Theranos just made some major changes to its company.

Late Wednesday, the blood-testing startup said that Sunny Balwani, the company's president and chief operating officer, is stepping down and retiring.

Balwani, who joined Theranos in 2009, also served on the company's board of directors.

Theranos will also be bringing in three new members to its board, including biotech veteran Fabrizio Bonanni. The other two--William Foege and Richard Kovacevich--will move over from Theranos's board of counselors.

Before retiring in 2013, Bonanni had been an executive vice president at Amgen, a biopharmaceutical company in Thousand Oaks, California.

Theranos has been embroiled in controversy ever since a Wall Street Journal report questioned the accuracy of its tests. Later, an investigation by the U.S. Centers for Medicare and Medicaid Services found that Theranos's Northern California lab was putting patients in "immediate jeopardy."

The company has since stopped running tests out of that lab and has responded to the agency with plans to address its concerns.

It said in a release that it also plans to reorganize its structure "with dedicated corporate divisions for technology and clinical operations."

Balwani's departure is the biggest leadership change to the company since its Northern California lab halted all testing. In April, Theranos announced the addition of a medical-advisory board.

This story first appeared on Business Insider.