Vinay Prasad’s ouster as the Food and Drug Administration’s top vaccine and gene therapy regulator came after frustration over his handling of experimental treatments.

The president overruled his HHS secretary and FDA chief, four people with knowledge of the decision tell POLITICO.

Dr. Vinay Prasad had been serving as the FDA's director of the Center for Biologics Evaluation and Research since May, and was later named chief medical and scientific officer.