San Diego, US May 23, 2007 Shire plc (LSE: SHP, NASDAQ: SHPGY, TSX: SHQ) announced today the positive results of studies of the investigational medication guanfacine extended release (GXR, previously referred to as SPD503), a selective alpha-2A-adrenoceptor agonist. These data from two short-term phase III placebo-controlled studies and two long-term phase III open-label studies, presented at the 2007 American Psychiatric Association (APA) annual meeting, demonstrated that GXR significantly improved all core symptoms of Attention-Deficit/Hyperactivity Disorder (ADHD) in children aged 6 to 17 years.

"Guanfacine extended release, the first selective alpha-2A-adrenoceptor agonist to be tested in well-controlled studies as a treatment for ADHD, holds potential based on the significant improvements in ADHD symptoms documented in four studies of this investigational drug," stated co-author Joseph Biederman, M.D., lead investigator, chief of clinical and research program in pediatric psychopharmacology at Massachusetts General Hospital and professor of psychiatry at Harvard Medical School. "Moreover, these data presented at this medical conference add evidence that GXR when dosed once daily may continue to control children's ADHD symptoms for up to 24 months."

GXR, a nonstimulant, is not a controlled substance and does not appear to have a mechanism for potential abuse or dependence. Shire submitted a New Drug Application (NDA) for GXR on August 24, 2006, which is currently under FDA review. The NDA provided data on GXR 1 mg to 4 mg taken once daily for the treatment of children and adolescents with ADHD.

GXR Yielded Significant Reductions in ADHD-RS-IV Scores in Two Short-Term Trials

Results from two short-term, double-blind, randomized phase III clinical trials presented at this medical conference, demonstrated that GXR significantly controlled all core symptoms of ADHD, including inattention, hyperactivity and impulsiv
'"/>

Contact: Marion E. Glick
212-601-8273
Porter Novelli
23-May-2007