In a landmark judgment, the Division Bench of the Delhi High Court has laid down a higher legal threshold to be applied for establishing a prima facie case of patent infringement in a quia timet action involving yet-to-be-launched products. While permitting Zydus to sell a biosimilar version of anti-cancer drug Nivolumab in India, in the absence of product-to-claim mapping, the Division Bench mandated proof via a “continuous and unbroken chain of circumstances” drawn exclusively from collateral material.
How the controversy arose:
US-based E.R. Squibb & Sons LLC filed a patent infringement action against Zydus in 2024. It alleged that Zydus was conducting clinical trials to seek approval of its biosimilar drug ZRC-3276, with the reference drug being Nivolumab, an anti-cancer drug essential for the treatment of a wide variety of life-threating carcinomas. Nivolumab is protected under Indian patent IN340060 held by E.R. Squibb.
E.R. Squibb approached the Delhi High Court seeking permanent and interim injunction in a quia timet action prior to the launch of Zydus’s product. Due to the unavailability of the Zydus product, E.R. Squibb was unable to undertake the conventional product-to-claim mapping as required under Rule 3A(ix) of the High Court of Delhi Rules Governing Patent Suits, 2022.
What the Single Judge held:
In July 2025, Zydus was injuncted at an interim stage by the Ld. Single Judge from launching its drug ZRC 3276. Agreeing with E.R. Squibb, the Ld. Single Judge held that lack of product to claim mapping was not detrimental to its case as Zydus’s drug does map on to the suit patent, based on other material filed by E.R. Squibb.
Challenge before the Division Bench:
In appeal, the Division Bench emphatically clarified that while the requirement of precise product-to-claim mapping is not a “cast-in-iron imperative,” its absence demands “overwhelming circumstantial material” to establish mapping of the Zydus drug with the granted claims of the asserted patent. The Division Bench further emphasized that the material establishing mapping in the absence of claim mapping must form an irrefutable chain (akin to standards under criminal law) leaving no room for any speculation. No room exists for ‘assumptions and presumptions’ or for product-to-product comparison. If collateral material and evidence such as regulatory filings or declarations of bio-similarity are being relied upon to establish that the defendant’s product maps on to the patented claim, such material must do so without gaps, resolving all technical disputes prima facie without necessitating trial-level expert evidence.
This heightened bar stems from the unique challenges faced by patentees when proceeding against unlaunched products. Without testing a sample of the allegedly infringing product, patentees cannot provide precise claim-to-product mapping and risk speculative injunctions that stifle innovation or public access, particularly for pharmaceutical products. In patent contexts, where Section 48 grants exclusive rights only over “that product,” the absence of infringing product coupled with weak evidentiary chains undermines the threshold required to establish a prima facie case in favour of the patentee.
This becomes significant in cases involving triable issues like claim construction or equivalence in biologics. Absent such overwhelming circumstantial proof, when precise product-to-claim charts are also not filed as the product is not yet launched, courts must be cautious in entertaining the prayer of interim injunction sought by the patentees.
In the Zydus case, the Division Bench held that E.R Squibb’s chain faltered critically. The suit patent (IN 340060) claimed an isolated monoclonal antibody binding “specifically” to PD-1 with defined CDR sequences. Facing Zydus’ unlaunched biosimilar ZRC 3276 (claimed similar to Nivolumab/5C4), E.R Squibb’s indirect chain of evidence was as follows:
- Sequence of amino acids in drug 5C4 maps to Nivolumab INN;
- ZRC 3276 is a Nivolumab biosimilar;
- Biosimilars share identical sequences per guidelines; and
- Sequence of amino acids in both the drugs were identical.
While the Ld. Single Judge accepted this claim as sufficient condition for granting interim injunction to Squibb, the Division Bench found it lacking at every link. The Division Bench held that:
- Step (i) was tautological as Nivolumab exemplifies the patent and mapping 5C4 to INN Nivolumab ‘is no more, and no less, than mapping onto oneself’;
- Step (ii) was admitted but the question that deemed importance was what follows with ZRC 3276 being a biosimilar;
- Step (iii) presumed identity where guidelines provide biologics are similar only in quality, safety and efficacy. The Court held that for patent infringement purposes, ‘what is needed is not similarity of amino acid sequencing, but identity.
Public interest cannot be overlooked:
In addition, the Division Bench also acknowledged that the case involved considerations of public interest in allowing the life-saving drug, ZRC-3276 of Zydus to be made available to the public. This was supported by Zydus’s argument that its drug was approximately 70% cheaper than E.R Squibb’s drug, 5C4 for cancer treatment.
Further, the Division Bench, in an effort to balance the interests of justice, modified the order of the Ld. Single Judge and directed the Zydus to file audited accounts earned by sale of drug. The court also highlighted that this arrangement could protect interests of both sides as the patent was expiring in May 2026.
Key takeaway:
Thus, while asserting patents in a qui timet actions against potential infringers has always remained a challenge, this judgment has further raised the benchmark by ensuring that the patentees must exercise utmost diligence to secure favourable chances of securing an interim injunction. In absence of claim to product mapping, there must be overwhelming collateral material for establishing a prima facie case of infringement comprising of a continuous and unbroken chain of irrefutable evidence.
