John O'Brien, the senior adviser to HHS Secretary Alex Azar on drug-pricing reform, will step down from his position Aug. 22.
Mr. O'Brien will leave less than one year after joining HHS. He was appointed in December after the death of former drug-pricing adviser Daniel Best.
John Brooks, principal deputy director of the Center for Medicare, will "expand his current responsibilities" and become the new senior adviser for drug-pricing reform, according to a statement from HHS.
"John Brooks will bring significant experience from the top levels of the White House, HHS, and CMS to continue delivering on President [Donald] Trump's vision for lower drug prices, lower out-of-pocket costs, and more affordable healthcare for all Americans," according to HHS.
Mr. O'Brien's departure comes as the Trump administration works on several proposals to lower prescription drug costs, many of which have received pushback from the drug industry and some Republican senators.