By Jigyasa Pareek

The Delhi High Court, in Esteve Pharmaceuticals S.A. vs Controller of Patents and Designs [C.A.(COMM.IPD-PAT) 118/2022; decision dated August 7, 2026], dismissed an appeal under Section 117A of the Patents Act, 1970, against the refusal of patent application no. 1435/DELNP/2012, entitled “Co-crystals of Tramadol and Coxibs”. The application was refused by the Controller on the grounds of lack of inventive step under Section 2(1)(ja), and lack of patentability under Sections 3(d) and 3(e) of the Act. The Court, however, confined its examination to the objection of lack of inventive step and upheld the refusal on that ground.

The application concerned co-crystals comprising tramadol, either as a free base or a physiologically acceptable salt, and at least one coxib selected from celecoxib or its salts, together with pharmaceutical compositions comprising the co-crystal. The specification described the invention as providing new druggable forms of tramadol intended, among other things, to improve its properties for the treatment of pain. The claimed advantages included improved solubility, dissolution, bioavailability and stability, the possibility of reducing the therapeutic dose, and a synergistic effect between tramadol and the coxib.

The claims included a co-crystal of tramadol and celecoxib, with dependent claims specifically covering (rac)-tramadol-HCl and celecoxib in a 1:1 molecular ratio, defined by particular PXRD, FTIR, unit-cell and melting-point characteristics. Claim 10 further covered a process for producing the co-crystal, and Claim 11 covered a pharmaceutical composition comprising the co-crystal.

In examining inventive step, the Court considered D5 and D7 to be the most relevant prior art documents.

D5, related to treatment of pain and pain-related conditions using a combination of a Non-Steroidal Anti Inflammatory Drug (NSAID) and slow-release tramadol. The document explained that combining opioids with non-opioid analgesics could reduce the amount of opioid required to achieve an equivalent degree of analgesia and noted that certain combinations could produce a synergistic analgesic effect.

The Court noted that D5 expressly contemplated modifying the illustrated tramadol-NSAID combination using other NSAIDs, including celecoxib. Thus, although naproxen was used in the examples, a person skilled in the art (PSITA) would know how to modify the combination using celecoxib. The Court thus found that D5 disclosed the use of celecoxib in combination with tramadol.

D7 disclosed a pharmaceutical co-crystals containing APIs, pharmaceutical compositions comprising such co-crystals and methods for their preparation. The document identified the desirability of obtaining new forms of APIs having improved properties, including increased aqueous solubility and stability, improved dissolution and bioavailability, and altered therapeutic characteristics. Its summary disclosed that new co-crystalline forms of APIs could improve the properties of APIs as compared to their non-co-crystalline forms. Claim 5 covered pharmaceutical co-crystal compositions comprising first and second APIs, while Claim 6 specified, inter alia, increased solubility, dose response, dissolution, bioavailability and stability. D7 also disclosed processes for preparing API-API co-crystals. The claims in D7 contemplated API-API co-crystals involving APIs listed in Table IV, which included both tramadol and celecoxib.

The Court approached the inventive-step objection by comparing the disclosures of D5 and D7 with the claimed invention.

In relation to Claim 1 of the subject application, the Court found that D5 disclosed the combination of tramadol and celecoxib, while D7 disclosed API-API co-crystals and specifically identified both tramadol and celecoxib in Table IV. On this basis, the Court concluded that the composition of tramadol and celecoxib was already disclosed through the combined teachings of the two documents.

The Court further found that the distinction between the claimed invention and the prior art could not be sustained merely on the basis that D5 dealt with the combination of the two APIs while D7 dealt with their co-crystallisation. D7 specifically taught that co-crystallisation could provide improved properties to APIs. Its disclosure included increased bioavailability, dose response, dissolution and stability, as well as modulation of other physical and pharmaceutical properties. These were substantially the same improvements relied upon in the subject application.

The Court particularly noted that the specification of the subject application itself defined a co-crystal as a crystalline material in which the components were held together by weak interactions, including hydrogen bonds. D7 similarly disclosed hydrogen bonding between the first and second APIs. This further reduced the distinction between the claimed co-crystal and the co-crystal compositions disclosed in D7.

The Court also found a teaching or motivation to combine the two disclosures. Notably, D5 identified the potential synergistic benefits of combinations of tramadol with NSAIDs. At the same time, D7 taught that co-crystallisation could improve the properties of APIs. According to the Court, these disclosures provided the motivation for a PSITA to apply the co-crystal approach disclosed in D7 to the tramadol-NSAID treatment disclosed in D5.

Further, D7 disclosed that co-crystals could be prepared by dissolving separate components in a solvent, combining them and allowing the resulting mixture to precipitate or crystallise as the solvent evaporated. The Court found that this process substantially overlapped with the process claimed in Claim 10 of the subject application.

Accordingly, after comparing the subject claims with the disclosure in D5 and D7, the Court concluded that the claimed invention lacked inventive step and was therefore barred under Section 2(1)(ja) of the Act.

Having upheld the objection of lack of inventive step on merits, the Court held that there was no requirement to examine the remaining objections. It relied on Kroll Information Assurance, LLC vs Controller General of Patents [C.A.(COMM.IPD-PAT) 439/2022], for this approach.