US drugmaker Alexion Pharmaceuticals has offered to buy Sweden’s Wilson Therapeutics in a deal worth approximately $855 million.

Stockholm-based Wilson develops novel therapies for patients with rare copper-mediated disorders. Its lead product is WTX101, which is currently in Phase 3 development for treating Wilson disease, a rare genetic disorder that leads to a build-up of copper in vital organs, such as the liver and brain. The condition can lead to severe liver disease as well as debilitating neurological morbidities such as impaired movement, gait, speech, swallowing and psychiatric disorders.

WTX101 is a first-in-class oral copper-binding agent with a unique mechanism of action and ability to access and bind copper from serum and promote its removal from the liver. The investigational therapy has received Fast Track designation in the US and Orphan Drug designation for treating Wilson disease in Europe and the US.

“WTX101 is an innovative product that addresses the underlying cause of the disease and has the potential to define a new standard of care in treating Wilson disease, an area that has not had a new treatment in over two decades,” said Alexion’s CEO, Ludwig Hantson. He added that Wilson Therapeutics is a strong strategic fit for Alexion, given the overlap with its current clinical and commercial focus on metabolic and neurologic disorders, as well as an important first step in rebuilding the company’s clinical pipeline.

The boards of both companies have unanimously approved the offer and Alexion said it had so far obtained shareholder support for 73.4% of outstanding shares. The offer is subject to regulatory approval but is expected to close in the second quarter. Alexion is funding the acquisition through cash on hand.