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Abstract: PO0561

Burosumab in X-Linked Hypophosphatemic Rickets Adult Patients: An Italian Center Experience

Session Information

Category: Bone and Mineral Metabolism

  • 402 Bone and Mineral Metabolism: Clinical

Authors

  • Foligno, Nadia Edvige, Nephrology and Dialysis Unit, IRCCS San Raffaele Scientific Institute, Vita-Salute University, Milan, Italy
  • Arcidiacono, Teresa, Nephrology and Dialysis Unit, IRCCS San Raffaele Scientific Institute, Vita-Salute University, Milan, Italy
  • Bologna, Arianna, Nephrology and Dialysis Unit, IRCCS San Raffaele Scientific Institute, Vita-Salute University, Milan, Italy
  • Brioni, Elena, Nephrology and Dialysis Unit, IRCCS San Raffaele Scientific Institute, Vita-Salute University, Milan, Italy
  • Avino, Monica, Nephrology and Dialysis Unit, IRCCS San Raffaele Scientific Institute, Vita-Salute University, Milan, Italy
  • Vezzoli, Giuseppe, Nephrology and Dialysis Unit, IRCCS San Raffaele Scientific Institute, Vita-Salute University, Milan, Italy
Background

X-linked Hypophosphatemic Rickets (XHR) is a rare disease caused by mutations in the PHEX gene leading to an increase in the serum levels of FGF23, which inhibits the tubular reabsorption of phosphates and the production of 1,25(OH)2D. This causes hypophosphataemia, rickets, bone deformities, growth retardation and muscle activity impairment.

Methods

Burosumab (B) is a monoclonal antibody against FGF23, used for the treatment of XHR patients. In Italy B can be employed in adults only as compassionate use. Starting in 2020 B (1 mg/kg sc every 4w) was administered to 4 adult subjects with XHR: VM (M, 32 yrs), ST (F, 47), ER (M, 46) and SM (F, 20) who showed legs deformities, musculoskeletal pain and severe movement limitations.

Results

In all patients, phosphorus levels were normalized by B, but tended to decrease during the 28 days following the administration. Plasma values of 1,25(OH)2D and CTX (marker of bone resorption) also increased to a peak which then decreased over months. In contrast, PTH and bALP values did not change during B therapy.
Scores provided by specific tests confirmed an improvement in the fatigue resistance and physical performance. Other tests showed the improvement of self-reported well-being and quality of life in all patients. These effects were not observed in adult patients on conventional therapy with phosphate salts and active vitamin D.

Conclusion

Despite the only temporary effect on phosphorus, Burosumab is right now the only therapy that improve the impact that XHR has on the quality of life of XHR patients.