Study to Investigate the Efficacy and Safety of Dupilumab in Pediatric Patients With Active Eosinophilic Esophagitis (EoE)

Part A: Percentage of Participants Achieving Peak Esophageal Intraepithelial Eosinophil Count of <15 Eosinophils/High Power Field at Week 16

Peak esophageal intraepithelial eosinophil count was measured from esophageal biopsies. A total of at least 9 mucosal pinch biopsies were collected from 3 esophageal regions: 3 proximal, 3 mid, and 3 distal. The peak esophageal intraepithelial eosinophil count at each visit was the maximum of the quantities of eosinophils in the most inflamed hpfs across the 3 regions. If the quantity of eosinophils was missing for 1 or 2 esophageal regions, the peak eosinophil count was the maximum of the quantities of eosinophils from the region(s) where eosinophil quantities were available.

Time frame: At Week 16

Part A: Percent Change From Baseline in Peak Esophageal Intraepithelial Eosinophil Count at Week 16

Peak esophageal intraepithelial eosinophil count was measured from esophageal biopsies. A total of at least 9 mucosal pinch biopsies were collected from 3 esophageal regions: 3 proximal, 3 mid, and 3 distal. The peak esophageal intraepithelial eosinophil count at each visit was the maximum of the quantities of eosinophils in the most inflamed hpfs across the 3 regions. If the quantity of eosinophils was missing for 1 or 2 esophageal regions, the peak eosinophil count was the maximum of the quantities of eosinophils from the region(s) where eosinophil quantities were available. Least squared (LS) mean and standard error (SE) from analysis of covariance (ANCOVA) model with Baseline measurement as covariate and the treatment, baseline weight group strata as fixed factors.

Time frame: Baseline, Week 16

Part A: Change From Baseline in Mean Eosinophilic Esophagitis Histology Scoring System (EoE-HSS) Grade Score at Week 16

EoE-HSS is a validated histologic scoring system that measures other histological abnormalities in addition to density of eosinophilic infiltration. Severity (grade) and extent (stage) of abnormalities will be scored using a 4-point scale (0 normal; 3 maximum change). Higher total score indicated greater severity \& extent of histological abnormalities. For each of 3 esophageal regions (proximal, mid, and distal), the ratio of the sum of assigned score for each evaluated feature divided by maximum possible score (maximum value is 24) was calculated. The mean grade scores summed over the 3 regions was the final score used in primary analysis, the mean grade score ranged from 0 to 3, with higher score indicating more severe.

Time frame: Baseline, Week 16

Part A: Change From Baseline in Mean Eosinophilic Esophagitis Histology Scoring System (EoE-HSS) Stage Score at Week 16

EoE-HSS is a validated histologic scoring system that measures other histological abnormalities in addition to density of eosinophilic infiltration. Severity (grade) and extent (stage) of abnormalities will be scored using a 4-point scale (0 normal; 3 maximum change). Higher total score indicated greater severity \& extent of histological abnormalities. For each of 3 esophageal regions (proximal, mid, and distal), the ratio of the sum of assigned score for each evaluated feature divided by maximum possible score (maximum value is 24) was calculated. The mean stage scores summed over the 3 regions was the final score used in primary analysis, the mean stage score ranged from 0 to 3, with higher score indicating more severe.

Time frame: Baseline, Week 16

Part A: Normalized Enrichment Score (NES) for the Relative Change From Baseline in the Type 2 Inflammation Signature (T2INF) at Week 16

A Normalized Enrichment Score (NES) is a way to generate a single numerical value to represent a complex gene expression signature. Changes in NES score represented the overall changes in the expression of that molecular phenotype. The NESs calculated for T2INF reflect the expression at Week 16 relative to Baseline of the pre-specified gene set as a way to evaluate normalization of type 2 inflammation with treatment. For each subject, an NES of 0 indicates no change from baseline, a negative score shows a reduction in disease score (more like normal) and positive score shows worsening (more active disease). NES does not have a minimum/maximum score.

Time frame: Baseline, Week 16

Part A: Normalized Enrichment Score (NES) for the Relative Change From Baseline in the Eosinophilic Esophagitis (EoE) Diagnostic Panel (EDP) at Week 16

A Normalized Enrichment Score (NES) is a way to generate a single numerical value to represent a complex gene expression signature. Changes in NES score represented the overall changes in the expression of that molecular phenotype. The NESs calculated for the EDP reflect the expression at Week 16 relative to Baseline of a gene set that is differentially expressed between esophageal biopsies from EoE participants compared to healthy controls as a way to evaluate normalization of the molecular pathology. For each subject, an NES of 0 indicates no change from baseline, a negative score shows a reduction in disease score (more like normal) and positive score shows worsening (more active disease). NES does not have minimum/maximum score.

Time frame: Baseline, Week 16

Part A: Absolute Change From Baseline in EoE Endoscopic Reference Total Score (EoE-EREFS) at Week 16

The EoE-EREFS is a validated endoscopic scoring system for inflammatory and remodeling features of EoE including edema, rings, exudates, furrows, and stricture. The score was assessed in the proximal and distal esophageal regions with each region scored from 0 to 9 with total scores ranging from 0 to 18. Higher scores indicate worse endoscopic inflammatory and remodeling findings.

Time frame: Baseline, Week 16

Part A: Change From Baseline in the Proportion of Days With 1 or More EoE Signs as Measured by Pediatric EoE Sign/Symptom Questionnaire - Caregiver Version (PESQ-C) at Week 16 (for Participants Aged ≥1 to <12 Years)

PESQ-C is a novel, observer-reported outcome measure intended to be completed independently by caregivers of all pediatric EoE participants in the study. PESQ-C measures the signs of EoE observed by the caregiver, including stomach pain, heartburn, acid reflux, regurgitation, vomiting, food refusal, and trouble swallowing food. Data from a 14-day period preceding the baseline visit and a 14-day period preceding week 16 will be used to calculate the proportion of days with 1 or more EoE symptoms.

Time frame: Baseline, Week 16

Part A: Number of Sign-free Days During the 14-day Period Preceding Week 16 as Measured by the PESQ-C (for Participants Aged ≥1 to <12 Years)

PESQ-C is a novel, observer-reported outcome measure intended to be completed independently by caregivers of all pediatric EoE participants in the study. The PESQ-C measures the signs of EoE observed by the caregiver, including stomach pain, heartburn, acid reflux, regurgitation, vomiting, food refusal, and trouble swallowing food. WOCF approach was used for imputing the missing data due to rescue treatment/AE/lack of efficacy, and the multiple imputations approach was used for the missing data due to other reasons. LS mean SE derived from ANCOVA model.

Time frame: Week 16

Part A: Change From Baseline in the Proportion of Total Segments Within a Day (Night, Morning, Afternoon, Evening) With 1 or More EoE Signs as Measured by the PESQ-C at Week 16

PESQ-C is a novel, observer-reported outcome measure intended to be completed independently by caregivers of all pediatric EoE participants in the study. The PESQ-C measured the occurrence of signs of EoE and was completed once daily via an electronic diary. Data from a 14-day period preceding the baseline visit and a 14-day period preceding week 16 will be used to calculate the total time segments within a day (night, morning, afternoon, evening) with 1 or more EoE symptoms.

Time frame: Baseline, Week 16

Part A: Change From Baseline in the Proportion of Days With 1 or More EoE Signs by Pediatric EoE Sign/Symptom Questionnaire - Participant Version (PESQ-P) (for Participants Aged ≥8 to <12 Years) at Week 16

The PESQ-P was a participant-reported outcome measure intended to be completed independently by participants ≥8 to \<12 years of age. The PESQ-P measured occurrence of signs of EoE and was completed once daily via an electronic diary. Data from a 14-day period preceding the baseline visit and a 14-day period preceding week 16 will be used to calculate the proportion of days with 1 or more EoE symptoms.

Time frame: Baseline, Week 16

Part A: Number of Symptom-free Days During the 14-day Period Preceding Week 16 as Measured by the PESQ-P (for Participants Aged ≥8 to <12 Years)

The PESQ-P was a participant-reported outcome measure intended to be completed independently by EoE participants ≥8 to \<12 years of age. The PESQ-P measures the signs of EoE, including stomach pain, heartburn, acid reflux, regurgitation, vomiting, food refusal, and trouble swallowing food. The PESQ-P score was calculated based on the daily responses over a 14-day period (i.e., the 14 days prior to the baseline visit and the week 16 visit). The score ranges from 0 to 1. WOCF approach was used for imputing the missing data due to rescue treatment/AE/lack of efficacy, and the multiple imputations approach was used for the missing data due to other reasons. LS Mean SE from ANCOVA.

Time frame: Week 16

Part A: Change From Baseline in the Proportion of Total Segments Within a Day (Night, Morning, Afternoon, Evening) With 1 or More EoE Signs as Measured by the PESQ-P (for Participants Aged ≥8 to <12 Years) at Week 16

The PESQ-P was a participant-reported outcome measure intended to be completed independently by EoE participants ≥8 to \<12 years of age. The PESQ-P measured the occurrence of signs of EoE and was completed once daily via an electronic diary. Data from a 14-day period preceding the baseline visit and a 14-day period preceding week 16 will be used to calculate the total time segments within a day (night, morning, afternoon, evening) with 1 or more EoE symptoms.

Time frame: Baseline, Week 16

Part A: Change From Baseline in Total Score as Measured by the Pediatric Eosinophilic Esophagitis Symptom Score (PEESS) Version 2.0 Caregiver Version (PEESSv2.0-C) at Week 16

The PEESSv2.0-C is a caregiver-reported outcome measure that assesses the frequency and severity of EoE symptoms among pediatric participants. The PEESSv2.0-C consists of 20 items and has a one-month recall period. Each item had a 0-4 scale, which was transformed to 0-100 as follows: 0 = 0, 1 = 25, 2 = 50, 3 = 75, 4 = 100. The mean total PEESSv2.0 score was computed as the sum of all the item scores over the number of items answered. The total PEESSv2.0-C score ranges from 0 to 100 where higher scores indicate greater symptom burden among pediatric EoE participants. Values after first rescue treatment use were set to missing (censoring). WOCF approach was used for imputing the missing data due to rescue treatment/AE/lack of efficacy, and the MI approach was used for the missing data due to other reasons. LS mean SE from ANCOVA model.

Time frame: Baseline, Week 16

Part A: Concentration of Functional Dupilumab in Serum at Baseline, Week 4 and 16

Concentration of functional dupilumab in serum at Baseline, Week 4 and 16 was reported in this outcome measure.

Time frame: Baseline, Week 4 and 16

Part B: Percentage of Participants Achieving Peak Esophageal Intraepithelial Eosinophil Count of ≤6 Eosinophils/High Power Field at Week 52

Peak esophageal intraepithelial eosinophil count was measured from esophageal biopsies. A total of at least 9 mucosal pinch biopsies were collected from 3 esophageal regions: 3 proximal, 3 mid, and 3 distal. The peak esophageal intraepithelial eosinophil count at each visit was the maximum of the quantities of eosinophils in the most inflamed hpfs across the 3 regions. If the quantity of eosinophils was missing for 1 or 2 esophageal regions, the peak eosinophil count was the maximum of the quantities of eosinophils from the region(s) where eosinophil quantities were available.

Time frame: At Week 52

Part B: Percentage of Participants Achieving Peak Esophageal Intraepithelial Eosinophil Count of <15 Eosinophils/High Power Field at Week 52

Peak esophageal intraepithelial eosinophil count was measured from esophageal biopsies. A total of at least 9 mucosal pinch biopsies were collected from 3 esophageal regions: 3 proximal, 3 mid, and 3 distal. The peak esophageal intraepithelial eosinophil count at each visit was the maximum of the quantities of eosinophils in the most inflamed hpfs across the 3 regions. If the quantity of eosinophils was missing for 1 or 2 esophageal regions, the peak eosinophil count was the maximum of the quantities of eosinophils from the region(s) where eosinophil quantities were available.

Time frame: At Week 52

Part B: Percent Change From Baseline in Peak Esophageal Intraepithelial Eosinophil Count at Week 52

Peak esophageal intraepithelial eosinophil count was measured from esophageal biopsies. A total of at least 9 mucosal pinch biopsies were collected from 3 esophageal regions: 3 proximal, 3 mid, and 3 distal. The peak esophageal intraepithelial eosinophil count at each visit was the maximum of the quantities of eosinophils in the most inflamed hpfs across the 3 regions. If the quantity of eosinophils was missing for 1 or 2 esophageal regions, the peak eosinophil count was the maximum of the quantities of eosinophils from the region(s) where eosinophil quantities were available.

Time frame: Baseline, Week 52

Part B: Change From Baseline in Mean Eosinophilic Esophagitis Histology Scoring System (EoE-HSS) Grade Score at Week 52

EoE-HSS is a validated histologic scoring system that measures other histological abnormalities in addition to density of eosinophilic infiltration. Severity (grade) and extent (stage) of abnormalities will be scored using a 4-point scale (0 normal; 3 maximum change). Higher total score indicated greater severity \& extent of histological abnormalities. For each of 3 esophageal regions (proximal, mid, and distal), the ratio of the sum of assigned score for each evaluated feature divided by maximum possible score (maximum value is 24) was calculated. The mean grade scores summed over the 3 regions was the final score used in primary analysis, the mean grade score ranged from 0 to 3, with higher score indicating more severe.

Time frame: Baseline, Week 52

Part B: Change From Baseline in Mean Eosinophilic Esophagitis Histology Scoring System (EoE-HSS) Stage Score at Week 52

EoE-HSS is a validated histologic scoring system that measures other histological abnormalities in addition to density of eosinophilic infiltration. Severity (grade) and extent (stage) of abnormalities will be scored using a 4-point scale (0 normal; 3 maximum change). Higher total score indicated greater severity \& extent of histological abnormalities. For each of 3 esophageal regions (proximal, mid, and distal), the ratio of the sum of assigned score for each evaluated feature divided by maximum possible score (maximum value is 24) was calculated. The mean stage scores summed over the 3 regions was the final score used in primary analysis, the mean stage score ranged from 0 to 3, with higher score indicating more severe.

Time frame: Baseline, Week 52

Part B: Absolute Change From Baseline in EoE Endoscopic Reference Total Score (EoE-EREFS) at Week 52

The EoE-EREFS is a validated endoscopic scoring system for inflammatory and remodeling features of EoE including edema, rings, exudates, furrows, and stricture. The score was assessed in the proximal and distal esophageal regions with each region scored from 0 to 9 with total scores possibly ranging from 0 to 18. Higher scores indicate worse endoscopic inflammatory and remodeling findings.

Time frame: Baseline, Week 52

Part B: Change From Baseline in the Proportion of Days With 1 or More EoE Signs Measured by Pediatric EoE Sign/Symptom Questionnaire - Caregiver Version (PESQ-C) at Week 52

PESQ-C is a novel, observer-reported outcome measure intended to be completed independently by caregivers of all pediatric EoE participants in the study.

Time frame: Baseline, Week 52

Part B: Number of Sign-free Days During the 14-day Period Preceding Week 52 as Measured by the PESQ-C (for Participants Aged ≥1 to <12 Years)

PESQ-C is a novel, observer-reported outcome measure intended to be completed independently by caregivers of all pediatric EoE participants in the study.

Time frame: Week 52

Part B: Change From Baseline in the Proportion of Total Segments Within a Day (Night, Morning, Afternoon, Evening) With 1 or More EoE Signs as Measured by the PESQ-C at Week 52

PESQ-C is a novel, observer-reported outcome measure intended to be completed independently by caregivers of all pediatric EoE participants in the study. The PESQ-C measured the occurrence of signs of EoE and was completed once daily via an electronic diary.

Time frame: Baseline, Week 52

Part B: Change From Baseline in the Proportion of Days With 1 or More EoE Signs by Pediatric EoE Sign/Symptom Questionnaire - Participant Version (PESQ-P) (for Participants Aged ≥8 to <12 Years) at Week 52

The PESQ-P was a participant-reported outcome measure intended to be completed independently by participants ≥8 to \<12 years of age. The PESQ-P measured occurrence of signs of EoE and was completed once daily via an electronic diary. Data from a 14-day period preceding the baseline visit and a 14-day period preceding week 16 will be used to calculate the proportion of days with 1 or more EoE symptoms.

Time frame: Baseline, Week 52

Part B: Number of Symptom-free Days During the 14-day Period Preceding Week 52 as Measured by the PESQ-P (for Participants Aged ≥8 to <12 Years)

The PESQ-P was a participant-reported outcome measure intended to be completed independently by participants ≥8 to \<12 years of age. The PESQ-P measures the signs of EoE, including stomach pain, heartburn, acid reflux, regurgitation, vomiting, food refusal, and trouble swallowing food.

Time frame: Week 52

Part B: Change From Baseline in the Proportion of Total Segments Within a Day (Night, Morning, Afternoon, Evening) With 1 or More EoE Signs as Measured by the PESQ-P (for Participants Aged ≥8 to <12 Years) at Week 52

The PESQ-P was a participant-reported outcome measure intended to be completed independently by EoE participants ≥8 to \<12 years of age. The PESQ-P measured the occurrence of signs of EoE and was completed once daily via an electronic diary. Data from a 14-day period preceding the baseline visit and a 14-day period preceding week 16 will be used to calculate the total time segments within a day (night, morning, afternoon, evening) with 1 or more EoE symptoms.

Time frame: Baseline, Week 52

Part B: Normalized Enrichment Score (NES) for the Relative Change From Baseline in the EoE Diagnostic Panel (EDP) at Week 52

A Normalized Enrichment Score (NES) is a way to generate a single numerical value to represent a complex gene expression signature. Changes in NES score represented the overall changes in the expression of that molecular phenotype. The NESs calculated for the EDP reflect the expression at post-baseline relative to Baseline of a gene set that is differentially expressed between esophageal biopsies from EoE participants compared to healthy controls as a way to evaluate normalization of the molecular pathology. For each subject, an NES of 0 indicates no change from baseline, a negative score shows a reduction in disease score (more like normal) and positive score shows worsening (more active disease). NES does not have minimum/maximum score.

Time frame: Baseline, Week 52

Part B: Normalized Enrichment Score (NES) for the Relative Change From Baseline in the Type 2 Inflammation Signature (T2INF) at Week 52

A Normalized Enrichment Score (NES) is a way to generate a single numerical value to represent a complex gene expression signature. Changes in NES score represented the overall changes in the expression of that molecular phenotype. The NESs calculated for T2INF reflect the expression at post-baseline relative to Baseline of the pre-specified gene set as a way to evaluate normalization of type 2 inflammation with treatment. For each subject, an NES of 0 indicates no change from baseline, a negative score shows a reduction in disease score (more like normal) and positive score shows worsening (more active disease). NES does not have minimum/maximum score.

Time frame: Baseline, Week 52

Part B: Change From Baseline in Body Weight for Age Percentile at Week 52

Body weight for age percentile was calculated based on the growth charts from the Centers for Disease Control and Prevention (CDC) for ages 0 to 20 years (for ages 2 to \<12 years) and World Health Organization (WHO) growth charts for ages 0 to \<2 years (for ages 1 to \<2 years). These charts included a set of smoothed percentiles along with CDC LMS (Lambda-Mu-Sigma) parameters to allow the calculation of percentiles.

Time frame: Baseline, Week 52

Part B: Change From Baseline in Body Mass Index (BMI) for Age Z-score for Participants ≥2 Years of Age at Week 52

BMI for age z-score indicates how much higher or lower a participant's BMI for age is relative to a reference growth chart (based on the growth charts from Centers for Disease Control and Prevention \[CDC\] for ages 0 to 20 years \[for ages 2 to \<12 years\]). A z-score of "0" represents the population mean. An increase in the mean change in BMI for age z-score (ie, increase in the standard deviation \[SD\] from the reference growth chart) indicates an increase in BMI for age relative to the reference.

Time frame: Baseline, Week 52

Part B: Change From Baseline in Weight for Age Z-score at Week 52

Weight for age z-score indicates how much higher or lower a participant's weight for age is relative to a reference growth chart (based on the growth charts from CDC for ages 0 to 20 years \[for ages 2 to \<12 years\] and World Health Organization (WHO) growth charts for ages 0 to \<2 years \[for ages 1 to \<2 years\]). A z-score of "0" represents the population mean. An increase in the mean change in weight for age z-score (increase in the SD from the reference growth chart) indicates an increase in weight for age relative to the reference.

Time frame: Baseline, Week 52

Part B: Change From Baseline in Body Weight From Height Z-score at Week 52

Weight for height z-score indicates how much higher or lower a participant's weight for height is relative to a reference growth chart (based on the growth charts from CDC for ages 0 to 20 years \[for ages 2 to \<12 years\] and WHO growth charts for ages 0 to \<2 years \[for ages 1 to \<2 years\]). A z-score of "0" represents the population mean. An increase in the mean change in weight for height z-score (increase in the SD from the reference growth chart) indicates an increase in weight for height relative to the reference.

Time frame: Baseline, Week 52

Part B: Concentration of Functional Dupilumab in Serum at Week 32 and 52

Concentration of functional dupilumab in serum at Week 32 and 52 was reported in this outcome measure.

Time frame: Week 32 and 52

Part A: Number of Participants With Treatment-Emergent Adverse Events (TEAEs), Serious TEAEs, Adverse Events of Special Interest (AESIs) and TEAEs Leading to Permanent Discontinuation of Study Drug

An adverse event (AE) was defined as any untoward medical occurrence in a participant or clinical investigation patient administered with a pharmaceutical product and which does not necessarily have to have a causal relationship with this treatment. A serious AE was any untoward medical occurrence that at any dose resulted in death, life-threatening, initial or prolonged inpatient hospitalization, persistent or significant disability/incapacity, congenital anomaly/birth defect, or a medically important event. The term TEAE is defined as AEs starting or worsening after the first intake of the study drug. TEAEs include both Serious TEAEs and non-serious TEAEs. An AESI was defined as one of scientific and medical concern specific to the Sponsor's product or program, for which ongoing monitoring and rapid communication by the Investigator to the Sponsor was appropriate.

Time frame: From Baseline up to Week 16 in Part A

Part B: Number of Participants With Treatment-Emergent Adverse Events (TEAEs), Serious TEAEs, Adverse Events of Special Interest (AESIs) and TEAEs Leading to Permanent Discontinuation of Study Drug

An AE was defined as any untoward medical occurrence in a participant or clinical investigation patient administered with a pharmaceutical product and which does not necessarily have to have a causal relationship with this treatment. A serious AE was any untoward medical occurrence that at any dose resulted in death, life-threatening, initial or prolonged inpatient hospitalization, persistent or significant disability/incapacity, congenital anomaly/birth defect, or a medically important event. The term TEAE is defined as AEs starting or worsening after the first intake of the study drug. TEAEs include both Serious TEAEs and non-serious TEAEs. An AESI was defined as one of scientific and medical concern specific to the Sponsor's product or program, for which ongoing monitoring and rapid communication by the Investigator to the Sponsor was appropriate.

Time frame: From Week 16 up to Week 52 in Part B

Part A: Number of Participants With Positive Treatment-emergent Antidrug Antibodies (ADA) Response

Treatment-emergent ADA was defined as a negative result or missing result at baseline with at least one positive post baseline result in the ADA assay. Samples positive in the dupilumab ADA assay were characterized for ADA titers (low, moderate and high). The low treatment-emergent ADA titer as defined as titer level \<1000, moderate as 1000 to 10000 and high as \>10000.

Time frame: From Baseline up to Week 16 in Part A

Part A: Number of Participants With Positive Treatment-emergent Antidrug Antibodies (ADA) by Maximum Titer Category

Treatment-emergent ADA was defined as a negative result or missing result at baseline with at least one positive post baseline result in the ADA assay. Samples positive in the dupilumab ADA assay were characterized for ADA titers (low, moderate and high). The low treatment-emergent ADA titer as defined as titer level \<1000, moderate as 1000 to 10000 and high as \>10000.

Time frame: From Baseline up to Week 16 in Part A

Part B: Number of Participants With Positive Treatment-emergent Antidrug Antibodies (ADA) Response and Titer

Treatment-emergent ADA was defined as a negative result or missing result at baseline with at least one positive post baseline result in the ADA assay. Samples positive in the dupilumab ADA assay were characterized for ADA titers (low, moderate and high). The low treatment-emergent ADA titer as defined as titer level \<1000, moderate as 1000 to 10000 and high as \>10000. No participant exhibited a treatment-emergent ADA response in Part B and titer was not reported.

Time frame: From Week 16 up to Week 52 in Part B

Part C: Percentage of Participants Achieving Peak Esophageal Intraepithelial Eosinophil Count of <15 Eos/Hpf At Week 100

Time frame: At Week 100

Part C: Percentage of Participants Achieving Peak Esophageal Intraepithelial Eosinophil Count of <15 Eos/Hpf At Week 160

Time frame: At Week 160

Part C: Percent Change in Peak Esophageal Intraepithelial Eosinophil Count (Eos/Hpf) From Baseline to Week 100

Time frame: Baseline to Week 100

Part C: Percent Change in Peak Esophageal Intraepithelial Eosinophil Count (Eos/Hpf) From Baseline to Week 160

Time frame: Baseline to Week 160

Part C: Absolute Change in Mean EoE-HSS From Baseline to Week 100

Time frame: Baseline to Week 100

Part C: Absolute Change in Mean EoE-HSS From Baseline to Week 160

Time frame: Baseline to Week 160

Part C: Absolute Change in EoE-EREFS From Baseline to Week 100

Time frame: Baseline to Week 100

Part C: Absolute Change in EoE-EREFS From Baseline to Week 160

Time frame: Baseline to Week 160

Part C: Change in Total Score as Measured by the PEESSv2.0- Caregiver Version Questionnaire From Baseline to Week 100

The PEESSv2.0-C is a caregiver-reported outcome measure that assesses the frequency and severity of EoE symptoms among pediatric participants. The PEESSv2.0-C consists of 20 items and has a one-month recall period. Each item had a 0-4 scale, which was transformed to 0-100 as follows: 0 = 0, 1 = 25, 2 = 50, 3 = 75, 4 = 100. The mean total PEESSv2.0 score was computed as the sum of all the item scores over the number of items answered. The total PEESSv2.0-C score ranges from 0 to 100 where higher scores indicate greater symptom burden among pediatric EoE participants.

Time frame: Baseline to Week 100

Part C: NES for the Relative Change in the EDP Transcriptome Signature From Baseline to Week 100

A Normalized Enrichment Score (NES) is a way to generate a single numerical value to represent a complex gene expression signature. Changes in NES score represented the overall changes in the expression of that molecular phenotype. The NESs calculated for the EDP reflect the expression at post-baseline relative to Baseline of a gene set that is differentially expressed between esophageal biopsies from EoE participants compared to healthy controls as a way to evaluate normalization of the molecular pathology. For each subject, an NES of 0 indicates no change from baseline, a negative score shows a reduction in disease score (more like normal) and positive score shows worsening (more active disease). NES does not have minimum/maximum score.

Time frame: Baseline to Week 100

Part C: NES for the Relative Change in the EDP Transcriptome Signature From Baseline to Week 160

A Normalized Enrichment Score (NES) is a way to generate a single numerical value to represent a complex gene expression signature. Changes in NES score represented the overall changes in the expression of that molecular phenotype. The NESs calculated for the EDP reflect the expression at post-baseline relative to Baseline of a gene set that is differentially expressed between esophageal biopsies from EoE participants compared to healthy controls as a way to evaluate normalization of the molecular pathology. For each subject, an NES of 0 indicates no change from baseline, a negative score shows a reduction in disease score (more like normal) and positive score shows worsening (more active disease). NES does not have minimum/maximum score.

Time frame: Baseline to Week 160

Part C: NES for the Relative Change in the Type 2 Inflammation Transcriptome Signature Baseline to Week 100

Time frame: Baseline to Week 100

Part C: NES for the Relative Change in the Type 2 Inflammation Transcriptome Signature From Baseline to Week 160

Time frame: Baseline to Week 160

Part C: Change in Body Weight for Age Percentile From Baseline up to Week 100

Body weight for age percentile was calculated based on the growth charts from the Centers for Disease Control and Prevention (CDC) for ages 0 to 20 years (for ages 2 to \<12 years) and World Health Organization (WHO) growth charts for ages 0 to \<2 years (for ages 1 to \<2 years). These charts included a set of smoothed percentiles along with CDC LMS (Lambda-Mu-Sigma) parameters to allow the calculation of percentiles.

Time frame: Baseline up to Week 100

Part C: Change in Body Mass Index for Age Z-score From Baseline up to Week 100

Difference in the 100-week change from baseline in BMI-for-age Z-score. BMI-for-age Z-scores are based on a reference growth chart (based on the growth charts from Centers for Disease Control and Prevention \[CDC\] for ages 0 to 20 years \[for ages 2 to \<12 years\]. A z-score of "0" represents the population mean. The Z-score indicates the number of standard deviations away from the mean of the reference population. A negative Z-score indicates values lower than the population mean while a positive Z-score indicates values higher than the population mean.

Time frame: Baseline up to Week 100

Part C: Change in Weight for Age Z-score From Baseline up to Week 100

Difference in the 100-week change from baseline in weight-for-age Z-score. Weight-for-age Z-scores are based on a reference growth chart (based on the growth charts from Centers for Disease Control and Prevention \[CDC\] for ages 0 to 20 years \[for ages 2 to \<12 years\]. A z-score of "0" represents the population mean. The Z-score indicates the number of standard deviations away from the mean of the reference population. A negative Z-score indicates values lower than the population mean while a positive Z-score indicates values higher than the population mean.

Time frame: Baseline up to Week 100

Part C: Change in Weight for Age Z-score From Baseline up to Week 160

Weight for age z-score indicates how much higher or lower a participant's weight for age is relative to a reference growth chart (based on the growth charts from CDC for ages 0 to 20 years \[for ages 2 to \<12 years\] and World Health Organization (WHO) growth charts for ages 0 to \<2 years \[for ages 1 to \<2 years\]). An increase in the mean change in weight for age z-score (increase in the SD from the reference growth chart) indicates an increase in weight for age relative to the reference.

Time frame: Baseline up to Week 160

Part C: Change in Weight for Height Z-score From Baseline up to Week 100

Difference in the 100-week change from baseline in Weight for height Z-score. Weight for height Z-scores are based on a reference growth chart (based on the growth charts from Centers for Disease Control and Prevention \[CDC\] for ages 0 to 20 years \[for ages 2 to \<12 years\]. A z-score of "0" represents the population mean. The Z-score indicates the number of standard deviations away from the mean of the reference population. A negative Z-score indicates values lower than the population mean while a positive Z-score indicates values higher than the population mean.

Time frame: Baseline up to Week 100

Part C: Change in Weight for Height Z-score From Baseline up to Week 160

Weight for height z-score indicates how much higher or lower a participant's weight for height is relative to a reference growth chart (based on the growth charts from CDC for ages 0 to 20 years \[for ages 2 to \<12 years\] and WHO growth charts for ages 0 to \<2 years \[for ages 1 to \<2 years\]). An increase in the mean change in weight for height z-score (increase in the SD from the reference growth chart) indicates an increase in weight for height relative to the reference.

Time frame: Baseline up to Week 160

Part C: Percentage of Participants Achieving Peak Esophageal Intraepithelial Eosinophil Count of ≤6 Eos/Hpf (400×) at Week 100

Time frame: At Week 100

Part C: Percentage of Participants Achieving Peak Esophageal Intraepithelial Eosinophil Count of ≤6 Eos/Hpf (400×) at Week 160

Time frame: At Week 160

Part C: Percentage of Participants (With Food Elimination Diet Regimens at Baseline) That Have a Re-introduction of a Previously Eliminated Food Group From Baseline up to Week 100

Time frame: Baseline up to Week 100

Part C: Percentage of Participants (With Food Elimination Diet Regimens at Baseline) That Have a Re-introduction of a Previously Eliminated Food Group From Baseline up to Week 160

Time frame: Baseline up to Week 160

Part C: Number of Participants With TEAEs

Time frame: Up to Week 152

Part C: Number of Participants With Treatment-emergent SAEs

Time frame: Up to Week 152

Part C: Number of Participants With Treatment-emergent AESIs

Time frame: Up to Week 152

Part C: Number of Participants With TEAEs Leading to Permanent Discontinuation of Study Treatment

Time frame: Up to Week 152

Part C: Number of Participants With Treatment-emergent ADA Responses

Time frame: From Week 52 up to Week 152

Part C: Concentration of Functional Dupilumab in Serum at Week 100

Time frame: At Week 100