By Jigyasa Pareek

Section 3(d) of the Patents Act bars from patentability those inventions that are mere discovery of a new form of a known substance which does not result in the enhancement of the known efficacy of that substance or the mere discovery of any new property or new use for a known substance or of the mere use of a known process, machine or apparatus unless such known process results in a new product or employs at least one new reactant.

The term ‘efficacy’, since Novartis AG vs Union of India [(2013) 6 SCC], in the context of pharmaceutical inventions has been understood as ‘therapeutic efficacy’ which relates to the medicine’s capacity to cure or effectively treat diseases. The Supreme Court in Novartis made it clear that for medicinal preparation or a drug, efficacy must be construed strictly and narrowly, and that improvements in physico-chemical properties, such as improved flow properties, thermostability or lower hygroscopicity, would not suffice as indicators of enhanced ‘therapeutic efficacy’. However, the decision was situated within the pharmaceutical context and was not intended to lay down a universal or cross-sectoral definition of “efficacy” under Section 3(d). The provision itself does not define the term, nor does it prescribe a uniform standard applicable across technologies.

It is in this backdrop that the Delhi High Court’s landmark decision in Syngenta Participations AG vs Controller of Patents and Designs [C.A.(COMM.IPD-PAT) 49/2023, decision dated May 4, 2026] assumes significance. The judgment articulates the meaning of ‘efficacy’ in the context of agrochemical inventions, and in doing so, moves beyond the confines of the ‘therapeutic efficacy’ standard to fundamentally different fields of technology.

The appeal concerned refusal of Syngenta’s patent application number 201617031900, directed to a monohydrate crystalline polymorph of compound of a known fungicidal compound (formula I). The invention was positioned as solving a formulation-level problem namely instability of existing form of compound in suspension concentrate (SC) formulations, leading to polymorphic conversion, crystal growth, thickening and solidification of the formulation, and eventual clogging of spray equipment under field conditions.

The applicant relied on experimental data to demonstrate that the claimed monohydrate polymorph exhibited enhanced thermal stability resulting in lowering phytotoxicity,as compared to the known anhydrous form. It was asserted that this stability ensured that the compound remained in a usable form even under elevated temperatures, thereby enabling consistent delivery and reducing issues such as crystallisation and blockage in spraying systems. On this basis, the applicant contended that the claimed polymorph involved a technical advance over the prior art and, in the context of agrochemicals, such improved stability also translated into enhanced efficacy, particularly by lowering phytotoxicity and improving applicability.

The Controller, however, did not accept these submissions and refused the application on the grounds of Secction 2(1)(ja) and Section 3(d). The Controller proceeded on the assumption that the difference in thermal stability is an inherent property of any monohydrate form as compared to its non-hydrate/ anhydrous form. On inventive step, the Controller took the view that the only distinguishing feature of the claimed invention over the prior art documents was the monohydrate form of formula I, and that the improvement in thermal stability did not amount to a “surprising technical effect”. The Controller opined that, to substantiate such an effect, the appellant ought to have furnished comparative data in terms of lowering phytotoxicity between the claimed monohydrate form and the non-hydrate form disclosed in the cited prior art documents. In the absence of such comparative evidence, the Controller concluded that there was no credible material on record to establish any unexpected or advantageous effect over the prior art. On Section 3(d), the Controller held that the claimed polymorph was merely a new form of a known substance and failed to demonstrate any enhancement in efficacy. The Controller reasoned that improvements such as thermal stability although may result in non-clogging of the spraying equipment, does not enhance the ‘therapeutic efficacy’ of the compound itself. The applicant’s reliance on reduced phytotoxicity and improved stability was thus rejected as insufficient to overcome the statutory bar.

The Delhi High Court, upon a detailed examination of the record, found the reasoning adopted by the Controller to be unsustainable, both on the question of inventive step as well as on the application of Section 3(d).

At the outset, the Court took serious exception to the Controller’s assumption that thermal stability is an inherent property of polymorphs, noting that such a finding was rendered without any supporting material or cited source. The Court emphasised that where “common general knowledge” is invoked, it must be substantiated through a source, failing which such conclusions cannot be sustained.

The Court undertook a detailed discussion on the existence of polymorphs, relying on scientific literature to underline that polymorphic forms are inherently unpredictable on the basis of the molecular structure, both in terms of their energies and their properties. It was observed that different polymorphs, though chemically identical, may exhibit significantly different physical and functional properties, including stability, solubility and behaviour in formulations. In this context, the Court rejected the assumption that thermal stability could be treated as an expected or routine consequence of polymorphic variation.

Turning to the material on record, the Court noted that the applicant had furnished experimental data, including DSC studies, phase diagrams and formulation-based experiments, demonstrating that the claimed monohydrate polymorph exhibited superior thermal stability in suspension concentrate formulations. The data showed that, under typical environmental conditions, the anhydrous form was prone to polymorphic conversion, resulting in crystal growth and consequent formulation instability, whereas the claimed polymorph remained stable and overcame such issues.

In this backdrop, the Court concluded that the finding of lack of inventive step under Section 2(1)(ja) was not supported by a proper analysis, particularly in light of the five-step test laid down in Roche. The failure to undertake this exercise, coupled with the disregard of experimental evidence, vitiated the impugned order on this ground.

The judgment assumes particular significance in its treatment of Section 3(d).

The Court noted that the Controller’s objection proceeded on a narrow understanding of efficacy, equating it with therapeutic efficacy, as applied in Novartis. This, according to the Court, was a misapplication of the law. It was observed that in Novartis, the Supreme Court was dealing specifically with pharmaceutical products, where the intended purpose of the invention is therapeutic, and therefore the test of efficacy must necessarily be therapeutic efficacy.

However, the Court emphasised that even in Novartis, the Supreme Court had clarified that the test of efficacy depends upon the function, utility or the purpose of the product under consideration. Thus, the standard of efficacy is not uniform, but context-dependent, varying with the function and purpose of the invention.

Applying this principle, the Court drew a distinction between pharmaceuticals and agrochemical inventions. In the case of agrochemicals, particularly polymorphs, demonstration of improved thermodynamic stability is sufficient to satisfy the efficacy standards under Section 3(d).

On facts, the Court took note of the conditions under which agrochemicals are typically deployed, particularly in India, where agricultural operations are often carried out at elevated temperatures ranging between 40°C to 50°C and above. In such conditions, instability of formulations leading to crystallisation and clogging would directly impair the usability of the product.

In this context, the Court held that the enhanced thermodynamic stability of the claimed polymorph, which prevents crystallisation and ensures smooth application through spraying equipment, constitutes enhancement of efficacy of the known substance.

On this basis, the Court concluded that, in the context of the present invention, enhancement of efficacy would include improved stability that enables effective application of the product and cannot be restricted to therapeutic parameters.

In arriving at this conclusion, the Court also considered the reasoning adopted by the Madras High Court in Novozymes vs. Assistant Controller of Patent [(T) CMA (PT) No.33 of 2023], where increased thermostability of an enzyme (biochemical substance) was held to enhance efficacy by enabling products, storage and sale in pellet form. The Court reiterated that there is nothing in the text of Section 3(d) that limits efficacy to a particular type of efficacy, and that the assessment must remain anchored to the function, utility and purpose of the invention.

Accordingly, while the Court set aside the impugned order and remanded the matter for fresh consideration on inventive step, it recorded a clear and categorical finding on Section 3(d).

The decision marks a crucial shift from a one-size-fits-all interpretation of efficacy to a context-driven, function-oriented standard, better aligned with the technological realities of different fields.