Dong-A ST's antibacterial drug Sivextro achieved sales of about 29 billion won ($23.9 million) in the U.S. last year, according to the 2021 performance data released Tuesday by Nabriva Therapeutics, the exclusive marketer of Sivextro in the U.S.

Sivextro accounted for 82 percent of Nabriva's total sales last year ($28.9 million). In addition, Nabriva's sales increased 5.8 times from $5 million in 2020, thanks to the success of Sivextro.

While the exact royalty income received by Dong-A ST is unknown, industry insiders estimate that the company would have received around 5-7 percent.

This is the first time Sivextro's U.S. performance data has been revealed.

Dong-A ST developed Sivextro and transferred its U.S. rights to Trius Therapeutics in 2007. The drug received approval from the Food and Drug Administration in 2014 and started local sales. Merck, also known as MSD outside of the U.S. and Canada, now has its sales rights after acquiring Cubist in 2014. Cubist took over Trius in the previous year.

However, Merck did not disclose the sales results of the drug as it was not a flagship product. Merck signed an exclusive sales contract for Sivextro with Nabriva in July 2020. Under the accord, Merck retains the license for Sivextro but grants only the U.S. sales right to Nabriva.

"We made excellent progress in 2021 despite the Covid-19 pandemic and are poised for continued growth in 2022," Nabriva Therapeutics CEO Ted Schroeder said. "We had a strong close to 2021 for Sivextro, which contributed to extending our cash runway well into the fourth quarter of 2021. In addition, we will continue to propel the product back to historical prescription trends through our promotional efforts."