Alexion Pharmaceuticals has offered to buy Wilson Therapeutics in a deal worth around $855 million.

Wilson is a Swedish biopharma developing novel therapies for patients with rare copper-mediated disorders.

The move would secure Alexion access to Wilson’s lead product, WTX101, currently in Phase III development for the rare genetic disorder Wilson’s disease, which leads to build up of copper in vital organs.

The condition can cause 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 drug has already bagged Fast Track designation in the US, and Orphan Drug Designation for the treatment of Wilson disease on both sides of the Atlantic.

“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 Ludwig Hantson, Alexion’s chief executive.

“The acquisition of Wilson Therapeutics is a strong strategic fit for Alexion given the overlap with our current clinical and commercial focus on metabolic and neurologic disorders, and is an important first step in rebuilding our clinical pipeline.”

Alexion said its tender offer is expected to complete and that the transaction should close in the second quarter of 2018.