Long-term Outcome of N-Carbamylglutamate Treatment in Propionic Acidemia and Methylmalonic Acidemia

Plain-language summary

Background: Very few drugs exist that treat hyperammonemia, specifically PA and MMA. Diet restrictions and alternate pathway agents are the current primary treatments, but they frequently fail to prohibit brain damage. Orthotopic liver transplantation cures the hyperammonemia of urea cycle disorders, but organ availability is limited and the procedure is highly invasive and requires life-long immunosuppression. A drug that could repair or stimulate a dysfunctional urea cycle such as this would have several advantages over current therapy. A drug called N-carbamyl-L-glutamate, Carglumic acid (NCG or Carbaglu)has recently been found to be virtually curative of another urea cycle defect called NAGS deficiency. In this disorder, treatment with NCG alone normalizes ureagenesis, blood ammonia and glutamine levels, allows normal protein tolerance and restores health. Knowledge from this study is being applied to acquired hyperammonemia, specifically in patients with propionic PA and MMA, to try and improve neurodevelopmental outcomes by improving the hyperammonemia. Aims: The overall objective of this project is to determine whether treatment of acute hyperammonemia with Carglumic acid in propionic acidemia (PA), methylmalonic acidemia (MMA) changes the long-term outcome of disease and to determine if it is effective in restoring urine ammonia levels to normal levels.

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