Trial Outcomes & Findings for Study to Investigate the Safety and Efficacy of Sofosbuvir/Velpatasvir in Adolescents and Children With Chronic HCV Infection (NCT NCT03022981)

Last Updated: 2020-10-08

Results Overview

AUCtau is defined as concentration of drug over time (the area under the concentration versus time curve over the dosing interval).

Recruitment status

COMPLETED

Study phase

PHASE2

Target enrollment

216 participants

Primary outcome timeframe

Day 7: 0 (predose), 0.5, 1, 2, 3, 4, 6 (Cohorts 1 and 2 only), 8, and 12 hours postdose

Results posted on

2020-10-08

Participant Flow

Participants were enrolled at 28 study sites in Belgium, Italy, the United Kingdom, and the United States. The first participant was screened on 26 January 2017. The last study visit occurred on 26 February 2020.

221 participants were screened.

Participant milestones

Participant milestones
Measure	12 to < 18 Years Old Pharmacokinetic (PK) Lead-in Phase: Sofosbuvir/Velpatasvir (SOF/VEL) fixed-dose combination (FDC) 400/100 mg tablets once daily for 7 days. Participants who completed the PK lead-in phase, continued into the treatment phase with no interruption of study drug administration and additional participants were enrolled into the treatment phase once the appropriateness of the dose was confirmed by PK results from the PK lead-in phase. Treatment Phase: SOF/VEL 400/100 mg (adult and smaller size tablets based on swallowability assessment) once daily for 12 weeks.	6 to < 12 Years Old PK Lead-in Phase: SOF/VEL FDC 200/50 mg tablets or oral granules once daily for 7 days. Participants who completed the PK lead-in phase, continued into the treatment phase with no interruption of study drug administration and additional participants were enrolled into the treatment phase once the appropriateness of the dose was confirmed by PK results from the PK lead-in phase. Treatment Phase: SOF/VEL FDC 200/50 mg tablets or oral granules once daily for 12 weeks.	3 to < 6 Years Old PK Lead-in Phase: SOF/VEL FDC 200/50 mg oral granules once daily for 7 days for participants who weighed ≥ 17 kg. SOF/VEL FDC 150/37.5 mg oral granules once daily for 7 days for participants who weighed \< 17 kg. Participants who completed the PK lead-in phase, continued into the treatment phase with no interruption of study drug administration and additional participants were enrolled into the treatment phase once the appropriateness of the dose was confirmed by PK results from the PK lead-in phase. Treatment Phase: SOF/VEL FDC 200/50 mg oral granules once daily for 12 weeks for participants who weighed ≥ 17 kg. SOF/VEL FDC 150/37.5 mg oral granules once daily for 12 weeks for participants who weighed \< 17 kg.
Overall Study STARTED	102	73	41
Overall Study Participated in PK Lead-in (PKL) Phase	17	20	19
Overall Study COMPLETED	96	69	35
Overall Study NOT COMPLETED	6	4	6

Reasons for withdrawal

Reasons for withdrawal
Measure	12 to < 18 Years Old Pharmacokinetic (PK) Lead-in Phase: Sofosbuvir/Velpatasvir (SOF/VEL) fixed-dose combination (FDC) 400/100 mg tablets once daily for 7 days. Participants who completed the PK lead-in phase, continued into the treatment phase with no interruption of study drug administration and additional participants were enrolled into the treatment phase once the appropriateness of the dose was confirmed by PK results from the PK lead-in phase. Treatment Phase: SOF/VEL 400/100 mg (adult and smaller size tablets based on swallowability assessment) once daily for 12 weeks.	6 to < 12 Years Old PK Lead-in Phase: SOF/VEL FDC 200/50 mg tablets or oral granules once daily for 7 days. Participants who completed the PK lead-in phase, continued into the treatment phase with no interruption of study drug administration and additional participants were enrolled into the treatment phase once the appropriateness of the dose was confirmed by PK results from the PK lead-in phase. Treatment Phase: SOF/VEL FDC 200/50 mg tablets or oral granules once daily for 12 weeks.	3 to < 6 Years Old PK Lead-in Phase: SOF/VEL FDC 200/50 mg oral granules once daily for 7 days for participants who weighed ≥ 17 kg. SOF/VEL FDC 150/37.5 mg oral granules once daily for 7 days for participants who weighed \< 17 kg. Participants who completed the PK lead-in phase, continued into the treatment phase with no interruption of study drug administration and additional participants were enrolled into the treatment phase once the appropriateness of the dose was confirmed by PK results from the PK lead-in phase. Treatment Phase: SOF/VEL FDC 200/50 mg oral granules once daily for 12 weeks for participants who weighed ≥ 17 kg. SOF/VEL FDC 150/37.5 mg oral granules once daily for 12 weeks for participants who weighed \< 17 kg.
Overall Study Adverse Event	0	1	0
Overall Study Investigator's Discretion	0	1	2
Overall Study Lost to Follow-up	6	2	1
Overall Study Non-Compliance With Study Drug	0	0	2
Overall Study Withdrew Assent By Parent/Guardian	0	0	1

Baseline Characteristics

Study to Investigate the Safety and Efficacy of Sofosbuvir/Velpatasvir in Adolescents and Children With Chronic HCV Infection

Baseline characteristics by cohort

Baseline characteristics by cohort
Measure	12 to < 18 Years Old n=102 Participants PK Lead-in Phase: Sofosbuvir/Velpatasvir (SOF/VEL) fixed-dose combination (FDC) 400/100 mg tablets once daily for 7 days. Participants who completed the PK lead-in phase, continued into the treatment phase with no interruption of study drug administration and additional participants were enrolled into the treatment phase once the appropriateness of the dose was confirmed by PK results from the PK lead-in phase. Treatment Phase: SOF/VEL 400/100 mg (adult and smaller size tablets based on swallowability assessment) once daily for 12 weeks.	6 to < 12 Years Old n=73 Participants PK Lead-in Phase: SOF/VEL FDC 200/50 mg tablets or oral granules once daily for 7 days. Participants who completed the PK lead-in phase, continued into the treatment phase with no interruption of study drug administration and additional participants were enrolled into the treatment phase once the appropriateness of the dose was confirmed by PK results from the PK lead-in phase. Treatment Phase: SOF/VEL FDC 200/50 mg tablets or oral granules once daily for 12 weeks.	3 to < 6 Years Old n=41 Participants PK Lead-in Phase: SOF/VEL FDC 200/50 mg oral granules once daily for 7 days for participants who weighed ≥ 17 kg. SOF/VEL FDC 150/37.5 mg oral granules once daily for 7 days for participants who weighed \< 17 kg. Participants who completed the PK lead-in phase, continued into the treatment phase with no interruption of study drug administration and additional participants were enrolled into the treatment phase once the appropriateness of the dose was confirmed by PK results from the PK lead-in phase. Treatment Phase: SOF/VEL FDC 200/50 mg oral granules once daily for 12 weeks for participants who weighed ≥ 17 kg. SOF/VEL FDC 150/37.5 mg oral granules once daily for 12 weeks for participants who weighed \< 17 kg.	Total n=216 Participants Total of all reporting groups
Age, Continuous	15 years STANDARD_DEVIATION 1.9 • n=5 Participants	8 years STANDARD_DEVIATION 1.6 • n=7 Participants	4 years STANDARD_DEVIATION 0.8 • n=5 Participants	10 years STANDARD_DEVIATION 4.5 • n=4 Participants
Sex: Female, Male Female	52 Participants n=5 Participants	38 Participants n=7 Participants	24 Participants n=5 Participants	114 Participants n=4 Participants
Sex: Female, Male Male	50 Participants n=5 Participants	35 Participants n=7 Participants	17 Participants n=5 Participants	102 Participants n=4 Participants
Race/Ethnicity, Customized Race · White	74 Participants n=5 Participants	66 Participants n=7 Participants	32 Participants n=5 Participants	172 Participants n=4 Participants
Race/Ethnicity, Customized Race · Black or African American	9 Participants n=5 Participants	4 Participants n=7 Participants	3 Participants n=5 Participants	16 Participants n=4 Participants
Race/Ethnicity, Customized Race · Asian	11 Participants n=5 Participants	1 Participants n=7 Participants	0 Participants n=5 Participants	12 Participants n=4 Participants
Race/Ethnicity, Customized Race · Other	5 Participants n=5 Participants	2 Participants n=7 Participants	5 Participants n=5 Participants	12 Participants n=4 Participants
Race/Ethnicity, Customized Race · American Indian or Alaska Native	2 Participants n=5 Participants	0 Participants n=7 Participants	0 Participants n=5 Participants	2 Participants n=4 Participants
Race/Ethnicity, Customized Race · Not Permitted	1 Participants n=5 Participants	0 Participants n=7 Participants	1 Participants n=5 Participants	2 Participants n=4 Participants
Race/Ethnicity, Customized Race · Native Hawaiian or Pacific Islander	0 Participants n=5 Participants	0 Participants n=7 Participants	0 Participants n=5 Participants	0 Participants n=4 Participants
Race/Ethnicity, Customized Ethnicity · Hispanic or Latino	14 Participants n=5 Participants	7 Participants n=7 Participants	4 Participants n=5 Participants	25 Participants n=4 Participants
Race/Ethnicity, Customized Ethnicity · Not Hispanic or Latino	83 Participants n=5 Participants	64 Participants n=7 Participants	36 Participants n=5 Participants	183 Participants n=4 Participants
Race/Ethnicity, Customized Ethnicity · Not Permitted	5 Participants n=5 Participants	2 Participants n=7 Participants	1 Participants n=5 Participants	8 Participants n=4 Participants
Region of Enrollment United States	77 Participants n=5 Participants	57 Participants n=7 Participants	38 Participants n=5 Participants	172 Participants n=4 Participants
Region of Enrollment Italy	17 Participants n=5 Participants	5 Participants n=7 Participants	2 Participants n=5 Participants	24 Participants n=4 Participants
Region of Enrollment United Kingdom	5 Participants n=5 Participants	9 Participants n=7 Participants	1 Participants n=5 Participants	15 Participants n=4 Participants
Region of Enrollment Belgium	3 Participants n=5 Participants	2 Participants n=7 Participants	0 Participants n=5 Participants	5 Participants n=4 Participants

PRIMARY outcome

Timeframe: Day 7: 0 (predose), 0.5, 1, 2, 3, 4, 6 (Cohorts 1 and 2 only), 8, and 12 hours postdose

Population: The Lead-in Phase Pharmacokinetic (PK) Analysis Set included all PK lead-in phase participants with available data who received at least 1 dose of study drug and whom at least one non-missing PK concentration data value is available from the PK Lead-in Phase intensive sampling.

AUCtau is defined as concentration of drug over time (the area under the concentration versus time curve over the dosing interval).

Outcome measures

Outcome measures
Measure	12 to < 18 Years Old n=16 Participants PK Lead-in Phase: Sofosbuvir/Velpatasvir (SOF/VEL) fixed-dose combination (FDC) 400/100 mg tablets once daily for 7 days.	6 to < 12 Years Old n=17 Participants PK Lead-in Phase: SOF/VEL FDC 200/50 mg tablets or oral granules once daily for 7 days.	3 to < 6 Years Old n=18 Participants PK Lead-in Phase: SOF/VEL FDC 200/50 mg oral granules once daily for 7 days for participants who weighed ≥ 17 kg. SOF/VEL FDC 150/37.5 mg oral granules once daily for 7 days for participants who weighed \< 17 kg.	6 to <12 Years Old Treatment Phase: SOF/VEL FDC 200/50 mg oral granules once daily for 12 weeks.	3 to < 6 Years Old Treatment Phase: SOF/VEL FDC 200/50 mg oral granules once daily for 12 weeks for participants who weighed ≥ 17 kg.	3 to <6 Years Old SOF/VEL FDC 150/37.5 mg oral granules once daily for 12 weeks for participants who weighed \< 17 kg.
PK Lead-in Phase: AUCtau: Area Under the Plasma Concentration Versus Time Curve Over the Dosing Interval of Velpatasvir (VEL)	4479.3 hoursnanograms per milliliter (hng/mL) Standard Deviation 2105.66	3697.5 hoursnanograms per milliliter (hng/mL) Standard Deviation 1653.25	4450.3 hoursnanograms per milliliter (hng/mL) Standard Deviation 3285.75	—	—	—

PRIMARY outcome

Timeframe: Day 7: 0 (predose), 0.5, 1, 2, 3, 4, 6 (Cohorts 1 and 2 only), 8, and 12 hours postdose

Population: Participants in the Lead-in Phase PK Analysis Set with available data were analyzed.

AUCtau is defined as concentration of drug over time (the area under the concentration versus time curve over the dosing interval).

Outcome measures

Outcome measures
Measure	12 to < 18 Years Old n=16 Participants PK Lead-in Phase: Sofosbuvir/Velpatasvir (SOF/VEL) fixed-dose combination (FDC) 400/100 mg tablets once daily for 7 days.	6 to < 12 Years Old n=17 Participants PK Lead-in Phase: SOF/VEL FDC 200/50 mg tablets or oral granules once daily for 7 days.	3 to < 6 Years Old n=17 Participants PK Lead-in Phase: SOF/VEL FDC 200/50 mg oral granules once daily for 7 days for participants who weighed ≥ 17 kg. SOF/VEL FDC 150/37.5 mg oral granules once daily for 7 days for participants who weighed \< 17 kg.	6 to <12 Years Old Treatment Phase: SOF/VEL FDC 200/50 mg oral granules once daily for 12 weeks.	3 to < 6 Years Old Treatment Phase: SOF/VEL FDC 200/50 mg oral granules once daily for 12 weeks for participants who weighed ≥ 17 kg.	3 to <6 Years Old SOF/VEL FDC 150/37.5 mg oral granules once daily for 12 weeks for participants who weighed \< 17 kg.
PK Lead-in Phase: AUCtau: Area Under the Plasma Concentration Versus Time Curve Over the Dosing Interval of Sofosbuvir (SOF)	3020.1 h*ng/mL Standard Deviation 1162.56	1764.5 h*ng/mL Standard Deviation 690.12	3306.2 h*ng/mL Standard Deviation 3499.49	—	—	—

PRIMARY outcome

Timeframe: Day 7: 0 (predose), 0.5, 1, 2, 3, 4, 6 (Cohorts 1 and 2 only), 8, and 12 hours postdose

Population: Participants in the Lead-in Phase PK Analysis Set with available data were analyzed.

AUCtau is defined as concentration of drug over time (the area under the concentration verses time curve over the dosing interval).

Outcome measures

Outcome measures
Measure	12 to < 18 Years Old n=16 Participants PK Lead-in Phase: Sofosbuvir/Velpatasvir (SOF/VEL) fixed-dose combination (FDC) 400/100 mg tablets once daily for 7 days.	6 to < 12 Years Old n=17 Participants PK Lead-in Phase: SOF/VEL FDC 200/50 mg tablets or oral granules once daily for 7 days.	3 to < 6 Years Old n=18 Participants PK Lead-in Phase: SOF/VEL FDC 200/50 mg oral granules once daily for 7 days for participants who weighed ≥ 17 kg. SOF/VEL FDC 150/37.5 mg oral granules once daily for 7 days for participants who weighed \< 17 kg.	6 to <12 Years Old Treatment Phase: SOF/VEL FDC 200/50 mg oral granules once daily for 12 weeks.	3 to < 6 Years Old Treatment Phase: SOF/VEL FDC 200/50 mg oral granules once daily for 12 weeks for participants who weighed ≥ 17 kg.	3 to <6 Years Old SOF/VEL FDC 150/37.5 mg oral granules once daily for 12 weeks for participants who weighed \< 17 kg.
PK Lead-in Phase: AUCtau: Area Under the Plasma Concentration Versus Time Curve Over the Dosing Interval of GS-331007 (Metabolite of SOF)	13852.9 h*ng/mL Standard Deviation 3565.85	9913.8 h*ng/mL Standard Deviation 3071.79	11604.0 h*ng/mL Standard Deviation 2732.57	—	—	—

PRIMARY outcome

Timeframe: From first dose through last dose of the study drug (Up to 12 weeks) plus 30 days

Population: The Safety Analysis Set included all participants who were enrolled into the study and received at least 1 dose of study drug (SOF/VEL FDC).

An AE is any untoward medical occurrence in a clinical study participant administered a medicinal product, which does not necessarily have a causal relationship with the treatment. An AE can therefore be any unfavorable and/or unintended sign, symptom, or disease temporally associated with the use of a medicinal product, whether or not considered related to the medicinal product. TEAEs were defined as 1 or both of the following: Any AEs with an onset date on or after the study drug start date and no later than 30 days after permanent discontinuation of study drug and/or Any AEs leading to premature discontinuation of study drug.

Outcome measures

Outcome measures
Measure	12 to < 18 Years Old n=102 Participants PK Lead-in Phase: Sofosbuvir/Velpatasvir (SOF/VEL) fixed-dose combination (FDC) 400/100 mg tablets once daily for 7 days.	6 to < 12 Years Old n=73 Participants PK Lead-in Phase: SOF/VEL FDC 200/50 mg tablets or oral granules once daily for 7 days.	3 to < 6 Years Old n=41 Participants PK Lead-in Phase: SOF/VEL FDC 200/50 mg oral granules once daily for 7 days for participants who weighed ≥ 17 kg. SOF/VEL FDC 150/37.5 mg oral granules once daily for 7 days for participants who weighed \< 17 kg.	6 to <12 Years Old Treatment Phase: SOF/VEL FDC 200/50 mg oral granules once daily for 12 weeks.	3 to < 6 Years Old Treatment Phase: SOF/VEL FDC 200/50 mg oral granules once daily for 12 weeks for participants who weighed ≥ 17 kg.	3 to <6 Years Old SOF/VEL FDC 150/37.5 mg oral granules once daily for 12 weeks for participants who weighed \< 17 kg.
Treatment Phase: Percentage of Participants Who Discontinued Study Drug Due to Any Treatment-Emergent Adverse Event (TEAE)	0.0 percentage of participants	2.7 percentage of participants	2.4 percentage of participants	—	—	—

SECONDARY outcome

Timeframe: Baseline; Day 7

Population: Participants in the Lead-in Phase PK Analysis Set with available data were analyzed.

Outcome measures

Outcome measures
Measure	12 to < 18 Years Old n=17 Participants PK Lead-in Phase: Sofosbuvir/Velpatasvir (SOF/VEL) fixed-dose combination (FDC) 400/100 mg tablets once daily for 7 days.	6 to < 12 Years Old n=20 Participants PK Lead-in Phase: SOF/VEL FDC 200/50 mg tablets or oral granules once daily for 7 days.	3 to < 6 Years Old n=19 Participants PK Lead-in Phase: SOF/VEL FDC 200/50 mg oral granules once daily for 7 days for participants who weighed ≥ 17 kg. SOF/VEL FDC 150/37.5 mg oral granules once daily for 7 days for participants who weighed \< 17 kg.	6 to <12 Years Old Treatment Phase: SOF/VEL FDC 200/50 mg oral granules once daily for 12 weeks.	3 to < 6 Years Old Treatment Phase: SOF/VEL FDC 200/50 mg oral granules once daily for 12 weeks for participants who weighed ≥ 17 kg.	3 to <6 Years Old SOF/VEL FDC 150/37.5 mg oral granules once daily for 12 weeks for participants who weighed \< 17 kg.
PK Lead-in Phase: Change From Baseline in Hepatitis C Virus (HCV) Ribonucleic Acid (RNA) at Day 7 Baseline	6.09 log10 international units per mL (IU/mL) Standard Deviation 0.569	5.84 log10 international units per mL (IU/mL) Standard Deviation 0.656	5.77 log10 international units per mL (IU/mL) Standard Deviation 1.275	—	—	—
PK Lead-in Phase: Change From Baseline in Hepatitis C Virus (HCV) Ribonucleic Acid (RNA) at Day 7 Change from Baseline at Day 7	-4.48 log10 international units per mL (IU/mL) Standard Deviation 0.656	-4.20 log10 international units per mL (IU/mL) Standard Deviation 0.642	-3.94 log10 international units per mL (IU/mL) Standard Deviation 1.082	—	—	—

SECONDARY outcome

Timeframe: First dose date up to Day 7

Population: Participants in the Lead-in Phase PK Analysis Set were analyzed.

Outcome measures

Outcome measures
Measure	12 to < 18 Years Old n=17 Participants PK Lead-in Phase: Sofosbuvir/Velpatasvir (SOF/VEL) fixed-dose combination (FDC) 400/100 mg tablets once daily for 7 days.	6 to < 12 Years Old n=20 Participants PK Lead-in Phase: SOF/VEL FDC 200/50 mg tablets or oral granules once daily for 7 days.	3 to < 6 Years Old n=19 Participants PK Lead-in Phase: SOF/VEL FDC 200/50 mg oral granules once daily for 7 days for participants who weighed ≥ 17 kg. SOF/VEL FDC 150/37.5 mg oral granules once daily for 7 days for participants who weighed \< 17 kg.	6 to <12 Years Old Treatment Phase: SOF/VEL FDC 200/50 mg oral granules once daily for 12 weeks.	3 to < 6 Years Old Treatment Phase: SOF/VEL FDC 200/50 mg oral granules once daily for 12 weeks for participants who weighed ≥ 17 kg.	3 to <6 Years Old SOF/VEL FDC 150/37.5 mg oral granules once daily for 12 weeks for participants who weighed \< 17 kg.
PK Lead-in Phase: Percentage of Participants Who Permanently Discontinued Study Drug Due to an Adverse Event (AE)	0.0 percentage of participants	0.0 percentage of participants	0.0 percentage of participants	—	—	—

SECONDARY outcome

Timeframe: Posttreatment Week 12

Population: The Full Analysis Set included all participants who were enrolled into the study and received at least 1 dose of study drug (SOF/VEL FDC).

SVR12 was defined as HCV RNA \< the lower limit of quantitation (LLOQ; ie, 15 IU/mL) at 12 weeks after stopping study treatment.

Outcome measures

Outcome measures
Measure	12 to < 18 Years Old n=102 Participants PK Lead-in Phase: Sofosbuvir/Velpatasvir (SOF/VEL) fixed-dose combination (FDC) 400/100 mg tablets once daily for 7 days.	6 to < 12 Years Old n=73 Participants PK Lead-in Phase: SOF/VEL FDC 200/50 mg tablets or oral granules once daily for 7 days.	3 to < 6 Years Old n=41 Participants PK Lead-in Phase: SOF/VEL FDC 200/50 mg oral granules once daily for 7 days for participants who weighed ≥ 17 kg. SOF/VEL FDC 150/37.5 mg oral granules once daily for 7 days for participants who weighed \< 17 kg.	6 to <12 Years Old Treatment Phase: SOF/VEL FDC 200/50 mg oral granules once daily for 12 weeks.	3 to < 6 Years Old Treatment Phase: SOF/VEL FDC 200/50 mg oral granules once daily for 12 weeks for participants who weighed ≥ 17 kg.	3 to <6 Years Old SOF/VEL FDC 150/37.5 mg oral granules once daily for 12 weeks for participants who weighed \< 17 kg.
Treatment Phase: Percentage of Participants With Sustained Virologic Response (SVR) at 12 Weeks After Discontinuation of Therapy (SVR12)	95.1 percentage of participants Interval 88.9 to 98.4	93.2 percentage of participants Interval 84.7 to 97.7	82.9 percentage of participants Interval 67.9 to 92.8	—	—	—

SECONDARY outcome

Timeframe: Posttreatment Week 4

Population: Participants in the Full Analysis Set were analyzed.

SVR4 was defined as HCV RNA \< LLOQ (ie, 15 IU/mL) at 4 weeks after stopping study treatment.

Outcome measures

Outcome measures
Measure	12 to < 18 Years Old n=102 Participants PK Lead-in Phase: Sofosbuvir/Velpatasvir (SOF/VEL) fixed-dose combination (FDC) 400/100 mg tablets once daily for 7 days.	6 to < 12 Years Old n=73 Participants PK Lead-in Phase: SOF/VEL FDC 200/50 mg tablets or oral granules once daily for 7 days.	3 to < 6 Years Old n=41 Participants PK Lead-in Phase: SOF/VEL FDC 200/50 mg oral granules once daily for 7 days for participants who weighed ≥ 17 kg. SOF/VEL FDC 150/37.5 mg oral granules once daily for 7 days for participants who weighed \< 17 kg.	6 to <12 Years Old Treatment Phase: SOF/VEL FDC 200/50 mg oral granules once daily for 12 weeks.	3 to < 6 Years Old Treatment Phase: SOF/VEL FDC 200/50 mg oral granules once daily for 12 weeks for participants who weighed ≥ 17 kg.	3 to <6 Years Old SOF/VEL FDC 150/37.5 mg oral granules once daily for 12 weeks for participants who weighed \< 17 kg.
Treatment Phase: Percentage of Participants With SVR at 4 Weeks After Discontinuation of Therapy (SVR4)	96.1 percentage of participants Interval 90.3 to 98.9	94.5 percentage of participants Interval 86.6 to 98.5	82.9 percentage of participants Interval 67.9 to 92.8	—	—	—

SECONDARY outcome

Timeframe: Posttreatment Week 24

Population: Participants in the Full Analysis Set were analyzed.

SVR 24 was defined as HCV RNA \< LLOQ (ie, 15 IU/mL) at 24 weeks after stopping study treatment.

Outcome measures

Outcome measures
Measure	12 to < 18 Years Old n=102 Participants PK Lead-in Phase: Sofosbuvir/Velpatasvir (SOF/VEL) fixed-dose combination (FDC) 400/100 mg tablets once daily for 7 days.	6 to < 12 Years Old n=73 Participants PK Lead-in Phase: SOF/VEL FDC 200/50 mg tablets or oral granules once daily for 7 days.	3 to < 6 Years Old n=41 Participants PK Lead-in Phase: SOF/VEL FDC 200/50 mg oral granules once daily for 7 days for participants who weighed ≥ 17 kg. SOF/VEL FDC 150/37.5 mg oral granules once daily for 7 days for participants who weighed \< 17 kg.	6 to <12 Years Old Treatment Phase: SOF/VEL FDC 200/50 mg oral granules once daily for 12 weeks.	3 to < 6 Years Old Treatment Phase: SOF/VEL FDC 200/50 mg oral granules once daily for 12 weeks for participants who weighed ≥ 17 kg.	3 to <6 Years Old SOF/VEL FDC 150/37.5 mg oral granules once daily for 12 weeks for participants who weighed \< 17 kg.
Treatment Phase: Percentage of Participants With SVR at 24 Weeks After Discontinuation of Therapy (SVR24)	95.1 percentage of participants Interval 88.9 to 98.4	93.2 percentage of participants Interval 84.7 to 97.7	82.9 percentage of participants Interval 67.9 to 92.8	—	—	—

SECONDARY outcome

Timeframe: Up to Posttreatment Week 24

Population: Participants in the Full Analysis Set were analyzed.

Virologic failure was defined as: On-treatment virologic failure - Breakthrough (confirmed HCV RNA ≥ LLOQ after having previously had HCV RNA \< LLOQ while on treatment), or Rebound (confirmed \> 1 log10 IU/mL increase in HCV RNA from nadir while on treatment), or Non-response (HCV RNA persistently ≥ LLOQ through 8 weeks of treatment); Virologic relapse: Confirmed HCV RNA ≥ LLOQ during the posttreatment period having achieved HCV RNA \< LLOQ at last on-treatment visit.

Outcome measures

Outcome measures
Measure	12 to < 18 Years Old n=102 Participants PK Lead-in Phase: Sofosbuvir/Velpatasvir (SOF/VEL) fixed-dose combination (FDC) 400/100 mg tablets once daily for 7 days.	6 to < 12 Years Old n=73 Participants PK Lead-in Phase: SOF/VEL FDC 200/50 mg tablets or oral granules once daily for 7 days.	3 to < 6 Years Old n=41 Participants PK Lead-in Phase: SOF/VEL FDC 200/50 mg oral granules once daily for 7 days for participants who weighed ≥ 17 kg. SOF/VEL FDC 150/37.5 mg oral granules once daily for 7 days for participants who weighed \< 17 kg.	6 to <12 Years Old Treatment Phase: SOF/VEL FDC 200/50 mg oral granules once daily for 12 weeks.	3 to < 6 Years Old Treatment Phase: SOF/VEL FDC 200/50 mg oral granules once daily for 12 weeks for participants who weighed ≥ 17 kg.	3 to <6 Years Old SOF/VEL FDC 150/37.5 mg oral granules once daily for 12 weeks for participants who weighed \< 17 kg.
Treatment Phase: Percentage of Participants With Virologic Failure	1.0 percentage of participants	1.4 percentage of participants	0.0 percentage of participants	—	—	—

SECONDARY outcome

Timeframe: Weeks 1, 4, 8, and 12

Population: Participants in the Full Analysis Set were analyzed.

Percentage of participants with HCV RNA \< LLOQ while on treatment by analysis visit.

Outcome measures

Outcome measures
Measure	12 to < 18 Years Old n=102 Participants PK Lead-in Phase: Sofosbuvir/Velpatasvir (SOF/VEL) fixed-dose combination (FDC) 400/100 mg tablets once daily for 7 days.	6 to < 12 Years Old n=73 Participants PK Lead-in Phase: SOF/VEL FDC 200/50 mg tablets or oral granules once daily for 7 days.	3 to < 6 Years Old n=41 Participants PK Lead-in Phase: SOF/VEL FDC 200/50 mg oral granules once daily for 7 days for participants who weighed ≥ 17 kg. SOF/VEL FDC 150/37.5 mg oral granules once daily for 7 days for participants who weighed \< 17 kg.	6 to <12 Years Old Treatment Phase: SOF/VEL FDC 200/50 mg oral granules once daily for 12 weeks.	3 to < 6 Years Old Treatment Phase: SOF/VEL FDC 200/50 mg oral granules once daily for 12 weeks for participants who weighed ≥ 17 kg.	3 to <6 Years Old SOF/VEL FDC 150/37.5 mg oral granules once daily for 12 weeks for participants who weighed \< 17 kg.
Treatment Phase: Percentage of Participants With HCV RNA < LLOQ On Treatment Week 1	44.1 percentage of participants Interval 34.3 to 54.3	39.7 percentage of participants Interval 28.5 to 51.9	36.8 percentage of participants Interval 21.8 to 54.0	—	—	—
Treatment Phase: Percentage of Participants With HCV RNA < LLOQ On Treatment Week 4	96.1 percentage of participants Interval 90.3 to 98.9	94.4 percentage of participants Interval 86.2 to 98.4	91.4 percentage of participants Interval 76.9 to 98.2	—	—	—
Treatment Phase: Percentage of Participants With HCV RNA < LLOQ On Treatment Week 8	100.0 percentage of participants Interval 96.4 to 100.0	98.6 percentage of participants Interval 92.3 to 100.0	100.0 percentage of participants Interval 89.7 to 100.0	—	—	—
Treatment Phase: Percentage of Participants With HCV RNA < LLOQ On Treatment Week 12	100.0 percentage of participants Interval 96.4 to 100.0	98.6 percentage of participants Interval 92.3 to 100.0	100.0 percentage of participants Interval 89.7 to 100.0	—	—	—

SECONDARY outcome

Timeframe: First dose date up to Posttreatment Week 24

Population: The Resistance Analysis Population with all adolescent or pediatric participants in the Safety Analysis Set with a virologic outcome with available data were analyzed.

Drug-resistant substitutions were analyzed as part of the Virology Study. Plasma samples were collected and stored for potential HCV sequencing. Impact on the treatment outcomes of SVR12 and SVR24 were observed during the study. Baseline deep sequencing of the HCV nonstructural protein (NS)5A and NS5B genes was performed for all participants at the first time point after virologic failure if the plasma or serum sample was available. Pretreatment full-length NS5A deep sequencing data were obtained at a 15% assay cutoff for the Resistance Analysis Population which covered all NS5A and NS5B nucleoside inhibitor (NI) resistance-associated variants (RAVs).

Outcome measures

Outcome measures
Measure	12 to < 18 Years Old n=98 Participants PK Lead-in Phase: Sofosbuvir/Velpatasvir (SOF/VEL) fixed-dose combination (FDC) 400/100 mg tablets once daily for 7 days.	6 to < 12 Years Old n=68 Participants PK Lead-in Phase: SOF/VEL FDC 200/50 mg tablets or oral granules once daily for 7 days.	3 to < 6 Years Old n=33 Participants PK Lead-in Phase: SOF/VEL FDC 200/50 mg oral granules once daily for 7 days for participants who weighed ≥ 17 kg. SOF/VEL FDC 150/37.5 mg oral granules once daily for 7 days for participants who weighed \< 17 kg.	6 to <12 Years Old Treatment Phase: SOF/VEL FDC 200/50 mg oral granules once daily for 12 weeks.	3 to < 6 Years Old Treatment Phase: SOF/VEL FDC 200/50 mg oral granules once daily for 12 weeks for participants who weighed ≥ 17 kg.	3 to <6 Years Old SOF/VEL FDC 150/37.5 mg oral granules once daily for 12 weeks for participants who weighed \< 17 kg.
Treatment Phase: Percentage of Participants Who Develop Viral Resistance to SOF and/or VEL During Treatment and After Discontinuation of Treatment Pretreatment NS5A NI RAVs	16.3 percentage of participants	10.2 percentage of participants	18.1 percentage of participants	—	—	—
Treatment Phase: Percentage of Participants Who Develop Viral Resistance to SOF and/or VEL During Treatment and After Discontinuation of Treatment Pretreatment NS5B NI RAVs	5.1 percentage of participants	0.0 percentage of participants	3.0 percentage of participants	—	—	—

SECONDARY outcome

Timeframe: Baseline; Weeks 1, 4, 8, and 12

Population: Participants in the Full Analysis Set with available data were analyzed.

Outcome measures

Outcome measures
Measure	12 to < 18 Years Old n=102 Participants PK Lead-in Phase: Sofosbuvir/Velpatasvir (SOF/VEL) fixed-dose combination (FDC) 400/100 mg tablets once daily for 7 days.	6 to < 12 Years Old n=73 Participants PK Lead-in Phase: SOF/VEL FDC 200/50 mg tablets or oral granules once daily for 7 days.	3 to < 6 Years Old n=41 Participants PK Lead-in Phase: SOF/VEL FDC 200/50 mg oral granules once daily for 7 days for participants who weighed ≥ 17 kg. SOF/VEL FDC 150/37.5 mg oral granules once daily for 7 days for participants who weighed \< 17 kg.	6 to <12 Years Old Treatment Phase: SOF/VEL FDC 200/50 mg oral granules once daily for 12 weeks.	3 to < 6 Years Old Treatment Phase: SOF/VEL FDC 200/50 mg oral granules once daily for 12 weeks for participants who weighed ≥ 17 kg.	3 to <6 Years Old SOF/VEL FDC 150/37.5 mg oral granules once daily for 12 weeks for participants who weighed \< 17 kg.
Treatment Phase: Change From Baseline in HCV RNA at Weeks 1, 4, 8, and 12 Baseline	6.06 log10 IU/mL Standard Deviation 0.585	5.87 log10 IU/mL Standard Deviation 0.686	5.86 log10 IU/mL Standard Deviation 1.057	—	—	—
Treatment Phase: Change From Baseline in HCV RNA at Weeks 1, 4, 8, and 12 Change from Baseline at Week 1	-4.46 log10 IU/mL Standard Deviation 0.661	-4.28 log10 IU/mL Standard Deviation 0.632	-4.06 log10 IU/mL Standard Deviation 0.914	—	—	—
Treatment Phase: Change From Baseline in HCV RNA at Weeks 1, 4, 8, and 12 Change from Baseline at Week 4	-4.89 log10 IU/mL Standard Deviation 0.578	-4.64 log10 IU/mL Standard Deviation 0.860	-4.49 log10 IU/mL Standard Deviation 1.040	—	—	—
Treatment Phase: Change From Baseline in HCV RNA at Weeks 1, 4, 8, and 12 Change from Baseline at Week 8	-4.91 log10 IU/mL Standard Deviation 0.588	-4.69 log10 IU/mL Standard Deviation 0.678	-4.56 log10 IU/mL Standard Deviation 1.066	—	—	—
Treatment Phase: Change From Baseline in HCV RNA at Weeks 1, 4, 8, and 12 Change from Baseline at Week 12	-4.91 log10 IU/mL Standard Deviation 0.588	-4.70 log10 IU/mL Standard Deviation 0.683	-4.56 log10 IU/mL Standard Deviation 1.066	—	—	—

SECONDARY outcome

Timeframe: Baseline; Week 12, End of Treatment (EOT), Posttreatment/Follow-up (FU) Week-12 (FU-12), and FU Week-24 (FU-24)

Population: Participants in the Full Analysis Set with available data were analyzed.

To evaluate the effect of treatment with SOF/VEL on general and disease-specific health-related QoL, the PedsQL™ Pediatric QoL Inventory V4.0 Short Form (SF15) was completed at Day 1, end of treatment, early termination (if applicable), and posttreatment Weeks 12 and 24. The SF15 questionnaire represented 4 domains: physical, emotional, social, and school functioning, with the emotional, social, and school functioning domains representing the psychosocial health summary. Neuropsychiatric assessment was conducted using the PedsQL™ Pediatric QoL Inventory V4.0 SF15 psychosocial domain-related scores. Items were calculated and transformed into an overall score with a range of 0 to 100 points, with more points indicating better QoL.

Outcome measures

Outcome measures
Measure	12 to < 18 Years Old n=102 Participants PK Lead-in Phase: Sofosbuvir/Velpatasvir (SOF/VEL) fixed-dose combination (FDC) 400/100 mg tablets once daily for 7 days.	6 to < 12 Years Old n=73 Participants PK Lead-in Phase: SOF/VEL FDC 200/50 mg tablets or oral granules once daily for 7 days.	3 to < 6 Years Old n=41 Participants PK Lead-in Phase: SOF/VEL FDC 200/50 mg oral granules once daily for 7 days for participants who weighed ≥ 17 kg. SOF/VEL FDC 150/37.5 mg oral granules once daily for 7 days for participants who weighed \< 17 kg.	6 to <12 Years Old Treatment Phase: SOF/VEL FDC 200/50 mg oral granules once daily for 12 weeks.	3 to < 6 Years Old Treatment Phase: SOF/VEL FDC 200/50 mg oral granules once daily for 12 weeks for participants who weighed ≥ 17 kg.	3 to <6 Years Old SOF/VEL FDC 150/37.5 mg oral granules once daily for 12 weeks for participants who weighed \< 17 kg.
Treatment Phase: Quality of Life (QoL) and Neuropsychiatric Assessments as Measured by PedsQL™ Pediatric QoL Survey Parents Reports, Total Score at Baseline	80.0 score on a scale Standard Deviation 17.71	79.7 score on a scale Standard Deviation 15.58	86.5 score on a scale Standard Deviation 12.43	—	—	—
Treatment Phase: Quality of Life (QoL) and Neuropsychiatric Assessments as Measured by PedsQL™ Pediatric QoL Survey Parents Reports, Total Score at Week 12	82.4 score on a scale Standard Deviation 18.13	82.8 score on a scale Standard Deviation 14.26	87.3 score on a scale Standard Deviation 11.31	—	—	—
Treatment Phase: Quality of Life (QoL) and Neuropsychiatric Assessments as Measured by PedsQL™ Pediatric QoL Survey Parents Reports, Total Score at EOT	82.4 score on a scale Standard Deviation 18.13	82.2 score on a scale Standard Deviation 14.95	87.0 score on a scale Standard Deviation 11.65	—	—	—
Treatment Phase: Quality of Life (QoL) and Neuropsychiatric Assessments as Measured by PedsQL™ Pediatric QoL Survey Parents Reports, Total Score at Follow Up-12	81.7 score on a scale Standard Deviation 17.39	81.5 score on a scale Standard Deviation 15.34	87.7 score on a scale Standard Deviation 14.11	—	—	—
Treatment Phase: Quality of Life (QoL) and Neuropsychiatric Assessments as Measured by PedsQL™ Pediatric QoL Survey Parents Reports, Total Score at Follow Up-24	80.8 score on a scale Standard Deviation 18.65	79.7 score on a scale Standard Deviation 15.30	88.3 score on a scale Standard Deviation 9.79	—	—	—
Treatment Phase: Quality of Life (QoL) and Neuropsychiatric Assessments as Measured by PedsQL™ Pediatric QoL Survey Participants Reports, Total Score at Baseline	79.9 score on a scale Standard Deviation 15.22	77.9 score on a scale Standard Deviation 13.33	82.2 score on a scale Standard Deviation 12.47	—	—	—
Treatment Phase: Quality of Life (QoL) and Neuropsychiatric Assessments as Measured by PedsQL™ Pediatric QoL Survey Participants Reports, Total Score at Week 12	80.9 score on a scale Standard Deviation 16.38	80.0 score on a scale Standard Deviation 14.21	83.3 score on a scale Standard Deviation 11.62	—	—	—
Treatment Phase: Quality of Life (QoL) and Neuropsychiatric Assessments as Measured by PedsQL™ Pediatric QoL Survey Participants Reports, Total Score at EOT	80.9 score on a scale Standard Deviation 16.38	79.7 score on a scale Standard Deviation 14.13	83.3 score on a scale Standard Deviation 11.62	—	—	—
Treatment Phase: Quality of Life (QoL) and Neuropsychiatric Assessments as Measured by PedsQL™ Pediatric QoL Survey Participants Reports, Total Score at Follow Up-12	82.5 score on a scale Standard Deviation 15.41	81.1 score on a scale Standard Deviation 13.32	80.5 score on a scale Standard Deviation 14.18	—	—	—
Treatment Phase: Quality of Life (QoL) and Neuropsychiatric Assessments as Measured by PedsQL™ Pediatric QoL Survey Participants Reports, Total Score at Follow Up-24	81.4 score on a scale Standard Deviation 16.34	81.7 score on a scale Standard Deviation 15.43	82.1 score on a scale Standard Deviation 12.56	—	—	—

SECONDARY outcome

Timeframe: Baseline; Weeks 1, 4, 8, 12, Follow-up (FU) Week 4 (FU-4), FU-12, and FU-24

Population: Participants in the Safety Analysis Set with available data were analyzed.

An age- and sex-specific percentile was derived for each weight, height, and body mass index (BMI) measurement according to the statistical analysis system (SAS) program available on the Centers for Disease Control and Prevention (CDC) website using the year 2000 growth charts.

Outcome measures

Outcome measures
Measure	12 to < 18 Years Old n=102 Participants PK Lead-in Phase: Sofosbuvir/Velpatasvir (SOF/VEL) fixed-dose combination (FDC) 400/100 mg tablets once daily for 7 days.	6 to < 12 Years Old n=73 Participants PK Lead-in Phase: SOF/VEL FDC 200/50 mg tablets or oral granules once daily for 7 days.	3 to < 6 Years Old n=41 Participants PK Lead-in Phase: SOF/VEL FDC 200/50 mg oral granules once daily for 7 days for participants who weighed ≥ 17 kg. SOF/VEL FDC 150/37.5 mg oral granules once daily for 7 days for participants who weighed \< 17 kg.	6 to <12 Years Old Treatment Phase: SOF/VEL FDC 200/50 mg oral granules once daily for 12 weeks.	3 to < 6 Years Old Treatment Phase: SOF/VEL FDC 200/50 mg oral granules once daily for 12 weeks for participants who weighed ≥ 17 kg.	3 to <6 Years Old SOF/VEL FDC 150/37.5 mg oral granules once daily for 12 weeks for participants who weighed \< 17 kg.
Treatment Phase: Change From Baseline in Growth and Development as Measured by Height Percentiles Baseline	44.5 percentile Interval 16.2 to 74.1	41.9 percentile Interval 20.5 to 65.2	39.3 percentile Interval 13.9 to 70.1	—	—	—
Treatment Phase: Change From Baseline in Growth and Development as Measured by Height Percentiles Change From Baseline at Week 1	0.0 percentile Interval -0.4 to 0.9	0.1 percentile Interval -0.7 to 2.4	0.5 percentile Interval -1.1 to 3.4	—	—	—
Treatment Phase: Change From Baseline in Growth and Development as Measured by Height Percentiles Change From Baseline at Week 4	0.0 percentile Interval -0.7 to 1.7	0.2 percentile Interval -1.9 to 1.9	1.4 percentile Interval -0.3 to 3.7	—	—	—
Treatment Phase: Change From Baseline in Growth and Development as Measured by Height Percentiles Change From Baseline at Week 8	0.0 percentile Interval -1.2 to 1.5	-0.1 percentile Interval -2.2 to 2.2	0.3 percentile Interval -2.1 to 3.6	—	—	—
Treatment Phase: Change From Baseline in Growth and Development as Measured by Height Percentiles Change From Baseline at Week 12	-0.1 percentile Interval -1.4 to 1.0	0.2 percentile Interval -2.6 to 2.8	0.2 percentile Interval -2.0 to 5.1	—	—	—
Treatment Phase: Change From Baseline in Growth and Development as Measured by Height Percentiles Change From Baseline at FU-4	0.0 percentile Interval -2.0 to 1.3	0.2 percentile Interval -2.3 to 2.5	1.2 percentile Interval -0.7 to 5.6	—	—	—
Treatment Phase: Change From Baseline in Growth and Development as Measured by Height Percentiles Change From Baseline at FU-12	-0.2 percentile Interval -2.4 to 1.4	0.1 percentile Interval -1.7 to 2.6	0.6 percentile Interval -3.1 to 4.6	—	—	—
Treatment Phase: Change From Baseline in Growth and Development as Measured by Height Percentiles Change From Baseline at FU-24	-0.6 percentile Interval -2.6 to 1.9	-0.2 percentile Interval -3.1 to 3.5	0.3 percentile Interval -2.1 to 6.0	—	—	—

SECONDARY outcome

Timeframe: Baseline; Weeks 1, 4, 8, 12, FU-4, FU-12, and FU-24

Population: Participants in the Safety Analysis Set with available data were analyzed.

An age- and sex-specific percentile was derived for each weight, height, and BMI measurement according to the SAS program available on the CDC website using the year 2000 growth charts.

Outcome measures

Outcome measures
Measure	12 to < 18 Years Old n=102 Participants PK Lead-in Phase: Sofosbuvir/Velpatasvir (SOF/VEL) fixed-dose combination (FDC) 400/100 mg tablets once daily for 7 days.	6 to < 12 Years Old n=73 Participants PK Lead-in Phase: SOF/VEL FDC 200/50 mg tablets or oral granules once daily for 7 days.	3 to < 6 Years Old n=41 Participants PK Lead-in Phase: SOF/VEL FDC 200/50 mg oral granules once daily for 7 days for participants who weighed ≥ 17 kg. SOF/VEL FDC 150/37.5 mg oral granules once daily for 7 days for participants who weighed \< 17 kg.	6 to <12 Years Old Treatment Phase: SOF/VEL FDC 200/50 mg oral granules once daily for 12 weeks.	3 to < 6 Years Old Treatment Phase: SOF/VEL FDC 200/50 mg oral granules once daily for 12 weeks for participants who weighed ≥ 17 kg.	3 to <6 Years Old SOF/VEL FDC 150/37.5 mg oral granules once daily for 12 weeks for participants who weighed \< 17 kg.
Treatment Phase: Change From Baseline in Growth and Development as Measured by Weight Percentiles Baseline	67.2 percentile Interval 31.5 to 84.1	45.9 percentile Interval 23.3 to 78.6	64.6 percentile Interval 38.0 to 86.7	—	—	—
Treatment Phase: Change From Baseline in Growth and Development as Measured by Weight Percentiles Change From Baseline at Week 1	0.0 percentile Interval -0.4 to 0.9	0.1 percentile Interval -0.6 to 1.2	-0.5 percentile Interval -2.7 to 0.7	—	—	—
Treatment Phase: Change From Baseline in Growth and Development as Measured by Weight Percentiles Change From Baseline at Week 4	0.0 percentile Interval -0.9 to 1.8	0.2 percentile Interval -1.4 to 1.5	0.3 percentile Interval -1.2 to 2.0	—	—	—
Treatment Phase: Change From Baseline in Growth and Development as Measured by Weight Percentiles Change From Baseline at Week 8	0.0 percentile Interval -1.3 to 2.1	0.1 percentile Interval -1.6 to 2.5	0.2 percentile Interval -3.7 to 2.5	—	—	—
Treatment Phase: Change From Baseline in Growth and Development as Measured by Weight Percentiles Change From Baseline at Week 12	0.2 percentile Interval -1.0 to 2.9	0.5 percentile Interval -1.7 to 2.5	-1.7 percentile Interval -4.7 to 0.6	—	—	—
Treatment Phase: Change From Baseline in Growth and Development as Measured by Weight Percentiles Change From Baseline at FU-4	0.1 percentile Interval -3.0 to 3.1	0.0 percentile Interval -2.3 to 2.6	-0.8 percentile Interval -4.9 to 2.4	—	—	—
Treatment Phase: Change From Baseline in Growth and Development as Measured by Weight Percentiles Change From Baseline at FU-12	0.0 percentile Interval -2.5 to 4.7	0.5 percentile Interval -2.2 to 4.9	-0.8 percentile Interval -6.6 to 2.2	—	—	—
Treatment Phase: Change From Baseline in Growth and Development as Measured by Weight Percentiles Change From Baseline at FU-24	0.1 percentile Interval -2.6 to 4.1	1.4 percentile Interval -1.2 to 5.7	-1.3 percentile Interval -3.5 to 2.9	—	—	—

SECONDARY outcome

Timeframe: Baseline; EOT, FU-12 and FU-24

Population: Participants in the Safety Analysis Set with available data were analyzed. Overall Number of Participants Analyzed for each arm is the total of male plus female participants.

Tanner Pubertal Staging was assessed for pubic hair growth and genitalia development (males) and for pubic hair growth and breast development (females) in stages 1 to 5. Tanner stages were used to evaluate the onset and progression of pubertal changes from stage 1 (pre-pubertal) to stage 5 (adult). If a participant had reached Tanner stage 5, no further Tanner pubertal stage assessments were to be completed. Pubic hair growth: Tanner stages (1: No hair, 2: Downy hair, 3: More coarse and curly hair, 4: Adult-like hair quality; 5: Hair extends to the medial surface of the thighs); Breast development: Tanner stages (1: No glandular tissue, 2: Breast bud forms,3: More elevated, outside areola, 4: Increased breast size,5: Final adult-size breasts); Genitalia development: Tanner stages (1: Testes, scrotum, and penis about same size, 2: Enlargement of scrotum, testes and penis, 3: Enlargement of penis, 4: Penis size enlargement, 5: Genitalia adult in size and shape).

Outcome measures

Outcome measures
Measure	12 to < 18 Years Old n=102 Participants PK Lead-in Phase: Sofosbuvir/Velpatasvir (SOF/VEL) fixed-dose combination (FDC) 400/100 mg tablets once daily for 7 days.	6 to < 12 Years Old n=73 Participants PK Lead-in Phase: SOF/VEL FDC 200/50 mg tablets or oral granules once daily for 7 days.	3 to < 6 Years Old n=41 Participants PK Lead-in Phase: SOF/VEL FDC 200/50 mg oral granules once daily for 7 days for participants who weighed ≥ 17 kg. SOF/VEL FDC 150/37.5 mg oral granules once daily for 7 days for participants who weighed \< 17 kg.	6 to <12 Years Old Treatment Phase: SOF/VEL FDC 200/50 mg oral granules once daily for 12 weeks.	3 to < 6 Years Old Treatment Phase: SOF/VEL FDC 200/50 mg oral granules once daily for 12 weeks for participants who weighed ≥ 17 kg.	3 to <6 Years Old SOF/VEL FDC 150/37.5 mg oral granules once daily for 12 weeks for participants who weighed \< 17 kg.
Treatment Phase: Changes in Growth and Development as Measured by Tanner Stage Assessment From Baseline Pubic Hair (Male): Baseline, Stage 1	4 Participants	31 Participants	17 Participants	—	—	—
Treatment Phase: Changes in Growth and Development as Measured by Tanner Stage Assessment From Baseline Pubic Hair (Male): Baseline, Stage 2	3 Participants	2 Participants	0 Participants	—	—	—
Treatment Phase: Changes in Growth and Development as Measured by Tanner Stage Assessment From Baseline Pubic Hair (Male): Baseline, Stage 3	10 Participants	1 Participants	0 Participants	—	—	—
Treatment Phase: Changes in Growth and Development as Measured by Tanner Stage Assessment From Baseline Pubic Hair (Male): Baseline, Stage 4	14 Participants	0 Participants	0 Participants	—	—	—
Treatment Phase: Changes in Growth and Development as Measured by Tanner Stage Assessment From Baseline Pubic Hair (Male): Baseline, Stage 5	19 Participants	0 Participants	0 Participants	—	—	—
Treatment Phase: Changes in Growth and Development as Measured by Tanner Stage Assessment From Baseline Pubic Hair (Male): EOT, Stage 1	2 Participants	28 Participants	13 Participants	—	—	—
Treatment Phase: Changes in Growth and Development as Measured by Tanner Stage Assessment From Baseline Pubic Hair (Male): EOT, Stage 2	4 Participants	3 Participants	0 Participants	—	—	—
Treatment Phase: Changes in Growth and Development as Measured by Tanner Stage Assessment From Baseline Pubic Hair (Male): EOT, Stage 3	7 Participants	1 Participants	0 Participants	—	—	—
Treatment Phase: Changes in Growth and Development as Measured by Tanner Stage Assessment From Baseline Pubic Hair (Male): EOT, Stage 4	13 Participants	0 Participants	0 Participants	—	—	—
Treatment Phase: Changes in Growth and Development as Measured by Tanner Stage Assessment From Baseline Pubic Hair (Male): EOT, Stage 5	24 Participants	0 Participants	0 Participants	—	—	—
Treatment Phase: Changes in Growth and Development as Measured by Tanner Stage Assessment From Baseline Pubic Hair (Male): FU-12, Stage 1	1 Participants	26 Participants	14 Participants	—	—	—
Treatment Phase: Changes in Growth and Development as Measured by Tanner Stage Assessment From Baseline Pubic Hair (Male): FU-12, Stage 2	5 Participants	3 Participants	0 Participants	—	—	—
Treatment Phase: Changes in Growth and Development as Measured by Tanner Stage Assessment From Baseline Pubic Hair (Male): FU-12, Stage 3	6 Participants	1 Participants	0 Participants	—	—	—
Treatment Phase: Changes in Growth and Development as Measured by Tanner Stage Assessment From Baseline Pubic Hair (Male): FU-12, Stage 4	10 Participants	0 Participants	0 Participants	—	—	—
Treatment Phase: Changes in Growth and Development as Measured by Tanner Stage Assessment From Baseline Pubic Hair (Male): FU-12, Stage 5	25 Participants	0 Participants	0 Participants	—	—	—
Treatment Phase: Changes in Growth and Development as Measured by Tanner Stage Assessment From Baseline Pubic Hair (Male): FU-24, Stage 1	1 Participants	29 Participants	14 Participants	—	—	—
Treatment Phase: Changes in Growth and Development as Measured by Tanner Stage Assessment From Baseline Pubic Hair (Male): FU-24, Stage 2	4 Participants	2 Participants	0 Participants	—	—	—
Treatment Phase: Changes in Growth and Development as Measured by Tanner Stage Assessment From Baseline Pubic Hair (Male): FU-24, Stage 3	2 Participants	1 Participants	0 Participants	—	—	—
Treatment Phase: Changes in Growth and Development as Measured by Tanner Stage Assessment From Baseline Pubic Hair (Male): FU-24, Stage 4	13 Participants	0 Participants	0 Participants	—	—	—
Treatment Phase: Changes in Growth and Development as Measured by Tanner Stage Assessment From Baseline Pubic Hair (Male): FU-24, Stage 5	25 Participants	0 Participants	0 Participants	—	—	—
Treatment Phase: Changes in Growth and Development as Measured by Tanner Stage Assessment From Baseline Genitalia (Male): Baseline, Stage 1	4 Participants	31 Participants	17 Participants	—	—	—
Treatment Phase: Changes in Growth and Development as Measured by Tanner Stage Assessment From Baseline Genitalia (Male): Baseline, Stage 2	3 Participants	2 Participants	0 Participants	—	—	—
Treatment Phase: Changes in Growth and Development as Measured by Tanner Stage Assessment From Baseline Genitalia (Male): Baseline, Stage 3	8 Participants	1 Participants	0 Participants	—	—	—
Treatment Phase: Changes in Growth and Development as Measured by Tanner Stage Assessment From Baseline Genitalia (Male): Baseline, Stage 4	16 Participants	0 Participants	0 Participants	—	—	—
Treatment Phase: Changes in Growth and Development as Measured by Tanner Stage Assessment From Baseline Genitalia (Male): Baseline, Stage 5	19 Participants	0 Participants	0 Participants	—	—	—
Treatment Phase: Changes in Growth and Development as Measured by Tanner Stage Assessment From Baseline Genitalia (Male): EOT, Stage 1	2 Participants	28 Participants	13 Participants	—	—	—
Treatment Phase: Changes in Growth and Development as Measured by Tanner Stage Assessment From Baseline Genitalia (Male): EOT, Stage 2	3 Participants	3 Participants	0 Participants	—	—	—
Treatment Phase: Changes in Growth and Development as Measured by Tanner Stage Assessment From Baseline Genitalia (Male): EOT, Stage 3	7 Participants	1 Participants	0 Participants	—	—	—
Treatment Phase: Changes in Growth and Development as Measured by Tanner Stage Assessment From Baseline Genitalia (Male): EOT, Stage 4	15 Participants	0 Participants	0 Participants	—	—	—
Treatment Phase: Changes in Growth and Development as Measured by Tanner Stage Assessment From Baseline Genitalia (Male): EOT, Stage 5	23 Participants	0 Participants	0 Participants	—	—	—
Treatment Phase: Changes in Growth and Development as Measured by Tanner Stage Assessment From Baseline Genitalia (Male): FU-12, Stage 1	1 Participants	26 Participants	14 Participants	—	—	—
Treatment Phase: Changes in Growth and Development as Measured by Tanner Stage Assessment From Baseline Genitalia (Male): FU-12, Stage 2	4 Participants	3 Participants	0 Participants	—	—	—
Treatment Phase: Changes in Growth and Development as Measured by Tanner Stage Assessment From Baseline Genitalia (Male): FU-12, Stage 3	7 Participants	1 Participants	0 Participants	—	—	—
Treatment Phase: Changes in Growth and Development as Measured by Tanner Stage Assessment From Baseline Genitalia (Male): FU-12, Stage 4	11 Participants	0 Participants	0 Participants	—	—	—
Treatment Phase: Changes in Growth and Development as Measured by Tanner Stage Assessment From Baseline Genitalia (Male): FU-12, Stage 5	24 Participants	0 Participants	0 Participants	—	—	—
Treatment Phase: Changes in Growth and Development as Measured by Tanner Stage Assessment From Baseline Genitalia (Male): FU-24, Stage 1	1 Participants	27 Participants	14 Participants	—	—	—
Treatment Phase: Changes in Growth and Development as Measured by Tanner Stage Assessment From Baseline Genitalia (Male): FU-24, Stage 2	2 Participants	4 Participants	0 Participants	—	—	—
Treatment Phase: Changes in Growth and Development as Measured by Tanner Stage Assessment From Baseline Genitalia (Male): FU-24, Stage 3	4 Participants	1 Participants	0 Participants	—	—	—
Treatment Phase: Changes in Growth and Development as Measured by Tanner Stage Assessment From Baseline Genitalia (Male): FU-24, Stage 4	13 Participants	0 Participants	0 Participants	—	—	—
Treatment Phase: Changes in Growth and Development as Measured by Tanner Stage Assessment From Baseline Genitalia (Male): FU-24, Stage 5	25 Participants	0 Participants	0 Participants	—	—	—
Treatment Phase: Changes in Growth and Development as Measured by Tanner Stage Assessment From Baseline Pubic Hair (Female): Baseline, Stage 1	2 Participants	31 Participants	24 Participants	—	—	—
Treatment Phase: Changes in Growth and Development as Measured by Tanner Stage Assessment From Baseline Pubic Hair (Female): Baseline, Stage 2	3 Participants	5 Participants	0 Participants	—	—	—
Treatment Phase: Changes in Growth and Development as Measured by Tanner Stage Assessment From Baseline Pubic Hair (Female): Baseline, Stage 3	9 Participants	2 Participants	0 Participants	—	—	—
Treatment Phase: Changes in Growth and Development as Measured by Tanner Stage Assessment From Baseline Pubic Hair (Female): Baseline, Stage 4	16 Participants	0 Participants	0 Participants	—	—	—
Treatment Phase: Changes in Growth and Development as Measured by Tanner Stage Assessment From Baseline Pubic Hair (Female): Baseline, Stage 5	22 Participants	0 Participants	0 Participants	—	—	—
Treatment Phase: Changes in Growth and Development as Measured by Tanner Stage Assessment From Baseline Pubic Hair (Female): EOT, Stage 1	2 Participants	29 Participants	21 Participants	—	—	—
Treatment Phase: Changes in Growth and Development as Measured by Tanner Stage Assessment From Baseline Pubic Hair (Female): EOT, Stage 2	2 Participants	5 Participants	0 Participants	—	—	—
Treatment Phase: Changes in Growth and Development as Measured by Tanner Stage Assessment From Baseline Pubic Hair (Female): EOT, Stage 3	6 Participants	2 Participants	0 Participants	—	—	—
Treatment Phase: Changes in Growth and Development as Measured by Tanner Stage Assessment From Baseline Pubic Hair (Female): EOT, Stage 4	10 Participants	1 Participants	0 Participants	—	—	—
Treatment Phase: Changes in Growth and Development as Measured by Tanner Stage Assessment From Baseline Pubic Hair (Female): EOT, Stage 5	30 Participants	0 Participants	0 Participants	—	—	—
Treatment Phase: Changes in Growth and Development as Measured by Tanner Stage Assessment From Baseline Pubic Hair (Female): FU-12, Stage 1	2 Participants	24 Participants	21 Participants	—	—	—
Treatment Phase: Changes in Growth and Development as Measured by Tanner Stage Assessment From Baseline Pubic Hair (Female): FU-12, Stage 2	1 Participants	7 Participants	0 Participants	—	—	—
Treatment Phase: Changes in Growth and Development as Measured by Tanner Stage Assessment From Baseline Pubic Hair (Female): FU-12, Stage 3	8 Participants	3 Participants	0 Participants	—	—	—
Treatment Phase: Changes in Growth and Development as Measured by Tanner Stage Assessment From Baseline Pubic Hair (Female): FU-12, Stage 4	8 Participants	1 Participants	0 Participants	—	—	—
Treatment Phase: Changes in Growth and Development as Measured by Tanner Stage Assessment From Baseline Pubic Hair (Female): FU-12, Stage 5	32 Participants	0 Participants	0 Participants	—	—	—
Treatment Phase: Changes in Growth and Development as Measured by Tanner Stage Assessment From Baseline Pubic Hair (Female): FU-24, Stage 1	2 Participants	24 Participants	20 Participants	—	—	—
Treatment Phase: Changes in Growth and Development as Measured by Tanner Stage Assessment From Baseline Pubic Hair (Female): FU-24, Stage 2	0 Participants	6 Participants	1 Participants	—	—	—
Treatment Phase: Changes in Growth and Development as Measured by Tanner Stage Assessment From Baseline Pubic Hair (Female): FU-24, Stage 3	8 Participants	1 Participants	0 Participants	—	—	—
Treatment Phase: Changes in Growth and Development as Measured by Tanner Stage Assessment From Baseline Pubic Hair (Female): FU-24, Stage 4	9 Participants	4 Participants	0 Participants	—	—	—
Treatment Phase: Changes in Growth and Development as Measured by Tanner Stage Assessment From Baseline Pubic Hair (Female): FU-24, Stage 5	31 Participants	0 Participants	0 Participants	—	—	—
Treatment Phase: Changes in Growth and Development as Measured by Tanner Stage Assessment From Baseline Breasts (Female): Baseline, Stage 1	1 Participants	29 Participants	24 Participants	—	—	—
Treatment Phase: Changes in Growth and Development as Measured by Tanner Stage Assessment From Baseline Breasts (Female): Baseline, Stage 2	5 Participants	6 Participants	0 Participants	—	—	—
Treatment Phase: Changes in Growth and Development as Measured by Tanner Stage Assessment From Baseline Breasts (Female): Baseline, Stage 3	6 Participants	3 Participants	0 Participants	—	—	—
Treatment Phase: Changes in Growth and Development as Measured by Tanner Stage Assessment From Baseline Breasts (Female): Baseline, Stage 4	17 Participants	0 Participants	0 Participants	—	—	—
Treatment Phase: Changes in Growth and Development as Measured by Tanner Stage Assessment From Baseline Breasts (Female): Baseline, Stage 5	23 Participants	0 Participants	0 Participants	—	—	—
Treatment Phase: Changes in Growth and Development as Measured by Tanner Stage Assessment From Baseline Breasts (Female): EOT, Stage 1	1 Participants	25 Participants	21 Participants	—	—	—
Treatment Phase: Changes in Growth and Development as Measured by Tanner Stage Assessment From Baseline Breasts (Female): EOT, Stage 2	2 Participants	9 Participants	0 Participants	—	—	—
Treatment Phase: Changes in Growth and Development as Measured by Tanner Stage Assessment From Baseline Breasts (Female): EOT, Stage 3	6 Participants	2 Participants	0 Participants	—	—	—
Treatment Phase: Changes in Growth and Development as Measured by Tanner Stage Assessment From Baseline Breasts (Female): EOT, Stage 4	14 Participants	1 Participants	0 Participants	—	—	—
Treatment Phase: Changes in Growth and Development as Measured by Tanner Stage Assessment From Baseline Breasts (Female): EOT, Stage 5	27 Participants	0 Participants	0 Participants	—	—	—
Treatment Phase: Changes in Growth and Development as Measured by Tanner Stage Assessment From Baseline Breasts (Female): FU-12, Stage 1	1 Participants	20 Participants	21 Participants	—	—	—
Treatment Phase: Changes in Growth and Development as Measured by Tanner Stage Assessment From Baseline Breasts (Female): FU-12, Stage 2	2 Participants	11 Participants	0 Participants	—	—	—
Treatment Phase: Changes in Growth and Development as Measured by Tanner Stage Assessment From Baseline Breasts (Female): FU-12, Stage 3	5 Participants	2 Participants	0 Participants	—	—	—
Treatment Phase: Changes in Growth and Development as Measured by Tanner Stage Assessment From Baseline Breasts (Female): FU-12, Stage 4	15 Participants	2 Participants	0 Participants	—	—	—
Treatment Phase: Changes in Growth and Development as Measured by Tanner Stage Assessment From Baseline Breasts (Female): FU-12, Stage 5	28 Participants	0 Participants	0 Participants	—	—	—
Treatment Phase: Changes in Growth and Development as Measured by Tanner Stage Assessment From Baseline Breasts (Female): FU-24, Stage 1	1 Participants	20 Participants	20 Participants	—	—	—
Treatment Phase: Changes in Growth and Development as Measured by Tanner Stage Assessment From Baseline Breasts (Female): FU-24, Stage 2	0 Participants	10 Participants	1 Participants	—	—	—
Treatment Phase: Changes in Growth and Development as Measured by Tanner Stage Assessment From Baseline Breasts (Female): FU-24, Stage 3	6 Participants	3 Participants	0 Participants	—	—	—
Treatment Phase: Changes in Growth and Development as Measured by Tanner Stage Assessment From Baseline Breasts (Female): FU-24, Stage 4	13 Participants	2 Participants	0 Participants	—	—	—
Treatment Phase: Changes in Growth and Development as Measured by Tanner Stage Assessment From Baseline Breasts (Female): FU-24, Stage 5	30 Participants	0 Participants	0 Participants	—	—	—

SECONDARY outcome

Timeframe: Day 1

Population: Participants in the Safety Analysis Set with available data were analyzed.

Mid-parental height was calculated as the average of the biological father's and mother's heights. For boys, the sex-adjusted mid-parental height was calculated by adding 2.5 inches or 6.5 cm to the mean of the parents' heights. For girls, 2.5 inches or 6.5 cm was subtracted from the mean of the parents' heights.

Outcome measures

Outcome measures
Measure	12 to < 18 Years Old n=53 Participants PK Lead-in Phase: Sofosbuvir/Velpatasvir (SOF/VEL) fixed-dose combination (FDC) 400/100 mg tablets once daily for 7 days.	6 to < 12 Years Old n=39 Participants PK Lead-in Phase: SOF/VEL FDC 200/50 mg tablets or oral granules once daily for 7 days.	3 to < 6 Years Old n=23 Participants PK Lead-in Phase: SOF/VEL FDC 200/50 mg oral granules once daily for 7 days for participants who weighed ≥ 17 kg. SOF/VEL FDC 150/37.5 mg oral granules once daily for 7 days for participants who weighed \< 17 kg.	6 to <12 Years Old Treatment Phase: SOF/VEL FDC 200/50 mg oral granules once daily for 12 weeks.	3 to < 6 Years Old Treatment Phase: SOF/VEL FDC 200/50 mg oral granules once daily for 12 weeks for participants who weighed ≥ 17 kg.	3 to <6 Years Old SOF/VEL FDC 150/37.5 mg oral granules once daily for 12 weeks for participants who weighed \< 17 kg.
Treatment Phase: Growth and Development as Measured by Parental Height	170.5 cm Interval 162.0 to 176.7	170.0 cm Interval 163.7 to 178.6	168.7 cm Interval 163.0 to 174.1	—	—	—

SECONDARY outcome

Timeframe: Baseline; FU-24

Population: Participants in the Full Analysis Set with available data were analyzed.

Bone age was determined based on x-ray of the left wrist, hand, and fingers. Baseline value is the last available value on or prior to first dose date of study drug.

Outcome measures

Outcome measures
Measure	12 to < 18 Years Old n=102 Participants PK Lead-in Phase: Sofosbuvir/Velpatasvir (SOF/VEL) fixed-dose combination (FDC) 400/100 mg tablets once daily for 7 days.	6 to < 12 Years Old n=73 Participants PK Lead-in Phase: SOF/VEL FDC 200/50 mg tablets or oral granules once daily for 7 days.	3 to < 6 Years Old n=41 Participants PK Lead-in Phase: SOF/VEL FDC 200/50 mg oral granules once daily for 7 days for participants who weighed ≥ 17 kg. SOF/VEL FDC 150/37.5 mg oral granules once daily for 7 days for participants who weighed \< 17 kg.	6 to <12 Years Old Treatment Phase: SOF/VEL FDC 200/50 mg oral granules once daily for 12 weeks.	3 to < 6 Years Old Treatment Phase: SOF/VEL FDC 200/50 mg oral granules once daily for 12 weeks for participants who weighed ≥ 17 kg.	3 to <6 Years Old SOF/VEL FDC 150/37.5 mg oral granules once daily for 12 weeks for participants who weighed \< 17 kg.
Treatment Phase: Change From Baseline in Growth and Development as Measured by Bone Age Baseline	15.5 years Interval 13.5 to 17.0	7.8 years Interval 6.8 to 9.0	4.8 years Interval 4.2 to 5.5	—	—	—
Treatment Phase: Change From Baseline in Growth and Development as Measured by Bone Age Change From Baseline at FU-24	0.6 years Interval 0.0 to 1.0	1.0 years Interval 0.0 to 1.2	0.5 years Interval 0.0 to 1.1	—	—	—

SECONDARY outcome

Timeframe: Baseline

Population: Participants in the Full Analysis Set with available data were analyzed. Swallowability assessment was performed in 12 to \<18 years old and 6 to \< 12 Years old only.

A SOF/VEL FDC swallowability assessment was performed using placebo tablets at baseline.

Outcome measures

Outcome measures
Measure	12 to < 18 Years Old n=102 Participants PK Lead-in Phase: Sofosbuvir/Velpatasvir (SOF/VEL) fixed-dose combination (FDC) 400/100 mg tablets once daily for 7 days.	6 to < 12 Years Old n=73 Participants PK Lead-in Phase: SOF/VEL FDC 200/50 mg tablets or oral granules once daily for 7 days.	3 to < 6 Years Old PK Lead-in Phase: SOF/VEL FDC 200/50 mg oral granules once daily for 7 days for participants who weighed ≥ 17 kg. SOF/VEL FDC 150/37.5 mg oral granules once daily for 7 days for participants who weighed \< 17 kg.	6 to <12 Years Old Treatment Phase: SOF/VEL FDC 200/50 mg oral granules once daily for 12 weeks.	3 to < 6 Years Old Treatment Phase: SOF/VEL FDC 200/50 mg oral granules once daily for 12 weeks for participants who weighed ≥ 17 kg.	3 to <6 Years Old SOF/VEL FDC 150/37.5 mg oral granules once daily for 12 weeks for participants who weighed \< 17 kg.
Treatment Phase: Swallowability of SOF/VEL as Assessed by the Participant's Ability to Swallow SOF/VEL Placebo Tablets at Baseline SOF/VEL 400/100mg Placebo Tablet, Able to Swallow	92 Participants	1 Participants	—	—	—	—
Treatment Phase: Swallowability of SOF/VEL as Assessed by the Participant's Ability to Swallow SOF/VEL Placebo Tablets at Baseline SOF/VEL 400/100mg Placebo, Not Able to Swallow	10 Participants	0 Participants	—	—	—	—
Treatment Phase: Swallowability of SOF/VEL as Assessed by the Participant's Ability to Swallow SOF/VEL Placebo Tablets at Baseline SOF/VEL 200/50mg Placebo, Able to Swallow	10 Participants	72 Participants	—	—	—	—
Treatment Phase: Swallowability of SOF/VEL as Assessed by the Participant's Ability to Swallow SOF/VEL Placebo Tablets at Baseline SOF/VEL 200/50mg Placebo, Not Able to Swallow	0 Participants	1 Participants	—	—	—	—

SECONDARY outcome

Timeframe: Day 1

Population: Participants in the Full Analysis Set with available data were analyzed.

Acceptability was assessed by numeric response marked on line between numbers 0 - 100. Higher scores indicate better acceptability and/or palatability.

Outcome measures

Outcome measures
Measure	12 to < 18 Years Old n=91 Participants PK Lead-in Phase: Sofosbuvir/Velpatasvir (SOF/VEL) fixed-dose combination (FDC) 400/100 mg tablets once daily for 7 days.	6 to < 12 Years Old n=11 Participants PK Lead-in Phase: SOF/VEL FDC 200/50 mg tablets or oral granules once daily for 7 days.	3 to < 6 Years Old n=72 Participants PK Lead-in Phase: SOF/VEL FDC 200/50 mg oral granules once daily for 7 days for participants who weighed ≥ 17 kg. SOF/VEL FDC 150/37.5 mg oral granules once daily for 7 days for participants who weighed \< 17 kg.	6 to <12 Years Old n=1 Participants Treatment Phase: SOF/VEL FDC 200/50 mg oral granules once daily for 12 weeks.	3 to < 6 Years Old n=29 Participants Treatment Phase: SOF/VEL FDC 200/50 mg oral granules once daily for 12 weeks for participants who weighed ≥ 17 kg.	3 to <6 Years Old n=12 Participants SOF/VEL FDC 150/37.5 mg oral granules once daily for 12 weeks for participants who weighed \< 17 kg.
Treatment Phase: Number of Participants With Acceptability of SOF/VEL as Measured by a Questionnaire to Assess Acceptability, Including Palatability at Day 1 Taste, Participants Who Did Not Taste Study Drug	61 Participants	5 Participants	42 Participants	0 Participants	8 Participants	5 Participants
Treatment Phase: Number of Participants With Acceptability of SOF/VEL as Measured by a Questionnaire to Assess Acceptability, Including Palatability at Day 1 Taste, Participants Who Marked > 60 to 100	16 Participants	3 Participants	11 Participants	0 Participants	6 Participants	3 Participants
Treatment Phase: Number of Participants With Acceptability of SOF/VEL as Measured by a Questionnaire to Assess Acceptability, Including Palatability at Day 1 Taste, Participants Who Marked 40 to 60	11 Participants	1 Participants	6 Participants	0 Participants	4 Participants	1 Participants
Treatment Phase: Number of Participants With Acceptability of SOF/VEL as Measured by a Questionnaire to Assess Acceptability, Including Palatability at Day 1 Taste, Participants Who Marked 0 to < 40	3 Participants	2 Participants	12 Participants	1 Participants	9 Participants	3 Participants
Treatment Phase: Number of Participants With Acceptability of SOF/VEL as Measured by a Questionnaire to Assess Acceptability, Including Palatability at Day 1 Easy to Take, Participants Who Marked > 60 to 100	82 Participants	9 Participants	60 Participants	0 Participants	13 Participants	4 Participants
Treatment Phase: Number of Participants With Acceptability of SOF/VEL as Measured by a Questionnaire to Assess Acceptability, Including Palatability at Day 1 Easy to Take, Participants Who Marked 40 to 60	5 Participants	1 Participants	3 Participants	0 Participants	4 Participants	2 Participants
Treatment Phase: Number of Participants With Acceptability of SOF/VEL as Measured by a Questionnaire to Assess Acceptability, Including Palatability at Day 1 Easy to Take, Participants Who Marked 0 to < 40	2 Participants	1 Participants	8 Participants	1 Participants	10 Participants	6 Participants

SECONDARY outcome

Timeframe: Week 12

Population: Participants in the Full Analysis Set with available data were analyzed.

Acceptability was assessed by numeric response marked on line between numbers 0 - 100. Higher scores indicate better acceptability and/or palatability.

Outcome measures

Outcome measures
Measure	12 to < 18 Years Old n=91 Participants PK Lead-in Phase: Sofosbuvir/Velpatasvir (SOF/VEL) fixed-dose combination (FDC) 400/100 mg tablets once daily for 7 days.	6 to < 12 Years Old n=11 Participants PK Lead-in Phase: SOF/VEL FDC 200/50 mg tablets or oral granules once daily for 7 days.	3 to < 6 Years Old n=72 Participants PK Lead-in Phase: SOF/VEL FDC 200/50 mg oral granules once daily for 7 days for participants who weighed ≥ 17 kg. SOF/VEL FDC 150/37.5 mg oral granules once daily for 7 days for participants who weighed \< 17 kg.	6 to <12 Years Old n=1 Participants Treatment Phase: SOF/VEL FDC 200/50 mg oral granules once daily for 12 weeks.	3 to < 6 Years Old n=29 Participants Treatment Phase: SOF/VEL FDC 200/50 mg oral granules once daily for 12 weeks for participants who weighed ≥ 17 kg.	3 to <6 Years Old n=12 Participants SOF/VEL FDC 150/37.5 mg oral granules once daily for 12 weeks for participants who weighed \< 17 kg.
Treatment Phase: Number of Participants With Acceptability of SOF/VEL as Measured by a Questionnaire to Assess Acceptability, Including Palatability at Week 12 Taste, Participants Who Did Not Taste Study Drug	49 Participants	2 Participants	33 Participants	0 Participants	8 Participants	2 Participants
Treatment Phase: Number of Participants With Acceptability of SOF/VEL as Measured by a Questionnaire to Assess Acceptability, Including Palatability at Week 12 Taste, Participants Who Marked > 60 to 100	24 Participants	5 Participants	14 Participants	0 Participants	4 Participants	1 Participants
Treatment Phase: Number of Participants With Acceptability of SOF/VEL as Measured by a Questionnaire to Assess Acceptability, Including Palatability at Week 12 Taste, Participants Who Marked 40 to 60	10 Participants	1 Participants	12 Participants	1 Participants	4 Participants	3 Participants
Treatment Phase: Number of Participants With Acceptability of SOF/VEL as Measured by a Questionnaire to Assess Acceptability, Including Palatability at Week 12 Taste, Participants Who Marked 0 to < 40	7 Participants	3 Participants	11 Participants	0 Participants	7 Participants	2 Participants
Treatment Phase: Number of Participants With Acceptability of SOF/VEL as Measured by a Questionnaire to Assess Acceptability, Including Palatability at Week 12 Easy to Take, Participants Who Marked > 60 to 100	83 Participants	9 Participants	65 Participants	1 Participants	20 Participants	6 Participants
Treatment Phase: Number of Participants With Acceptability of SOF/VEL as Measured by a Questionnaire to Assess Acceptability, Including Palatability at Week 12 Easy to Take, Participants Who Marked 40 to 60	3 Participants	0 Participants	5 Participants	0 Participants	1 Participants	1 Participants
Treatment Phase: Number of Participants With Acceptability of SOF/VEL as Measured by a Questionnaire to Assess Acceptability, Including Palatability at Week 12 Easy to Take, Participants Who Marked 0 to < 40	3 Participants	2 Participants	0 Participants	0 Participants	2 Participants	1 Participants
Treatment Phase: Number of Participants With Acceptability of SOF/VEL as Measured by a Questionnaire to Assess Acceptability, Including Palatability at Week 12 Feel About Taking Pills, Who Marked > 60 to 100	82 Participants	8 Participants	60 Participants	NA Participants Data not applicable for the oral granules group.	NA Participants Data not applicable for the oral granules group.	NA Participants Data not applicable for the oral granules group.
Treatment Phase: Number of Participants With Acceptability of SOF/VEL as Measured by a Questionnaire to Assess Acceptability, Including Palatability at Week 12 Feel About Taking Pills, Who Marked 40 to 60	3 Participants	1 Participants	7 Participants	NA Participants Data not applicable for the oral granules group.	NA Participants Data not applicable for the oral granules group.	NA Participants Data not applicable for the oral granules group.
Treatment Phase: Number of Participants With Acceptability of SOF/VEL as Measured by a Questionnaire to Assess Acceptability, Including Palatability at Week 12 Feel About Taking Pills, Who Marked 0 to < 40	3 Participants	2 Participants	3 Participants	NA Participants Data not applicable for the oral granules group.	NA Participants Data not applicable for the oral granules group.	NA Participants Data not applicable for the oral granules group.

Adverse Events

12 to < 18 Years Old

Serious events: 2 serious events

Other events: 65 other events

Deaths: 0 deaths

6 to < 12 Years Old

Serious events: 2 serious events

Other events: 53 other events

Deaths: 0 deaths

3 to < 6 Years Old

Serious events: 0 serious events

Other events: 26 other events

Deaths: 0 deaths

Serious adverse events

Serious adverse events
Measure	12 to < 18 Years Old n=102 participants at risk PK Lead-in Phase: Sofosbuvir/Velpatasvir (SOF/VEL) fixed-dose combination (FDC) 400/100 mg tablets once daily for 7 days. Participants who completed the PK lead-in phase, continued into the treatment phase with no interruption of study drug administration and additional participants were enrolled into the treatment phase once the appropriateness of the dose was confirmed by PK results from the PK lead-in phase. Treatment Phase: SOF/VEL 400/100 mg (adult and smaller size tablets based on swallowability assessment) once daily for 12 weeks.	6 to < 12 Years Old n=73 participants at risk PK Lead-in Phase: SOF/VEL FDC 200/50 mg tablets or oral granules once daily for 7 days. Participants who completed the PK lead-in phase, continued into the treatment phase with no interruption of study drug administration and additional participants were enrolled into the treatment phase once the appropriateness of the dose was confirmed by PK results from the PK lead-in phase. Treatment Phase: SOF/VEL FDC 200/50 mg tablets or oral granules once daily for 12 weeks.	3 to < 6 Years Old n=41 participants at risk PK Lead-in Phase: SOF/VEL FDC 200/50 mg oral granules once daily for 7 days for participants who weighed ≥ 17 kg. SOF/VEL FDC 150/37.5 mg oral granules once daily for 7 days for participants who weighed \< 17 kg. Participants who completed the PK lead-in phase, continued into the treatment phase with no interruption of study drug administration and additional participants were enrolled into the treatment phase once the appropriateness of the dose was confirmed by PK results from the PK lead-in phase. Treatment Phase: SOF/VEL FDC 200/50 mg oral granules once daily for 12 weeks for participants who weighed ≥ 17 kg. SOF/VEL FDC 150/37.5 mg oral granules once daily for 12 weeks for participants who weighed \< 17 kg.
Gastrointestinal disorders Constipation	0.00% 0/102 • Adverse Events: From first dose through last dose of the study drug (Up to 12 weeks) plus 30 days; All-Cause Mortality: First dose date up to Posttreatment Week 24 The Safety Analysis Set included all participants who were enrolled into the study and received at least 1 dose of study drug (SOF/VEL FDC).	1.4% 1/73 • Adverse Events: From first dose through last dose of the study drug (Up to 12 weeks) plus 30 days; All-Cause Mortality: First dose date up to Posttreatment Week 24 The Safety Analysis Set included all participants who were enrolled into the study and received at least 1 dose of study drug (SOF/VEL FDC).	0.00% 0/41 • Adverse Events: From first dose through last dose of the study drug (Up to 12 weeks) plus 30 days; All-Cause Mortality: First dose date up to Posttreatment Week 24 The Safety Analysis Set included all participants who were enrolled into the study and received at least 1 dose of study drug (SOF/VEL FDC).
Psychiatric disorders Bipolar disorder	0.98% 1/102 • Adverse Events: From first dose through last dose of the study drug (Up to 12 weeks) plus 30 days; All-Cause Mortality: First dose date up to Posttreatment Week 24 The Safety Analysis Set included all participants who were enrolled into the study and received at least 1 dose of study drug (SOF/VEL FDC).	0.00% 0/73 • Adverse Events: From first dose through last dose of the study drug (Up to 12 weeks) plus 30 days; All-Cause Mortality: First dose date up to Posttreatment Week 24 The Safety Analysis Set included all participants who were enrolled into the study and received at least 1 dose of study drug (SOF/VEL FDC).	0.00% 0/41 • Adverse Events: From first dose through last dose of the study drug (Up to 12 weeks) plus 30 days; All-Cause Mortality: First dose date up to Posttreatment Week 24 The Safety Analysis Set included all participants who were enrolled into the study and received at least 1 dose of study drug (SOF/VEL FDC).
Psychiatric disorders Hallucination, auditory	0.00% 0/102 • Adverse Events: From first dose through last dose of the study drug (Up to 12 weeks) plus 30 days; All-Cause Mortality: First dose date up to Posttreatment Week 24 The Safety Analysis Set included all participants who were enrolled into the study and received at least 1 dose of study drug (SOF/VEL FDC).	1.4% 1/73 • Adverse Events: From first dose through last dose of the study drug (Up to 12 weeks) plus 30 days; All-Cause Mortality: First dose date up to Posttreatment Week 24 The Safety Analysis Set included all participants who were enrolled into the study and received at least 1 dose of study drug (SOF/VEL FDC).	0.00% 0/41 • Adverse Events: From first dose through last dose of the study drug (Up to 12 weeks) plus 30 days; All-Cause Mortality: First dose date up to Posttreatment Week 24 The Safety Analysis Set included all participants who were enrolled into the study and received at least 1 dose of study drug (SOF/VEL FDC).
Psychiatric disorders Suicidal ideation	2.0% 2/102 • Adverse Events: From first dose through last dose of the study drug (Up to 12 weeks) plus 30 days; All-Cause Mortality: First dose date up to Posttreatment Week 24 The Safety Analysis Set included all participants who were enrolled into the study and received at least 1 dose of study drug (SOF/VEL FDC).	0.00% 0/73 • Adverse Events: From first dose through last dose of the study drug (Up to 12 weeks) plus 30 days; All-Cause Mortality: First dose date up to Posttreatment Week 24 The Safety Analysis Set included all participants who were enrolled into the study and received at least 1 dose of study drug (SOF/VEL FDC).	0.00% 0/41 • Adverse Events: From first dose through last dose of the study drug (Up to 12 weeks) plus 30 days; All-Cause Mortality: First dose date up to Posttreatment Week 24 The Safety Analysis Set included all participants who were enrolled into the study and received at least 1 dose of study drug (SOF/VEL FDC).
Psychiatric disorders Suicide attempt	0.98% 1/102 • Adverse Events: From first dose through last dose of the study drug (Up to 12 weeks) plus 30 days; All-Cause Mortality: First dose date up to Posttreatment Week 24 The Safety Analysis Set included all participants who were enrolled into the study and received at least 1 dose of study drug (SOF/VEL FDC).	0.00% 0/73 • Adverse Events: From first dose through last dose of the study drug (Up to 12 weeks) plus 30 days; All-Cause Mortality: First dose date up to Posttreatment Week 24 The Safety Analysis Set included all participants who were enrolled into the study and received at least 1 dose of study drug (SOF/VEL FDC).	0.00% 0/41 • Adverse Events: From first dose through last dose of the study drug (Up to 12 weeks) plus 30 days; All-Cause Mortality: First dose date up to Posttreatment Week 24 The Safety Analysis Set included all participants who were enrolled into the study and received at least 1 dose of study drug (SOF/VEL FDC).

Other adverse events

Additional Information

Gilead Clinical Study Information Center

Gilead Sciences

Phone: 1-833-445-3230 (GILEAD-0)

Email: [email protected]

Results disclosure agreements

Principal investigator is a sponsor employee After conclusion of the study and without prior written approval from Gilead, investigators in this study may communicate, orally present, or publish in scientific journals or other media only after the following conditions have been met: The results of the study in their entirety have been publicly disclosed by or with the consent of Gilead in an abstract, manuscript, or presentation form; or The study has been completed at all study sites for at least 2 years.
Publication restrictions are in place

Restriction type: OTHER