Can two separate prior art documents, neither of which discloses the claimed invention on its own be combined to defeat a patent application? The Delhi High Court answered yes in Esteve Pharmaceuticals S.A. v Controller of Patents and Designs1(judgment dated 7 August 2026), dismissing Esteve’s appeal against the rejection of its patent application for a co-crystal of tramadol and celecoxib. Justice Tushar Rao Gedela held that reading two prior art documents together one teaching that tramadol could be combined with celecoxib for pain relief, the other teaching general co-crystal formation techniques and their benefits rendered the specific claimed co-crystal obvious under Section 2(1)(ja)2 of the Patents Act, 1970.
Esteve filed a national phase application in India in February 2012, claiming priority from October 2009, for a co-crystal combining tramadol, an opioid analgesic with celecoxib, a coxib-class NSAID (Nonsteroidal anti-inflammatory drug). Esteve’s case was that combining the two known painkillers into a single crystalline form produced a novel solid with improved bioavailability, solubility, and a synergistic pain-relief effect exceeding either drug alone. The Assistant Controller of Patents rejected the application in February 2020 on multiple grounds: lack of inventive step under Section 2(1)(ja), and lack of patentability under Sections 3(d) (mere new form of a known substance) and 3(e)3 (mere admixture of known substances). Esteve appealed, arguing that since the impugned order had not ultimately sustained an objection of lack of novelty, the Section 3(d)4 objection could not stand either, and that neither of the two prior art documents relied on by the Controller, referred to as D5 and D7 disclosed or motivated the specific claimed co-crystal.
The Court’s Reasoning
The Court focused its analysis on the inventive step objection, treating it as potentially dispositive. It examined D5 (a US patent application disclosing methods of treating pain using a combination of an NSAID and slow-release tramadol) and D7 (a broader patent application on API-API co-crystal compositions and their preparation) side by side against Esteve’s claims. D5 was found to expressly list celecoxib among the NSAIDs that could be combined with tramadol, stating that “the person skilled in the art will know how the combination may be modified using other NSAIDs such as Celecoxib,” and separately noting that “some of these combination products also have the advantage of producing a synergistic analgesic effect.” D7, meanwhile, listed both celecoxib and tramadol in its Table IV of usable APIs, and disclosed general advantages of co-crystals as a class of increased solubility, dose response, bioavailability, and stability compared to an API alone.
Comparing these disclosures to the advantages Esteve claimed for its specific tramadol-celecoxib co-crystal, the Court found the overlap decisive: “the disclosure in D7 also specifies… increased bioavailability in the co-crystals compared to the individual APIs; dose response of the co-crystal is increased as compared to an API; increase in stability of the co-crystal. These parameters are also claimed in the present invention.” On the combination itself, the Court concluded that “reading of the prior art D5… which discloses the combination of tramadol and celecoxib as a method of treating pain, along with the disclosure under prior art D7, would render the present invention obvious.” The Court also noted that D7’s own general preparation method of dissolving components in a solvent and allowing the co-crystal to precipitate as the solvent evaporates overlapped with the process Esteve had claimed. On this basis, the Court held that “the invention claimed under the subject application lacks inventive step and therefore, barred under Section 2(1)(ja) of the Act.”
Having disposed of the appeal on the inventive step ground, the Court declined to examine the Section 3(d) and 3(e) objections at all, relying on its own earlier decision in Kroll Information Assurance, LLC v The Controller General of Patents5 for the proposition that once an appeal fails on one dispositive ground, the remaining objections need not be separately addressed. Esteve’s argument that D7’s priority date (2004) preceded the claimed invention by six years without anyone else developing the specific combination offered as evidence of non-obviousness was recorded in the judgment but not separately engaged with in the Court’s reasoning, which rested instead on the express textual overlap between the two prior art documents and the claimed invention.
Jurisprudential Significance
The Court’s method here is worth noting for what it actually did, not just what it concluded: it built a side-by-side comparison table setting the subject application’s claims against the disclosures of D5 and D7 and separately matched the specific advantages claimed for the co-crystal bioavailability, dose response, stability against the general advantages D7 already attributed to co-crystals as a class. Neither D5 nor D7 alone disclosed the claimed tramadol-celecoxib co-crystal; the finding of obviousness rested on reading the two together D5 supplying the motivation to combine tramadol with celecoxib specifically, D7 supplying the general co-crystallisation technique and its expected benefits. This distinguishes a case built on a single anticipating reference from one built by combining references, and the Court’s own comparison table shows exactly how it tested each element of the claim against that combined disclosure.
The order also turned on how the Court read Esteve’s claimed advantages against D7’s stated advantages. Because D7 already listed increased bioavailability, dose response, and stability as general benefits of co-crystals, the Court treated Esteve’s claim to those same benefits for its specific combination as falling within what D7 had already disclosed, rather than as a separate showing of inventive step (para 34). Esteve’s contrary argument that D7’s 2004 priority date and the absence of anyone else combining tramadol and celecoxib for six years pointed to non-obviousness appears in the recital of submissions but is not addressed in the Court’s reasoning at paras, which rests on the textual overlap between the prior art and the claims rather than on this kind of secondary evidence.
Citations
Expositor(s): Adv. Pratistha Dahiya
