As well as having shown potential in the treatment of phenylketonuria (PKU), there is preliminary clinical evidence that suggests that the active ingredient in Phenoptin (sapropterin hydrochloride), a synthetic form of the naturally occurring enzyme cofactor 6R-BH4, may also be useful in the treatment of other serious diseases, including diabetes and cardiovascular diseases.
By the terms of their agreement, Serono acquires exclusive rights to market the products in all territories outside the US and Japan and BioMarin retains exclusive rights to market the products in the US. Serono will make an upfront payment of $25 million to BioMarin, and will make additional milestone payments of up to $232 million based on the successful development and registration of both products in multiple indications, of which $45 million are associated specifically with Phenoptin in PKU.
Serono will also pay BioMarin undisclosed royalties on its net sales of the products. The companies will share equally all development costs following successful completion of phase II trials for each product candidate in each indication.
BioMarin is currently investigating Phenoptin in a phase III clinical trial for the treatment of PKU. PKU is an inherited metabolic disease caused by a deficiency of the enzyme phenylalanine hydroxylase, resulting in elevated levels of phenylalanine in the blood, which can result in serious neurological damage. There is currently no approved drug to treat PKU, which affects at least 50,000 diagnosed patients under the age of 40 worldwide.
Phenylase (phenylalanine ammonia lyase), an enzyme substitution therapy for the treatment of severe forms of PKU, is currently in preclinical development.