For more than a decade, Section 3(d) has been read through a single lens — the pharmacy counter. Ever since the Supreme Court’s Glivec ruling in Novartis AG v. Union of India, (2013) 6 SCC 1, “efficacy” in Section 3(d) has meant therapeutic efficacy, and a new polymorph that merely flows better, stores better or resists heat better has been sent home. So what happens when the “known substance” is not a medicine at all, but a fungicide sprayed on a paddy field in 45°C heat? In Syngenta Participations AG v. Controller of Patents and Designs [C.A.(COMM.IPD-PAT) 49/2023, decided 4 May 2026], the Delhi High Court gave an answer agrochemical patentees will frame and hang on the wall: efficacy means whatever the invention is for — and for a fungicide, staying stable in the can counts.
The invention, and a refusal on autopilot
The application (no. 201617031900) claimed a monohydrate crystalline polymorph of a known fungicidal compound (“formula I”). The pitch was formulation-level, not molecular: the anhydrous form is unstable in suspension concentrate (SC) formulations — it undergoes polymorphic conversion, grows crystals, thickens, solidifies, and ultimately clogs spray equipment in the field. The claimed monohydrate, Syngenta said, is thermally stable, which lowers phytotoxicity and keeps the sprayer flowing. It backed this with differential scanning calorimetry (DSC) data, phase diagrams and formulation experiments.
The Controller refused under Sections 2(1)(ja) and 3(d). The reasoning ran on autopilot: thermal stability, it was assumed, is simply an inherent property of any monohydrate; the improvement was not a “surprising technical effect”; comparative phytotoxicity data against the anhydrous form should have been filed; and, in any event, better thermostability is not “therapeutic efficacy,” so Section 3(d) barred the claim outright.
What the Court actually held
The Delhi High Court took the order apart on four fronts. First, it refused to let “common general knowledge” do unsourced heavy lifting: if the Office asserts that thermal stability is inherent to monohydrates, it must cite something for that proposition. Second, it reminded everyone that polymorphs are inherently unpredictable in their energies and properties — you cannot wave away a demonstrated property as “routine.” Third, the Controller had simply ignored the DSC, phase-diagram and formulation evidence on record, and had never run the five-step inventive-step analysis from F. Hoffmann-La Roche v. Cipla; the inventive-step finding was therefore set aside and remanded.
The fourth holding is the one worth bookmarking. Section 3(d)’s “efficacy,” the Court held, is not monolithic. Even Novartis said the test of efficacy “depends upon the function, utility or the purpose of the product under consideration.” For a medicine, that purpose is therapeutic, so the yardstick is therapeutic efficacy. For an agrochemical — whose job is to be sprayable, stable and non-phytotoxic in brutal field conditions — enhanced thermodynamic stability that prevents crystallisation and clogging is enhancement of efficacy. The Court drew support from the Madras High Court’s decision in Novozymes v. Assistant Controller, where the increased thermostability of an enzyme was held to enhance efficacy by enabling storage and sale in pellet form, and stressed that nothing in the text of Section 3(d) confines efficacy to a single type.
Why it matters — and the catch
This is a sensible, textually honest un-shackling of Section 3(d) from the pharmaceutical context. The provision never said “therapeutic,” and in a country where spraying happens at 40–50°C, formulation stability is a genuine functional benefit, not a cosmetic flourish. For agro-innovators, the message is liberating: frame the invention around its real-world purpose, bring data tied to that purpose, and thermostability can clear the 3(d) bar.
But there is a catch worth naming. Novartis was strict precisely because physico-chemical tweaks — flow, hygroscopicity, thermostability — are the classic evergreening levers; paragraph 187 of Novartis expressly parked thermostability outside therapeutic efficacy. Syngenta now lets thermostability back in, for agrochemicals, on a “function-dependent efficacy” rationale. That rationale is principled, but it places enormous weight on how the invention’s “purpose” is characterised, and applicants will be tempted to define purpose around whichever property happened to improve. The guardrail, as the Court itself insisted, has to be the evidence: real, comparative, purpose-linked data — not assertion. Expect the next battles to be fought over what counts as the relevant “function,” and whether this reasoning travels to food, cosmetics, catalysts and beyond.
A final reality check for Syngenta: the win is partial. The Section 3(d) finding is categorical and favourable, but inventive step has gone back to the Controller for a fresh, properly-reasoned look. The doctrine has moved; the patent has not yet been granted.
Sources & further reading: Novartis AG v. Union of India, (2013) 6 SCC 1; F. Hoffmann-La Roche v. Cipla (five-step test); Novozymes v. Assistant Controller (Madras HC); Section 3(d), Patents Act.
Educational note: This case summary is general information, not legal advice.