The Indian Supreme Court rejected a Swiss drug maker’s patent application for a major cancer drug Monday in a landmark ruling that will allow poor patients continued access to many of the world’s best drugs, at least for a while. The ruling allows Indian makers of generic drugs to continue making copycat versions of the Novartis drug Gleevec — spelled Glivec in some markets, like Europe — which can have a seemingly miraculous effect on some forms of leukemia.

But the ruling’s effect will be felt well beyond the limited number of patients in India who need Gleevec, because it will help maintain India’s role as the world’s most important provider of inexpensive medicines, which is critical in the global fight against HIV/AIDS and other diseases. Gleevec can cost as much as $70,000 per year, while Indian generic versions cost about $2,500 year. ‘‘The judgment in the Novartis case is a victory for patients both in India and around the world,’’ Dr. Yusuf K. Hamied, chairman of Cipla, an Indian generic drug giant, wrote in an e-mail. ‘‘India, being the pharmacy capital of the world, can continue to produce affordable, high-quality medicines without the threat of patents for minor modifications of known medicines.’’

In a televised interview, Ranjit Shahani, vice chairman of Novartis’s Indian subsidiary, said that India would suffer as a result of the ruling because companies like Novartis would invest less money in research there. ‘‘We will continue with our investments in India, even though cautiously,’’ he said. ‘‘We hope that the ecosystem for intellectual property in the country improves.’’

The ruling is a landmark in one of the most important economic battles of the 21st century, in which rich nations that increasingly rely on the creation of ideabased products like computer programs and medicines try to compel mostly poor countries that make physical things like clothing and toys to pay for their ideas.

While the goods made by poor countries cannot easily be shared or stolen, the ideas that power the economies of rich countries can be. So rich countries have insisted that poor countries give some of the world’s most profitable companies government-sanctioned monopolies for what the rich nations see as innovative ideas. But a few of these poorer countries — particularly India, Brazil and China — have begun to question the price they must pay for these idea-based products and whether paying such prices does them any good.

On Monday, the Indian Supreme Court ruled that the patent that Novartis sought for Gleevec did not represent a novel invention. In many ways, this ruling is something of a historic anomaly. India’s 2005 patent law allowed for drug patents on medicines discovered after 1995. In 1993, Novartis patented a version of Gleevec that it later abandoned in development, but the Indian judges ruled that the early and later versions were not different enough for the later one to merit a separate patent.

Leena Menghaney, a patient advocate at Medecins Sans Frontieres, said the ruling Monday was a reprieve from more expensive medicines, but only for a while.

‘‘The great thing about this ruling is that we don’t have to worry about the drugs we’re currently using,’’ Ms. Menghaney said. ‘‘But the million-dollar question is what is going to happen for new drugs that have not yet come out.’’

But Anand Grover, a lawyer who argued the case on behalf of the Cancer Patients Aid Association of India, said that the ruling confirmed that the country had a very high bar for approving patents on medicines. He noted that the majority of patented drugs in the United States won patents for fairly minimal discoveries — like a new form of drug delivery or for certain manufacturing techniques.

In a classic example, Nexium, a heartburn pill by AstraZeneca that was long one of the world’s biggest-selling drugs, is almost identical to Prilosec. But both medicines managed to win patent protection in the United States, something that would not happen in India under the new ruling, Mr. Grover said.