At the 2019 annual meeting of The Endocrine Society, ENDO 2019, results from a recent study evaluating burosumab for the treatment of X-linked hypophosphatemia (XLH) were presented. This drug was approved by the FDA last April. This new study aimed to decipher if it is truly more effective than traditional approaches.
The Endocrine Society
The Endocrine Society is an international organization dedicated to endocrine research. In fact it is the largest and oldest of all of the endocrine organizations worldwide. They currently have over 18,000 members who reside in 122 different countries. Members include scientists, students, physicians, nurses, and educators all dedicated to research for hormone-related conditions such as XLH.
XLH is an inherited form of rickets which causes bone pain, bowed legs, and short stature.
Burosumab works by inhibiting FGF23, high numbers of which are a hallmark characteristic of XLH. This hormone causes low levels of phosphorus. Typically, patients are given oral phosphate as well as active vitamin D multiple times each day to treat the condition.
Burosumab is an injectable medicine and only needs to be administered every two weeks. It is currently approved for XLH patients who are one year old or older.
This study was funded by both Ultragenyx Pharmaceutical Inc., burosumab’s manufacturer as well as Kyowa Kirin International in Japan. It was an international study, taking place at sites in the United States, Japan, Korea, the UK, Sweden, Canada, and Australia.
This study was phase 3 and included 61 XLH patients between the ages of 1 and 12. All of the participants had been receiving conventional therapy prior to the study, and despite that, they all still had signs of rickets (as evaluated through x-rays). The patients were randomly assigned to either continue traditional treatment or begin treatment with burosumab. Physicians who did not know which group the patients had been assigned to evaluated their x-rays throughout the study for signs of rickets. Final results were documented at 40 weeks.
Overall, the burosumab group had significantly better outcomes. 72% of patients in the burosumab group experienced “substantial healing” of rickets versus just 6% in the group treated with oral phosphate and vitamin D. Additional positive outcomes for the burosumab group included a larger increase in active vitamin D levels and serum phosphorus in the body and improvements in height, leg deformities, and walking speed.
An added benefit of the burosumab therapy is that it only needs to be administered once every two weeks as opposed to multiple times daily.
This study is so important because it clearly showcases what is the superior therapy for XLH patients. As the knowledge gained from this trial spreads, more physicians will be able to make better informed decisions for their patients.
Ultimately, treatment with burosumab could significantly improve the quality of life of those living with XLH.
You can read more about bursosumab and this phase 3 study here.