Under section 3(d) of the Patents Act, 1970, the mere discovery of a new form of a known substance is…

Section 3(d) of the Patents Act, 1970 excludes from the meaning of invention "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". Its Explanation treats salts, esters, ethers, polymorphs, metabolites, pure form, particle size, isomers, mixtures of isomers, complexes, combinations and other derivatives of a known substance as the same substance unless they differ significantly in properties with regard to efficacy. In Novartis AG v. Union of India (2013), the Supreme Court held that for medicines "efficacy" means therapeutic efficacy.

A new derivative form alone, or the mere discovery of a new property or new use for a known substance, is excluded by the same clause, and a foreign patent does not make the substance patentable in India. Since the Patents (Amendment) Act, 2005 (which omitted former s.5, under which only processes were patentable for food, medicine and chemical substances), product patents are available for such substances subject to section 3(d) and the other requirements of the Act.