Glycerol phenylbutyrate

Absorption

Glycerol phenylbutyrate is a prodrug in which phenylbutyrate (PBA) is released from the glycerol backbone by lipases in the gastrointestinal tract. PBA then undergoes beta-oxidtion to form PAA. When a single oral dose of 2.9 mL/m2 of Glycerol phenylbutyrate is given to fasting adult subjects, the pharmacokinetic parameters are as follows: Tmax: PBA = 2 hours; PAA = 4 hours; PAGN = 4 hours. Cmax: PBA = 37.0 μg/mL; PAA = 14.9 μg/mL; PAGN = 30.2 μg/mL. In healthy subjects, the hydrolysis of glycerol phenylbutyrate is incomplete, but to what extent is unknown. When glycerol phenylbutyrate is given to adult UCD patients, maximum plasma concentrations at steady state (Cmaxss) of PBA, PAA, and PAGN occurred at 8 h, 12 h, and 10 h, respectively, after the first dose in the day. Intact glycerol phenylbutyrate was not detectable in plasma in UCD patients.

Toxicity

Most common adverse reactions in ≥10% of patients are diarrhea, flatulence, and headache.

The Uses of Glycerol phenylbutyrate

Tri(4-phenylbutyryl)glycerol is a drug that is currently under development for treatment of urea cyclic disorders (UCDs). It works by preventing the harmful buildup of ammonia in the body.

Background

Glycerol phenylbutyrate is a nitrogen-binding agent. Chemically, it is a triglyceride in which three molecules of phenylbutyrate are linked to a glycerol backbone. FDA approved on February 1, 2013.

Indications

Glycerol phenylbutyrate is a nitrogen-binding agent for the chronic management of adult and pediatric patients ≥2 years of age with urea cycle disorders (UCDs) who cannot be managed by dietary protein restriction and/or amino acid supplementation alone.

Definition

ChEBI: Glycerol phenylbutyrate is a triglyceride.

Pharmacokinetics

Glycerol phenylbutyrate prolongs the QTc interval.

Metabolism

Pancreatic lipases hydrolyze glycerol phenylbutyrate to release PBA from the glycerol backbone. PBA undergoes β-oxidation to PAA, which is conjugated with glutamine in the liver and in the kidney through the enzyme phenylacetyl-CoA: L-glutamine-N-acetyltransferase to form PAGN.