Arginine and Buphenyl in Patients With Argininosuccinic Aciduria (ASA), a Urea Cycle Disorder

Phase 2

Completed

Conditions: Argininosuccinic Aciduria
Amino Acid Metabolism, Inborn Errors
Urea Cycle Disorders

Interventions: Drug: Sodium Phenylbutyrate
Drug: Arginine

Registration Number: NCT00345605

Lead Sponsor: Brendan Lee

Brief Summary: Urea cycle disorders are inherited illnesses in which the body does not produce enough of the chemicals that remove ammonia, a byproduct of protein metabolism, from the blood stream. Elevated ammonia levels can lead to brain damage and death. Argininosuccinic aciduria (ASA) is a type of urea cycle disorder that is characterized specifically by high levels of argininosuccinic acid, a chemical involved in the urea cycle. People with ASA are at risk for serious liver damage, which may be due to the elevated levels of argininosuccinic acid. Sodium phenylbutyrate (Buphenyl-TM) is a drug that has been used to treat other types of urea cycle disorders. This study will evaluate whether Buphenyl-TM in conjunction with decreased arginine dose (in addition to a normal regimen of protein) will improve short-term liver function and decrease plasma citrulline and ASA levels in people with ASA.

Detailed Description: The cause of liver damage in people with ASA is unknown. However, because ASA is the only urea cycle disorder that is characterized by both liver damage and elevated levels of argininosuccinic acid, researchers believe that the elevated acid levels cause the liver damage. Common treatments for urea cycle disorders include a low-protein diet and arginine supplementation, which, when combined, help to decrease ammonia levels in the blood. Buphenyl-TM may aid in lowering ammonia and argininosuccinic acid levels. Although Buphenyl-TM has been FDA-approved for use in people with some types of urea cycle disorders, there is little information on the effectiveness of the drug in children with ASA. This study will evaluate whether treatment of ASA patients with Buphenyl-TM in conjunction with lowered doses of arginine improves liver function as measured by short-term assessment of synthetic activity and the use of stable isotope tracers to assess ureagenesis and nitric oxide production.

Initially, participants in this double-blind, placebo-controlled, crossover study will undergo a 3-day washout period during which no Buphenyl-TM will be given. They will then be randomly assigned to one of two groups: either Buphenyl-TM (500 mg/kg/day or 10 grams/m2) and arginine (100 mg/kg/day or 2 grams/m2)), or arginine alone (500 mg/kg/day or 10 grams/m2). Participants will remain on this initial treatment arm for 1 week, at the conclusion of which an assessment of hepatic synthetic function, ureagenesis, and nitric oxide production will be performed. After this assessment, participants will undergo a second 3-day washout and then crossover to the other treatment arm for 1 week. At the end of the 1-week treatment period, a second assessment will be performed. During the washout period before each treatment period, no Buphenyl-TM will be administered, and arginine will be administered at the standard therapeutic dose of 500 mg/kg/day or 10 grams/2.

Recruitment & Eligibility

Status: COMPLETED

Sex: All

Target Recruitment: 12

Inclusion Criteria

Has confirmed diagnosis of ASA by amino acid or enzyme assay
Has a history of adequate compliance to the diet and treatment
Able to take oral or G-tube medication
Able to perform 24 hour urine collection
Agrees to travel to Baylor College of Medicine
If female, of child bearing potential, and sexually active, agrees to use an acceptable method of birth control
Greater than 5 years of age

Exclusion Criteria

Has a history of congestive heart failure, severe renal insufficiency, or any condition that causes sodium retention or edema
Currently taking Probenecid, Haloperidol, Valproate or oral corticosteroids
Pregnant or lactating
Currently being treated for an acute illness
Has co-morbid associations causing difficulties in the detection of hyperammonemic episodes, liver damage, or difficulties in the diet compliance
Has known hypersensitivity to sodium phenylbutyrate
Has taken any experimental medication within the last 30 days
Has renal insufficiency with creatinine greater than 1.5 mg/dl at screening

Study & Design

Study Type: INTERVENTIONAL

Study Design: CROSSOVER

Arm && Interventions

Group	Intervention	Description
LDA	Sodium Phenylbutyrate	Low Dose Arm Wash-out followed by 7 days of: Arg 100 mg/kg/d or 2 g/m2 BSA NaPBA 500 mg/kg/d or 10 g/m2 BSA
HDA	Sodium Phenylbutyrate	High Dose Arm Wash-out then 7 days of: Arg 500 mg/kg/d or 10 g/m2 BSA Placebo instead of NaPBA
HDA	Arginine	High Dose Arm Wash-out then 7 days of: Arg 500 mg/kg/d or 10 g/m2 BSA Placebo instead of NaPBA
LDA	Arginine	Low Dose Arm Wash-out followed by 7 days of: Arg 100 mg/kg/d or 2 g/m2 BSA NaPBA 500 mg/kg/d or 10 g/m2 BSA

Primary Outcome Measures

Name	Time	Method
Measures of Liver Function: AST and ALT	Measured after each 1-week treatment period	Plasma aspartate aminotransferase (AST) and alanine aminotransferase (ALT) levels were measured.
Measures of Liver Function: PT and PTT	Measured after each 1-week treatment period	Prothrombin time (PT) and partial thromboplastin time (PTT) were measured PT measures factors I (fibrinogen), II (prothrombin), V, VII, and X, while PTT is a performance indicator of the efficacy of the common coagulation pathways.
Measures of Liver Function: Coagulation Factors	Measured after each 1-week treatment period	Plasma levels of coagulation factors I and IX were used as measures of hepatic synthetic function since the treatment duration was short.
Measures of Liver Function: INR	Measured after each 1-week treatment period	The result (in seconds) for a prothrombin time performed on a normal individual will vary according to the type of analytical system employed. This is due to the variations between different batches of manufacturer's tissue factor used in the reagent to perform the test. The INR was devised to standardize the results. Each manufacturer assigns an ISI value (International Sensitivity Index) for any tissue factor they manufacture. The ISI value indicates how a particular batch of tissue factor compares to an international reference tissue factor. The ISI is usually between 1.0 and 2.0. The INR is the ratio of a patient's prothrombin time to a normal (control) sample, raised to the power of the ISI value for the analytical system being used.

Secondary Outcome Measures

Name	Time	Method
Argininosuccinic Acid Levels	Measured after each 1-week treatment period
Arginine Levels	Measured after each 1-week treatment period
Urea Production Rate	Measured after each 1-week treatment period