Sephience is the first and only oral phenylalanine hydroxylase activator approved for the treatment of hyperphenylalaninemia in adults and children with sepiapterin-responsive phenylketonuria. By delivering sepiapterin, which converts into tetrahydrobiopterin and also prevents PAH misfolding, it enhances enzyme function to reduce blood phenylalanine levels, offering patients a steroid-free, non-invasive, and more convenient alternative to dietary restriction alone.