LP-533401 HCl is an inhibitor of tryptophan hydroxylase-1 (Tph-1), the initial enzyme in gut-derived serotonin (GDS) biosynthesis..

Fenclonine [para -chlorophenylalanine (PCPA)], is a selective and irreversible inhibitor of tryptophan hydroxylase, which is a rate-limiting enzyme in the biosynthesis of serotonin.

Telotristat ethyl (formerly LX-1032; LX-1606; LX-1032; LX-1606; trade name: Xermelo), the ethyl ester prodrug form of Telotristat, is an orally bioavailable tryptophan hydroxylase (TPH) inhibitor (IC50 = 0.028 μM) with antiserotonergic and anti-diarrhea activity.