Phase 3 Study of Lisdexamfetamine Dimesylate (LDX) for Maintenance Treatment of ADHD in Children and Adolescents

Shire announced results of a Phase 3 study which demonstrated the long-term maintenance of efficacy of lisdexamfetamine dimesylate (LDX) in children and adolescents aged 6–17 years with moderately symptomatic Attention-Deficit/Hyperactivity Disorder (ADHD).

The trial was a double-blind, placebo-controlled, randomized withdrawal, multicenter, extension study to evaluate the long-term maintenance of efficacy, as well as safety, of LDX. Children and adolescents diagnosed with ADHD were treated with LDX (30, 50 or 70mg/day) during an open-label period (comprising dose optimization, maintenance, and fixed dose periods) of at least 26 weeks before entering a 6-week double-blind randomized withdrawal period, where subjects received either LDX or placebo.

Results showed maintenance of efficacy in children and adolescents who continued to receive LDX, as demonstrated by a significantly lower proportion of ADHD treatment failures (13.5%) in this group, compared with placebo (65.8%); and the majority of placebo-treated subjects who met protocol-defined ADHD symptom relapse criteria did so within 2 weeks following randomization. Relapse or treatment failure in this study was determined to have occurred when a subject has both a ≥50% increase (or worsening) in ADHD-Rating Scale-IV (ADHD-RS-IV) total score, and a ≥2-point increase (or worsening) in Clinical Global Impressions-Severity of Illness (CGI-S) rating scale score, at any double-blind visit relative to the respective scores at randomization.

LDX (Vyvanse; Shire) is a schedule II narcotic approved for the treatment of ADHD in children and adolescents aged 6–17 and adults, as well as maintenance treatment of ADHD in adults 18–55 years of age. A stimulant, LDX is a prodrug of dextroamphetamine. After oral administration, LDX is rapidly absorbed from the gastrointestinal tract and hydrolyzed primarily in whole blood to dextroamphetamine, which is responsible for the drug's activity.

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