Rare Disease Report

FDA Approves First Treatment for Hypophosphatasia

OCTOBER 23, 2015
Rebekah Harrison
The good news keeps on coming. The FDA approved Alexion’s Stensiq (asfotase alfa), the first approved treatment for perinatal, infantile and juvenile-onset hypophosphatasia (HPP).

What is hypophosphatasia?

Hypophosphatasia is an inherited rare metabolic bone disease that disrupts bone mineralization. Symptoms include weakening and softening of the bones that cause skeletal abnormalities.
Hypophosphatasia affects an estimated 1 in 100,000 newborns.

Clinical Data

Approval was based on data from 4 clinical trials and supporting extension trials comprising patients with perinatal-, infantile- and juvenile-onset HPP who received treatment with Strensiq for up to 6.5 years.
In patients (ages 1 day to 6.5 years) with perinatal/infantile-onset HPP, treatment with Strensiq resulted in a significant survival benefit compared to historical control patients with similar clinical characteristics. At week 48, the estimate of overall survival was 97% for treated patients (n=68) compared to 42% for historical control patients (n=48).
In addition, estimated invasive ventilator-free survival was 96% for treated patients (n=54) compared to 31 percent for historical control patients (n=48). Study results also demonstrated substantial improvements in the skeletal manifestations of HPP, as assessed by the Radiographic Global Impression of Change (RGI-C) scale, and improvements in height and weight, as measured by z-scores, in patients treated with Strensiq.
In patients (ages 6 to 12 years) with juvenile-onset HPP, treatment with Strensiq resulted in significant improvements in the skeletal manifestations of HPP at 24 weeks, as measured by RGI-C, compared to historical controls. By month 54, 100% of Strensiq-treated juvenile-onset patients were responders to treatment (n=8), as measured by substantial bone healing, compared to 6% of patients in the historial control group (n=32) at last assessment. In addition, patients treated with Strensiq had improvements in height and weight, as measured by z-scores, compared with untreated historical controls, as well as improvements in gait and mobility. By 4 years of treatment, 100% of patients assessed (n=6) achieved the 6 Minute Walk Test within the normal range for age-, sex- and height-matched peers, whereas no patients were in the normal range at baseline.
Stensiq is the 5th therapy approved by the FDA this week.
“The FDA approval of Strensiq brings a highly innovative treatment to patients who, until now, have had no effective therapy to treat this ultra-rare genetic metabolic disease that causes premature death in infants and devastating consequences in those who survive,” said David Hallal, CEO of Alexion. “We are pleased that the label includes a survival benefit in infants, substantial bone healing, and improvements in growth and mobility in patients with HPP who had symptoms prior to the age of 18 and were treated with Strensiq. We look forward to rapidly bringing this life-transforming therapy to patients with HPP and their physicians in the United States.”


FDA approves new treatment for rare metabolic disorder [news release]. U.S. Food and Drug Administration; October 23, 2015. http://www.fda.gov/NewsEvents/Newsroom/PressAnnouncements/ucm468836.htm

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