Tetrahydrobiopterin
BH₄
What it isObligate cofactor for phenylalanine hydroxylase, and for tyrosine and tryptophan hydroxylase and nitric oxide synthase.
Why this oneGiving it raises residual PAH activity in responsive phenylketonuria — the mechanism of sapropterin, and of sepiapterin, which is converted to it.
What limits itOnly a minority of PKU genotypes respond, so a trial of therapy is how responsiveness is established.
NO BOXED WARNINGS
Classes and tags
Clinical profile
Defining liabilityPhenylalanine imbalance and gastrointestinal inflammation