A Study to Investigate the Pharmacokinetics and Safety of Dupilumab in Participants ≥2 Years to <12 Years of Age With Uncontrolled Chronic Spontaneous Urticaria (CSU) (LIBERTY-CSU CUPIDKids)

Blood samples were collected at specified timepoints to obtain dupilumab concentration.

Time frame: Weeks 12 and 24

Population: The pharmacokinetic (PK) population included all enrolled and treated participants (safety population) with at least 1 post-baseline PK result. Only those participants with data collected at Weeks 12 or 24 are reported.

The C-DLQI assesses impact of skin disease on children's health-related quality of life (HRQoL) over the previous week, contains 10 questions related to symptoms feelings associated with disease, impact of disease on leisure, school or holidays, personal relationships, sleep, and side effects of treatment for the skin disease. All questions were scored on 4-point Likert scale:0 (not at all),1 (a little),2 (a lot),3 (very much). Total C-DLQI was calculated by summing the score of each question and ranged from 0 (no impact) to 30 (severe impact). Higher scores indicated poor HRQoL. Mean is presented. Baseline was defined as closest assessment to first study intervention administration on or prior to Day 1 but no later than Day 4.

Time frame: Baseline (Day 1) and Week 24

Population: The intent-to-treat (ITT) population included all enrolled participants. Only those participants with data collected at Baseline and Week 24 are reported.

The HSS7 score is the sum of daily HSS ranging from ranging from 0 to 3 (0 = absent; 1 = mild \[1 to \<10 wheals/24 hours\]; 2 = moderate \[10 to 30 wheals/24 hours\]; and 3 = intense: \[\>30 wheals/24 hours or large confluent areas of wheals\]) recorded by a participant at the same time of each day over 7 days with an overall scale of 0 (no hives) to 21 (severe hives). Higher scores indicate greater intensity of hives. Mean is presented. Baseline was defined as sum of the 7 daily measurements obtained within the 7 days prior to first study intervention administration.

Time frame: Baseline (Day -7 to Day 1) and Week 24

Population: The ITT population included all enrolled participants. Only those participants with data collected at Baseline and Week 24 are reported.

The IDQOL questionnaire is completed by child's caregiver/guardian with a recall period of 7 days;consists of 10 questions focusing on life quality index (LQI) scored on 4-point Likert scale. An additional question on dermatitis severity is scored on a 5-point Likert scale (0 \[none\] to 4 \[extremely severe\]); it is not considered for calculating total IDQOL. For LQI, score ranges are as follows: Questions 1, 5 to 10: 0 (none) to 3 (all the time/very much). Question 2: 0 (happy), 1 (slightly fretful), 2 (very fretful),3 (always crying). Question 3: 0 (0-15 minutes), 1 (15 minutes-1 hour), 2 (1-2 hours),3 (\>2 hours).Question 4: 0 (\<1 hour), 1 (1-2 hours), 2 (3-4 hours),3 (\>=5 hours). IDQOL total score is the sum of the score of each question of LQI, ranges from 0 (no impact) to 30 (maximum impact). Higher scores indicated poor HRQoL. Mean is presented. Baseline was defined as closest assessment to first study intervention administration on or prior to Day 1 but no later than Day 4.

Time frame: Baseline (Day 1) and Week 24

Population: The ITT population included all enrolled participants. Only those participants with data collected at Baseline and Week 24 are reported.

The ISS represents severity of itch on a scale ranging from 0 (none) to 3 (intense). The ISS7 score was the sum of daily ISS scores recorded by a participant at the same time each day over 7 days with an overall scale of 0 (no impact) to 21 (severe impact). Higher scores indicated greater intensity of itch. Mean is presented. Baseline was defined as sum of the 7 daily measurements obtained within the 7 days prior to first study intervention administration.

Time frame: Baseline (Day -7 to Day 1) and Week 24

Population: The ITT population included all enrolled participants. Only those participants with data collected at Baseline and Week 24 are reported.

A modified version of the UAS (mUAS) was used for the smaller body surface area of child and adolescent participants. The mUAS was derived from the sum of daily hives severity score (HSS) (ranging from 0 to 3 \[0 = absent; 1 = mild {1 to \<10 wheals/24 hours}; 2 = moderate: {10 to 30 wheals/24 hours}; and 3 = intense: {\>30 wheals/24 hours or large confluent areas of wheals}\]) and daily itch severity score (ISS) (ranging from 0 = none to 3 = intense). Daily mUAS total scores range from 0 to 6 (0 to 3 for ISS and 0 to 3 for HSS). Daily mUAS scores were summed over 7-day period to create total score ranging from 0 (no urticaria) to 42 (severe urticaria). Completion of mUAS7 was done by the child or parent(s)/caregiver(s)/legal guardian(s) for participants aged \>=4 years and by parent(s)/caregiver(s) for participants aged \<4 years. Mean is presented. Baseline was defined as sum of the 7 daily measurements obtained within the 7 days prior to first study intervention administration.

Time frame: Baseline (Day -7 to Day 1) and Week 24

Population: The ITT population included all enrolled participants. Only those participants with data collected at Baseline and Week 24 are reported.

Blood samples were collected at specified timepoints and ADA samples were assayed using validated methods. Treatment-emergent ADA response was defined as a positive response in the ADA assay post first dose when baseline results were negative or missing. Number of participants with treatment-emergent ADA response is presented.

Time frame: From the first dose of study intervention (Day 1) up to end of follow-up, maximum up to 36 weeks

Population: The ADA population included all enrolled participants treated with dupilumab with at least 1 post-baseline ADA result (positive, negative or inconclusive).

An adverse event (AE) was defined as any untoward medical occurrence in a participant or clinical trial participant, temporally associated with the use of study intervention, whether or not considered related to study intervention. Serious adverse event (SAE) was any untoward medical occurrence that at any dose: resulted in death, was life-threatening, required inpatient hospitalization or prolongation of existing hospitalization, resulted in persistent or significant disability/incapacity, was a congenital anomaly/birth defect or was an important medical event. TEAEs were defined as AEs that developed, worsened or became serious during the TE period.

Time frame: From the first dose of study intervention (Day 1) up to end of follow-up, maximum up to 36 weeks

Population: The safety population included all enrolled participants who took at least 1 dose of the study intervention, regardless of the amount of intervention administered.