Therapeutic efficacy under Section 3(d) must be demonstrated through specific data

Introduction: The case of Zeria Pharmaceutical Co. Ltd. v. The Controller of Patents is a pivotal judgment from the Delhi High Court that reinforces the interpretative approach toward patentability criteria under the Indian Patents Act, 1970, particularly concerning the tests laid out under Section 2(1)(ja) and Section 3(d). The Court’s analysis offers essential guidance on what constitutes an “inventive step” and how the “therapeutic efficacy” of pharmaceutical compounds must be substantiated to satisfy the stringent demands of patent law in India.

Factual Background: Zeria Pharmaceutical Co. Ltd., a Japanese pharmaceutical company, filed Indian Patent Application No. 3630/DELNP/2011 on May 13, 2011. This application was a divisional application from an earlier application numbered 1090/DELNP/2007 and claimed a novel intermediate compound described as 2-[(2-hydroxy-4,5-dimethoxybenzoyl) amino]-1,3-thiazole-4-carboxylic acid methyl ester. The company claimed the invention involved a methyl ester functional group on a thiazole ring system and was an essential intermediate for the synthesis of an active pharmaceutical ingredient. The compound was distinguished from the prior art primarily by the substitution of a methoxycarbonyl group instead of an ethoxycarbonyl group.

Procedural Background: The Indian Patent Office issued the First Examination Report (FER) on February 24, 2015, raising objections under Section 2(1)(ja) on lack of inventive step and Section 3(d) for being a mere derivative of a known compound without enhanced efficacy. Following a written response by the applicant and a hearing on June 12, 2016, the Assistant Controller of Patents refused the application via an order dated October 20, 2016. Aggrieved, Zeria Pharmaceutical appealed under Section 117A of the Patents Act before the Delhi High Court. The appeal was heard and reserved on April 23, 2025, and the judgment was pronounced on May 27, 2025.

Legal Issue: The central legal issue before the Court was whether the subject invention satisfied the dual statutory requirements of inventive step under Section 2(1)(ja) and non-attractiveness of Section 3(d) of the Patents Act, 1970? Specifically, the Court was called upon to decide whether the claimed compound, being a structural variation of a compound disclosed in prior art, constituted a patentable invention or fell within the exclusion of Section 3(d) for lacking therapeutic efficacy?

Discussion on Judgments: The appellant relied on the judgment of the Delhi High Court in F. Hoffmann-La Roche Ltd. & Anr. v. Cipla Ltd., 2015 SCC OnLine Del 13619, to argue that an invention must be assessed on whether a person skilled in the art (PSITA) would be motivated to modify the teachings of prior art to arrive at the claimed invention. The appellant also cited Agriboard International LLC v. Deputy Controller of Patents and Designs, 2022 SCC OnLine Del 940, to contend that the Controller must provide cogent reasoning on how the invention would be obvious to a PSITA, rather than relying on broad conclusions.

In response, the Controller relied on the landmark decision of the Supreme Court in Novartis AG v. Union of India, (2013) 6 SCC 1, where it was categorically held that the test of efficacy under Section 3(d) in the context of pharmaceutical products means “therapeutic efficacy.” The Court held that mere improvements in physical properties like solubility or stability, unless linked to therapeutic benefit, are not relevant under Section 3(d). The Controller also cited Novozymes v. Assistant Controller of Patents & Designs, T. CMA (PT) No. 33 of 2023 (Madras High Court), which clarified that Section 3(d) operates as a statutory exclusion and may independently bar patentability even if Section 2(1)(j) or (ja) is satisfied. Additionally, the decision in Astrazeneca AB and Another v. Torrent Pharmaceuticals Ltd., 2020 SCC OnLine Del 1446, was invoked to rebut the appellant’s “teaches away” argument, emphasizing that mere absence of direction toward an invention does not imply discouragement or negation by prior art.

Reasoning and Analysis of the Judge: The Court observed that while the invention might satisfy the criteria for novelty, it failed to pass the filter of Section 3(d) due to lack of evidence demonstrating therapeutic efficacy. The claimed compound and the compound in the prior art differed only in the substitution of a methoxy group for an ethoxy group, which, in the Court’s view, was a minor and obvious variation for any person skilled in the art.

The Court critically examined the experimental data submitted by the appellant and noted that it failed to demonstrate any enhancement in therapeutic efficacy. Even the appellant had conceded in submissions that therapeutic efficacy could not be measured as the compound was merely an intermediate. The Court emphasized that the burden lay on the applicant to establish significant difference in efficacy, and this burden had not been discharged.

On the issue of inventive step under Section 2(1)(ja), the Court held that the invention was obvious in light of the teachings of prior art documents D1 (EP 0994108 A1) and D2 (US 5981557 A). Both prior arts disclosed compounds structurally similar to the claimed compound and described alkoxy substitutions including methoxy and ethoxy. The Court found the claimed invention to be a predictable variant within the realm of routine experimentation, not amounting to a technical advancement or economic significance.

Further, the Court rejected the appellant’s argument that prior art D1 “taught away” from the claimed invention. It held that the absence of specific guidance toward the invention does not imply discouragement, and thus does not negate obviousness if the path to invention is reasonably discernible to a skilled artisan.

Final Decision: The Delhi High Court upheld the decision of the Controller of Patents, dismissing the appeal filed by Zeria Pharmaceutical Co. Ltd. The Court concluded that the subject application failed both the inventive step requirement under Section 2(1)(ja) and the efficacy bar under Section 3(d) of the Patents Act. It found no merit in the applicant’s claim that the compound was patentable and accordingly affirmed the rejection of the patent application.

Law Settled in This Case: Firstly, Section 3(d) is an independent and absolute bar to patentability and may exclude a claim even if novelty or inventive step is satisfied under Section 2(1)(j) or (ja). Secondly, therapeutic efficacy under Section 3(d) must be demonstrated through specific data and cannot be presumed from structural variations or physico-chemical improvements. Thirdly, routine substitutions or modifications known to a skilled artisan cannot constitute inventive step unless they result in unexpected advantages or substantial technical advancements. Lastly, the Zeria Pharmaceutical, which was absent in the present case.

Zeria Pharmaceutical Co. Ltd. Vs. The Controller of Patents: May 27, 2025:C.A. (COMM.IPD-PAT) 452/2022: 2025:DHC:4431High Court of Delhi: Hon’ble Mr. Justice Saurabh Banerjee

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Written By: Advocate Ajay Amitabh Suman, IP Adjutor [Patent and Trademark Attorney], High Court of Delhi