"Evergreening" refers to various legal and commercial strategies employed by companies to maximise profits and frustrate competition, such as making relatively minor changes to existing drugs with soon-to-expire patents in order to obtain further patent protection. While "evergreening" is not a formal concept of patent law, the attempts by governments to circumvent such strategies have caused controversy in the pharmaceutical industry – and India is one such example.

India stopped granting drug patents in the 1970s, and only resumed granting drug patents in 2005 as part of a World Trade Organisation agreement. However, medicines created prior to 1995 are excluded. Further, there is a provision in India’s patent law which prohibits a new form of a known substance from receiving a patent unless it significantly improves the medicine’s "efficacy" (which is not defined). The provision was ostensibly aimed at preventing "evergreening".

The Swiss drug company Novartis has been involved in a long-running battle (since 2006) for an Indian patent for imatinib mesylate which is the leukaemia drug known as  Glivec (Gleevec in the US). Glivec has shown success in turning deadly chronic myelogenous leukaemia into a manageable chronic disease for patients. Novartis developed a predecessor compound to imatinib mesylate in the early 1990s, which was not patented in India (because India did not grant drug patents at that time). However, this older compound was never marketed as a drug. Novartis says the current version of Glivec, which is currently patented in over 40 countries, is 30 per cent easier for the body to absorb than the older compound. Novartis alleges that the meaning of “efficacy” should be interpreted to include modifications which make a drug safer or easier to use, not just more effective in treating a disease.

With its arguments having been rejected below, Novartis has brought its final challenge before India’s highest court, with the hearing before Justices Aftab Alam and Ranajan Prakash Desai commencing on Tuesday. Even if Novartis is successful before the Supreme Court of India, generic versions of Glivec will still be able to be sold in India because they were marketed prior to 2005 and have protection under Indian patent law. While Novartis might not have much to gain directly from this case, the ruling is likely to be important because it may determine the limits of patentability of developed compounds in India.

The hearing is expected to last for at least two months.