Merck Serono has reversed its deal with BioMarin for the rights to Kuvan and Peg-Pal as it seeks to strengthen its focus on its core businesses.

Merck acquired the rights to the two drugs in markets outside of the US and Japan in 2005. Kuvan (sapropterin) is the first treatment approved for hyperphenylalaninemia due to the rare metabolism disorder phenylketonuria (PKU) and has orphan drug exclusivity in Europe until 2020. Peg-Pal (pegvaliase) is an investigational treatment that is also designed to treat PKU.

Now, though, it is returning those rights to BioMarin for an upfront payment of  $379 million for Kuvan – equal to five times the drug’s annual sales – plus up to $206 million in additional milestones for both products.

“Returning the rights of these drugs to BioMarin will allow Merck to fully focus on its core businesses, as well as further align R&D investment behind key strategic areas," says Belén Garijo, member of the executive board of Merck and CEO of healthcare.

Over the past years, Merck has been realigning its healthcare businesses to focus on neurology, oncology, immuno-oncology and immunology.