Section 3(d) of the Patents Act

Section 3(d) of the Patents Act prevents a patent from being granted merely because someone discovers a new form of an already known medicine. Such a form must show enhancement of the known efficacy of the substance; for medicines, the relevant standard is therapeutic efficacy, meaning effectiveness in producing the intended therapeutic result.

The statutory threshold

Section 3(d) of the Patents Act, 1970 excludes the mere discovery of a new form of a known substance when it does not enhance that substance's known efficacy.

• The provision's Explanation treats salts, esters, polymorphs and other specified derivatives of a known substance as the same substance unless they differ significantly in properties with regard to efficacy.
• Therefore, a change in a medicine's chemical or physical form does not, by itself, establish patentability.
• The section also excludes the mere discovery of a new property or new use of a known substance; identifying another use does not by itself make the substance patentable.

What counts as enhanced efficacy for medicines?

In Novartis AG v. Union of India (2013), the Supreme Court held that efficacy must be understood according to the product's function. For a medicine intended to treat disease, the test is enhanced therapeutic efficacy.

• Better flow properties, greater thermodynamic stability or lower hygroscopicity do not establish therapeutic efficacy merely because they improve manufacturing or storage characteristics.
• Improved bioavailability, meaning greater availability of the drug in the body, does not necessarily establish enhanced therapeutic efficacy; its therapeutic significance must be specifically demonstrated through research data.
• The comparison concerns the efficacy of the new form relative to the known substance, not merely whether the modified medicine works.

How this fits into patentability

Section 3(d) is an additional patentability filter, not a substitute for the ordinary requirements of novelty, inventive step and industrial applicability.

• Showing enhanced therapeutic efficacy does not automatically secure a patent; the application must also meet the other statutory requirements.
• The provision checks evergreening, where successive patents on minor modifications can prolong patent-based exclusivity without a corresponding therapeutic advance.
• It does not prohibit all incremental pharmaceutical innovation: a modified medicine may qualify if it clears Section 3(d) and the remaining patentability requirements.