Treatment with CRYSVITA® demonstrated rapid, significant and sustained improvements in children with XLH¹⁻³

After 10 years of clinical testing, CRYSVITA was approved* in the EU in 2018 for the treatment of children with XLH4

CRYSVITA is indicated for the treatment of XLH with radiographic evidence of bone disease in children 1 year of age and older and adolescents with growing skeletons.5

*CRYSVITA has a conditional Marketing Authorisation in Europe. For explanation of the abbreviations of the terms used in this diagram please click on 'Abbreviations' at the bottom of this page.

Efficacy and safety of CRYSVITA in children aged 1 to 4 years with XLH has been established in a phase 2 study (NCT02750618; UX023-CL205)2

Study design2

An open-label phase 2 trial held at 3 sites to investigate the efficacy and safety of CRYSVITA in 13 young children, aged 1–4 years at baseline, with XLH. The study was 64 weeks and participants could continue to receive CRYSVITA for up to an additional 96 weeks during the extension period.

CRYSVITA dosing: Initiated at 0.8 mg/kg every 2 weeks for 64 weeks. The dose was increased to 1.2 mg/kg if two consecutive pre-dose serum phosphate concentrations were below 1.03 mmol/L, serum phosphate had increased by less than 0.16 mmol/L from baseline and a dose of burosumab had not been missed.

Co-primary endpoints2

  • Change from baseline in serum phosphate concentration at week 40
  • Safety

Secondary endpoints2

  • Change from baseline in RGI-C at week 40 and week 64
  • Pharmacodynamics: Change from baseline in ALP and serum 1,25(OH)2D
  • Change in recumbent length (or standing height Z scores), physical ability (evaluated by the 6-minute walk test) and patient reported pain and functional disability

Key findings2

...
  • CRYSVITA increased fasting serum phosphate concentrations to within the normal range and were sustained throughout the study
...
  • CRYSVITA resulted in the substantial healing of rickets and a positive lower limb deformity score by week 40 in all patients, indicating improvement
    • Gains were sustained at week 64 and were consistent with improvements seen with CRYSVITA in children aged 5–12 years in another phase 2 study
...
  • CRYSVITA increased serum 1,25(OH)2D
...
  • CRYSVITA had an acceptable safety profile

CRYSVITA treatment starting at 0.8 mg/kg in children with XLH aged 1–4 years restores phosphate homoeostasis and significantly improves rickets

Efficacy and safety of CRYSVITA in children aged 5 to 12 years with XLH has been established in a Phase 2 study (NCT02163577; UX023-CL201)1

Study design1

A randomised, open-label, parallel-group, phase 2 trial at 9 sites, to investigate the efficacy and safety of CRYSVITA in 52 children, aged 5-12 years, with XLH. The study was 64 weeks and patients had the option to enrol in an open-label extension.

CRYSVITA dosing: Initiated at 0.1 mg/kg every 2 weeks or 0.2 mg/kg every 4 weeks. If no severe side effects were observed, patients were assigned sequentially to receive escalating doses of 0.2 or 0.3 mg/kg every 2 weeks, or 0.4 or 0.6 mg/kg every 4 weeks.

Primary endpoint1

  • Change from baseline in total RSS at week 40 and week 64

Secondary endpoints1

  • Change from baseline in RGI-C at week 40 and week 64
  • Pharmacodynamics: Change from baseline in serum phosphate, TmP/GFR, serum 1,25(OH)2D, ALP
  • Change in growth velocity and height Z scores
  • Safety

Key findings1

...
  • CRYSVITA treatment increased serum phosphate levels to within normal limits
    • CRYSVITA administered once every 2 weeks provided a sustained increase in the serum phosphate level to normal or near normal levels after dose adjustment
    • Every-4-week dosing was associated with lower levels of serum phosphate at the end of each dose interval
...
  • The improvement in phosphate metabolism corresponded to a decrease in rickets severity
    • This may have contributed to concurrent improvements in growth and physical activity and a reduction in pain
...
  • CRYSVITA treatment improved RGI-C scores, with a small but significant reduction in leg deformity
...
  • No clinically significant safety findings were observed with CRYSVITA

CRYSVITA treatment provides therapeutic benefits by restoring phosphate homeostasis and improving rickets in children with XLH aged 5-12 years, who previously received conventional therapy with limited clinical improvement

Following the positive findings from the phase 2 trials, a phase 3 clinical study was conducted to investigate the efficacy and safety of CRYSVITA compared with conventional therapy in children aged 1-12 years.

Efficacy and safety of CRYSVITA in children with XLH has been established in a phase 3 study (NCT915705; UX023-CL301)3

Study design3

A randomised, active-controlled, open-label, phase 3 trial at 16 clinical sites, compared the efficacy and safety of CRYSVITA with conventional therapy in children with XLH aged 1-12 years, over a 64 week period.

Study population
  • Children with XLH, aged 1-12 years old
  • N=61
  • Fasting serum phosphate <0.97 mmol/L (3.0 mg/dL)
  • Confirmed PHEX mutation or variant of unknown significance in the patient or a family member
  • Prior conventional therapy
    • ≥12 consecutive months for ages ≥3 years old
    • ≥6 consecutive months for ages <3 years old
  • Total RSS ≥2.0
  • CRYSVITA dosing: Initiated at a dose of SC 0.8 mg/kg Q2W; increased to 1.2 mg/kg Q2W if two consecutive pre-dose, fasting, serum phosphate concentrations were below 1.03 mmol/L (3.2 mg/dL) and serum phosphate had increased by <0.16 mmol/L (<0.5 mg/dL) from baseline on a single measurement.


    Conventional therapy dosing: The recommended oral phosphate dose in children is 20–60 mg/kg/day divided into three to five doses per day and alfacalcidol 40–60 ng/kg/day or calcitriol 20–30 ng/kg/day; depending on the formulation, the active vitamin D could be given one to three times a day.


    §Primary assessments of recumbent length/standing height Z-score and lower limb deformity score are at Week 64.

    Primary endpoint3

    • Change in rickets severity from baseline at Week 40 as assessed by the Radiographic Global Impression of Change (RGI-C) global score

    Secondary endpoints3

    • Change in rickets severity from baseline at Week 64 as assessed by the RGI-C global score
    • Proportion of subjects with a mean RGI-C global score ≥ +2.0 (substantial healing) at Week 40 and Week 64
    • Change from baseline at Week 40 and 64 in Thacher Rickets Severity Score
    • Change from baseline in lower limb deformity as assessed by RGI-C long leg score at Week 40 and 64
    • Change from baseline at Week 40 and 64 in growth outcomes:
      • Height-for-age Z scores
      • Growth velocity
    • Change from baseline in the 6MWT total distance and percent of predicted normal (for subjects ≥ 5 years of age at the screening visit) at Weeks 24, 40, and 64
    • Change from baseline over time in serum phosphate
    • Change from baseline over time in serum 1,25(OH)2D
    • Change from baseline over time in ratio of TmP/GFR
    • Change from baseline over time in alkaline phosphatase

    Patient characteristics3

    Characteristic Conventional therapy (n=32) CRYSVITA SC Q2W (n=29)
    Age, years, mean (SD) 6.3 (3.2) 5.8 (3.4)
    Girls, n (%) 18 (56%) 16 (55%)
    Boys, n (%) 14 (44%) 13 (45%)
    White, n (%) 25 (78.1%) 25 (86.2%)
    Height Z score
      Mean (SD)
      Median
     

    –2.1 (0.9)
    –2.1
    [–2.51 to –1.44]

    –2.3 (1.2)
    –2.3
    [–3.05 to –1.45]
    Weight Z score
      Mean (SD)
      Median
     

    –0.6 (0.9)
    –0.7
    [-1.17 to 0.05]

    –0.9 (1.2)
    –0.8
    [-1.75 to 0.59]
    Tanner stage, n(%)
    1 31 (97%) 27 (93%)
    2 1 (3%) 2 (7%)
    Serum phosphate, mmol/L, mean (SD) 0.74 (0.08) 0.78 (0.08)
    Serum TmP/GFR, mmol/L, mean (SD) 0.65 (0.11) 0.71 (0.12)
    Serum 1,25(OH)2D, pmol/L, mean (SD) 96 (36) 110 (48)
    Serum 25(OH)D, nmol/L, mean (SD) 79.38 (25.14) 80.63 (26.15)
    Alkaline phosphatase, U/L, mean (SD) 523.4 (154.4) 510.8 (124.9)
    Duration of conventional therapy, years, mean (SD) Median [min, max] 4.3 (3.0) 3.5 [1.88, 6.33] 3.3 (3.1) 2.2 [1.56, 3.47]
    Total Thacher RSS, mean (SD) Median [range] 3.2 (1.1) 3.0 [2.50, 4.00] 3.2 (1.0) 3.0 [2.50, 3.50]

    Baseline values were assessed after a 7-day washout period, in which patients stopped treatment with conventional therapy.

    Treatment with CRYSVITA restores phosphate homeostasis in children with XLH3

    CRYSVITA achieved significantly greater improvements in mean serum phosphate levels compared with conventional therapy as early as Week 2, which were sustained over 64 weeks3

    Assessments at Weeks 2, 12 and 33 only occurred in the CRYSVITA group. Post baseline values are off set to avoid overlapping error bars.

    CRYSVITA achieved significantly greater increases in serum 1,25(OH)2D compared with conventional therapy over 64 weeks

    †Based on comparison between treatment groups in the LS mean change from baseline using a GEE model. Assessments at Weeks 2,12 and 33 (See Fig 3 Imel 2019) only occurred in the CRYSVITA group. Some post-baseline values are slightly offset from the actual treatment week to avoid overlapping error bars.

    CRYSVITA achieved significantly greater improvements in renal phosphate reabsorption (as measured by TmP/GFR) compared with conventional therapy as early as Week 4, which were sustained over 64 weeks3

    Assessments at Weeks 2, 12 and 33 only occurred in the CRYSVITA group.

    CRYSVITA improves biochemical markers of bone health3

    CRYSVITA achieved significantly greater reductions in alkaline phosphatase activity compared with conventional therapy over 64 weeks3

    Based on comparison between treatment groups in the LS mean change from baseline using a GEE model. Some post-baseline values are slightly offset from the actual treatment week to avoid overlapping error bars.


    Normal range varies depending on sex and age within males and females aged 1–15 years; the upper limit ranged from 297 to 385 U/L.

    CRYSVITA heals rickets and reduces severity in children with XLH3

    CRYSVITA achieved significantly higher RGI-C global scores versus conventional therapy at Week 40 and Week 643

    Based on the comparison between treatment groups in the LS mean change, using the ANCOVA model at Week 40 and the GEE model for Week 64.

    CRYSVITA achieved substantial or complete healing of rickets (RGI-C score ≥2.0) in a significantly greater proportion of children (87%) than conventional therapy (19%) at Week 643

    GEE model includes treatment, visit, interaction between treatment group and visit and baseline age stratification as factors, and baseline RSS total score as a continuous covariate.

    CRYSVITA achieved significantly greater improvements in total Thacher rickets severity score compared with conventional therapy at Week 40 and Week 643

    Based on the comparison between treatment groups in the LS mean change, using the ANCOVA model at Week 40 and the GEE model for Week 64.

    Improvement in rickets in a 4-year-old girl with XLH treated with CRYSVITA3

    Score Baseline Week 40
    Thacher RSS
    Wrist 2.0 0.5
    Knee 1.5 1.0
    Total 3.5 1.5
    RGI-C score†
    Wrist - +2.3
    Knee - +2.0
    Global - +2.0

    Substantial healing is defined as an RGI-C score ≥+2.0.

    CRYSVITA helps correct lower leg deformity in children with XLH3

    CRYSVITA achieved significantly higher RGI-C lower limb deformity scores versus conventional therapy at Week 40 and Week 643

    Based on the comparison between treatment groups in the LS mean change from baseline using the GEE model.

    CRYSVITA prevents early decline in growth in children with XLH3

    CRYSVITA achieved significantly greater improvements in recumbent length/standing height Z score compared with conventional therapy at Week 40 and Week 643

    Based on comparison between treatment groups in the LS mean change from baseline using the GEE model for recumbent length/standing height Z score and the ANCOVA model for growth velocity Z score. Some post-baseline values are slightly offset from the actual treatment week to avoid overlapping error bars.

    CRYSVITA achieved significantly greater improvements in mean growth velocity Z score versus conventional therapy at Week 643

    Based on comparison between treatment groups in the LS mean change from baseline for recumbent length/standing height Z score and the ANCOVA model for growth velocity Z score.

    CRYSVITA improves mobility in children with XLH3

    CRYSVITA achieved significantly greater increases in percent predicted distance walked in the 6-minute walk test compared with conventional therapy at Week 643

    †Based on comparison between treatment groups in the LS mean change from baseline using a GEE model.
    6MWT was assessed in patients ≥5 years old and able to complete the test. Some post-baseline values are slightly offset from the actual treatment week to avoid overlapping error bars.

    Most common treatment-emergent adverse events (TEAEs) reported in children with XLH up to 64 weeks3

    Assessment Conventional therapy (n=32)
    n (%)
    CRYSVITA SC Q2W (n=29)
    n (%)
    Pyrexia 6 (19%) 16 (55%)
    Cough 6 (19%) 15 (52%)
    Arthralgia 10 (31%) 13 (45%)
    Vomiting 8 (25%) 12 (41%)
    Nasopharyngitis 14 (44%) 11 (38%)
    Pain in extremity 10 (31%) 11 (38%)
    Headache 6 (19%) 10 (34%)
    Injection site erythema 0 9 (31%)
    Dental caries 2 (6%) 9 (31%)
    Tooth abscess 3 (9%) 8 (28%)
    Injection site reaction 0 7 (24%)
    Rhinorrhoea 2 (6%) 7 (24%)
    Diarrhoea 2 (6%) 7 (24%)
    Vitamin D decrease 1 (3%) 6 (21%)
    Constipation 0 5 (17%)

    Most events were mild and related to injection site reactions that resolved within a few days3

    No adverse drug reactions led to treatment discontinuation3

    No events of hyperphosphataemia were reported3

    Adverse reactions in the frequency category of ‘very common’ (≥1/10) Injection site reaction is a grouped term that includes injection site reaction, erythema, pruritus, rash, erosion, swelling, urticaria, discomfort, hypersensitivity, inflammation and papule. Please refer to the Summary of Product Characteristics for details on full safety profile of CRYSVITA.

    1. Carpenter TO, et al. N Engl J Med. 2018;378:1987-1998. 2. Whyte MP, et al. Lancet Diabetes Endocrinol 2019;7:189-199. 3. Imel EA,et al. Lancet. 2019;393:2416–2427. 4. Lamb YN. Drugs. 2018;78(6):707–714. 5. Kyowa Kirin Limited. CRYSVITA (burosumab). Summary of Product Characteristics. February 2019

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