In Crystal Crop Protection Ltd. vs Assistant Controller of Patents and Designs [C.A.(COMM.IPD-PAT) 19/2023], the Delhi High Court was called upon to examine the refusal of patent application number 2228/DEL/2011, entitled ‘Herbicidal Composition for Field Crops’, directed to a herbicidal composition comprising halosulfuron-methyl and metribuzin, claimed to exhibit a synergistic effect in controlling unwanted vegetation in a variety of agricultural crops. The application was refused on the basis of the grounds urged in the pre-grant opposition filed under Section 25(1) as well as in the examination process under Sections 12-15, viz., lack of inventive steps (Sections 2(1)(ja) and 64(1)(e)) and non-patentability (mere admixture under Section 3(e); Section 25(1)(f)).

At the outset, the Court dealt with an application filed by Respondent No. 2 (Haryana Pesticides Manufacturers’ Association/pre-grant opponent) under Order XLI Rule 27 of the CPC read with Rule 6(v)(xii) of the IPD Rules, seeking to place additional prior art documents on record. The Appellant opposed the application on the ground that the Respondent had ample opportunity to introduce such material during the pre-grant opposition proceedings and had failed to demonstrate due diligence. It was further contended that the attempt was nothing but an effort to fill lacunae in the opposition at the appellate stage, which is impermissible in law.

The Court, however, was not persuaded by these objections. Placing reliance on the framework of the IPD Rules and the principles underlying Order XLI Rule 27, the Court held that the determinative consideration is whether the additional material is necessary to enable the Court to pronounce a satisfactory judgment. The additional documents, which pertained to known herbicidal compositions and the functional properties of the relevant compounds, were found to be directly relevant to the case and were accordingly taken on record.

On merits, the dispute centred on whether the claimed composition comprising halosulfuron-methyl in the range of 10-15% and metribuzin in the range of 50-60% could be said to involve an inventive step and, whether it attracted the exclusion under Section 3(e) for being a mere admixture. The Appellant’s case rested squarely on the assertion of a synergistic effect. It was contended that the specific combination and concentration of the two active ingredients resulted in enhanced weed control at reduced dosages, thereby demonstrating a technical advance over the prior art and a synergistic effect. The Appellant pointed out that the trial data provided in the patent application established that the claimed composition was not attributed merely to higher formulation dosage per acre as alleged by the Respondents. The Appellant further argued a PSITA would not expect any “enhancement” in control of weeds by reducing the amounts of the actives as compared to the expected additive effect at comparable amounts of actives. Any such reasoning, it was submitted, would be affected by hindsight bias.

The Respondents, on the other hand, emphasised that the use of both the active compounds (halosulfuron-methyl and metribuzin) in herbicidal combination stood documented in the prior art documents. The essence of the invention, according to the Respondents, lay merely in the selection of a particular range of concentrations, which does not, in itself, constitute inventive step and synergistic effect. It was contended that the data relied upon by the Appellant merely reflected improved efficacy corresponding to increased dosage, rather than any unexpected or synergistic effect.

The Court’s analysis proceeds along the lines of the established principles but is nonetheless instructive in the clarity with which it applies them. It first noted that the prior art on record disclosed compositions containing the combinations of sulfonylurea class herbicides (halosulfuron-methyl is a member of said class) with metribuzin were well-known, and that the variation in proportions claimed by the Appellant fell within a range that a PSITA could arrive at through routine experimentation. The Court thus rejected the contention that the claimed invention involved any technical advance, observing that merely increasing the quantity of both active ingredients across treatments does not satisfy the requirement of inventive step under Section 2(1)(ja).

The Court subjected the claim of synergy to close scrutiny. It reiterated that, in the context of Section 3(e), it is not sufficient to merely assert that a combination performs better than its individual components. What must be demonstrated is a synergistic effect by a combined effect of increase in bio-efficacy and stability of the admixture beyond the sum of their individual effects. The Court found that the experimental data placed on record did not meet this threshold. In particular, it was observed that the improved weed control was explained by the increased effective quantity of the active ingredients rather than any inherent interaction between them producing an unexpected result. In the absence of clear and convincing evidence of such interaction, the composition was held to be nothing more than a combination of known substances. The Court emphasised that synergistic effect should be clearly brought out in the description by way of comparison at the time of filing of the application itself.

On this basis, the Court concluded that the subject application was squarely hit by Section 3(e). The Court also declined to interfere with the Controller’s findings, noting that they were reasoned and did not suffer from any legal infirmity warranting appellate intervention.