Browsing by Author "Portale, Anthony"

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    OR13-2 Burosumab Resulted in Greater Improvement in Rickets Than Conventional Therapy in Children with X-Linked Hypophosphatemia (XLH)
    (Oxford University Press, 2019-04-15) Imel, Erik; Whyte, Michael; Munns, Craig; Portale, Anthony; Ward, Leanne; Nilsson, Ola; Simmons, Jill; Padidela, Raja; Namba, Noriyuki; Cheong, Hae Il; Mao, Meng; Chen, Chao-Yin; Skrinar, Alison; San Martin, Javier; Glorieux, Francis; Medicine, School of Medicine
    XLH is characterized by excess FGF23, hypophosphatemia, skeletal deformities, and growth impairment. For the last 40 years, XLH has been treated with multiple daily doses of oral phosphate and active vitamin D (Pi/D). Burosumab, a fully human monoclonal antibody to FGF23, has been approved by the FDA for the treatment of XLH in patients ≥1 year-old. In this Phase 3 trial (NCT02915705), 61 children with XLH (1-12 years old) were randomized (1:1) to receive subcutaneous burosumab starting at 0.8 mg/kg every 2 weeks or continue Pi/D titrated and individualized for each subject by investigators. Eligibility criteria included a Total Rickets Severity Score (RSS) ≥2.0 despite prior treatment with Pi/D (>7-day washout before baseline). The primary endpoint was healing of rickets at Week 40 assessed by radiologists blinded to treatment using the Radiographic Global Impression of Change (RGI-C). The mean ± SE daily oral phosphate dose from baseline to Week 40 was 37.8 ± 3.2 mg/kg, with >99% compliance reported based on days of dosing. Compared with Pi/D, 40 weeks of burosumab resulted in a greater LS mean ± SE increase in serum phosphorus (0.92 ± 0.08 vs 0.20 ± 0.06 mg/dL), TmP/GFR (1.19 ± 0.11 vs -0.16 ± 0.05 mg/dL), and 1,25(OH)2D (30 ± 4 vs 19 ± 4 pg/mL). At Week 40, rickets improved in both groups; RGI-C global score was significantly higher in burosumab subjects than in Pi/D subjects (LS mean ± SE: +1.9 ± 0.1 vs +0.8 ± 0.1; p<0.0001). More burosumab subjects had substantial healing (RGI-C ≥+2.0), compared with Pi/D subjects (21/29, 72% vs 2/32, 6%; odds ratio of 39.1, p<0.0001). Improvement in the RGI-C lower limb deformity score was greater with burosumab than with Pi/D (+0.62 ± 0.12 vs +0.21 ± 0.12; p=0.02). Alkaline phosphatase decreased more with burosumab compared with Pi/D (-131 ± 13 vs 35 ± 19; p<0.0001). Consistent with decreases in rickets severity, burosumab improved growth and mobility. Standing height Z-score increased by a LS mean change (95% CI) of +0.15 (0.05, 0.25) for burosumab and +0.08 (-0.02, 0.19) for Pi/D. The 6 Minute Walk Test percent predicted distance increased with burosumab (Baseline to Week 40: 62% to 72%) and was unchanged with Pi/D (76% to 75%). Nephrocalcinosis score (range 0-4) shifted 0 in 20 Pi/D and 24 burosumab subjects; +1 in 3 Pi/D and 0 burosumab subjects; and -1 in 3 Pi/D and 2 burosumab subjects. Pre-defined adverse events (AEs) of interest, including hypersensitivity and injection site reactions, were higher in the burosumab group and were mild to moderate in severity overall. There were 4 serious AEs (3 burosumab, 1 Pi/D); none were treatment-related and all resolved. No subject discontinued study drug in either group. Data after 64 weeks of treatment will be available at the time of presentation. In this randomized Phase 3 trial, burosumab resulted in increases in growth and mobility, and significantly greater improvements in rickets than Pi/D in 1-12 year-old children with XLH.
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    OR13-2 Characterizing the Impact of Burosumab on Bone Health in Children with X-Linked Hypophosphatemia: Results from Year 1 of the Disease Monitoring Program
    (Oxford University Press, 2022) Carpenter, Thomas; Cassinelli, Hamilton; Glorieux, Francis; Hetzer, Joel; Merritt, J. Lawrence, II; Moreira, Carolina A.; Portale, Anthony; Ward, Leanne; Woo, Claudine; Imel, Erik; Medicine, School of Medicine
    X-linked hypophosphatemia (XLH) is a rare, heritable disorder wherein excess FGF23 leads to renal phosphate wasting and impaired activation of vitamin D. XLH is characterized by rickets and osteomalacia leading to bone pain, skeletal deformities, and short stature. The XLH Disease Monitoring Program (DMP; NCT03651505) is a prospective, multinational outcomes study of the longitudinal progression of clinical, radiographic, and biochemical features of XLH in children and adults. We assessed the impact of the recombinant human IgG1 monoclonal antibody to FGF23, burosumab, on measures of bone health in children with XLH at Year 1 of the DMP. As of March 2021, 287 children (<18 years) had completed the Year 1 visit. Participants were grouped by when they first received burosumab: Group 1, prior to DMP enrollment (N=68; mean (SD) age 9.5 (3.6) years); Group 2, during the DMP (N=150; 8.7 (5.0) years); Group 3, never, but receiving conventional therapy (N=69; 8.8 (5.3) years). Before receiving burosumab, serum phosphorus levels were below normal; after burosumab initiation, serum phosphorus in Groups 1 and 2 rapidly normalized, with sustained improvements up to 3 years of treatment. Serum phosphorus remained low in Group 3. Before burosumab, serum alkaline phosphatase levels were above normal; with continued burosumab therapy, mean levels gradually declined towards normal and were maintained for up to 4 years. The Radiographic Global Impression of Change (RGI-C) assessed rickets and lower limb deformity from DMP baseline to Year 1, with positive values denoting improvement. Mean (SD) RGI-C rickets global scores were +1.0 (0.9) for Group 1 (n=44), +1.5 (0.7) for Group 2 (n=39), and +0.3 (1.2) for Group 3 (n=3). Lower limb deformity RGI-C scores were +0.3 (0.6) for Group 1 (n=42), +0.4 (0.8) for Group 2 (n=39), and +0.8 (1.1) for Group 3 (n=3). Height Z-score change from DMP baseline at Year 1 was 0.1 (0.3) for Group 1 (n=58), 0.1 (0.4) for Group 2 (n=90), and -0.8 (3.1) for Group 3 (n=18). There were no new safety concerns or reports of hyperphosphatemia. These real-world data affirm that normalization of serum phosphorus is rapid and sustained following burosumab initiation, resulting in improved serum alkaline phosphatase levels which positively impact bone mineralization. Improvements in rickets, growth, and lower limb deformity occur in the first year of burosumab treatment and continue in those who started burosumab prior to entering the DMP. The absence of new safety concerns or reports of hyperphosphatemia up to 4 years after burosumab initiation is also notable. The 10-year DMP study design will provide understanding of long-term effects in these patients with continued burosumab therapy.