Trial Outcomes & Findings for Study of KRN23 (Burosumab), a Recombinant Fully Human Monoclonal Antibody Against Fibroblast Growth Factor 23 (FGF23), in Pediatric Subjects With X-linked Hypophosphatemia (XLH) (NCT NCT02163577)

Last Updated: 2024-05-06

Results Overview

The RSS system is a 10-point radiographic scoring method that was developed to assess the severity of nutritional rickets in the wrists and knees based on the degree of metaphyseal fraying, cupping, and the proportion of the growth plate affected. Scores are assigned for the unilateral wrist and knee X-rays deemed by the rater to be the more severe of the bilateral images. The maximum total score on the RSS is 10 points and the minimum score is 0, with a total possible score of 4 points for the wrists and 6 points for the knees. Higher scores indicate greater rickets severity.

Recruitment status

COMPLETED

Study phase

PHASE2

Target enrollment

52 participants

Primary outcome timeframe

Baseline, Week 40, 64, 160

Results posted on

2024-05-06

Participant Flow

Participant milestones

Participant milestones
Measure	Burosumab Q2W Burosumab subcutaneous (SC) injections every 2 weeks (Q2W). Dose was determined by the participant's weight and prescribed dose by their study doctor.	Burosumab Q4W Then Q2W Burosumab SC injections every 4 weeks (Q4W). Dose was determined by the participant's weight and prescribed dose by their study doctor. Participants in Q4W were to switch to Q2W beginning with Week 64 dosing.
Overall Study STARTED	26	26
Overall Study COMPLETED	26	26
Overall Study NOT COMPLETED	0	0

Reasons for withdrawal

Withdrawal data not reported

Baseline Characteristics

participants with a Baseline measurement

Baseline characteristics by cohort

Baseline characteristics by cohort
Measure	Burosumab Q2W n=26 Participants Burosumab SC injections every 2 weeks (Q2W). Dose is determined by the participant's weight and prescribed dose by their study doctor.	Burosumab Q4W Then Q2W n=26 Participants Burosumab subcutaneous (SC) injections every 4 weeks (Q4W). Dose is determined by the participant's weight and prescribed dose by their study doctor. Participants in Q4W were to switch to Q2W beginning with Week 64 dosing.	Total n=52 Participants Total of all reporting groups
Age, Continuous	8.7 years STANDARD_DEVIATION 1.72 • n=26 Participants	8.3 years STANDARD_DEVIATION 2.04 • n=26 Participants	8.5 years STANDARD_DEVIATION 1.87 • n=52 Participants
Sex: Female, Male Female	14 Participants n=26 Participants	14 Participants n=26 Participants	28 Participants n=52 Participants
Sex: Female, Male Male	12 Participants n=26 Participants	12 Participants n=26 Participants	24 Participants n=52 Participants
Race/Ethnicity, Customized Black or African American	2 Participants n=26 Participants	0 Participants n=26 Participants	2 Participants n=52 Participants
Race/Ethnicity, Customized White	23 Participants n=26 Participants	23 Participants n=26 Participants	46 Participants n=52 Participants
Race/Ethnicity, Customized Other, Not Specified	1 Participants n=26 Participants	3 Participants n=26 Participants	4 Participants n=52 Participants
Race/Ethnicity, Customized Hispanic or Latino	0 Participants n=26 Participants	2 Participants n=26 Participants	2 Participants n=52 Participants
Race/Ethnicity, Customized Not Hispanic or Latino	26 Participants n=26 Participants	24 Participants n=26 Participants	50 Participants n=52 Participants
Rickets Severity Score (RSS) Total Score	1.92 score on a scale STANDARD_DEVIATION 1.172 • n=26 Participants	1.67 score on a scale STANDARD_DEVIATION 0.999 • n=26 Participants	1.80 score on a scale STANDARD_DEVIATION 1.086 • n=52 Participants
Serum Phosphorus	2.38 mg/dL STANDARD_DEVIATION 0.405 • n=26 Participants	2.28 mg/dL STANDARD_DEVIATION 0.299 • n=26 Participants	2.33 mg/dL STANDARD_DEVIATION 0.356 • n=52 Participants
Serum 1, 25-Dihydroxyvitamin D	41.28 pg/mL STANDARD_DEVIATION 21.967 • n=26 Participants	41.37 pg/mL STANDARD_DEVIATION 15.293 • n=26 Participants	41.33 pg/mL STANDARD_DEVIATION 18.740 • n=52 Participants
Ratio of Renal Tubular Maximum Reabsorption Rate of Phosphate to Glomerular Filtration Rate(TmP/GFR)	2.176 mg/dL STANDARD_DEVIATION 0.4925 • n=25 Participants • participants with a Baseline measurement	1.978 mg/dL STANDARD_DEVIATION 0.3474 • n=25 Participants • participants with a Baseline measurement	2.077 mg/dL STANDARD_DEVIATION 0.4335 • n=50 Participants • participants with a Baseline measurement
RSS Knee and Wrist Scores Knee Score	1.21 score on a scale STANDARD_DEVIATION 0.681 • n=26 Participants	1.19 score on a scale STANDARD_DEVIATION 0.601 • n=26 Participants	1.20 score on a scale STANDARD_DEVIATION 0.636 • n=52 Participants
RSS Knee and Wrist Scores Wrist Score	0.71 score on a scale STANDARD_DEVIATION 0.619 • n=26 Participants	0.48 score on a scale STANDARD_DEVIATION 0.519 • n=26 Participants	0.60 score on a scale STANDARD_DEVIATION 0.578 • n=52 Participants
Growth Velocity	5.45 cm/year STANDARD_DEVIATION 1.171 • n=25 Participants • Data presented for participants with evaluable growth velocity data at Baseline. Growth velocity could not be calculated for 3 participants for whom pretreatment height data were not available within 2 years prior to Baseline.	5.24 cm/year STANDARD_DEVIATION 1.402 • n=24 Participants • Data presented for participants with evaluable growth velocity data at Baseline. Growth velocity could not be calculated for 3 participants for whom pretreatment height data were not available within 2 years prior to Baseline.	5.35 cm/year STANDARD_DEVIATION 1.280 • n=49 Participants • Data presented for participants with evaluable growth velocity data at Baseline. Growth velocity could not be calculated for 3 participants for whom pretreatment height data were not available within 2 years prior to Baseline.
Standing Height Z-Score	-1.72 Z score STANDARD_DEVIATION 1.026 • n=26 Participants	-2.05 Z score STANDARD_DEVIATION 0.957 • n=26 Participants	-1.89 Z score STANDARD_DEVIATION 0.996 • n=52 Participants
Growth (Standing Height, Sitting Height, Arm Length, Leg Length) Standing Height	123.28 cm STANDARD_DEVIATION 10.326 • n=26 Participants	119.42 cm STANDARD_DEVIATION 12.623 • n=26 Participants	121.35 cm STANDARD_DEVIATION 11.584 • n=52 Participants
Growth (Standing Height, Sitting Height, Arm Length, Leg Length) Sitting Height	70.10 cm STANDARD_DEVIATION 5.632 • n=26 Participants	67.04 cm STANDARD_DEVIATION 5.691 • n=26 Participants	68.57 cm STANDARD_DEVIATION 5.815 • n=52 Participants
Growth (Standing Height, Sitting Height, Arm Length, Leg Length) Arm Length	54.80 cm STANDARD_DEVIATION 4.930 • n=26 Participants	52.59 cm STANDARD_DEVIATION 6.129 • n=26 Participants	53.70 cm STANDARD_DEVIATION 5.619 • n=52 Participants
Growth (Standing Height, Sitting Height, Arm Length, Leg Length) Leg Length	66.06 cm STANDARD_DEVIATION 7.027 • n=26 Participants	63.71 cm STANDARD_DEVIATION 8.322 • n=26 Participants	64.89 cm STANDARD_DEVIATION 7.718 • n=52 Participants
6-Minute Walk Test (6MWT) Distance (Predicted Percent of Normal)	79.32 percentage of predicted distance STANDARD_DEVIATION 13.257 • n=26 Participants	81.42 percentage of predicted distance STANDARD_DEVIATION 15.101 • n=26 Participants	80.37 percentage of predicted distance STANDARD_DEVIATION 14.109 • n=52 Participants
POSNA-PODCI Normative Scores Upper Extremity Scale	52.1 T-score STANDARD_DEVIATION 6.77 • n=26 Participants • one participant in the "Burosumab Q4W then Q2W" group did not have a Baseline assessment	48.5 T-score STANDARD_DEVIATION 13.04 • n=25 Participants • one participant in the "Burosumab Q4W then Q2W" group did not have a Baseline assessment	50.3 T-score STANDARD_DEVIATION 10.39 • n=51 Participants • one participant in the "Burosumab Q4W then Q2W" group did not have a Baseline assessment
POSNA-PODCI Normative Scores Transfer and Basic Mobility Scale	45.7 T-score STANDARD_DEVIATION 10.88 • n=26 Participants • one participant in the "Burosumab Q4W then Q2W" group did not have a Baseline assessment	46.0 T-score STANDARD_DEVIATION 10.53 • n=25 Participants • one participant in the "Burosumab Q4W then Q2W" group did not have a Baseline assessment	45.8 T-score STANDARD_DEVIATION 10.61 • n=51 Participants • one participant in the "Burosumab Q4W then Q2W" group did not have a Baseline assessment
POSNA-PODCI Normative Scores Sports/Physical Functioning Scale	34.6 T-score STANDARD_DEVIATION 15.70 • n=26 Participants • one participant in the "Burosumab Q4W then Q2W" group did not have a Baseline assessment	32.2 T-score STANDARD_DEVIATION 19.29 • n=25 Participants • one participant in the "Burosumab Q4W then Q2W" group did not have a Baseline assessment	33.4 T-score STANDARD_DEVIATION 17.42 • n=51 Participants • one participant in the "Burosumab Q4W then Q2W" group did not have a Baseline assessment
POSNA-PODCI Normative Scores Pain/Comfort Scale	35.2 T-score STANDARD_DEVIATION 15.26 • n=26 Participants • one participant in the "Burosumab Q4W then Q2W" group did not have a Baseline assessment	34.8 T-score STANDARD_DEVIATION 16.76 • n=25 Participants • one participant in the "Burosumab Q4W then Q2W" group did not have a Baseline assessment	35.0 T-score STANDARD_DEVIATION 15.85 • n=51 Participants • one participant in the "Burosumab Q4W then Q2W" group did not have a Baseline assessment
POSNA-PODCI Normative Scores Happiness Scale	43.6 T-score STANDARD_DEVIATION 13.75 • n=26 Participants • one participant in the "Burosumab Q4W then Q2W" group did not have a Baseline assessment	43.4 T-score STANDARD_DEVIATION 13.69 • n=25 Participants • one participant in the "Burosumab Q4W then Q2W" group did not have a Baseline assessment	43.5 T-score STANDARD_DEVIATION 13.58 • n=51 Participants • one participant in the "Burosumab Q4W then Q2W" group did not have a Baseline assessment
POSNA-PODCI Normative Scores Global Functioning Scale	37.5 T-score STANDARD_DEVIATION 13.96 • n=26 Participants • one participant in the "Burosumab Q4W then Q2W" group did not have a Baseline assessment	35.6 T-score STANDARD_DEVIATION 17.24 • n=25 Participants • one participant in the "Burosumab Q4W then Q2W" group did not have a Baseline assessment	36.6 T-score STANDARD_DEVIATION 15.52 • n=51 Participants • one participant in the "Burosumab Q4W then Q2W" group did not have a Baseline assessment
Fractional Excretion of Phosphorus (FEP)	13.91 percentage of phosphorus excreted STANDARD_DEVIATION 6.775 • n=25 Participants • participants with a Baseline assessment	15.42 percentage of phosphorus excreted STANDARD_DEVIATION 7.373 • n=26 Participants • participants with a Baseline assessment	14.68 percentage of phosphorus excreted STANDARD_DEVIATION 7.056 • n=51 Participants • participants with a Baseline assessment
Procollagen Type 1 N Propeptide (P1NP)	843.11 ng/mL STANDARD_DEVIATION 214.367 • n=24 Participants • participants with a Baseline assessment	742.35 ng/mL STANDARD_DEVIATION 209.727 • n=26 Participants • participants with a Baseline assessment	790.72 ng/mL STANDARD_DEVIATION 215.864 • n=50 Participants • participants with a Baseline assessment
Carboxy-Terminal Crosslinked Telopeptide of Type I Collagen (CTx)	2.23 ng/mL STANDARD_DEVIATION 0.642 • n=26 Participants	2.10 ng/mL STANDARD_DEVIATION 0.679 • n=26 Participants	2.16 ng/mL STANDARD_DEVIATION 0.658 • n=52 Participants
Alkaline Phosphatase (ALP)	461.92 U/L STANDARD_DEVIATION 110.209 • n=26 Participants	456.08 U/L STANDARD_DEVIATION 101.157 • n=26 Participants	459.00 U/L STANDARD_DEVIATION 104.779 • n=52 Participants
Bone Specific Alkaline Phosphatase (BALP)	163.54 mcg/L STANDARD_DEVIATION 58.610 • n=20 Participants • participants with a baseline assessment	165.62 mcg/L STANDARD_DEVIATION 45.534 • n=20 Participants • participants with a baseline assessment	164.58 mcg/L STANDARD_DEVIATION 51.814 • n=40 Participants • participants with a baseline assessment
Burosumab Concentration	25.00 ng/mL STANDARD_DEVIATION 0.000 • n=26 Participants	25.00 ng/mL STANDARD_DEVIATION 0.000 • n=26 Participants	25.00 ng/mL STANDARD_DEVIATION 0.000 • n=52 Participants

PRIMARY outcome

Timeframe: Baseline, Week 40, 64, 160

Population: Intent to Treat (ITT) Analysis Set: all participants who received at least 1 dose of study therapy and had at least 1 post-dose measurement at given time point.

Outcome measures

Outcome measures
Measure	Burosumab Q2W n=26 Participants Burosumab SC injections Q2W. Dose was determined by the participant's weight and prescribed dose by their study doctor.	Burosumab Q4W Then Q2W n=26 Participants Burosumab SC injections Q4W. Dose was determined by the participant's weight and prescribed dose by their study doctor. Participants in Q4W were to switch to Q2W beginning with Week 64 dosing.
Change From Baseline in RSS Total Score Over Time Change to Week 40	-1.06 score on a scale Standard Error 0.100	-0.73 score on a scale Standard Error 0.100
Change From Baseline in RSS Total Score Over Time Change to Week 64	-1.00 score on a scale Standard Error 0.110	-0.84 score on a scale Standard Error 0.098
Change From Baseline in RSS Total Score Over Time Change to Week 160	-0.98 score on a scale Standard Error 0.129	-0.83 score on a scale Standard Error 0.122

PRIMARY outcome

Timeframe: Baseline, Week 40, 64, 160

Population: Pharmacokinetic/Pharamcodynamic (PK/PD) Analysis Set: all participants who received at least 1 dose of therapy and had evaluable serum data at given time point.

Outcome measures

Outcome measures
Measure	Burosumab Q2W n=26 Participants Burosumab SC injections Q2W. Dose was determined by the participant's weight and prescribed dose by their study doctor.	Burosumab Q4W Then Q2W n=26 Participants Burosumab SC injections Q4W. Dose was determined by the participant's weight and prescribed dose by their study doctor. Participants in Q4W were to switch to Q2W beginning with Week 64 dosing.
Change From Baseline in Serum Phosphorus Over Time Change at Week 40	0.92 mg/dL Standard Deviation 0.480	0.57 mg/dL Standard Deviation 0.265
Change From Baseline in Serum Phosphorus Over Time Change at Week 64	0.99 mg/dL Standard Deviation 0.502	0.69 mg/dL Standard Deviation 0.370
Change From Baseline in Serum Phosphorus Over Time Change at Week 160	0.97 mg/dL Standard Deviation 0.338	1.08 mg/dL Standard Deviation 0.377

PRIMARY outcome

Timeframe: Baseline, Week 40, 64, 160

Population: PK/PD Analysis Set: all participants who received at least 1 dose of therapy and had evaluable serum data at given time point.

Outcome measures

Outcome measures
Measure	Burosumab Q2W n=26 Participants Burosumab SC injections Q2W. Dose was determined by the participant's weight and prescribed dose by their study doctor.	Burosumab Q4W Then Q2W n=26 Participants Burosumab SC injections Q4W. Dose was determined by the participant's weight and prescribed dose by their study doctor. Participants in Q4W were to switch to Q2W beginning with Week 64 dosing.
Change From Baseline in Serum 1,25(OH)2D Over Time Change at Week 160	17.03 pg/mL Standard Deviation 24.889	19.64 pg/mL Standard Deviation 22.857
Change From Baseline in Serum 1,25(OH)2D Over Time Change at Week 40	28.27 pg/mL Standard Deviation 29.312	17.62 pg/mL Standard Deviation 18.802
Change From Baseline in Serum 1,25(OH)2D Over Time Change at Week 64	23.58 pg/mL Standard Deviation 24.502	11.50 pg/mL Standard Deviation 16.522

PRIMARY outcome

Timeframe: Baseline, Week 40, 64, 160

Population: PK/PD Analysis Set: all participants who received at least 1 dose of therapy and had evaluable serum data at given time point.

Data for urinary phosphorus and TRP were used in calculation TmP/GFR.

Outcome measures

Outcome measures
Measure	Burosumab Q2W n=26 Participants Burosumab SC injections Q2W. Dose was determined by the participant's weight and prescribed dose by their study doctor.	Burosumab Q4W Then Q2W n=26 Participants Burosumab SC injections Q4W. Dose was determined by the participant's weight and prescribed dose by their study doctor. Participants in Q4W were to switch to Q2W beginning with Week 64 dosing.
Change From Baseline in TmP/GFR Over Time Change at Week 40	1.14 mg/dL Standard Deviation 0.686	0.80 mg/dL Standard Deviation 0.506
Change From Baseline in TmP/GFR Over Time Change at Week 64	1.11 mg/dL Standard Deviation 0.626	0.90 mg/dL Standard Deviation 0.632
Change From Baseline in TmP/GFR Over Time Change at Week 160	1.24 mg/dL Standard Deviation 0.548	1.45 mg/dL Standard Deviation 0.653

SECONDARY outcome

Timeframe: Baseline, Week 40, 64, 160

Population: ITT Analysis Set: all participants who received at least 1 dose of study therapy and had at least 1 post-dose measurement at given time point.

Outcome measures

Outcome measures
Measure	Burosumab Q2W n=26 Participants Burosumab SC injections Q2W. Dose was determined by the participant's weight and prescribed dose by their study doctor.	Burosumab Q4W Then Q2W n=26 Participants Burosumab SC injections Q4W. Dose was determined by the participant's weight and prescribed dose by their study doctor. Participants in Q4W were to switch to Q2W beginning with Week 64 dosing.
Change From Baseline in RSS Knee Scores Over Time Change at Week 40	-0.62 score on a scale Standard Error 0.08	-0.55 score on a scale Standard Error 0.08
Change From Baseline in RSS Knee Scores Over Time Change at Week 64	-0.70 score on a scale Standard Error 0.087	-0.61 score on a scale Standard Error 0.072
Change From Baseline in RSS Knee Scores Over Time Change at Week 160	-0.70 score on a scale Standard Error 0.105	-0.62 score on a scale Standard Error 0.093

SECONDARY outcome

Timeframe: Baseline, Week 40, 64, 160

Population: ITT Analysis Set: all participants who received at least 1 dose of study therapy and had at least 1 post-dose measurement at given time point.

Outcome measures

Outcome measures
Measure	Burosumab Q2W n=26 Participants Burosumab SC injections Q2W. Dose was determined by the participant's weight and prescribed dose by their study doctor.	Burosumab Q4W Then Q2W n=26 Participants Burosumab SC injections Q4W. Dose was determined by the participant's weight and prescribed dose by their study doctor. Participants in Q4W were to switch to Q2W beginning with Week 64 dosing.
Change From Baseline in RSS Wrist Scores Over Time Change at Week 40	-0.44 score on a scale Standard Error 0.05	-0.18 score on a scale Standard Error 0.05
Change From Baseline in RSS Wrist Scores Over Time Change at Week 64	-0.30 score on a scale Standard Error 0.057	-0.24 score on a scale Standard Error 0.051
Change From Baseline in RSS Wrist Scores Over Time Change at Week 160	-0.27 score on a scale Standard Error 0.065	-0.20 score on a scale Standard Error 0.047

SECONDARY outcome

Timeframe: Baseline, Week 40, 64, 160

Population: ITT Analysis Set: all participants who received at least 1 dose of study therapy and had at least 1 post-dose measurement at given time point.

Changes in the severity of rickets and bowing were assessed centrally by three independent pediatric radiologists contracted by a central imaging facility using a disease specific qualitative RGI-C scoring system. The RGI-C is a seven point ordinal scale with possible values: +3 = very much better (complete or near complete healing of rickets), +2 = much better (substantial healing of rickets), +1 = minimally better (i.e., minimal healing of rickets), 0 = unchanged, -1 = minimally worse (minimal worsening of rickets), -2 = much worse (moderate worsening of rickets), -3 = very much worse (severe worsening of rickets).

Outcome measures

Outcome measures
Measure	Burosumab Q2W n=26 Participants Burosumab SC injections Q2W. Dose was determined by the participant's weight and prescribed dose by their study doctor.	Burosumab Q4W Then Q2W n=26 Participants Burosumab SC injections Q4W. Dose was determined by the participant's weight and prescribed dose by their study doctor. Participants in Q4W were to switch to Q2W beginning with Week 64 dosing.
Radiographic Global Impression of Change (RGI-C) Global Scores Over Time Change at Week 40	1.67 score on a scale Standard Error 0.12	1.46 score on a scale Standard Error 0.12
Radiographic Global Impression of Change (RGI-C) Global Scores Over Time Change at Week 64	1.56 score on a scale Standard Error 0.112	1.58 score on a scale Standard Error 0.112
Radiographic Global Impression of Change (RGI-C) Global Scores Over Time Change at Week 160	1.92 score on a scale Standard Error 0.111	1.86 score on a scale Standard Error 0.119

SECONDARY outcome

Timeframe: Baseline, Week 40, 64, 160

Population: ITT Analysis Set: all participants who received at least 1 dose of study therapy and had at least 1 post-dose measurement at given time point.

Outcome measures

Outcome measures
Measure	Burosumab Q2W n=26 Participants Burosumab SC injections Q2W. Dose was determined by the participant's weight and prescribed dose by their study doctor.	Burosumab Q4W Then Q2W n=26 Participants Burosumab SC injections Q4W. Dose was determined by the participant's weight and prescribed dose by their study doctor. Participants in Q4W were to switch to Q2W beginning with Week 64 dosing.
RGI-C Knee Scores Over Time Change at Week 40	1.60 score on a scale Standard Error 0.13	1.34 score on a scale Standard Error 0.13
RGI-C Knee Scores Over Time Change at Week 64	1.57 score on a scale Standard Error 0.104	1.53 score on a scale Standard Error 0.099
RGI-C Knee Scores Over Time Change at Week 160	2.01 score on a scale Standard Error 0.106	1.85 score on a scale Standard Error 0.118

SECONDARY outcome

Timeframe: Baseline, Week 40, 64, 160

Population: ITT Analysis Set: all participants who received at least 1 dose of study therapy and had at least 1 post-dose measurement at given time point.

Outcome measures

Outcome measures
Measure	Burosumab Q2W n=26 Participants Burosumab SC injections Q2W. Dose was determined by the participant's weight and prescribed dose by their study doctor.	Burosumab Q4W Then Q2W n=26 Participants Burosumab SC injections Q4W. Dose was determined by the participant's weight and prescribed dose by their study doctor. Participants in Q4W were to switch to Q2W beginning with Week 64 dosing.
RGI-C Wrist Scores Over Time Change at Week 40	1.64 score on a scale Standard Error 0.14	1.45 score on a scale Standard Error 0.14
RGI-C Wrist Scores Over Time Change at Week 64	1.65 score on a scale Standard Error 0.153	1.55 score on a scale Standard Error 0.124
RGI-C Wrist Scores Over Time Change at Week 160	1.78 score on a scale Standard Error 0.133	1.83 score on a scale Standard Error 0.132

SECONDARY outcome

Timeframe: Baseline, Week 40, 64, 160

Population: ITT Analysis Set: all participants who received at least 1 dose of study therapy and had at least 1 post-dose measurement at given time point.

Outcome measures

Outcome measures
Measure	Burosumab Q2W n=25 Participants Burosumab SC injections Q2W. Dose was determined by the participant's weight and prescribed dose by their study doctor.	Burosumab Q4W Then Q2W n=24 Participants Burosumab SC injections Q4W. Dose was determined by the participant's weight and prescribed dose by their study doctor. Participants in Q4W were to switch to Q2W beginning with Week 64 dosing.
Change From Baseline in Growth Velocity Over Time Week 0 to Week 40: Change from Baseline	0.96 cm/year Standard Deviation 1.677	0.39 cm/year Standard Deviation 2.559
Change From Baseline in Growth Velocity Over Time Week 0 to Week 64: Change from Baseline	0.73 cm/year Standard Deviation 1.399	0.37 cm/year Standard Deviation 2.164
Change From Baseline in Growth Velocity Over Time Week 64 to Week 112: Change from Baseline	0.29 cm/year Standard Deviation 2.284	0.09 cm/year Standard Deviation 2.523
Change From Baseline in Growth Velocity Over Time Week 112 to Week 160: Change from Baseline	0.67 cm/year Standard Deviation 2.318	0.54 cm/year Standard Deviation 3.158

SECONDARY outcome

Timeframe: Baseline, Week 40, 64, 160

Population: ITT Analysis Set: all participants who received at least 1 dose of study therapy and had at least 1 post-dose measurement at given time point.

Standing height Z scores are measures of height adjusted for a child's age and sex. The Z score indicates the number of standard deviations away from a reference population (from the CDC growth charts) in the same age range and with the same sex. A Z score of 0 is equal to the mean with negative numbers indicating values lower than the mean and positive values higher. Higher Z scores indicate a better outcome.

Outcome measures

Outcome measures
Measure	Burosumab Q2W n=26 Participants Burosumab SC injections Q2W. Dose was determined by the participant's weight and prescribed dose by their study doctor.	Burosumab Q4W Then Q2W n=26 Participants Burosumab SC injections Q4W. Dose was determined by the participant's weight and prescribed dose by their study doctor. Participants in Q4W were to switch to Q2W beginning with Week 64 dosing.
Change From Baseline in Standing Height Z Score Over Time Change to Week 40	0.17 Z score Standard Error 0.042	0.10 Z score Standard Error 0.051
Change From Baseline in Standing Height Z Score Over Time Change to Week 64	0.19 Z score Standard Error 0.051	0.12 Z score Standard Error 0.061
Change From Baseline in Standing Height Z Score Over Time Change to Week 160	0.35 Z score Standard Error 0.084	0.19 Z score Standard Error 0.089

SECONDARY outcome

Timeframe: Baseline, Week 40, 64, 160

Population: ITT Analysis Set: all participants who received at least 1 dose of study therapy and had at least 1 post-dose measurement at given time point.

Outcome measures

Outcome measures
Measure	Burosumab Q2W n=26 Participants Burosumab SC injections Q2W. Dose was determined by the participant's weight and prescribed dose by their study doctor.	Burosumab Q4W Then Q2W n=26 Participants Burosumab SC injections Q4W. Dose was determined by the participant's weight and prescribed dose by their study doctor. Participants in Q4W were to switch to Q2W beginning with Week 64 dosing.
Change From Baseline in Growth (Standing Height) Over Time Change at Week 40	5.03 cm Standard Deviation 1.232	4.49 cm Standard Deviation 1.455
Change From Baseline in Growth (Standing Height) Over Time Change at Week 64	7.48 cm Standard Deviation 1.934	6.98 cm Standard Deviation 1.594
Change From Baseline in Growth (Standing Height) Over Time Change at Week 160	18.38 cm Standard Deviation 2.958	17.22 cm Standard Deviation 2.653

SECONDARY outcome

Timeframe: Baseline, Week 40, 64, 160

Population: ITT Analysis Set: all participants who received at least 1 dose of study therapy and had at least 1 post-dose measurement at given time point.

Outcome measures

Outcome measures
Measure	Burosumab Q2W n=26 Participants Burosumab SC injections Q2W. Dose was determined by the participant's weight and prescribed dose by their study doctor.	Burosumab Q4W Then Q2W n=26 Participants Burosumab SC injections Q4W. Dose was determined by the participant's weight and prescribed dose by their study doctor. Participants in Q4W were to switch to Q2W beginning with Week 64 dosing.
Change From Baseline in Growth (Sitting Height) Over Time Change at Week 40	2.66 cm Standard Deviation 5.496	2.39 cm Standard Deviation 1.486
Change From Baseline in Growth (Sitting Height) Over Time Change at Week 64	3.08 cm Standard Deviation 2.405	3.45 cm Standard Deviation 1.390
Change From Baseline in Growth (Sitting Height) Over Time Change at Week 160	8.29 cm Standard Deviation 2.928	8.62 cm Standard Deviation 2.163

SECONDARY outcome

Timeframe: Baseline, Week 40, 64, 160

Population: ITT Analysis Set: all participants who received at least 1 dose of study therapy and had at least 1 post-dose measurement at given time point.

Outcome measures

Outcome measures
Measure	Burosumab Q2W n=26 Participants Burosumab SC injections Q2W. Dose was determined by the participant's weight and prescribed dose by their study doctor.	Burosumab Q4W Then Q2W n=26 Participants Burosumab SC injections Q4W. Dose was determined by the participant's weight and prescribed dose by their study doctor. Participants in Q4W were to switch to Q2W beginning with Week 64 dosing.
Change From Baseline in Growth (Arm Length) Over Time Change at Week 40	2.36 cm Standard Deviation 1.058	2.08 cm Standard Deviation 0.905
Change From Baseline in Growth (Arm Length) Over Time Change at Week 64	3.99 cm Standard Deviation 1.556	4.77 cm Standard Deviation 7.382
Change From Baseline in Growth (Arm Length) Over Time Change at Week 160	8.50 cm Standard Deviation 1.537	8.32 cm Standard Deviation 1.798

SECONDARY outcome

Timeframe: Baseline, Week 40, 64, 160

Population: ITT Analysis Set: all participants who received at least 1 dose of study therapy and had at least 1 post-dose measurement at given time point.

Outcome measures

Outcome measures
Measure	Burosumab Q2W n=26 Participants Burosumab SC injections Q2W. Dose was determined by the participant's weight and prescribed dose by their study doctor.	Burosumab Q4W Then Q2W n=26 Participants Burosumab SC injections Q4W. Dose was determined by the participant's weight and prescribed dose by their study doctor. Participants in Q4W were to switch to Q2W beginning with Week 64 dosing.
Change From Baseline in Growth (Leg Length) Over Time Change to Week 40	2.90 cm Standard Deviation 1.365	2.82 cm Standard Deviation 1.270
Change From Baseline in Growth (Leg Length) Over Time Change at Week 64	5.03 cm Standard Deviation 1.879	5.16 cm Standard Deviation 1.283
Change From Baseline in Growth (Leg Length) Over Time Change at Week 160	11.78 cm Standard Deviation 3.040	11.67 cm Standard Deviation 2.338

SECONDARY outcome

Timeframe: Baseline, Week 40, 64, 160

Population: ITT Analysis Set: all participants who received at least 1 dose of study therapy and had at least 1 post-dose measurement at given time point.

The total distance walked (meters) in a 6-minute period was measured. The percent of predicted values were calculated using published normative data based on age, gender, and height (Geiger et al. 2007).

Outcome measures

Outcome measures
Measure	Burosumab Q2W n=26 Participants Burosumab SC injections Q2W. Dose was determined by the participant's weight and prescribed dose by their study doctor.	Burosumab Q4W Then Q2W n=26 Participants Burosumab SC injections Q4W. Dose was determined by the participant's weight and prescribed dose by their study doctor. Participants in Q4W were to switch to Q2W beginning with Week 64 dosing.
6MWT Distance (Predicted Percent of Normal) Change From Baseline Over Time Change to Week 40	3.25 percentage of predicted distance Standard Error 1.841	0.24 percentage of predicted distance Standard Error 2.153
6MWT Distance (Predicted Percent of Normal) Change From Baseline Over Time Change to Week 64	5.29 percentage of predicted distance Standard Error 1.568	3.70 percentage of predicted distance Standard Error 1.731
6MWT Distance (Predicted Percent of Normal) Change From Baseline Over Time Change to Week 160	1.96 percentage of predicted distance Standard Error 1.483	2.15 percentage of predicted distance Standard Error 1.932

SECONDARY outcome

Timeframe: Baseline, Week 40, 64, 160

Population: ITT Analysis Set: all participants who received at least 1 dose of study therapy and had at least 1 post-dose measurement at given time point.

The POSNA-PODCI yields 4 functional assessment scores: Upper Extremity Function,Transfers and Basic Mobility, Sports and Physical Function, and Comfort/Pain. In addition, a Global Function score, which is an average of the 4 functional assessments, and a Happiness score are calculated. Raw, mean, standardized, and normative scores are calculated for each scale. Normative scores are calculated so that higher scores indicate better functioning. All scores are referenced to the general, healthy population with a normative mean score of 50 and a standard deviation of 10.

Outcome measures

Outcome measures
Measure	Burosumab Q2W n=26 Participants Burosumab SC injections Q2W. Dose was determined by the participant's weight and prescribed dose by their study doctor.	Burosumab Q4W Then Q2W n=25 Participants Burosumab SC injections Q4W. Dose was determined by the participant's weight and prescribed dose by their study doctor. Participants in Q4W were to switch to Q2W beginning with Week 64 dosing.
Change From Baseline in POSNA-PODCI (Normative Score) Upper Extremity Scale Scores Over Time Change at Week 40	2.97 T-score Standard Error 0.710	2.97 T-score Standard Error 1.212
Change From Baseline in POSNA-PODCI (Normative Score) Upper Extremity Scale Scores Over Time Change at Week 64	1.89 T-score Standard Error 0.914	3.20 T-score Standard Error 0.911
Change From Baseline in POSNA-PODCI (Normative Score) Upper Extremity Scale Scores Over Time Change at Week 160	-0.02 T-score Standard Error 0.740	1.82 T-score Standard Error 1.449

SECONDARY outcome

Timeframe: Baseline, Week 40, 64, 160

Population: ITT Analysis Set: all participants who received at least 1 dose of study therapy and had at least 1 post-dose measurement at given time point.

Outcome measures

Outcome measures
Measure	Burosumab Q2W n=26 Participants Burosumab SC injections Q2W. Dose was determined by the participant's weight and prescribed dose by their study doctor.	Burosumab Q4W Then Q2W n=25 Participants Burosumab SC injections Q4W. Dose was determined by the participant's weight and prescribed dose by their study doctor. Participants in Q4W were to switch to Q2W beginning with Week 64 dosing.
Change From Baseline in POSNA-PODCI (Normative Score) Transfer and Basic Mobility Scale Scores Over Time Change at Week 40	4.04 T-score Standard Error 0.827	3.69 T-score Standard Error 1.648
Change From Baseline in POSNA-PODCI (Normative Score) Transfer and Basic Mobility Scale Scores Over Time Change at Week 64	-0.34 T-score Standard Error 3.123	4.32 T-score Standard Error 1.364
Change From Baseline in POSNA-PODCI (Normative Score) Transfer and Basic Mobility Scale Scores Over Time Change at Week 160	1.88 T-score Standard Error 3.285	5.44 T-score Standard Error 1.113

SECONDARY outcome

Timeframe: Baseline, Week 40, 64, 160

Population: ITT Analysis Set: all participants who received at least 1 dose of study therapy and had at least 1 post-dose measurement at given time point.

Outcome measures

Outcome measures
Measure	Burosumab Q2W n=26 Participants Burosumab SC injections Q2W. Dose was determined by the participant's weight and prescribed dose by their study doctor.	Burosumab Q4W Then Q2W n=25 Participants Burosumab SC injections Q4W. Dose was determined by the participant's weight and prescribed dose by their study doctor. Participants in Q4W were to switch to Q2W beginning with Week 64 dosing.
Change From Baseline in POSNA-PODCI (Normative Score) Sports/Physical Functioning Scale Scores Over Time Change at Week 40	9.78 T-score Standard Error 1.679	9.15 T-score Standard Error 2.249
Change From Baseline in POSNA-PODCI (Normative Score) Sports/Physical Functioning Scale Scores Over Time Change at Week 64	7.74 T-score Standard Error 2.636	9.84 T-score Standard Error 2.534
Change From Baseline in POSNA-PODCI (Normative Score) Sports/Physical Functioning Scale Scores Over Time Change at Week 160	12.04 T-score Standard Error 2.102	14.33 T-score Standard Error 1.834

SECONDARY outcome

Timeframe: Baseline, Week 40, 64, 160

Population: ITT Analysis Set: all participants who received at least 1 dose of study therapy and had at least 1 post-dose measurement at given time point.

Outcome measures

Outcome measures
Measure	Burosumab Q2W n=26 Participants Burosumab SC injections Q2W. Dose was determined by the participant's weight and prescribed dose by their study doctor.	Burosumab Q4W Then Q2W n=25 Participants Burosumab SC injections Q4W. Dose was determined by the participant's weight and prescribed dose by their study doctor. Participants in Q4W were to switch to Q2W beginning with Week 64 dosing.
Change From Baseline in POSNA-PODCI (Normative Score) Pain/Comfort Scale Scores Over Time Change at Week 40	7.67 T-score Standard Error 2.399	7.39 T-score Standard Error 2.477
Change From Baseline in POSNA-PODCI (Normative Score) Pain/Comfort Scale Scores Over Time Change at Week 64	5.60 T-score Standard Error 2.904	7.74 T-score Standard Error 2.077
Change From Baseline in POSNA-PODCI (Normative Score) Pain/Comfort Scale Scores Over Time Change at Week 160	13.06 T-score Standard Error 2.187	12.38 T-score Standard Error 2.265

SECONDARY outcome

Timeframe: Baseline, Week 40, 64, 160

Population: ITT Analysis Set: all participants who received at least 1 dose of study therapy and had at least 1 post-dose measurement at given time point.

Outcome measures

Outcome measures
Measure	Burosumab Q2W n=26 Participants Burosumab SC injections Q2W. Dose was determined by the participant's weight and prescribed dose by their study doctor.	Burosumab Q4W Then Q2W n=25 Participants Burosumab SC injections Q4W. Dose was determined by the participant's weight and prescribed dose by their study doctor. Participants in Q4W were to switch to Q2W beginning with Week 64 dosing.
Change From Baseline in POSNA-PODCI (Normative Score) Happiness Scale Scores Over Time Change at Week 40	2.84 T-score Standard Error 2.328	3.01 T-score Standard Error 1.902
Change From Baseline in POSNA-PODCI (Normative Score) Happiness Scale Scores Over Time Change at Week 64	2.18 T-score Standard Error 1.914	3.34 T-score Standard Error 1.914
Change From Baseline in POSNA-PODCI (Normative Score) Happiness Scale Scores Over Time Change at Week 160	6.46 T-score Standard Error 2.486	9.19 T-score Standard Error 1.075

SECONDARY outcome

Timeframe: Baseline, Week 40, 64, 160

Population: ITT Analysis Set: all participants who received at least 1 dose of study therapy and had at least 1 post-dose measurement at given time point.

Outcome measures

Outcome measures
Measure	Burosumab Q2W n=26 Participants Burosumab SC injections Q2W. Dose was determined by the participant's weight and prescribed dose by their study doctor.	Burosumab Q4W Then Q2W n=25 Participants Burosumab SC injections Q4W. Dose was determined by the participant's weight and prescribed dose by their study doctor. Participants in Q4W were to switch to Q2W beginning with Week 64 dosing.
Change From Baseline in POSNA-PODCI (Normative Score) Global Functioning Scale Scores Over Time Change at Week 40	9.06 T-score Standard Error 1.560	8.12 T-score Standard Error 2.351
Change From Baseline in POSNA-PODCI (Normative Score) Global Functioning Scale Scores Over Time Change at Week 64	6.02 T-score Standard Error 2.706	8.72 T-score Standard Error 2.019
Change From Baseline in POSNA-PODCI (Normative Score) Global Functioning Scale Scores Over Time Change at Week 160	11.37 T-score Standard Error 1.804	11.94 T-score Standard Error 2.024

SECONDARY outcome

Timeframe: Baseline, Week 40, 64, 160

Population: Safety Analysis Set: All participants who received at least 1 dose of study therapy and had an assessment at given time point.

FEP is defined as 100% × (urine phosphorus × serum creatinine)/(urine creatinine × serum phosphorus), where the 2-hour urine sample was used for urine phosphorus and urine creatinine.

Outcome measures

Outcome measures
Measure	Burosumab Q2W n=25 Participants Burosumab SC injections Q2W. Dose was determined by the participant's weight and prescribed dose by their study doctor.	Burosumab Q4W Then Q2W n=26 Participants Burosumab SC injections Q4W. Dose was determined by the participant's weight and prescribed dose by their study doctor. Participants in Q4W were to switch to Q2W beginning with Week 64 dosing.
Change From Baseline in FEP Over Time Change at Week 40	-3.97 percentage of phosphorus excreted Standard Deviation 7.161	-4.85 percentage of phosphorus excreted Standard Deviation 7.170
Change From Baseline in FEP Over Time Change at Week 64	-2.63 percentage of phosphorus excreted Standard Deviation 4.446	-3.96 percentage of phosphorus excreted Standard Deviation 7.522
Change From Baseline in FEP Over Time Change at Week 160	-5.43 percentage of phosphorus excreted Standard Deviation 6.985	-6.47 percentage of phosphorus excreted Standard Deviation 8.072

SECONDARY outcome

Timeframe: Baseline, Week 40, 64

Population: PK/PD Analysis Set: all participants who received at least 1 dose of therapy and had evaluable serum data at given time point.

Outcome measures

Outcome measures
Measure	Burosumab Q2W n=24 Participants Burosumab SC injections Q2W. Dose was determined by the participant's weight and prescribed dose by their study doctor.	Burosumab Q4W Then Q2W n=26 Participants Burosumab SC injections Q4W. Dose was determined by the participant's weight and prescribed dose by their study doctor. Participants in Q4W were to switch to Q2W beginning with Week 64 dosing.
Change From Baseline in P1NP Over Time Change at Week 40	275.98 ng/mL Standard Deviation 329.587	224.91 ng/mL Standard Deviation 161.053
Change From Baseline in P1NP Over Time Change at Week 64	137.35 ng/mL Standard Deviation 354.315	133.56 ng/mL Standard Deviation 192.306

SECONDARY outcome

Timeframe: Baseline, Week 40, 64

Population: PK/PD Analysis Set: all participants who received at least 1 dose of therapy and had evaluable serum data at given time point.

Outcome measures

Outcome measures
Measure	Burosumab Q2W n=26 Participants Burosumab SC injections Q2W. Dose was determined by the participant's weight and prescribed dose by their study doctor.	Burosumab Q4W Then Q2W n=26 Participants Burosumab SC injections Q4W. Dose was determined by the participant's weight and prescribed dose by their study doctor. Participants in Q4W were to switch to Q2W beginning with Week 64 dosing.
Change From Baseline in CTx Over Time Change at Week 40	1.01 ng/mL Standard Deviation 0.802	0.64 ng/mL Standard Deviation 0.578
Change From Baseline in CTx Over Time Change at Week 64	1.08 ng/mL Standard Deviation 0.870	0.81 ng/mL Standard Deviation 0.706

SECONDARY outcome

Timeframe: Baseline, Week 40, 64, 160

Population: PK/PD Analysis Set: all participants who received at least 1 dose of therapy and had evaluable serum data at given time point.

Outcome measures

Outcome measures
Measure	Burosumab Q2W n=26 Participants Burosumab SC injections Q2W. Dose was determined by the participant's weight and prescribed dose by their study doctor.	Burosumab Q4W Then Q2W n=26 Participants Burosumab SC injections Q4W. Dose was determined by the participant's weight and prescribed dose by their study doctor. Participants in Q4W were to switch to Q2W beginning with Week 64 dosing.
Change From Baseline in ALP Over Time Change at Week 40	-79.4 U/L Standard Deviation 97.40	-47.8 U/L Standard Deviation 70.86
Change From Baseline in ALP Over Time Change at Week 64	-113.9 U/L Standard Deviation 81.28	-80.9 U/L Standard Deviation 67.11
Change From Baseline in ALP Over Time Change at Week 160	-153.1 U/L Standard Deviation 132.45	-140.0 U/L Standard Deviation 115.82

SECONDARY outcome

Timeframe: Baseline, Week 40, 64, 160

Population: PK/PD Analysis Set: all participants who received at least 1 dose of therapy and had evaluable serum data at given time point.

Outcome measures

Outcome measures
Measure	Burosumab Q2W n=20 Participants Burosumab SC injections Q2W. Dose was determined by the participant's weight and prescribed dose by their study doctor.	Burosumab Q4W Then Q2W n=20 Participants Burosumab SC injections Q4W. Dose was determined by the participant's weight and prescribed dose by their study doctor. Participants in Q4W were to switch to Q2W beginning with Week 64 dosing.
Change From Baseline in BALP Over Time Change at Week 40	-35.55 mcg/L Standard Deviation 46.738	-27.80 mcg/L Standard Deviation 31.409
Change From Baseline in BALP Over Time Change at Week 64	-50.40 mcg/L Standard Deviation 36.478	-47.13 mcg/L Standard Deviation 28.822
Change From Baseline in BALP Over Time Change at Week 160	-67.25 mcg/L Standard Deviation 59.309	-56.73 mcg/L Standard Deviation 52.284

SECONDARY outcome

Timeframe: Week 40, 64, 160

Population: PK/PD Analysis Set: all participants who received at least 1 dose of therapy and had evaluable serum data at given time point.

Outcome measures

Outcome measures
Measure	Burosumab Q2W n=26 Participants Burosumab SC injections Q2W. Dose was determined by the participant's weight and prescribed dose by their study doctor.	Burosumab Q4W Then Q2W n=26 Participants Burosumab SC injections Q4W. Dose was determined by the participant's weight and prescribed dose by their study doctor. Participants in Q4W were to switch to Q2W beginning with Week 64 dosing.
Serum Pre-Dose Concentrations of Burosumab Week 40	13188.81 ng/mL Standard Deviation 7188.588	6443.08 ng/mL Standard Deviation 3266.215
Serum Pre-Dose Concentrations of Burosumab Week 64	15846.65 ng/mL Standard Deviation 9385.393	8525.63 ng/mL Standard Deviation 3968.821
Serum Pre-Dose Concentrations of Burosumab Week 160	13975.27 ng/mL Standard Deviation 8168.877	13163.96 ng/mL Standard Deviation 6593.120

SECONDARY outcome

Timeframe: Up to 216 weeks

Population: Safety Analysis Set: All participants who received at least 1 dose of study therapy.

An AE is defined as any untoward medical occurrence associated with the use of a drug in humans, whether or not considered drug related. An SAE is defined as an AE or suspected adverse reaction that at any dose results in any of the following outcomes: death; life-threatening AE; inpatient hospitalization or prolongation of existing hospitalization; persistent or significant incapacity or substantial disruption of the ability to conduct normal life functions; a congenital anomaly/birth defect. Severity was graded as 1 (mild), 2 (moderate), 3 (severe), 4 (life-threatening), 5 (death). TEAEs are defined as AEs with onset on or after the time of initiation of study drug administration.

Outcome measures

Outcome measures
Measure	Burosumab Q2W n=26 Participants Burosumab SC injections Q2W. Dose was determined by the participant's weight and prescribed dose by their study doctor.	Burosumab Q4W Then Q2W n=26 Participants Burosumab SC injections Q4W. Dose was determined by the participant's weight and prescribed dose by their study doctor. Participants in Q4W were to switch to Q2W beginning with Week 64 dosing.
Number of Participants With Treatment Emergent Adverse Events (TEAEs), Serious Adverse Events (SAEs) and Discontinuations Due to Adverse Events (AEs) All TEAEs	26 Participants	26 Participants
Number of Participants With Treatment Emergent Adverse Events (TEAEs), Serious Adverse Events (SAEs) and Discontinuations Due to Adverse Events (AEs) Serious TEAE	0 Participants	1 Participants
Number of Participants With Treatment Emergent Adverse Events (TEAEs), Serious Adverse Events (SAEs) and Discontinuations Due to Adverse Events (AEs) Related TEAE	17 Participants	21 Participants
Number of Participants With Treatment Emergent Adverse Events (TEAEs), Serious Adverse Events (SAEs) and Discontinuations Due to Adverse Events (AEs) Serious Related TEAE	0 Participants	1 Participants
Number of Participants With Treatment Emergent Adverse Events (TEAEs), Serious Adverse Events (SAEs) and Discontinuations Due to Adverse Events (AEs) Grade 3 or 4 TEAE	1 Participants	1 Participants
Number of Participants With Treatment Emergent Adverse Events (TEAEs), Serious Adverse Events (SAEs) and Discontinuations Due to Adverse Events (AEs) TEAE Leading to Study Discontinuation	0 Participants	0 Participants
Number of Participants With Treatment Emergent Adverse Events (TEAEs), Serious Adverse Events (SAEs) and Discontinuations Due to Adverse Events (AEs) TEAE Leading to Treatment Discontinuation	0 Participants	0 Participants
Number of Participants With Treatment Emergent Adverse Events (TEAEs), Serious Adverse Events (SAEs) and Discontinuations Due to Adverse Events (AEs) TEAE Leading to Death	0 Participants	0 Participants

Adverse Events

Burosumab Q2W

Serious events: 0 serious events

Other events: 26 other events

Deaths: 0 deaths

Burosumab Q4W Then Q2W

Serious events: 1 serious events

Other events: 26 other events

Deaths: 0 deaths

Serious adverse events

Serious adverse events
Measure	Burosumab Q2W n=26 participants at risk Burosumab SC injections Q2W. Dose was determined by the participant's weight and prescribed dose by their study doctor.	Burosumab Q4W Then Q2W n=26 participants at risk Burosumab SC injections Q4W. Dose was determined by the participant's weight and prescribed dose by their study doctor. Participants in Q4W were to switch to Q2W beginning with Week 64 dosing.
General disorders Pyrexia	0.00% 0/26 • Up to 216 weeks TEAEs, defined as AEs with onset on or after the time of initiation of study drug administration, are presented.	3.8% 1/26 • Up to 216 weeks TEAEs, defined as AEs with onset on or after the time of initiation of study drug administration, are presented.
Musculoskeletal and connective tissue disorders Myalgia	0.00% 0/26 • Up to 216 weeks TEAEs, defined as AEs with onset on or after the time of initiation of study drug administration, are presented.	3.8% 1/26 • Up to 216 weeks TEAEs, defined as AEs with onset on or after the time of initiation of study drug administration, are presented.
Nervous system disorders Headache	0.00% 0/26 • Up to 216 weeks TEAEs, defined as AEs with onset on or after the time of initiation of study drug administration, are presented.	3.8% 1/26 • Up to 216 weeks TEAEs, defined as AEs with onset on or after the time of initiation of study drug administration, are presented.

Other adverse events

Additional Information

Medical Information

Ultragenyx Pharmaceutical Inc

Phone: 1-888-756-8567

Email: [email protected]

Results disclosure agreements

Principal investigator is a sponsor employee The only disclosure restriction on the PI is that the sponsor can review results communications prior to public release and can embargo communications regarding trial results for a period that is more than 60 days but less than or equal to 180 days from the time submitted to the sponsor for review. The sponsor cannot require changes to the communication and cannot extend the embargo.
Publication restrictions are in place

Restriction type: OTHER