ZURICH (Reuters) - Switzerland has agreed to extradite a Chinese researcher to the United States where prosecutors have charged him with helping his scientist sister steal secrets allegedly worth $550 million from British drugmaker GlaxoSmithKline.

Gongda Xue, a 20-year Swiss resident, has been fighting extradition and was labeled a potential flight risk after he was detained by Swiss authorities earlier this year.

The Swiss Federal Office of Justice confirmed on Wednesday that the U.S. request for his extradition was approved earlier this month, though Gongda Xue still has until mid-August to appeal to the Swiss Federal Criminal Court to block it.

The Basel-area researcher, who worked at Switzerland’s Friedrich Miescher Institute for Biomedical Research until 2014, is the brother of Yu “Joyce” Xue, a Chinese-American scientist who last August pleaded guilty at the U.S. District Court in Pennsylvania to pilfering secrets from a facility of GlaxoSmithKline.

Gongda Xue faces up to 20 years in a U.S. prison if convicted. According to the U.S. indictment, he received stolen GSK secrets from his sister, performed tests at Miescher’s facilities and sent results to accomplices in China.

The stolen information, prosecutors allege, involved antibodies that bind to tumor cells and kill them.

His Swiss lawyer did not return a request seeking comment.

There was no immediate reaction from U.S. authorities or the British company.

Yu Xue, his biochemist sister who worked at Glaxo in Pennsylvania until 2016, is awaiting sentencing in her case.

Reporting by John Miller; Editing by Andrew Cawthorne