President Trump announced Friday his intention to nominate Stephen Hahn, the chief medical officer of MD Anderson Cancer Center in Houston, as the next commissioner of the Food and Drug Administration.

But in a surprise move, acting FDA commissioner Norman “Ned” Sharpless, will immediately return to his previous position as the director of the National Cancer Institute, and Brett Giroir, a top official at the Department of Health and Human Services, will oversee the FDA until Hahn is confirmed, according to individuals who spoke on the condition of anonymity to discuss personnel issues.

Sharpless has been acting commissioner since April, when the previous commissioner, Scott Gottlieb, stepped down. However, Sharpless’ term as acting agency head expires Friday. His time at FDA could be extended only if the White House officially nominated a successor, which it cannot do because the Hahn paperwork isn’t finished, according to people familiar with the situation.

Hahn, a radiation and medical oncologist, oversees clinical care at the cancer center. Previously, he served as chief operating officer of the hospital, and has been praised for helping engineer its financial turnaround.

Hahn’s nomination is occurring at a critical time for the agency, which is at the center of a debate about banning almost all flavors in e-cigarettes, a step designed to stem sharp increases in youth vaping. Trump announced plans for the ban in September, but the agency has not yet issued its final policy.

In September, officials said the ban would include mint and menthol, but recently two people familiar with the discussions said the White House is considering excluding menthol and possibly mint from the ban because of concerns about political backlash.

A medical and radiation oncologist, Hahn is described by friends and colleagues as an energetic consensus-builder with a disarming, folksy manner.

Hahn, after a stint at NCI, joined the University of Pennsylvania in 1996, serving as chair of radiation oncology from 2005 to 2014. He then moved to MD Anderson to become division head of radiation oncology. He has conducted an array of clinical trials, including trials of treating prostate cancer with proton therapy and new ways to combine immunotherapy and radiation.

Sharpless, an oncologist who also was a contender for the FDA job on a permanent basis, had strong support from medical and other groups. In September, the groups and several previous FDA commissioners released letters endorsing him for the position.

The news about Giroir becoming interim head of FDA was initially reported by Inside Health Policy.

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