Alexion Pharmaceuticals has signed an agreement to acquire all the capital stock of the biopharmaceutical company Enobia Pharma in a $610-million all-cash transaction. The acquisition will provide Alexion with a potential treatment for patients with hypophosphatasia, a rare genetic metabolic disease that currently has no approved treatments.

"Hypophosphatasia is an ultra-rare and life-threatening disease, and those patients who survive live with debilitating morbidities including skeletal deformity, severe muscle weakness, and progressive damage to vital organs," Leonard Bell, Chief Executive Officer of Alexion, said in a statement.

Enobia Pharma’s lead product candidate for hypophosphatasia, ENB-0040 (asfotase alfa), is a human recombinant targeted alkaline phosphatase enzyme-replacement therapy. The compound is currently in Phase II clinical development, and was awarded orphan drug designation in the EU and the US in 2008 and 2009 respectively. According to the joint press statement from the companies, the compound has, to date, showed promising results in Phase II in infants and juveniles. Hypophosphatasia can affect all ages, but 50% of infant with the disease do not survive beyond one year of age.

In addition to the upfront $610 million, Alexion will also pay $470 million in cash upon achievement of various regulatory and sales milestones. The transaction has been approved by the boards of both companies and is expected to be completed in the first quarter of 2012. Alexion will finance the acquisition through cash on hand and $300 million of committed bank debt.