately compensated in damages.

Natco also relied upon FMC’s litigation conduct, pointing out that FMC had been denied interim injunctions in earlier suits concerning the same patent family and that FMC’s repeated attempts to enforce different claims of overlapping patents demonstrated the fragility of its asserted rights. According to Natco, these circumstances further weighed against the grant of discretionary interim relief.

On the other hand, FMC emphasised that Natco had admitted to manufacturing and using the very intermediate claimed under Claim 12, and that such admitted use constituted a clear prima facie case of infringement. It further submitted that the filing of a revocation petition by Natco did not amount to “clearing the way” and could not, by itself, constitute a credible challenge to validity.

On merits, FMC refuted Natco’s case of prior claiming and anticipation. It asserted that IN’104 could not be treated as prior art, since it was published only in 2008, well after the priority date of the suit patent (7 December 2004), and that Section 11(8) of the Patents Act barred reliance on later-published documents to assail novelty. FMC also denied that Claim 12 was anticipated by WO’226, contending that the international publication neither specifically disclosed nor enabled the intermediate claimed under proviso (d) of Claim 12, and that Natco’s attempt to derive the intermediate by reverse-engineering end products disclosed in WO’226 amounted to impermissible hindsight analysis.

FMC further submitted that Claim 12 disclosed a limited class of intermediates, several of which were specifically exemplified in the specification, and that the claimed intermediate exhibited technical advantages, including improved yield when used in the manufacturing process. It rejected Natco’s “species-genus” and evergreening arguments, asserting that the intermediate constituted a distinct invention, separately patentable notwithstanding the existence of other patents covering the final product or process.

At the outset, the Court reiterated settled principles governing interim injunctions in patent matters. Relying on Section 13(4) of the Patents Act and precedents such as Bishwanath Prasad Radhey Shyam vs Hindustan Metal Industries, Ten XC Wireless vs Mobi Antenna, and F. Hoffmann-La Roche vs Cipla, the Court emphasised that:

• There is no presumption of validity of a patent, even after grant.
• At the interim stage, the defendant need only raise a credible or substantial challenge, demonstrating vulnerability rather than conclusively proving invalidity.
• Where such vulnerability is shown, the Court should ordinarily decline injunctive relief.

The Court identified two principal questions for consideration at the interim stage:

1. whether Claim 12 was anticipated by prior claiming under IN’104, and
2. whether it lacked novelty in view of WO’226.

Prior Claiming by IN’104

The Court clarified that for the purpose of determining whether a patent is prior art under Section 64 (1)(a), the relevant date is the date of priority, not the date of publication.  The Court noted that IN’104 has been filed as a divisional of IN’417, and, because, the priority date of a divisional application is the date of filing of that specification in which the matter was first disclosed, it automatically inherited the earlier priority date of January 22, 2002. The Court found substance in Natco’s submission that the priority date of IN’104 had not shifted to 2008, notwithstanding amendments made during its prosecution, and that the records of the Indian Patent Office reflected January 22, 2002, as the priority date.

The Court further observed that the patented intermediate compound has been specifically claimed in IN’104, making the suit patent vulnerable to anticipation by prior claiming. The Court concurred with Natco that there existed a genus-species relationship between the suit patent and IN’104. Both Claim 1 of IN’104 and Claim 12 of the suit patent were Markush structures sharing a common core structure of 2 aminobenzamides. The Court emphasised that if even one of the variations arising from the core structure is known in a prior art, the same would be susceptible to the challenge of not being novel under the Act.

Anticipation by WO’226

The Court observed that WO’226 was published on July 31, 2003, while the priority date of the suit patent was December 7, 2004. It observed that, although WO’226 was an international application, it was relevant for the purpose of Section 64 (1)(e) because it entered India as a national phase application and was granted as IN’417, with the divisional application, IN’104.

The Court clarified that the complete specification of a divisional application cannot be inconsistent with the disclosure contained in the complete specification of the parent application. Consequently, the disclosures in the complete specification of IN’104 necessarily fall within the scope of the disclosures made in IN’417 and, by extension, its international counterpart, WO’226. In view of the prima facie finding that the intermediate compound claimed in Claim 12 of the suit patent was already claimed and disclosed in IN’104, the Court held that it would logically follow that the same intermediate compound was also disclosed in WO’226. On this basis, the Court held that Natco had raised a credible challenge to the novelty of Claim 12 in light of WO’226.

Gillette Defence

The Court remarked that since the intermediate compound in question was claimed and disclosed in IN’104 and WO’226, Natco had a right to practice this compound after the expiry of IN’104. It held that the defence was prima facie tenable.

Balance of Convenience

The Court placed reliance on the principle that a defendant may avoid an interlocutory injunction in circumstances where litigation is inevitable upon commercialisation of a product, provided the defendant has cleared the way prior to launch. It observed that the objective of this concept is to avoid multiplicity of proceedings. The legal framework expressly enables a defendant to clear the way by initiating revocation proceedings and seeking a declaration of non-infringement before commercial launch. The Court noted that Natco had filed a revocation petition challenging the validity of Claim 12 prior to the institution of the present suit. It further took note of the fact that Natco had disclosed the impugned product, Cyantraniliprole 10.26% OD, in a suit for non-infringement filed by Natco in respect of another FMC patent. The Court held that this demonstrated that Natco had cleared the way prior to launch.

The Court further took into account that Natco had made substantial investments in infrastructure and manufacturing facilities, obtained regulatory approvals, and commenced commercial manufacture of the impugned product. In light of the impending expiry of the suit patent and Natco having raised a credible challenge to the validity of Claim 12, the Court held that the balance of convenience was in favour of the Natco. Natco was directed to continue disclosing details of the quantities and value of products manufactured and sold.