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Smith W, Diaz GA, Lichter-Konecki U, Berry SA, Harding CO, McCandless SE, LeMons C, Mauney J, Dickinson K, Coakley DF, Moors TL, Mokhtarani M, Mokhtarani M, Scharschmidt BF, Lee B. Ammonia control in children ages 2 months through 5 years with urea cycle disorders: comparison of sodium phenylbutyrate and glycerol phenylbutyrate. J Pediatr 2013; 162:1228-34, 1234.e1. [PMID: 23324524 PMCID: PMC4017326 DOI: 10.1016/j.jpeds.2012.11.084] [Citation(s) in RCA: 33] [Impact Index Per Article: 3.0] [Reference Citation Analysis] [What about the content of this article? (0)] [Affiliation(s)] [Abstract] [Key Words] [Track Full Text] [Journal Information] [Submit a Manuscript] [Subscribe] [Scholar Register] [Received: 08/02/2012] [Revised: 10/02/2012] [Accepted: 11/29/2012] [Indexed: 11/16/2022]
Abstract
OBJECTIVES To examine ammonia levels, pharmacokinetics, and safety of glycerol phenylbutyrate (GPB; also referred to as HPN-100) and sodium phenylbutyrate (NaPBA) in young children with urea cycle disorders (UCDs). STUDY DESIGN This open label switch-over study enrolled patients ages 29 days to under 6 years taking NaPBA. Patients underwent 24-hour blood and urine sampling on NaPBA and again on a phenylbutyric acid-equimolar dose of GPB and completed questionnaires regarding signs and symptoms associated with NaPBA and/or their UCD. RESULTS Fifteen patients (8 argininosuccinate lyase deficiency, 3 argininosuccinic acid synthetase deficiency, 3 ornithine transcarbamylase deficiency, 1 arginase deficiency) ages 2 months through 5 years enrolled in and completed the study. Daily ammonia exposure (24-hour area under the curve) was lower on GPB and met predefined noninferiority criteria (ratio of means 0.79; 95% CI 0.593-1.055; P=.03 Wilcoxon; 0.07 t test). Six patients experienced mild adverse events on GPB; there were no serious adverse events or significant laboratory changes. Liver tests and argininosuccinic acid levels among patients with argininosuccinate lyase deficiency were unchanged or improved on GPB. Eleven of 15 patients reported 35 symptoms on day 1; 23 of these 35 symptoms improved or resolved on GPB. Mean systemic exposure to phenylbutyric acid, phenylacetic acid, and phenylacetylglutamine (PAGN) were similar and phenylacetic acid exposure tended to be higher in the youngest children on both drugs. Urinary PAGN concentration was greater on morning voids and varied less over 24 hours on GPB versus NaPBA. CONCLUSIONS GPB results in more evenly distributed urinary output of PAGN over 24 hours were associated with fewer symptoms and offers ammonia control comparable with that observed with NaPBA in young children with UCDs.
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Affiliation(s)
- W Smith
- Maine Medical Center, 1577 Congress Street, 2nd Floor, Portland, ME 04102
| | - GA Diaz
- Mount Sinai School of Medicine, Department of Genetics and Genomic Sciences, Department of Pediatrics, 1428 Madison Avenue, New York, NY 10029
| | - U Lichter-Konecki
- Children’s National Medical Center, Division of Genetics and Metabolism, 111 Michigan Avenue NW #1950, Washington, DC 20010
| | - SA Berry
- University of Minnesota, 420 Delaware St. SE, MMC 75, Minneapolis, MN 55455
| | - CO Harding
- Oregon Health Sciences University, 3181 SW Sam Jackson Park Road, A036/B198, Mailcode L103, Portland, OR 97239
| | - SE McCandless
- University Hospitals Case Medical Center and Case Western Reserve University, 11100 Euclid Avenue, Cleveland, OH 44106
| | - C LeMons
- National Urea Cycle Disorders Foundation, 75 South Grand Avenue, Pasadena, CA 91105
| | - J Mauney
- Chiltern, 2520 Independence Blvd., Ste. 202, Wilmington NC
| | - K Dickinson
- Hyperion Therapeutics, 601 Gateway Blvd, Suite 200, South San Francisco, CA 94080
| | - DF Coakley
- Hyperion Therapeutics, 601 Gateway Blvd, Suite 200, South San Francisco, CA 94080
| | - TL Moors
- Hyperion Therapeutics, 601 Gateway Blvd, Suite 200, South San Francisco, CA 94080
| | - M Mokhtarani
- Hyperion Therapeutics, 601 Gateway Blvd, Suite 200, South San Francisco, CA 94080
| | - M Mokhtarani
- Hyperion Therapeutics, 601 Gateway Blvd, Suite 200, South San Francisco, CA 94080
| | - BF Scharschmidt
- Hyperion Therapeutics, 601 Gateway Blvd, Suite 200, South San Francisco, CA 94080
| | - B Lee
- Baylor College of Medicine, One Baylor Plaza, Room R814, Houston, TX 77030,Howard Hughes Medical Institute, One Baylor Plaza, Room R814, Houston, TX 77030
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Mokhtarani M, Diaz GA, Rhead W, Lichter-Konecki U, Bartley J, Feigenbaum A, Longo N, Berquist W, Berry SA, Gallagher R, Bartholomew D, Harding CO, Korson MS, McCandless SE, Smith W, Vockley J, Bart S, Kronn D, Zori R, Cederbaum S, Dorrani N, Merritt JL, Sreenath-Nagamani S, Summar M, Lemons C, Dickinson K, Coakley DF, Moors TL, Lee B, Scharschmidt BF. Urinary phenylacetylglutamine as dosing biomarker for patients with urea cycle disorders. Mol Genet Metab 2012; 107:308-14. [PMID: 22958974 PMCID: PMC3608516 DOI: 10.1016/j.ymgme.2012.08.006] [Citation(s) in RCA: 31] [Impact Index Per Article: 2.6] [Reference Citation Analysis] [What about the content of this article? (0)] [Affiliation(s)] [Abstract] [MESH Headings] [Grants] [Track Full Text] [Journal Information] [Submit a Manuscript] [Subscribe] [Scholar Register] [Received: 06/18/2012] [Revised: 08/07/2012] [Accepted: 08/07/2012] [Indexed: 11/22/2022]
Abstract
UNLABELLED We have analyzed pharmacokinetic data for glycerol phenylbutyrate (also GT4P or HPN-100) and sodium phenylbutyrate with respect to possible dosing biomarkers in patients with urea cycle disorders (UCD). STUDY DESIGN These analyses are based on over 3000 urine and plasma data points from 54 adult and 11 pediatric UCD patients (ages 6-17) who participated in three clinical studies comparing ammonia control and pharmacokinetics during steady state treatment with glycerol phenylbutyrate or sodium phenylbutyrate. All patients received phenylbutyric acid equivalent doses of glycerol phenylbutyrate or sodium phenylbutyrate in a cross over fashion and underwent 24-hour blood samples and urine sampling for phenylbutyric acid, phenylacetic acid and phenylacetylglutamine. RESULTS Patients received phenylbutyric acid equivalent doses of glycerol phenylbutyrate ranging from 1.5 to 31.8 g/day and of sodium phenylbutyrate ranging from 1.3 to 31.7 g/day. Plasma metabolite levels varied widely, with average fluctuation indices ranging from 1979% to 5690% for phenylbutyric acid, 843% to 3931% for phenylacetic acid, and 881% to 1434% for phenylacetylglutamine. Mean percent recovery of phenylbutyric acid as urinary phenylacetylglutamine was 66.4 and 69.0 for pediatric patients and 68.7 and 71.4 for adult patients on glycerol phenylbutyrate and sodium phenylbutyrate, respectively. The correlation with dose was strongest for urinary phenylacetylglutamine excretion, either as morning spot urine (r = 0.730, p < 0.001) or as total 24-hour excretion (r = 0.791 p<0.001), followed by plasma phenylacetylglutamine AUC(24-hour), plasma phenylacetic acid AUC(24-hour) and phenylbutyric acid AUC(24-hour). Plasma phenylacetic acid levels in adult and pediatric patients did not show a consistent relationship with either urinary phenylacetylglutamine or ammonia control. CONCLUSION The findings are collectively consistent with substantial yet variable pre-systemic (1st pass) conversion of phenylbutyric acid to phenylacetic acid and/or phenylacetylglutamine. The variability of blood metabolite levels during the day, their weaker correlation with dose, the need for multiple blood samples to capture trough and peak, and the inconsistency between phenylacetic acid and urinary phenylacetylglutamine as a marker of waste nitrogen scavenging limit the utility of plasma levels for therapeutic monitoring. By contrast, 24-hour urinary phenylacetylglutamine and morning spot urine phenylacetylglutamine correlate strongly with dose and appear to be clinically useful non-invasive biomarkers for compliance and therapeutic monitoring.
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Affiliation(s)
- M Mokhtarani
- Hyperion Therapeutics, 601 Gateway Blvd, Suite 200, South San Francisco, CA 94080, USA.
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