BioMarin Pharmaceutical Inc. and Serono announced positive results of a Phase 3, double-blind, placebo-controlled clinical study of Phenoptin (sapropterin dihydrochloride), an investigational oral small molecule for the treatment of phenylketonuria (PKU). Results confirm that all pre-specified primary and secondary endpoints were met and data from the Phase 3 study demonstrate a statistically significant reduction at six weeks in blood phenylalanine (Phe) levels (p<0.0001) in patients receiving Phenoptin, compared with those receiving placebo.

Emil Kakkis, Chief Medical Officer of BioMarin stated, "This is an exciting day for PKU patients worldwide as a simple oral treatment that could potentially help them reach their treatment goals is now one step closer to becoming a reality. For many patients with genetic diseases, not enough has been done to push forward important new treatments, and we are particularly happy to be able to collaborate with the numerous clinicians and investigators worldwide who have worked on tetrahydrobiopterin and transform their hard work into what could become the first approved drug therapy for this disease."

The study enrolled 89 patients with elevated blood Phe levels aged eight years and above at 29 sites in the United States, Europe and Canada. All patients had demonstrated a reduction in blood Phe levels (approximately 30 percent or more) following treatment with Phenoptin in a Phase 2 screening study.

The patients were randomly assigned to receive placebo or 10 mg/kg of Phenoptin daily for six weeks. Patients were evaluated every two weeks for changes in blood Phe levels and adverse events. The primary endpoint of the study was the difference in mean blood Phe levels between the placebo and Phenoptin groups at Week 6, adjusted for baseline levels. A total of 87 patients completed six weeks of treatment.

Following the six-week double-blind study, patients were eligible to enrol into an on-going 22 week Phase 3 open-label extension study designed to further evaluate the long-term safety and efficacy of Phenoptin, as well as dose titration. BioMarin and Serono expect to file marketing authorization applications for Phenoptin for PKU in the United States and European Union in 2007. BioMarin has licensed to Serono exclusive rights for Phenoptin outside of the United States and Japan, added the release.