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15.2 This is, to our mind, fundamentally flawed, as it would envisage a product-to-product mapping, whereas patent infringement is to be FAO(OS) (COMM) 120/2025 KUMAR Signing Date:12.01.2026 12:10:17 assessed on the basis of a product-to-claim mapping. In fact, the position would be that neither ZRC 3276, nor 5C4, would actually map onto the granted claim in the suit patent.

16. On the second aspect of the claim in the suit patent, of amino- acid sequencing, the learned Single Judge observes that (i) the appellant had sought exemption from detailed drug control research on the ground that ZRC 3276 is a biosimilar of Nivolumab which was, therefore, the "reference biologic" of ZRC 3276, (ii) 5C4, which was the claimed antibody in the suit patent, had the same amino acid sequencing as in Nivolumab and (iii) biosimilars had necessarily to have the same amino acid sequencing. Once, therefore, as its biosimilar, ZRC 3276 had the same amino acid sequencing as Nivolumab, and 5C4 also had the same amino acid sequencing as Nivolumab, the corollary would be that ZRC 3276 and 5C4 have the same amino acid sequences. If a equals b, and c equals b, holds the learned Single Judge, a must necessarily equal c.

17. It is in premise (iii) of this reasoning that, to our mind, the learned Single Judge has erred. There is nothing, in the impugned judgment, to indicate, as an inflexible principle, that biosimilars have the same amino acid sequencing.

18. Apart from this "biosimilar analysis", there is nothing, in the impugned judgment, to sustain the prima facie finding that ZRC 3276 has the same amino acid sequences as 5C4. Indeed, there could be none, as there has never been, at any stage, mapping of the appellant's ZRC 3276 product to the respondent's granted claim in the suit patent.

(i) The amino acid sequence of the respondents' 5C4 antibody mapped onto the amino acid sequence of INN Nivolumab.

(ii) The appellant's ZRC 3276 claimed to be a biosimilar of INN Nivolumab.

7 1990 Supp SCC 727 FAO(OS) (COMM) 120/2025 KUMAR Signing Date:12.01.2026 12:10:17

(iii) Biosimilars necessarily had to have the same amino acid sequence.

26.2.5.3 The issue of whether a biosimilar product can, on that basis alone, be said to be infringing of the reference biologic, appears to us to be extremely thorny. If the impugned judgment is accepted, every biosimilar product would, on that basis alone, infringe the patent claimed by the reference biologic.

26.2.5.4 As we have already noted, the Claims in the suit patent, which are alleged to be infringed, have, as their distinguishing features, their "specific" binding to the PD-1, and the amino acid sequencing in their chains. The learned Single Judge holds that, having claimed itself to be biosimilar to INN Nivolumab, the amino acid sequences of ZRC 3276 and Nivolumab were necessarily identical.