BioMarin, Serono say all primary, secondary endpoints met in Phenoptin study

By Elaine Rigoli

Tampa, Fla., March 15 - BioMarin Pharmaceutical, Inc. and Serono, Inc. announced Wednesday the 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), a genetic disorder.

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 a placebo, according to a company news release.

"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," said Emil Kakkis, chief medical officer of BioMarin, in a statement.

"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% or more) following treatment with Phenoptin in a phase 2 screening study, the release said.

The patients were randomly assigned to receive a 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 six, adjusted for baseline levels. A total of 87 patients completed six weeks of treatment, the release said.

Patients treated with Phenoptin for six weeks had a mean decrease in blood Phe level of 236 mM (29%) compared to a mean increase of 3 mM (3%) in the placebo group (p<0.0001). Prior to treatment, patients in the Phenoptin group and placebo group had mean blood Phe levels of 843 mM and 888 mM, respectively.

At week six, the percentage of patients in the Phenoptin group with blood Phe levels less than or equal to 600 mM was 54% compared to 23% in the placebo group (p=0.004). At baseline the proportions were 17% and 19% for the Phenoptin and placebo groups, respectively.

The mean blood Phe level at each visit among patients receiving Phenoptin showed a consistent reduction compared to the blood Phe levels in patients receiving a placebo (p<0.001) throughout the six-week period, the release said.

Serono is a global biotechnology products company located in Geneva, Switzerland.

BioMarin, located in Novato, Calif., develops and commercializes innovative biopharmaceuticals for serious diseases and medical conditions.

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