India's top court is set to rule Monday on a patent challenge by Swiss pharmaceutical giant Novartis that activists say threatens access to cheap generic versions of life-saving drugs in poor nations.

Generic drug firms in India -- long known as the "pharmacy to the developing world" -- have been a major supplier of copycat medicines to treat diseases such as cancer, TB and AIDS for those who cannot afford expensive branded versions.

A Novartis win in the Supreme Court would "be dire for people in the developing world who depend on generic drugs made in this country. It could seriously curb access", said Leena Menghaney, a lawyer with medical charity Medecins Sans Frontieres (MSF).

The landmark challenge -- watched closely by global pharmaceutical firms -- involves an updated version of Novartis' blockbuster cancer drug Glivec, for which the company is seeking patent protection.

India's patent office has refused protection, asserting that the amended form of Glivec was not vastly different from the earlier version.

The challenge strikes at the heart of India's patent act, which restricts pharmaceutical companies from seeking fresh patents for making only small modifications to existing drugs -- an industry practice known as "evergreening".

Novartis says the updated form of Glivec merits a patent, arguing that it is a significant improvement from the earlier version because it is more easily absorbed by the body.

But critics such as MSF describe the changes in Glivec -- often hailed as a "silver bullet" for its breakthrough in treating a deadly form of leukaemia -- as "an obvious, routine modification".

A Novartis win would "set a dangerous precedent, severely weakening India's legal norms against 'evergreening'," Menghaney said.

"You could have drug companies claiming one new drug and then patenting it over and over again for routine improvements," she told AFP.

The Novartis case is the most high-profile of several drug patent battles being waged in the country and is seen as having far-reaching implications in defining the extent of patent protection in India.

It is being watched closely by other global drug firms hoping to sell branded medicines in the country of 1.2 billion, whose growing affluence has created a highly lucrative market.

The companies say they cannot afford to be absent from India where the pharmaceutical market is expected to touch $74 billion in sales by 2020 from $11 billion in 2011, according to a PricewaterhouseCoopers study.

India's powerhouse copycat drugs industry, which supplies one-fifth of the world's generics, grew rapidly largely because the country did not issue drug patents until 2005 when it began complying with World Trade Organisation rules.

India currently allows patents for inventions after 1995 or for an updated drug which displays greater therapeutic efficacy.

The cost difference between generic and brand name drugs is crucial for poor people around the world, MSF said, noting that generics from India have pushed down prices for older anti-AIDS drugs by up to 99 percent.

The Glivec generic version costs 4,000 rupees a month ($73) compared to $4,000 for the branded product, said MSF.

Glivec is one of Novartis's biggest-earning drugs, with global sales of $4.7 billion in 2011. But only a fraction of those sales are in India.

Novartis and other global drugmakers say India's generics industry reduces incentives to produce cutting-edge medicines. They believe the ruling will be crucial in bringing more clarity to India's patent law.

"Looking at recent cases, the mood in India makes it more likely we would have a more negative (court) response," Paul Herrling, Novartis corporate research head, said last week.

Last year, an Indian court threw out a patent infringement case launched against Cipla by Swiss drugmaker F. Hoffmann-La Roche over the Mumbai firm's version of a lung-cancer drug, ruling it had a different molecular makeup.

Also in 2012, an Indian drugmaker was allowed to produce a vastly cheaper version of a kidney and liver cancer drug made by Bayer Corp.

Source: AFP