Kidney Week

Abstract: TH-PO0226

Effects of Long-Term Burosumab Treatment on Kidney Health in X-Linked Hypophosphatemia: Results from the XLH Disease Monitoring Program

Session Information

• Bone and Mineral Metabolism: Clinical Reports and Practice
  November 06, 2025 | Location: Exhibit Hall, Convention Center
  Abstract Time: 10:00 AM - 12:00 PM

Category: Bone and Mineral Metabolism

• 502 Bone and Mineral Metabolism: Clinical

Authors

• Portale, Anthony A., UCSF Benioff Children's Hospital, San Francisco, California, United States

Anthony A. Portale, MD

• Ward, Leanne M., Children's Hospital of Eastern Ontario, Ottawa, Ontario, Canada

Leanne M. Ward, MD

• Dahir, Kathryn M, Vanderbilt University Medical Center, Nashville, Tennessee, United States

Kathryn M Dahir, MD

• Florenzano, Pablo, Pontificia Universidad Catolica de Chile, Santiago, Santiago Metropolitan Region, Chile

Pablo Florenzano

• Ing, Steven, The Ohio State University Wexner Medical Center, Columbus, Ohio, United States

Steven Ing, MD

• Jan de Beur, Suzanne M., University of Virginia School of Medicine, Charlottesville, Virginia, United States

Suzanne M. Jan de Beur, MD

• Martin, Regina Matsunaga, Hospital das Clinicas da Faculdade de Medicina da Universidade de Sao Paulo, São Paulo, SP, Brazil

Regina Matsunaga Martin, MD

• Meza Martinez, Adriana Isabel, Hospital Infantil Universitario de San José, Bogota, DC, Colombia

Adriana Isabel Meza Martinez

• Paloian, Neil J., University of Wisconsin School of Medicine and Public Health, Madison, Wisconsin, United States

Neil J. Paloian, MD

• Ashraf, Ambika P, University of Alabama at Birmingham, Birmingham, Alabama, United States

Ambika P Ashraf, MD

• Dixon, Bradley P., University of Colorado School of Medicine, Aurora, Colorado, United States

Bradley P. Dixon, MD, FASN

• Moreira, Carolina Aguiar, Federal University of Parana, Endocrine Division (SEMPR), Department of Internal Medicine, Curitiba, Brazil

Carolina Aguiar Moreira, MD, PhD

• Simmons, Jill, Vanderbilt University School of Medicine, Nashville, Tennessee, United States

Jill Simmons, MD

• Carpenter, Thomas, Yale University School of Medicine, New Haven, Connecticut, United States

Thomas Carpenter, MD

• Chen, Zunqiu, Ultragenyx Pharmaceutical Inc, Novato, California, United States

Zunqiu Chen, MS, MSc

• Krolczyk, Stanley, Ultragenyx Pharmaceutical Inc, Novato, California, United States

Stanley Krolczyk, DO

• Imel, Erik, Indiana University School of Medicine, Indianapolis, Indiana, United States

Erik Imel, MD, MS

Group or Team Name

• On behalf of the XLH-DMP Investigators.

Background

X-linked hypophosphatemia (XLH) is a rare disorder characterized by FGF23-mediated renal phosphate wasting leading to significant bone abnormalities. Previously, conventional therapy (CT) was oral phosphate and active vit. D, which confers risk of nephrocalcinosis (NC). Burosumab, a human FGF23-neutralizing antibody, improves renal phosphate wasting and vit. D synthesis. The present study aimed to document the frequency and evolution of NC in burosumab-treated patients with XLH.

Methods

Children and adults in the longitudinal XLH Disease Monitoring Program combined with data from burosumab clinical trials were analyzed. We examined serial renal ultrasounds scored for NC and biochemistries including the change in estimated glomerular filtration rates (eGFR), for up to ~9 yrs of burosumab therapy.

Results

Prior to burosumab (baseline; BL), 17% of 225 children (mean±SD age, 8±5 yrs) and 39% of 185 adults (40±13 yrs) had NC. Most had previously received CT. At last visit, patients received burosumab for a median (range) 4.0 (1, 9.5) yrs. Of those without BL NC (grade 0), NC scores at last visit remained zero in 96% of children and 94% of adults. Of those with BL NC (grades 1, 2 or 3), NC scores at last exam in children were unchanged in 66%, lower in 24%, and worsened in 11%, and in adults were unchanged in 44%, lower in 47%, and worsened in 10%. eGFR was decreased (CKD Stage 2) in 10% of children at BL and 10% of children at last examination, with no change from BL in mean eGFR regardless of NC status. eGFR in adults was decreased (CKD Stage 2, 3, 4) in 15% at BL and 24% at last exam. In adults, mean eGFR decreased from BL to last visit by ~1 ml/min/1.73m² per yrs regardless of NC status. Serum phosphorus and alkaline phosphatase improvements were sustained, and serum Ca and parathyroid hormone remained stable.

Conclusion

The risk of de novo or worsening NC during burosumab treatment was low. In those with NC at BL, NC scores were stable or improved in most patients during burosumab treatment. Continued monitoring of renal health is important in patients with XLH on burosumab or CT.

Funding

• Commercial Support – Ultragenyx Pharmaceutical Inc.

Digital Object Identifier (DOI)

• doi: 10.1681/ASN.20250vvfbnxk