A Fungicide Patent Case Just Tested How Far India's Section 3(d) Efficacy Rule Stretches
By Prashant Kotian, PhD Researcher (Chemistry), ICT Mumbai
On May 2026, the Delhi High Court handed down a ruling in Syngenta Participations AG v. Controller of Patents and Designs that sounds like it belongs in an agrochemical trade journal, not a pharma patent briefing. But the reasoning inside it goes straight to the heart of Section 3(d), the same provision that decided the Glivec case and that every generic manufacturer in India relies on to keep secondary drug patents honest.
The patent application covered a monohydrate crystalline polymorph of an existing fungicidal compound. In plain terms: the same active molecule, but a different solid-state packing arrangement. Syngenta's data showed this particular crystal form stayed thermodynamically stable at 50 to 60 degrees Celsius and resisted crystal growth over time, which matters a great deal in a suspension formulation. An unstable polymorph in a fungicide suspension tends to thicken, coarsen, and eventually clog spraying equipment in the field.
The Patent Office refused the application on two grounds: no inventive step, and a Section 3(d) violation. On the second point, the Controller treated the new polymorph the way Section 3(d) treats a new drug polymorph, that is, as a "new form of a known substance" that has to show enhanced efficacy over the known form to be patentable at all. Since Syngenta's data was about thermal and physical stability, not any therapeutic-style effect, the Controller found no enhanced efficacy and refused the case.
Syngenta's appeal argued that this was the wrong yardstick entirely. Section 3(d)'s efficacy requirement, born out of the Novartis Glivec litigation, was built for medicines, where "does it work better on the disease" is a coherent question. A fungicide doesn't have a disease it treats in the patient-outcome sense. Applying the same test mechanically, Syngenta argued, ignored what "efficacy" should even mean outside a therapeutic context.
The Delhi High Court agreed with that framing, at least on the legal principle. It set aside the refusal and sent the application back to the Patent Office for a fresh decision within six months, this time properly reasoned. The core of the ruling is this: "efficacy" under Section 3(d) has to be judged against what the product is actually for, not applied as a one-size-fits-all therapeutic-effect test borrowed wholesale from pharmaceutical cases. For an agrochemical, the Court held, real-world field performance, including formulation stability, shelf life, and reduced crop damage, can be the correct measure of efficacy. The Court leaned on the Madras High Court's earlier Novozymes ruling, where improved thermal stability of an industrial enzyme was accepted as enhanced efficacy precisely because thermostability is what determines whether that enzyme actually functions in its intended industrial process.
Here is the part that should matter to anyone defending a Section 3(d) opposition on a drug polymorph: the Delhi High Court did not open the door to "any physical property improvement counts as efficacy." It did the opposite. The Court was explicit that Novartis's therapeutic-efficacy standard for medicines was never disturbed and was not read as a template to be swapped out for a different discipline's version of efficacy. What changed is that the Court refused to let a therapeutic-efficacy test be force-fit onto a product category where "does it treat a disease" was never the right question in the first place. For an actual drug polymorph, the product category where the Novartis standard was built and where it stays, better thermal stability, better solubility, or easier crystallization still has to translate into a demonstrated therapeutic benefit to clear Section 3(d). That bar has not moved.
That distinction is the whole case, and it is good news dressed up as a technical footnote. A ruling that let "the crystal is more stable" satisfy Section 3(d) for a drug the way it now can for a fungicide would have quietly widened the door for exactly the kind of secondary polymorph patents Section 3(d) exists to stop. This ruling closes that door by keeping the Novartis efficacy test tied to the product category it was written for, while giving other fields of chemistry, agrochemicals, industrial enzymes, and similar cases, their own honest efficacy standard instead of an ill-fitting borrowed one.
Two things remain genuinely open. First, whether Syngenta's fungicide patent actually gets granted is not decided. It goes back to the Controller for a fresh, reasoned examination within six months, and that outcome could go either way on the facts. Second, this is a single-judge Delhi High Court ruling, and how other benches or the Supreme Court eventually treat the pharma versus non-pharma line it draws is not something we are predicting here. What is decided, and what we think is worth flagging today, is the legal reasoning itself: Indian courts are actively working out how far Section 3(d)'s language stretches across different kinds of chemistry, and so far, the pharma-specific efficacy bar from Novartis has held its ground.
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