Fenclonine

Fenclonine, also known as para-chlorophenylalanine (PCPA), acts as a selective and irreversible inhibitor of tryptophan hydroxylase, which is a rate-limiting enzyme in the biosynthesis of serotonin.^[2]

Fenclonine

Clinical data
Other names	CP-10188; Fenclonina; Fencloninum; NSC-77370; Parachlorophenylalanine[1]
ATC code	None
Identifiers
IUPAC name (S)-2-Amino-3-(4-chlorophenyl)propanoic acid
CAS Number	7424-00-2 Y
PubChem CID	4652
IUPHAR/BPS	5240
ChemSpider	4491 Y
UNII	R5J7E3L9SP
KEGG	D04143 Y
CompTox Dashboard (EPA)	DTXSID4045139
ECHA InfoCard	100.028.229
Chemical and physical data
Formula	C9H10ClNO2
Molar mass	199.63 g·mol−1
3D model (JSmol)	Interactive image
Density	1.336 g/cm3
Melting point	240 °C (464 °F)
Boiling point	339.5 °C (643.1 °F)
SMILES Clc1ccc(cc1)CC(C(=O)O)N
InChI InChI=1S/C9H10ClNO2/c10-7-3-1-6(2-4-7)5-8(11)9(12)13/h1-4,8H,5,11H2,(H,12,13) Y Key:NIGWMJHCCYYCSF-UHFFFAOYSA-N Y
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It has been used experimentally to treat carcinoid syndrome, but the side effects, mostly hypersensitivity reactions and psychiatric disturbances, have prevented development for this use.^[3]

The effects of serotonin depletion from fenclonine are so drastic that serotonin cannot even be detected immunohistochemically within the first day after administration of a control dose. Tryptophan hydroxylase activity can be detected neither in cell bodies or nerve terminals. After one week 10% of control values (the baseline extrapolated for the study) had replenished in the raphe nucleus, and after two weeks from initial treatment as much was again detected in the hypothalamus region. Aromatic L-amino acid decarboxylase (AADC) levels were at no time affected.^[4]

It is used in scientific research in humans^[5] and animals^[2] to investigate the effects of serotonin depletion.