Vinay Prasad stepped down as head of the FDA’s Center for Biologics Evaluation and Research, with his deputy Katherine Szarama taking over in an acting capacity while the search for a permanent director continues. Szarama’s appointment places an acting leader at the helm of a center that regulates vaccines, gene therapies, and the blood supply—areas where the FDA has faced sustained industry scrutiny. The leadership change follows a period of high-profile regulatory conflicts involving rare disease therapies and rare biologics, and sets a near-term tone for how biologics evidence is evaluated in the coming weeks.