This was a long-term safety study HPN-100 in urea cycle disorder (UCD) subjects. Subjects were assessed regularly for safety and control of their venous ammonia. Hyperammonemic events were characterized with respect to contributing factors, such as intercurrent illness, diet, and noncompliance with medication.

This was a one year long-term safety study of HPN-100 in UCD subjects. Subjects were assessed regularly for safety and control of their venous ammonia. Hyperammonemic events were characterized with respect to contributing factors, such as intercurrent illness, diet, and noncompliance with medication.

Forty subjects with a diagnosis of UCD who completed Study HPN-100-006 were enrolled.

Twenty additional UCD subjects ≥ 6 years of age were enrolled. These subjects included those who did not qualify for HPN-100-006 [e.g., subjects between the ages of 6-17; subjects with other UCD subtypes or adult subjects who have not taken sodium phenylbutyrate (NaPBA) in the past 6 months, etc.]. For adult subjects not receiving NaPBA in the past 6 months, subjects must, in the judgment of the investigator, be anticipated to benefit from the addition of a nitrogen-scavenging agent to their current treatment. See the inclusion criteria for examples of clinical evidence of potential benefit.

Monthly assessments included safety laboratory tests, amino acid panel, vital signs, electrocardiogram (ECG) monitoring, venous ammonia, and blood and urine metabolites. Adverse events (AEs) and concomitant medications were recorded on an ongoing basis.

Study acquired from Horizon in 2024.

Inclusion Criteria:

• Male and female subjects who completed HPN-100-006:

  *Additionally, approximately 20 UCD subjects ≥ 6 years of age may be enrolled who have not participated in HPN-100-006. These subjects may include those who did not qualify HPN-100-006 (e.g., subjects between the ages of 6-17 years, subjects with other UCD subtypes, or adult subjects who have not taken sodium phenylbutyrate (NaPBA) in the past 6 months, etc.). For adult subjects not receiving NaPBA in the past 6 months, subjects must, in the judgment of the investigator, be anticipated to benefit from the addition of a nitrogen-scavenging agent to their current treatment. Clinical evidence of potential benefit from introduction of an ammonia-scavenging agent might include a recent history (in the past year) of clinically overt hyperammonemia accompanied by a venous ammonia ≥ 100 μmol/L, a recent history (within the past year) of protein intolerance, or a history of abnormally high venous ammonia levels accompanied by symptoms (e.g., headache) that might reasonably be attributed to hyperammonemia.

• Signed informed consent by subject and/or subject's legally acceptable representative.

• Diagnosis of urea cycle disorder (enzyme or transporter deficiency) confirmed via enzymatic, biochemical, or genetic testing.

• Able to perform and comply with study activities, including blood draws.

• Negative pregnancy test for all females of childbearing potential.

• All females of childbearing potential and all sexually active males must agree to use an acceptable method of contraception throughout the study.

Exclusion Criteria:

• Screening venous ammonia level of ≥ 100 μmol/L or signs and symptoms indicative of hyperammonemia; subjects may be re-screened after their venous ammonia is controlled, at the discretion of the investigator.
• History of 4 or more hyperammonemic events as defined in Section 3.5.1 in the preceding 12 months.
• Active infection (viral or bacterial) or any other condition that may increase venous ammonia levels.
• Any clinical or laboratory abnormality or medical condition that, at the discretion of the investigator, may put the subject at increased risk by participating in this study.
• Use of any medication known to significantly affect renal clearance (e.g., probenecid) or to increase protein catabolism (e.g., corticosteroids), or other medication known to increase venous ammonia levels (e.g., valproate), within the 24 hours prior to Day 1 and throughout the study.
• History of QTc (QT interval corrected) prolongation, or a QTc interval ≥ 450 msec or an increase of ≥ 60 msec during the previous HPN-100 study if applicable.
• Known hypersensitivity to PAA or PBA.
• Liver transplant, including hepatocellular transplant.
• Breastfeeding or lactating females.

De-identified individual patient data for variables necessary to address the specific research question in an approved data sharing request.

Data sharing requests relating to this study will be considered beginning 18 months after the study has ended and either 1) the product and indication have been granted marketing authorization in both the US and Europe or 2) clinical development for the product and/or indication discontinues and the data will not be submitted to regulatory authorities. There is no end date for eligibility to submit a data sharing request for this study.

Qualified researchers may submit a request containing the research objectives, the Amgen product(s) and Amgen study/studies in scope, endpoints/outcomes of interest, statistical analysis plan, data requirements, publication plan, and qualifications of the researcher(s). In general, Amgen does not grant external requests for individual patient data for the purpose of re-evaluating safety and efficacy issues already addressed in the product labelling. Requests are reviewed by a committee of internal advisors. If not approved, a Data Sharing Independent Review Panel will arbitrate and make the final decision. Upon approval, information necessary to address the research question will be provided under the terms of a data sharing agreement. This may include anonymized individual patient data and/or available supporting documents, containing fragments of analysis code where provided in analysis specifications. Further details are available at the URL below.