Teva has been equally fierce in defending its own branded turf. In April, a judge upheld a patent on Seasonique, a Teva birth control brand, preventing a rival firm from making a generic alternative.

Since 1999, Teva has acquired about a dozen drug ingredient and generic makers around the globe. Now some generic and name-brand companies come to buy their drug components from Teva, giving the company insight into the competition. Buying up generic makers in growth markets also keeps Teva’s competitors at bay.

“They have been very successful at keeping out competition from India and China,” says Tarun Khanna, a professor at the Harvard Business School and lead author of its Teva case study. “I’m not quite sure how they pulled that off. They are just buying things up much faster.”

AS recently as a decade ago, the pharmaceutical industry disparaged generics as “copycat” drugs that profit off the innovations and research of brand-name makers. But lately, some of the biggest name-brand makers have been buying stakes in or doing distribution deals with generic makers, particularly in Brazil, India and other emerging markets.

But name-brand makers accustomed to wide margins may not be able to keep up with Teva, says Mr. Khanna.

“If you are used to the fat margins of big pharma, it’s hard to compete in the rough and tumble of price-cutting generics,” he says.

Generic drugs saved the American health care system $734 billion between 1999 and 2008, according to a study by IMS, the research firm. That may be no consolation to name-brand drug makers whose profits Teva has helped erode, or to rival generic makers that lack Teva’s resources.

But for patients, its ascent means that medicine has ultimately become much more affordable.

“We are aggressive and not everybody likes us,” Mr. Marth says. “But we are doing something every day that lowers health care costs and helps consumers.”