Identification of phenylbutyrate-generated metabolites in Huntington disease patients using parallel LC/EC-array/MS and off-line tandem MS. Anal Biochem

Center for Biomedical Mass Spectrometry and Department of Biochemistry, Boston University School of Medicine, Boston, MA 02118, USA.
Analytical Biochemistry (Impact Factor: 2.22). 04/2010; 399(2):152-61. DOI: 10.1016/j.ab.2010.01.010
Source: PubMed


Oral sodium phenylbutyrate (SPB) is currently under investigation as a histone deacetylation (HDAC) inhibitor in Huntington disease (HD). Ongoing studies indicate that symptoms related to HD genetic abnormalities decrease with SPB therapy. In a recently reported safety and tolerability study of SPB in HD, we analyzed overall chromatographic patterns from a method that employs gradient liquid chromatography with series electrochemical array, ultraviolet (UV), and fluorescence (LCECA/UV/F) for measuring SPB and its metabolite phenylacetate (PA). We found that plasma and urine from SPB-treated patients yielded individual-specific patterns of approximately 20 metabolites that may provide a means for the selection of subjects for extended trials of SPB. The structural identification of these metabolites is of critical importance because their characterization will facilitate understanding the mechanisms of drug action and possible side effects. We have now developed an iterative process with LCECA, parallel LCECA/LCMS, and high-performance tandem MS for metabolite characterization. Here we report the details of this method and its use for identification of 10 plasma and urinary metabolites in treated subjects, including indole species in urine that are not themselves metabolites of SPB. Thus, this approach contributes to understanding metabolic pathways that differ among HD patients being treated with SPB.

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    • "For example, neuroblastoma cells differentiate in response to HDAC8-selective inhibitors or targeted knockdown of HDAC8 (Oehme et al., 2009b), and human leukemia differentiate after treatment with HDAC inhibitors FK228 and sodium phenylbutyrate (Savickiene et al., 2010). Sodium phenylbutyrate has been used clinically in the treatment of disorders such as maple syrup urine disease (Brunetti-Pierri et al., 2010), and there is growing interest in the neuroprotective properties of this compound and its metabolites (Gardian et al., 2005; Ryu et al., 2005; Petri et al., 2006; Hogarth et al., 2007; Ebbel et al., 2010). A recently completed Phase 2 study in patients with amyotrophic lateral sclerosis (Lou Gehrig's disease) concluded that blood levels of phenylbutyrate, and of its primary metabolite phenylacetate, increased with dosage, and that 9 g/day was effective for improving histone acetylation status (Cudkowicz et al., 2009). "
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