Hanmi Pharmaceutical on Wednesday became the first Korean drug maker to obtain sales approval for an incrementally modified drug from the U.S. Food and Drug Administration, Health Ministry officials said.

Esomezol is a modified version of AstraZeneca’s Nexium that treats gastro-esophageal reflux disease, commonly known as acid reflux.

The sales approval from the U.S. regulator came after the two pharmaceutical companies reached an agreement in June that the IMD product didn’t infringe the patent rights of the original drug Nexium, officials said. The two had been in a legal battle over the patent since 2010.

“The case which overcame patent disputes is expected to encourage other Korean drug makers to enter the world’s largest drug market,” an official said.

By Cho Chung-un (christory@heraldcorp.com)