LONDON-- GlaxoSmithKline PLC said it would stop seeking patents for its drugs in low-income countries, a move the drugmaker said could help the world's poorest people access copycat versions of its medicines at affordable prices.

The U.K.-based company said it would take this approach in low-income and least-developed countries, a group totaling around 85 nations. In so-called lower-middle-income countries, a group of 51 nations that includes Vietnam, Cameroon and Sri Lanka, it said it would file patents but aim to grant licenses to generic manufacturers to supply low-cost versions of its drugs in those markets in return for a small royalty.

Glaxo previously filed patents in most lower-middle-income countries, and in low-income nations where a patent office exists. But that "patchwork" approach meant that generic drugmakers held back from manufacturing copycat medicines for these markets owing to the risk of being sued by pharmaceutical companies, according to Glaxo Chief Executive Andrew Witty.

"By doing this we're taking away one potential issue or excuse...which is that generic companies hold back because they don't know what intellectual property exists," he said.

Mr. Witty said the decision wouldn't significantly affect Glaxo's revenue or profit as the countries in question don't have well-developed markets for pharmaceuticals. Still, he added that the company's success in India--its biggest market by volume--illustrated that a flexible approach to intellectual property didn't necessarily dent a company's commercial prospects.

Glaxo has a "handful" of patents in India but doesn't rely heavily on intellectual-property rights, Mr. Witty said. Instead, he said, Glaxo provided drugs at "Indian prices" and competed with the generic drugmakers. As India is a member of the Group of 20 industrial and developing nations, Glaxo will continue to seek patents there.

Pharmaceutical companies rely on patents to secure the exclusive right to sell the drugs they develop, allowing them to charge high prices and recoup the investment they plow into research. But they have made various moves to relax their approach to intellectual property in recent years, in response to increasing political pressure to make medicines more widely available. In most cases, this involves relinquishing patent rights for a particular drug in certain markets, paving the way for generic-drug makers to start manufacturing cheaper versions.

Critics question the extent to which such approaches can meaningfully increase access to medicines. One reason: Most of the world's generic-drug makers operate in middle- or high-income countries, where pharmaceutical companies still enforce their patents. That means those manufacturers must strike case-by-case agreements with pharmaceutical companies permitting them to supply copycat drugs in particular markets.

Glaxo hopes the scale of its approach--giving unfettered access to 85 countries with a combined population of two billion people--will make it more commercially attractive for generic companies to make copycat versions of its drugs for poor countries, according to a company spokeswoman.

Rohit Malpani, director of policy and advocacy for Doctors Without Borders, said that while Glaxo had gone further than others, the move would have a limited effect. That is partly because the 48 nations that fall under the United Nations' "least-developed countries" category already are exempt from patent enforcement until at least 2033 under a World Trade Organization agreement. In addition, he said, three-quarters of the world's poorest people live in middle-income countries, around half of which won't benefit from any special provisions.

Still, Glaxo's Mr. Witty said he hoped the company's move would "stimulate a movement" to increase access to drugs. "Hopefully people can work with us and we can make stuff happen," he said. "We have to wait and see."

Write to Denise Roland at Denise.Roland@wsj.com