INDIA- Section 3(d) of the Indian Patents Act: Comprehending identification of "A Known Substance"

Section 3(d) of the Patents Act, 1970 (hereinafter referred to as ‘the Act’), is one of the most scrutinized provision in India’s intellectual property regime, particularly for its role in setting a high standard for patentability. It provides a unique safeguard against patenting of trivial modifications to existing substances, requiring Applicants to demonstrate that a new form of a known substance significantly enhances its known efficacy.

The principal clause of Section 3(d) contains three limbs, which are separated by the disjunctive “or”. The three limbs are as under:

1. The mere discovery of a new form of a known substance which does not result in the enhancement of the known efficacy of that substance;

2. The mere discovery of any new property or new use for a known substance;

3. The 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.

   
   

Each of the above limb serves a specific function, and among the various elements of this provision, the concept of a “known substance” forms the cornerstone of its application. This term is not merely a statutory phrase but a legal and scientific yardstick that determines whether the provision’s stringent requirements are triggered. Understanding what qualifies as ‘a known substance’ is pivotal, as it is the first step in assessing whether an invention meets the patentability requirements under Section 3(d) of the Act.

It is noteworthy that Section 3(d) focuses specifically on the relationship between the claimed invention and its prior art counterpart. Thus, the identification of a known substance serves as a benchmark for evaluating whether the claimed new form offers a genuine improvement in therapeutic efficacy. The complexity of determining whether a substance is “known” often arises in cases involving broad or generalized disclosures in prior art. A single mention of a chemical class or a compound family does not necessarily render all its derivatives or variants known. Error in identifying or interpreting the known substance can render the entire patentability analysis flawed, as seen in numerous disputes before Indian Courts and tribunals. This article delves into the intricacies of Section 3(d) by examining its distinct components and emphasizing on the critical role of identification of the “known substance” in shaping its application.

The case of Fresenius Kabi Oncology Limited vs. Glaxo Group Limited & Anr. (ORA/17/2012/PT/KOL) provides a nuanced interpretation of Section 3(d) of the Act, particularly with respect to its application to the first limb concerning new form of a known substance. The case revolved around an application for revocation of the Respondent’s patent for an invention titled ‘Bicyclic Heteroaromatic Compounds’ on the grounds of obviousness, insufficiency of description, non-patentability under Section 3(d) and non-disclosure under Section 8 of the Act.

The now defunct Intellectual Property Appellate Board (IPAB) meticulously examined whether the impugned patent was a derivative of prior art compounds, thus, falling under the purview of a ‘new form of a known substance’. It emphasized that while a patentee must prove the enhanced therapeutic efficacy of his invention, but in a case for revocation, the burden of establishing that the invention does not qualify the bar of Section 3(d) and has the same therapeutic efficacy as the known substance, lies with the challenger or Applicant, who must substantiate their pleadings with documented evidence of prior art. The relevant portion of the order is reiterated hereinbelow:

“56. …It is not enough to plead that because Ex1 and 2 are admitted prior arts, this is only a new form of those compounds. That is vague. It is only when the pleadings show how the invention is one kind of a derivative of known substance the patentee will have to explain how the grant of patent is justified because of the enhancement of therapeutic efficacy. In this case the pleadings are not adequate. We hold that the S.3(d) ground has not been proved.”

Placing reliance on the above judgement, the Hon’ble Delhi High Court in the case of DS Biopharma Limited vs. The Controller of Patents & Designs & Anr. (C.A. (COMM.IPD-PAT) 6/2021) held that for an objection under Section 3(d) to be raised, the basic pre-condition would be identification of the ‘a known substance’. It highlighted that it cannot be left to the Applicant to deduce as to what is the known substance and thereafter give efficacy data qua that known substance, based on the said deduction. Further, it was stressed that for the purposes of a Section 3(d) objection, the one specific known substance has to be identified and the manner in which the claimed compounds are ‘new forms’ ought to be mentioned by the Patent Office, at least briefly if not in detail.

On similar lines, in Nippon Steel Corporation vs. Controller General of Patents, Designs & Trademarks & Anr. (C.A.(COMM.IPD-PAT) 323/2022), the Hon’ble Delhi High Court insisted on the requirement of first specifying as to what is the “known process, machine, or apparatus”, so as to make a rejection under Section 3(d) of the Act.

Another notable aspect concerning the interpretation of ‘known substance’ was discussed in Pfizer Products Inc. vs. The Controller of Patent & Designs (OA/2/2016/PT/MUM), where it was elucidated that for ascertaining the applicability of section 3(d), the invention should be ‘a mere discovery’, there should be ‘known substance’ and the ‘known substance should have a known efficacy’. It was stressed that if for a compound claimed, a known substance with a known efficacy can be identified, then for the said claimed compound to be patentable, the Applicant is required to furnish data to show enhancement in efficacy vis-a-vis the known substance.

The matter revolved around an objection under Section 3(d) of the Act based on the Applicant's own application (WO0142246, D1), disclosed in the background of the complete specification of the claimed invention, wherein it was objected that the claimed enantiomeric compound was a mere modification of a racemic mixture disclosed in prior art D1 without any evidence of enhanced therapeutic efficacy.

Negating the Respondent’s argument that WO0142246 is a valid prior art for Section 3(d) as it was Applicant's own application and hence, "known" to the Applicant, the Hon’ble Court observed as follows with respect to validity of the prior art:

“40. …The prior art has to be known to the public and not the inventor/applicant of the patent specification. Inventor's knowledge is immaterial in patentability analysis. While D1 was filed earlier, it was not a prior public document and therefore the compound disclosed therein, in particular compound of Example 14 was published after the priority date of the present application.”

Elucidating on whether an invention qualifies as a valid prior art for the purpose of construing ‘a known substance’ under Section 3(d) was also discussed in the case of Mr. Tony Mon George, Constituted Attorney of AbbVie Inc. vs. Deputy Controller of Patents and Designs ((T) CMA (PT) No.150 of 2023), where the Hon’ble Madras High Court held that a parent compound if disclosed in a document that was made known to the public after the priority date of the claimed invention, the same would not qualify as a “known substance” for purposes of Section 3(d) of the Act. Further, the Hon’ble Court emphasized that once it is concluded that the claimed invention is not a new form of a known substance, it is not necessary for the Appellant to cross the hurdle of Section 3. Hence, enhanced efficacy over such substance need not be shown.

The principles laid down in Pfizer Products Inc. vs. The Controller of Patent & Designs and Mr. Tony Mon George, Constituted Attorney of AbbVie Inc. vs. Deputy Controller of Patents and Designs were upheld in another judgment by the Hon’ble Madras High Court in M/s. Guangzhou Ocusun Ophthalmic Biotechnology Company Limited vs. Joint Controller of Patents & Designs (CMA(PT)/23 of 2024), wherein it was accentuated that in order to apply Section 3(d) of the Act, it is necessary for the Patent Office to identify the known substance. 

Conclusion

As may be noted from the plethora of cases discussed above, the concept of a “known substance” is not merely a theoretical construct but a practical criterion that influences the application of Section 3(d) of the Act. The precise identification of the known substance establishes the baseline for determining whether the claimed invention offers a meaningful improvement. It ensures that the efficacy comparison is grounded in clear and objective evidence, enabling a thorough and fair evaluation. By emphasizing the identification of “known substance” as a pre-requisite, the provision upholds the principle that patent protection should be reserved for innovations that genuinely advance the state of the art.