BioMarin Pharmaceuticals announced results from the PKU-016 ASCEND study, the largest randomized controlled study evaluating neuropsychiatric outcomes in phenylketonuria (PKU) patients treated with the approved drug Kuvan (sapropterin dihydrochloride).

The PKU-015 study is a double-blind, placebo-controlled, randomized study to evaluate the safety and therapeutics effects of Kuvan on neuropsychiatric symptoms in patients with PKU. The study enrolled 206 patients, 118 of whom were responders to Kuvan as determined by a drop in blood phenylalanine (Phe) levels. The study included a two-week screening period, a 13-week double-blind randomized treatment period and a 13-week open-label treatment period at a dose of 20 mg/kg/day.

The study evaluated medically important symptoms similar to attention deficit hyperactivity disorder (ADHD) in PKU patients whose blood levels of Phe were reduced by Kuvan. The primary endpoint of the study was evaluated using an attention deficit hyperactivity rating scale (ADHD-RS), commonly used to evaluate symptoms of inattentiveness and hyperactivity. Kuvan improved the ADHD-RS (P=0.085), driven by a statistically significant change in the inattention component of the score (P=0.036). PKU patients have a lower degree of hyperactivity as compared to ADHD patients, which likely resulted in the less prominent benefits in this domain. The neurocognitive benefit of Kuvan in patients who respond to Kuvan was corroborated by the Behavior Rating Inventory of Executive Function (BRIEF), in children who were rated by their parents. Moderate to severe inattention deficit affected approximately one-third of patients in the study. Preliminary analysis of safety indicates that it is consistent with the general experience with Kuvan.

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