India's Supreme Court has rejected a bid by Swiss drug maker Novartis for a new patent on a top-selling cancer drug, a decision that opens the door for production of cheaper, generic drugs to treat the world's poor.

In a landmark ruling Monday, the court dismissed patent protection to an updated version of the drug Glivec. The ruling is a precedent that prevents international pharmaceutical companies from obtaining fresh patents in India on slightly altered versions of existing drugs, which Indian law prohibits.

International drug makers seek to maintain patents on top-selling drugs for as long as possible, to prevent other manufacturers from copying them and selling them at much lower prices. Glivec can cost up to $70,000 a year, with Indian generic versions of it selling for about $2,500.

A patient advocate for Doctors Without Borders, Leena Menghaney, said the ruling would prevent issuance of multiple patents on the same drug in India. She said that would keep cheaper, generic drugs available for the masses who cannot afford the patented versions.

"This doesn't mean that no patents will be granted. Patents will continue to be granted by India, but definitely the abusive practice of getting many patents on one drug will be put at curb, and that is really very crucial to bring drugs into the public domain."

In its decision, the Supreme Court decided that the updated Glivec did not satisfy the "novelty" aspect required by Indian patent law.

The ruling is a victory for India's multi-billion-dollar generic drug industry that provides cheap medicines to millions around the world.

Novartis has been fighting since 2006 to win a patent for the amended form of Glivec.