Phenoptin Significantly Increases Phenylalanine Tolerance in BH4-Responsive Patients; All Pre-Specified Endpoints Met GENEVA, Switzerland, January 16 /PRNewswire-FirstCall/ -- Merck Serono (virt-x: SEO and NYSE: SRA) today announced positive results from the Phase III diet study of Phenoptin(TM) (sapropterin dihydrochloride), in combination with diet, in 4-12 year old patients. Phenoptin is an investigational oral small molecule, being developed in partnership with BioMarin, for the treatment of patients with phenylketonuria (PKU), who have elevated phenylalanine (Phe) levels. The results show that all pre-specified efficacy and safety endpoints of the double-blind, placebo-controlled study were met. Phenoptin treatment caused a significant increase in phenylalanine tolerance as well as a reduction in blood phenylalanine levels. In addition, the data showed that Phenoptin was well tolerated in younger PKU patients who were under dietary control. Dr. Harvey Levy, Professor of Pediatrics at Harvard Medical School and Senior Associate in Medicine and Genetics at Children's Hospital Boston, stated, "This is the first time a controlled study has demonstrated the potential of tetrahydrobiopterin, or 6R-BH4, to liberalize diet in PKU patients. If approved, Phenoptin offers patients who respond to BH4 a real opportunity to relax their diets and the possibility to perhaps reduce or even eliminate the need for nutritional supplementation from medical food." Key findings from the study: - In the primary endpoint, Phenoptin enabled a mean increase of 20.9 mg/kg/day in Phe supplementation for those patients on Phenoptin (p