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India- What constitutes ‘therapeutic efficacy’ when determining patentability of ‘new forms of known substances’

The Delhi High Court recently rendered a significant decision clarifying the concept of enhanced therapeutic efficacy, when determining the patentability of new forms of known substances. The case involved an appeal by the patent applicant challenging the rejection of their patent application under Section 3(d) of the Patents Act, 1970 (as amended) (the ‘Act’). Section 3(d) of the Act stipulates that the following are not patentable- 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, or the mere discovery of any new property or new use for a known substance.

Factual matrix:

An Appeal was filed by the Appellant– Ischemix LLC seeking inter alia, an order to set aside the decision of the Respondents– the Controller General of Patents and Designs. The Respondent had refused an application for a patent titled “‘Compositions and Methods for Treating Ischemia and Ischemia-Reperfusion Injury’ bearing number ‘9739/DELNP/2011’ on the ground of non-patentability under Section 3(d) of the Act.

Appellant’s submissions:

The Appellant challenged the rejection of the Respondents order on the basis that it lacked reasoning. They drew the court’s attention to the data included in the specification and the clinical trial data presented during the prosecution stage to prove the superior therapeutic effectiveness of the claimed isomer. Furthermore, they pointed out that the Respondents had not considered the findings of two experts who supported the unexpected and remarkable therapeutic efficacy of the claimed isomer.


The Respondents argued that although some data had been provided, the connection between the data and the claim of increased therapeutic effectiveness was not evident from the submissions made.

Court’s decision:

The High Court disagreed with the Respondents’ position. Citing the Supreme Court’s precedent in Novartis AG v Union of India, the court ruled that in order to establish therapeutic efficacy, applicants must adduce robust evidence. This includes, without limitation, providing comparative tables and a clear explanation of how the new form of the known substance exhibits a significant increase in therapeutic efficacy during the patent prosecution process. Said evidence may even be in the form of comparative in-vitro and in-vivo data, as well as clinical trial data.

Moreover, the court emphasized that patent applications should initially include data demonstrating efficacy. If additional data becomes available later on, it must be submitted to the Indian Patent office prior to the final hearing date. Citing the case of AstraZeneca AB and Ors v Intas Pharmaceuticals Limited and Ors, the court allowed the submission of post-priority-date data, provided it is supported by the complete specification. Considering the challenges of drug development, as outlined in the Calcutta High Court’s ruling in Oyster Point Pharma Inc v The Controller of Patents and Designs, the court concluded that clinical trial data can be presented to support the Appellant’s claims in the specification, showing a significant enhancement in therapeutic efficacy.

This decision offers much-needed clarity on the requirements for demonstrating enhanced therapeutic efficacy under Section 3(d) of the Act, providing valuable guidance for innovators seeking to navigate this regulatory landscape successfully.