Alexion Pharmaceuticals ended 2011 by announcing a deal to buy Enobia Pharma, and its hypophosphatasia drug, for up to $1.08 billion.

Alexion is offering $610 million in cash upon completion of the transaction and up to $470 million more upon achievement of various regulatory and sales milestones. The key attraction of Enobia, a private company based in Montreal, Canada and Cambridge, Massachusetts is ENB-0040 (asfotase alfa), which is in Phase II for hypophosphatasia, "an ultra-rare, life-threatening, genetic metabolic disease for which there are no approved treatment options".

HPP is characterised by defective bone mineralisation and impaired phosphate and calcium regulation leading to progressive damage to multiple vital organs. This includes destruction and deformity of bones, profound muscle weakness, seizures, impaired renal function and respiratory failure. About 50% of infants with the disease do not survive past one year of age.

Alexion chief executive Leonard Bell said that asfotase alfa, which has orphan drug designation in the USA and Europe, has shown "very compelling Phase II clinical data in infants and juveniles with hypophosphatasia". He added that the acquisition of Enobia "is very well aligned with Alexion’s objective to develop and deliver life-transforming therapies for patients suffering with ultra-rare, severe and life-threatening disorders".

Alexion, which markets the blood disorder drug Soliris (eculizumab) for the treatment of atypical haemolytic uremic syndrome and paroxysmal nocturnal haemoglobinuria, intends to finance the acquisition through cash on hand and $300 million of committed bank debt.