Section 3(d)

You have made a salt of a known drug that is easier to formulate, more stable and better absorbed. Every chemist would call that an improvement. Indian patent law asks a narrower question.

In simple words

A provision that treats a new form of a known substance as unpatentable unless it differs significantly in properties with regard to efficacy, and also bars the mere discovery of a new property or new use of a known substance.

Think of it as

A second gate that pharmaceutical and chemical inventions must pass, after novelty and inventive step.

Why it matters

The Explanation deems salts, esters, ethers, polymorphs, metabolites, pure form, particle size, isomers, mixtures of isomers, complexes and combinations to be the same substance unless a significant difference in efficacy is shown. For a medicine, the Supreme Court has held that efficacy here means therapeutic efficacy, judged strictly - and that improved bioavailability does not by itself establish it.

A simple example

A crystalline form with better flow properties, lower hygroscopicity and around 30 per cent higher bioavailability was held not to clear section 3(d) in the absence of evidence of enhanced therapeutic effect.

Common mistake

Assuming section 3(d) blocks all incremental innovation. It does not. It requires evidence of enhanced therapeutic efficacy - which means the data has to be generated and put on the file.

Where it comes from

Patents Act 1970, section 3(d) and its Explanation; construed in Novartis AG v Union of India (2013) 6 SCC 1