BioMarin Pharmaceutical Inc. announced that it expects to initiate a six-week, multi-centre, international, double-blind, placebo-controlled phase 3 clinical trial of Phenoptin (sapropterin hydrochloride) in phenylketonuria (PKU) in the first quarter of 2005, based on its recent meeting with the US FDA.

As a primary efficacy endpoint, the trial will measure the changes in blood phenylalanine (Phe) level in patients receiving Phenoptin compared to patients receiving placebo.

"After discussing the critical components of our plan with the FDA, we can now advance Phenoptin into late-stage clinical development. Based on the anticipated patient enrolment schedule, we expect to announce results of the double-blind portion of the Phase 3 clinical trial in the second half of 2005," stated Louis Drapeau, acting CEO at BioMarin.

Phenoptin (sapropterin hydrochloride, also known as 6R-BH4) is an investigational oral small molecule therapeutic for the treatment of primarily the moderate to mild forms of the genetic disease phenylketonuria (PKU). BioMarin received orphan drug designation for Phenoptin to treat PKU from both the FDA and EMEA. BioMarin would receive seven years of market exclusivity in United States and 10 years in the European Union if it were first to receive approval for 6R-BH4 to treat PKU.

PKU, a genetic disorder affecting at least 50,000 diagnosed patients under the age of 40 in the developed world, an estimated half of whom have the moderate to mild form of the disease, is caused by a deficiency of the enzyme, phenylalanine hydroxylase (PAH). As a result of global newborn screening efforts implemented in the 1960s and early 1970s, virtually all PKU patients in developed countries have been diagnosed at birth. The only treatment currently available for PKU patients is a highly restrictive and expensive medical food diet that most patients find difficult to maintain.