1. Core Legal Answer & Context: Section 3(d) of the Indian Patents Act, 1970, is a crucial provision designed to prevent 'evergreening' of patents, particularly in the pharmaceutical sector. Evergreening refers to the practice of extending the patent life of a drug by making minor modifications to an existing patented compound, without significantly enhancing its therapeutic efficacy. The ambit and scope of Section 3(d) are to ensure that only genuine inventions, representing a significant therapeutic advancement, are granted patents, thereby balancing innovation with public health access to affordable medicines. It specifically states that 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 process, substance or machine, or 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, is not an invention.

2. Relevant Statutes and Sections: Section 3(d) of the Indian Patents Act, 1970 (as amended in 2005): "The following are not inventions within the meaning of this Act: ... (d) 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 process, substance or machine unless such known process results in a new product or employs at least one new reactant."

3. Important Landmark Cases: Novartis AG v. Union of India & Ors. (2013): This is the seminal case that defined the scope and interpretation of Section 3(d). Novartis, a Swiss pharmaceutical company, sought a patent for the beta-crystalline form of Imatinib Mesylate, marketed as 'Glivec,' a cancer drug. This was a modified version of Imatinib, for which a patent had already been granted in the US. Novartis argued that the beta-crystalline form had improved bioavailability and therapeutic efficacy compared to the original Imatinib.

The Supreme Court of India, in its landmark judgment, rejected Novartis's patent application. The Court held that:

• 'Efficacy' in Section 3(d) refers specifically to 'therapeutic efficacy' in the context of pharmaceutical substances. It is not enough to show improved physical properties (like bioavailability) unless those improvements translate into enhanced therapeutic effect.
• The beta-crystalline form of Imatinib Mesylate did not demonstrate a significant enhancement in therapeutic efficacy over the known substance (Imatinib) to qualify as an 'invention' under Section 3(d).
• The purpose of Section 3(d) is to prevent evergreening and ensure that patents are granted only for genuine inventions that contribute to public health, not for minor modifications of existing drugs.

4. Clear Conclusion: The Novartis judgment firmly established the stringent interpretation of Section 3(d) of the Indian Patents Act, 1970. It clarified that for a new form of a known substance to be patentable, it must demonstrate a significant enhancement in 'therapeutic efficacy,' not just improved physical properties. This provision and its judicial interpretation serve as a robust safeguard against evergreening, promoting genuine pharmaceutical innovation while ensuring access to affordable medicines, thereby balancing the interests of patentees with public health concerns in India.