Introduction
In a significant ruling on patentability of agrochemical compositions, the Delhi High Court on 28 February 2026 dismissed an appeal by Crystal Crop Protection Ltd. and upheld the Assistant Controller’s decision rejecting its patent application for a herbicidal composition.
The invention involved a ready-to-use synergistic mixture of two known herbicides — halosulfuron-methyl (a sulfonylurea) and metribuzin (a triazinone) — in specific weight percentages for controlling weeds in field crops like sugarcane.
Delhi High Court held that the claimed binary composition was a mere admixture of known substances that did not demonstrate any unexpected synergistic effect or technical advancement over prior art.
The court also allowed additional prior art documents filed by the opponent at the appellate stage, emphasizing that in patent appeals involving public interest and monopoly rights, courts can admit relevant evidence to ensure only genuine inventions receive protection.
The judgment reinforces that incremental changes in ratios or combinations of known active ingredients require clear proof of synergy or inventive step to overcome statutory bars under the Patents Act.
This decision provides practical guidance for companies in the crop protection sector:
- Simply combining known herbicides will not qualify for patent protection.
- Optimized proportions alone are insufficient.
- Clear proof of synergy or inventive step is mandatory.
- Results must go beyond what a skilled person would expect.
Factual Background
Crystal Crop Protection Ltd. (formerly Crystal Phosphates Ltd.) filed Indian Patent Application No. 2228/DEL/2011 on 5 August 2011 for a “Herbicidal Composition for Field Crops.”
The complete specification was filed on 6 August 2012.
The invention claimed a synergistic herbicidal ready-to-use composition comprising:
| Component | Concentration | Function |
|---|---|---|
| Halosulfuron-methyl | 10–15% w/w | Inhibits amino acid synthesis (systemic action) |
| Metribuzin | 50–60% w/w | Disrupts photosynthesis |
The appellant asserted that their specific combination produced:
- Enhanced weed control at lower doses
- Broad-spectrum efficacy against narrow and broad-leaf weeds
- Improved performance in crops like sugarcane
- Cost-effectiveness
- Environmentally friendlier outcomes
The application was published in 2013, and a request for examination was filed in 2012.
Pre-grant oppositions were filed as follows:
- Haryana Pesticides Manufacturers’ Association (Respondent No. 2) in 2017
- Dr. Meera Sharma (Respondent No. 3) in 2022
The First Examination Report was issued in 2018, and the appellant responded with replies and claim amendments.
Hearings were conducted, and post-hearing submissions were exchanged.
On 28 March 2023, the Assistant Controller rejected the application under Section 25(1) of the Patents Act, primarily on the following grounds:
- Lack of inventive step (Section 25(1)(e))
- Non-patentability as a mere admixture under Section 3(e) (via Section 25(1)(f))
Procedural Background
After filing the application, the patent office issued the FER in January 2018. The appellant filed its response in May 2018. Respondent No. 2 filed Pre-Grant Opposition in March 2017, to which the appellant replied in July 2021. Respondent No. 3 filed Pre-Grant Opposition II in January 2022, prompting further replies and minor claim amendments in October 2022 and March 2023. A hearing notice was issued in December 2022 for a hearing in February 2023. Both parties filed post-hearing written submissions in February-March 2023. The Assistant Controller passed the impugned rejection order on 28 March 2023, finding the claims anticipated or obvious over cited prior arts (including WO2000027203, US patents, and other documents) and falling under the Section 3(e) bar as a mere aggregation of known properties without synergy.
The appellant filed the present appeal under Section 117A before the Delhi High Court. During the appeal proceedings, Respondent No. 2 filed I.A. 20715/2025 under Order XLI Rule 27 CPC and IPD Rules seeking to place additional documents on record, including EPA registrations, scientific articles on herbicide modes of action, and product labels demonstrating known combinations and uses of the active ingredients. The court heard arguments on this application alongside the main appeal and delivered a common judgment on 28 February 2026.
Timeline Summary
| Event | Date |
|---|---|
| FER Issued | January 2018 |
| Appellant Response | May 2018 |
| Pre-Grant Opposition (R2) | March 2017 |
| Reply to Opposition | July 2021 |
| Pre-Grant Opposition II (R3) | January 2022 |
| Hearing Notice | December 2022 |
| Hearing Conducted | February 2023 |
| Rejection Order | 28 March 2023 |
| High Court Judgment | 28 February 2026 |
Reasoning
The High Court first addressed the application for additional evidence. It noted that the documents were publicly available prior art (EPA records, university publications, and product labels) relevant to assessing inventive step and Section 3(e). Although the opponent had opportunities during pre-grant proceedings, the court exercised discretion under the IPD Rules and Order XLI Rule 27 CPC, holding that in patent matters — which grant monopolies operating against the public (in rem) — courts should admit relevant evidence if it aids in pronouncing a just judgment and prevents erroneous grants. The appellant’s objections on delay and lack of due diligence were overruled, as the documents helped complete the record on common general knowledge and motivation for a skilled person (PSITA).
On the merits, the court examined the claimed invention against prior arts. It found that combinations of halosulfuron-methyl and metribuzin (or closely related sulfonylureas with metribuzin) were already known in documents like GWN-9889 (EPA-registered product with similar ratios), WO publications, and tank-mix studies. The specific percentages claimed fell within or were obvious variations of disclosed ranges. The court observed that omitting an optional third component (tribenuron-methyl) or substituting components with known functional equivalents (e.g., replacing a PPO inhibitor with a PSII inhibitor like metribuzin for sugarcane use) would be a predictable, routine modification for a person skilled in the art.
Regarding synergy, the court scrutinized Table 1 in the specification showing weed control data. It held that the results did not demonstrate unexpected enhancement beyond additive effects. Improved control at certain doses was attributable to higher concentrations or expected aggregation of properties rather than true synergy. The appellant’s argument that lower combined doses yielded better results than individual components was not persuasive enough to overcome the Section 3(e) bar, which prohibits patents for mere admixtures resulting only in the sum of known properties.
The court emphasized that the burden lies on the applicant to prove inventive step and technical advancement under Section 2(1)(ja). Mere optimization of known ingredients without clear data showing surprising results or economic significance does not suffice. Hindsight analysis was avoided, but the prior arts provided clear motivation for the claimed combination in the context of sugarcane weed control.
Key Legal Principles (Quick Points)
- Public interest outweighs procedural delay in patent evidence admission
- Known combinations without synergy fail under Section 3(e)
- Burden of proof lies on the applicant for inventive step
- Routine substitutions are not patentable inventions
- Patent validity can be challenged at appellate stage
Key Judgments Discussed with Citations and Context
The judgment extensively discussed principles from landmark cases to explain patentability standards in a simple, accessible manner:
- Novartis AG v. Union of India, (2013) 6 SCC 1: The Supreme Court laid down that incremental inventions, especially new forms or combinations of known substances, must demonstrate significant technical advance or enhanced efficacy to qualify for patents in India. The court applied this to stress that the appellant failed to show anything beyond expected additive effects of the two known herbicides.
- F. Hoffmann-La Roche Limited v. Cipla Ltd., 2009 (40) PTC 125 (Del): This Delhi High Court decision (and related appeals) was cited for the principle that patent examination is not infallible, and courts in appeals can scrutinize validity based on all available prior art to protect public interest against unwarranted monopolies.
- Biomoneta Research Pvt. Ltd. v. Controller General of Patents, Designs and Anr., 2023 SCC OnLine Del 1482: Referenced by the appellant for the proposition that true synergistic combinations exceeding additive effects can be patentable. The court distinguished it, finding no such clear synergy established here.
- Union of India v. Ibrahim Uddin, (2012) 8 SCC 148: Cited in arguments on additional evidence. The court clarified its application in patent contexts, allowing admission where necessary for just adjudication, especially given the public interest in preventing invalid patents.
- K. Venkataramiah v. A. Seetharama Reddy, 1963 SCC OnLine SC 216 and Wadi v. Amilal, (2015) 1 SCC 677: Used to explain the restrictive yet flexible scope of Order XLI Rule 27 CPC for additional evidence in appeals, balancing diligence with the need for complete justice.
- Other cases like Macleods Pharmaceuticals Ltd. v. Controller of Patents (2025) and Bristol-Myers Squibb decisions reinforced that patent grants do not create irrebuttable presumptions of validity, and opponents can challenge them with relevant prior art even at appellate stages.
Final Decision Of The Court
The Delhi High Court dismissed the appeal and upheld the Assistant Controller’s order dated 28 March 2023 rejecting the patent application. It allowed the application for additional documents (I.A. 20715/2025) and took them on record as relevant prior art. The court found no merit in the claims of inventive step or synergy, holding the composition as a mere admixture barred under Section 3(e). No costs were awarded.
Point Of Law Settled In The Case
This judgment settles important practical points for anyone involved in patents, explained simply:
Admission Of Additional Prior Art Documents
- In patent appeals, especially for compositions of known substances, courts can admit additional relevant prior art documents under Order XLI Rule 27 CPC and IPD Rules.
- Such documents may be considered even if not filed earlier, if they help reach a correct decision on patentability.
- This is because patents affect the public at large and prevent unjust monopolies.
Non-Patentability Of Mere Admixture
- A combination of two known active ingredients (like herbicides) is not patentable if it is merely an admixture.
- The properties must not be just the predictable sum of individual components.
- There must be clear evidence of unexpected synergistic effects or technical advancement under Section 3(e) and Section 2(1)(ja).
- Optimizing ratios or omitting optional components does not automatically create an inventive step.
- The applicant must prove surprising benefits beyond what a skilled farmer or scientist would expect.
Burden Of Proof On Applicant
- The burden remains on the patent applicant to demonstrate inventive step with supporting data.
- Prior art disclosures of similar combinations or uses in the same crop (e.g., sugarcane) make obviousness easier to establish.
- Section 3(e) acts as a strong filter against routine formulations lacking real innovation.
Public Interest In Agrochemical Patents
- In agrochemical patents, courts prioritize public interest in accessible farming solutions.
- This takes precedence over procedural technicalities when admitting evidence that completes the picture of existing knowledge.
Case Details
| Particulars | Details |
|---|---|
| Case Title | Crystal Crop Protection Ltd Vs. Assistant Controller of Patents and Designs & Ors. |
| Date of Order | 28 February 2026 |
| Case Number | C.A.(COMM.IPD-PAT) 19/2023 |
| Neutral Citation | 2026:DHC: 1828 |
| Name of Court | High Court of Delhi |
| Name of Hon’ble Judge | Justice Tejas Karia |
Disclaimer Readers are advised not to treat this as substitute for legal advise as it may contain errors in perception, interpretation, and presentation.
Written By: Advocate Ajay Amitabh Suman, IP Adjutor [Patent and Trademark Attorney], High Court of Delhi
