Pharmaceutical co-crystals are developed by combining active pharmaceutical ingredients or other suitable compounds in a crystalline form to improve properties such as solubility, stability, bioavailability and therapeutic performance. However, the formation of a new co-crystal does not automatically establish inventiveness under the Patents Act, 1970. The claimed invention must satisfy the requirement of inventive step under Section 2(1)(ja), particularly where the individual components and methods of co-crystal preparation are already disclosed in the prior art. The assessment therefore requires consideration of whether the prior art provides sufficient teaching, suggestion or motivation for a person skilled in the art to arrive at the claimed invention.
The Delhi High Court dismissed the appeal against the order of the Controller refusing a patent application for a pharmaceutical invention titled “Co-crystals of Tramadol and Coxibs”, filed by Esteve Pharmaceuticals S.A. In Esteve Pharmaceuticals S.A. v. Controller of Patents and Designs [C.A.(COMM.IPD-PAT) 118/2022], decided on August 7, 2026, the Court upheld the decision of the Controller, ruling that the claimed tramadol and celecoxib co-crystal lacked inventive step under Section 2(1)(ja) of the Patents Act, 1970.
Comparing the teachings of the cited prior art documents with the claimed invention, the Court concluded that the combination of the known components and the disclosed co-crystal preparation techniques made the claimed invention obvious to a person skilled in the art. Although the Controller had also refused the application under Sections 3(d) and 3(e), the Court declined to examine these objections after upholding the refusal on the ground of lack of inventive step. Relying on its earlier ruling in Kroll Information Assurance, LLC v. Controller General of Patents [C.A.(COMM.IPD-PAT) 439/2022], the Court held that once an objection sufficient to sustain the refusal had been examined and upheld on merits, it was unnecessary to examine the remaining objections.
Factual Matrix
Esteve Pharmaceuticals S.A. filed a national-phase patent application, No. 1435/DELNP/2012, for an invention titled “Co-crystals of Tramadol and Coxibs”. According to the applicant, the invention relates to co-crystals of tramadol and non-steroidal anti-inflammatory drugs (NSAIDs), such as coxibs, processes for their preparation, and their uses as medicaments or in pharmaceutical formulations, particularly for the treatment of pain. The application claimed priority from October 16, 2009 and was filed in India on February 15, 2012.
The respondent Controller cited prior art documents, including US 2008/0031950 A1 (D5) and WO 2004/078163 A2 (D7), and rejected the claimed invention on the ground that it lacked inventive step under Section 2(1)(ja) in view of the teachings disclosed in D5 and D7. The Controller also raised objections under Sections 3(d) and 3(e). Aggrieved by the refusal order dated February 12, 2020, the applicant preferred an appeal before the Delhi High Court.
Case of the Appellant
On Section 2(1)(ja)
The appellant contended that when the respondent raised objections on account of lack of novelty, the applicant amended its claims and limited them to “a co-crystal of tramadol and celecoxib”. The appellant submitted that the initial objection under Section 2(1)(j) of the Act had been met, as the said objection was not sustained in the impugned order. However, the respondent rejected the subject invention on the ground that the claimed subject matter did not involve an inventive step under Section 2(1)(ja).
The appellant argued that D5 disclosed a combination of tramadol with NSAIDs, but did not teach or suggest the specific co-crystal of tramadol and celecoxib. Similarly, D7 generally disclosed co-crystalline forms of active pharmaceutical ingredients but did not specifically teach the claimed co-crystal combination. The appellant contended that merely identifying tramadol and celecoxib among several possible compounds would not provide sufficient motivation for a person skilled in the art to arrive at the claimed invention.
The appellant further submitted that D7 was published several years before the priority date of the claimed invention, yet the specific co-crystal combination of tramadol and celecoxib had not been developed during that period. According to the appellant, the absence of such development despite the availability of D7 was indicative of the non-obvious nature of the claimed invention.
Respondent’s Reply
The respondent submitted that the patent application claimed co-crystals of known therapeutic active agents, namely tramadol and celecoxib, which were already known and disclosed in the cited prior art. The respondent contended that D5 and D7, when read together, were sufficient to establish lack of inventive step and obviousness. D5 disclosed the combination of tramadol with NSAIDs for the treatment of pain and identified celecoxib as one of the NSAIDs that could be used. D7 disclosed the preparation of co-crystals of active pharmaceutical ingredients and their potential advantages over non-co-crystalline forms.
The respondent further submitted that D7 disclosed improved properties of co-crystals, including solubility, dissolution, bioavailability, stability and dose response. A person skilled in the art would therefore be aware of the potential advantages of preparing co-crystals of known active pharmaceutical ingredients and would be motivated to apply the teachings of D7 to the combination disclosed in D5.
Additionally, the respondent contended that the process claimed in Claim 10 of the subject application was obvious to a person skilled in the art in view of the processes disclosed in D7. The latter described preparation of co-crystals by dissolving separate components in a solvent, adding one solution to the other and allowing the co-crystal to precipitate or crystallise through slow evaporation. Alternatively, the components could be dissolved in the same solvent or a mixture of solvents. The respondent maintained that the claimed invention lacked inventive step in view of the cumulative teachings of D5 and D7.
Court’s Analysis and Findings
On perusal of the complete specification and claims, the Court found that the main object of the claimed invention was a co-crystal comprising tramadol, either as a free base or as a physiologically acceptable salt, and at least one coxib selected from celecoxib or its salts. The Court examined the cited prior art and found that D5 and D7 were the most relevant documents for determining whether the claimed invention involved an inventive step under Section 2(1)(ja).
The Court observed that D5 disclosed the use of tramadol in combination with NSAIDs for treating pain and reducing the side effects associated with opioid analgesics. D5 also identified celecoxib as one of the NSAIDs which could be used in combination with tramadol. The Court referred to paragraphs [0012] and [0068] of D5, which disclosed that such combinations could produce synergistic analgesic effects and that the invention could be modified using other NSAIDs, including celecoxib.
The Court further examined D7, which disclosed co-crystalline forms of active pharmaceutical ingredients and the advantages associated with such forms, including improved solubility, bioavailability, dose response and stability. The Court noted that D7 identified both tramadol and celecoxib in Table IV and described methods for preparing co-crystals through crystallisation from solution.
Comparing the claimed invention with the disclosures of D5 and D7, the Court found that D5 provided the teaching for combining tramadol and celecoxib, whereas D7 disclosed the preparation of co-crystals and the advantages associated with such crystalline forms. The Court also noted that the process disclosed in D7 overlapped with the process claimed in the subject application.
The Court concluded that the cumulative teachings of D5 and D7 provided sufficient motivation for a person skilled in the art to arrive at the claimed invention. Accordingly, the Court held that the subject application lacked inventive step under Section 2(1)(ja) and upheld the decision of the Controller.
Since the refusal had been upheld on the ground of lack of inventive step, the Court found it unnecessary to examine the other objections raised under Sections 3(d) and 3(e) of the Act. The Court relied on the decision in the Kroll case and dismissed the appeal along with the pending applications.
Concluding remarks
This case highlights the importance of examining the cumulative teachings of the cited prior art while determining inventive step under Section 2(1)(ja) of the Patents Act, 1970. The Court analysed the disclosures of D5 and D7 and found that D5 taught the combination of tramadol and celecoxib for pain treatment, whereas D7 disclosed co-crystal formation techniques and identified both active pharmaceutical ingredients. The Court concluded that these disclosures, when read together, made the claimed tramadol–celecoxib co-crystal obvious to a person skilled in the art.
The decision also raises the issue of the sequence in which patentability objections may be examined during adjudication of patent appeals. Following the principle applied in the Kroll case, the Court found that once the refusal was sustained on the ground of lack of inventive step under Section 2(1)(ja), it was unnecessary to separately examine the objections under Sections 3(d) and 3(e). The ruling indicates that where one ground of refusal is sufficient to dispose of an appeal, the Court may decline to examine the remaining objections.
The Delhi High Court accordingly dismissed the appeal and upheld the refusal of the patent application. The decision reinforces that the mere formation of a co-crystal from known active pharmaceutical ingredients does not necessarily establish inventive step where the cited prior art provides sufficient teaching or motivation to arrive at the claimed invention.
Author: DPS Parmar