To Evaluate the Safety of Long-term Use of HPN-100 in the Management of Urea Cycle Disorders (UCDs)

Blood samples were collected for the assessment of plasma ammonia concentrations at baseline, at least every 6 months, at all unscheduled visits, and at the end of study participation. Ammonia level data were obtained from different local laboratories and each laboratory may have used a slightly different normal reference range. Therefore, the ammonia level data were normalized to a standard laboratory reference range before performing any analysis of ammonia data.

An hyperammonemic crisis (HAC) was defined as clinical symptoms associated with a venous ammonia concentration of ≥100 μmol/L.

An hyperammonemic crisis (HAC) was defined as clinical symptoms associated with a venous ammonia concentration of ≥100 μmol/L. Peak observed ammonia concentrations during an HAC, precipitating factors, and symptoms recorded as suggestive to hyperammonemia were documented. There can be multiple contributing factors to an hyperammonemic crisis; in some cases several causes were identified.

The Wechsler Abbreviated Scale of Intelligence (WASI) was administered to adults and pediatric participants who were at least 6 years of age. It was used to estimate general intellectual ability (IQ) based on the vocabulary and matrix reasoning subtests. The vocabulary subtest included 4 images and 38 verbal items. In the matrix reasoning subtest, the participant viewed 35 incomplete grid patterns and was asked to complete the pattern using responses from 5 possible choices. The number of correct responses for each of the subtests was converted to a T-score using the WASI assessment manual; T-scores are standard scores with a mean of 50 and a standard deviation (SD) of 10. Raw scores for the 2 subtests were summed, and converted to a standard score (mean of 100 with SD of 15) for the general IQ score for adults and to a T-score for children in accordance with the WASI manual. Higher scores indicate a higher level of intelligence.

The Child Behavior Checklist (CBCL) is a widely-used method of identifying problem behavior. Two versions of the CBCL were used in this study; the assessment for children 6-18 years of age was used for participants ≥6 years of age, and the assessment for children 1.5-5 years of age was used for those who were at least 5 years old but <6 years of age. Parents/caregivers answered questions (120 and 100 questions, respectively, for the older and younger populations) using a 3-point Likert scale (0= not true; 1= somewhat or sometimes true; 2 =very true or often true). Using a computer program, responses to similar questions were grouped together into 20 domains (e.g., activities, social, school, etc.), and domain response scores were converted to T-scores and percentiles. A mean score of 50 is average, with a standard deviation of 10 points. Higher scores indicate greater problems. The total problems score is the sum of all of the problem items.

The Behavior Rating Inventory of Executive Function (BRIEF) is designed to assess executive functioning in children and adolescents ages 5 to 18 years of age. Parents/caregivers answered 86 questions on a 3-point scale (never, sometimes, often). Similar questions were grouped together into 8 scales; these scales were summed to produce 2 index measures and a global executive composite score. Raw scores for the indices/scales and composite score were converted to T-scores with corresponding 90% confidence intervals using computer software. Higher T-scores indicate a higher level of dysfunction.

The California Verbal Learning Test - Second Edition (CVLT-II) assesses recall and recognition of word lists over several immediate- and delayed-memory trials. In the learning phase, adult participants were presented a list of 16 words (List A; 4 words each in 4 categories [e.g., fruit, toys, etc.]) for 5 trials, but words from the same category were never presented consecutively. An interference list (List B) of 16 different words was then presented for 1 trial. Short-and long-delay recalls for List A, yes/no recognition trials of List A, and a forced-choice recognition trial of List A was also administered. The total score for the 5 immediate-recall trials was converted to a T-score. Lower T-scores reflect worse performance.

The California Verbal Learning Test - Second Edition (CVLT-II) assesses recall and recognition of word lists over several immediate- and delayed-memory trials. In the learning phase, adult participants were presented a list of 16 words (List A; 4 words each in 4 categories [e.g., fruit, toys, etc.]) for 5 trials, but words from the same category were never presented consecutively. An interference list (List B) of 16 different words was then presented for 1 trial. Short-and long-delay recalls for List A, yes/no recognition trials of List A, and a forced-choice recognition trial of List A was also administered. The scores for the learning slope, the short- and long-delay scores and total word recognition discrimination scores were converted to Z-scores by computer software. The CVLT-II Z-score has a mean of 0 and a standard deviation of 1. Negative scores indicate below-average performance.