Alexion Pharmaceuticals has agreed to acquire Enobia Pharma for up to US$1.08 B in order to gain access to ENB-0040 (asfotase alpha), an enzyme replacement therapy in Phase II development for hypophosphatasia, an ultra-rare genetic metabolic bone disease for which there are no approved therapies. The drug candidate has thus far demonstrated an impressive safety and efficacy profile. Alexion will pay US$610 M upon deal completion and up to US$470 M upon the achievement of various regulatory and sales milestones.