The U.S. FDA approved Alexion Pharmaceuticals’ Strensiq (asfotase alfa) for the treatment of patients with perinatal-, infantile- and juvenile-onset hypophosphatasia (HPP). Strensiq is an innovative enzyme replacement therapy (ERT) and it is the first therapy approved in the U.S. for the treatment of patients with HPP. The FDA approved Strensiq under Priority Review, and had granted Breakthrough Therapy designation for Strensiq. HPP is a genetic, chronic, progressive, and life-threatening ultra-rare metabolic disease that is caused by mutations in the gene encoding an enzyme known as tissue non-specific alkaline phosphatase (TNSALP). It is characterized by low alkaline phosphatase activity and defective bone mineralization that can lead to destruction and deformity of bones and other skeletal abnormalities.