Introduction

An invention relating to chemical compositions or pharmaceutical substances must overcome, not only the standard requirements of Novelty, Inventive Step and Industrial Application under the Patents Act, 1970, but also the additional hurdle of non-patentability under Section 3(d).  Section 3 of the Patents Act, 1970 establishes a statutory exclusion by creating a legal fiction that renders certain categories of subject matter non-patentable. Section 3(d) specifically excludes from patentability:

  • Mere discovery of a new form of a known substance which does not result in the enhancement of the known efficacy of that substance;
  • Mere discovery of any new property or new use for a known substance;
  • 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 primary objective of Section 3(d) is to prevent patent evergreening, a strategy employed by patent-holders particularly in the pharmaceutical sector to extend patent protection by making minor modifications to existing inventions and thereby delay their entry into the public domain.

However, the section provides an exception wherein a proposed invention demonstrating “enhanced efficacy” beyond the known substance may qualify for patentability despite the bar under Section 3(d). But the ambiguity around the meaning and scope of the term “efficacy” leads to the erroneous application of Section 3(d).

Efficacy: Judicial Interpretation and Scope

The meaning and the ambit of the term “efficacy” was first dealt with in the case of Novartis AG v. Union of India (MANU/SC/0281/2013). The Hon’ble Supreme Court of India, defined efficacy as “the ability to produce a desired or intended result”. Therefore, the test for efficacy must be ascertained on a case-by-case basis depending on the intended use, utility and purpose of the substance in question.

Therapeutic Efficacy: Test for Pharmaceutical Patents under Section 3(d)

In Novartis AG v. Union of India (MANU/SC/0281/2013) the Hon’ble Supreme Court dealt with the patentability of the beta crystalline form of Imatinib Mesylate, used for treating patients with Chronic Myeloid Leukaemia. The Court clarified that, in the context of pharmaceutical patents, the test of efficacy refers specifically to therapeutic efficacy, which relates to the medicine’s capacity to cure or effectively treat diseases.

The Court adopted a narrow and strict interpretation of the term “enhanced efficacy” in the context of pharmaceutical compositions. The Court held that only those properties of an invention that directly contribute to its therapeutic efficacy, that is, its ability to cure or effectively treat diseases, are relevant, for consideration under section 3(d). Other advantageous properties that do not have direct bearing on therapeutic efficacy are immaterial for this assessment. The court further clarified that physico-chemical improvements of the compositions such as improved flow properties, thermostability or lower hygroscopicity do not qualify as indicators of enhanced efficacy, since they do not influence the therapeutic efficacy of the drug.

Another important contention assessed by the Hon’ble Supreme Court was whether improved bioavailability could, by itself, lead to an enhancement of therapeutic efficacy. The Court answered this in the negative, holding that increased bioavailability does not necessarily equate to enhanced therapeutic efficacy, and any such claim must be substantiated with appropriate research data.

This position was relied upon and further explained by the Division Bench of the Hon’ble High Court of Delhi in Natco Pharma v. Novartis A.G and Anr, (MANU/DE/3072/2024) , wherein the Court held that bioavailability is a pharmacokinetic factor and therefore, cannot be regarded as a measure of efficacy under section 3(d). Therefore, only those factors that contribute to the purpose of curing and treating diseases and ailments are relevant for ascertaining therapeutic efficacy. Conversely, ancillary properties, though beneficial to the working of the pharmaceutical composition, do not contribute to its medical or therapeutic value and therefore do not enhance efficacy of the invention.

Applicability of Section 3(d) for Non- Pharmaceutical Patents

The issue of whether Section 3(d) applies to chemical compositions other than pharmaceutical substances was taken into consideration by the Hon’ble High Court of Madras in the case of Novozymes v. Assistant Controller of Patents and Designs (MANU/TN/5373/2023).The Court held that the application of Section 3(d) is not limited to pharmacology but other chemical substances such as agro-chemical and biochemical substances as well.

However, the Court clarified that the scope of the Explanation to Section 3(d) is confined exclusively to pharmaceutical inventions. The Explanation to Section 3(d) provides a list of chemicals of known substances such as salts, ethers etc., which along with its derivates will be considered the same substance, unless “they differ significantly in properties with regard to efficacy.”

The list of chemicals provided in the Explanation ends with a generic expression “and other derivatives of known substance” which was held by the Court to only include synthesized chemicals following the principle of ejusdem generis. Therefore, chemical compositions other than pharmaceutical substances do not fall within the scope of the Explanation. However, such compositions are still subject to examination under section 3(d) and therefore must pass the test of enhanced efficacy as well.

Efficacy from the lens of the European Parliament

The Explanation to Section 3(d) draws conceptual guidance from Directive 2001/83/EC of the European Parliament, which defines the term “generic substances”. Accordingly, an examination of the Directive’s intent and scope provides valuable insight into the meaning of efficacy under the explanation to section 3(d).

According to Part II, Annex 1 of the Directive, a substance qualifies as “generic” only when it contains the same therapeutic moiety as the original, innovative substance. Where the therapeutic moiety differs, the substance must be regarded as a new active substance. The Directive thus establishes a clear boundary: while certain derivatives may fall within the definition of generic substances, those exhibiting variations in therapeutic moiety or significant changes - whether enhancement or reduction in efficacy cannot be regarded as generics under its framework.

In order to determine what amounts to enhanced efficacy Reflection paper on considerations given to designation of a single stereo isomeric form (enantiomer), a complex, a derivative, or a different salt or ester as new active substance in relation to the relevant reference active substance states that evidence likely to be considered adequate includes:

  • Substantial changes in dosing frequency or route of administration due to safety or efficacy improvements;
  • Clinically and statistically significant improvements in therapeutic outcomes;
  • Altered contraindications, adverse reactions, or drug–drug interactions that impact the eligible patient population;
  • Clinically relevant enhancements enabling use in previously excluded patient groups;
  • Compelling preclinical data demonstrating differences in toxicity or carcinogenicity.

Conversely, evidence limited to pharmacokinetic variations, inconclusive preclinical findings, extrapolated results lacking direct head-to-head comparison, or unsupported expansion of the patient population is typically deemed insufficient to establish enhanced efficacy.

Conclusion: Overcoming an objection under Section 3(d)

To bypass an objection under Section 3(d), the applicant must establish enhanced efficacy by demonstrating that the claimed substance exhibits a meaningful improvement in its intended performance compared to the known substance.

In the case of pharmaceutical inventions, this requires proving that the claimed compound or its active substance shows an improved therapeutic efficacy in curing diseases and treating the patient’s medical condition. Factors that do not directly contribute to the therapeutic effect but merely contribute to the working of the substance are immaterial to the consideration of efficacy.

Similarly for non-pharmaceutical chemical inventions, the applicant must establish that the modification leads to a quantifiable functional benefit in the substance’s intended use. Enhancements that do not contribute to achieving the intended technical effect but merely contribute to its working is immaterial in the consideration of efficacy.

The applicant ought to include experimental data or test results demonstrating such enhancement in the specification itself. However, where additional supporting data becomes available subsequently, the same may be submitted before the Patent Office before the final hearing as upheld in Ischemix LLC Vs. The Controller of Patents (MANU/DE/7930/2023), where post-filing data was accepted as corroborative evidence of efficacy. Similarly, the Hon’ble Calcutta High court in Oyster Point Pharma Inc v. The Controller of Patents and Designs (MANU/WB/1544/2023), recognized the admissibility of post-priority date data for establishing enhanced efficacy.