Indian patent law differs from that in most other countries in that, for pharmaceutical products to be patented, as well as being novel and containing an 'inventive step' in their creation (that is, being non-obvious), new forms of known compounds must overcome the additional hurdle of showing increased efficacy. For example, different salts, polymorphs or isomers of known substances are not patentable — because they are considered to be the same substance — unless they “differ significantly in properties with regard to efficacy”.
This clause was designed to prevent a practice known as 'evergreening', whereby the lifespan of patent protection for a drug is extended by the patenting of incremental modifications to the drug. This increased efficacy bar is thought by some to be set too high (see Nature Rev. Drug Discov. 6, 180–180; 2007), because scientific discovery often advances in small, but important, stages. Indeed, in a separate case, Novartis had challenged this aspect of Indian patent law under the World Trade Organization (WTO) Agreement on Trade-Related Aspects of Intellectual Property Rights (TRIPS), but the court had deferred a decision, saying that it had no jurisdiction over WTO rules.
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