Trial Outcomes & Findings for Study to Evaluate the Safety, Efficacy, and Pharmacokinetics of Recombinant Coagulation Factor VIII Fc Fusion Protein (rFVIIIFc) in Previously Treated Pediatric Subjects With Hemophilia A (NCT NCT01458106)

Results Overview

An inhibitor test result ≥0.6 Bethesda units (BU)/mL, confirmed on 2 separate samples drawn 2 to 4 weeks apart, was considered positive. Both tests were to be performed by the central laboratory using the Nijmegen-modified Bethesda Assay. Incidences were summarized for any positive inhibitor for participants with ≥50 EDs to rFVIIIFc. In addition, the incidence for all participants, regardless of their EDs to rFVIIIFc, was also summarized. An exact 95% CI for the proportion of participants with a confirmed inhibitor was calculated using the Clopper-Pearson exact method for a binomial proportion.

Recruitment status

COMPLETED

Study phase

PHASE3

Target enrollment

71 participants

Primary outcome timeframe

Up to Week 26 +/- 7 days, or up to 50 exposure days (EDs) if reached prior to Week 26

Results posted on

2020-12-19

Participant Flow

Participant milestones

Participant milestones
Measure	Participants < 6 Years Old Pharmacokinetic (PK) subgroup: After a Washout Period of ≥72 hrs, at the Baseline Visit (28±7 days prior to Day 1), participants receive a single IV injection of prestudy FVIII over 5±2 minutes at a dose of 50 IU/kg, rounded up to the nearest 250 IU increment, for PK assessment. Following a second Washout Period of ≥72 hrs, participants receive a single IV injection of rFVIIIFc over 5±2 mins at a dose of 50 IU/kg for PK assessment. The first prophylactic dose of rFVIIIFc is administered at a starting dose of 25 IU/kg IV injection on Day 1 and 50 IU/kg on Day 4. Dose increases to a maximum of 80 IU/kg, and frequency of administration to a minimum interval of once every 2 days, are allowed as indicated. Non-PK subgroup: On Day 1, a first prophylactic dose of rFVIIIFc of 25 IU/kg IV injection is given, followed by a dose of 50 IU/kg on Day 4. Dose increases to a maximum of 80 IU/kg, and frequency of administration to a minimum interval of once every 2 days, are allowed as indicated.	Participants 6 to < 12 Years Old PK subgroup: After a Washout Period of ≥72 hours, at the Baseline Visit (28±7 days prior to Day 1), participants receive a single IV injection of prestudy FVIII over 5 (±2) minutes at a dose of 50 IU/kg, rounded up to the nearest 250 IU increment, for a PK assessment. Following a second Washout Period of ≥72 hours, participants receive a single IV injection of rFVIIIFc over 5 (±2) minutes at a dose of 50 IU/kg for PK assessment. The first prophylactic dose of rFVIIIFc is administered at a starting dose of 25 IU/kg IV injection on Day 1 and 50 IU/kg on Day 4. Dose increases to a maximum of 80 IU/kg, and frequency of administration to a minimum interval of once every 2 days, are allowed as indicated. Non-PK subgroup: On Day 1, a first prophylactic dose of rFVIIIFc of 25 IU/kg IV injection is given, followed by a dose of 50 IU/kg on Day 4. Dose increases to a maximum of 80 IU/kg, and frequency of administration to a minimum interval of once every 2 days, are allowed as indicated.
Overall Study STARTED	36	35
Overall Study PK Subgroup	25	35
Overall Study Non-PK Subgroup	11	0
Overall Study COMPLETED	33	34
Overall Study NOT COMPLETED	3	1

Reasons for withdrawal

Reasons for withdrawal
Measure	Participants < 6 Years Old Pharmacokinetic (PK) subgroup: After a Washout Period of ≥72 hrs, at the Baseline Visit (28±7 days prior to Day 1), participants receive a single IV injection of prestudy FVIII over 5±2 minutes at a dose of 50 IU/kg, rounded up to the nearest 250 IU increment, for PK assessment. Following a second Washout Period of ≥72 hrs, participants receive a single IV injection of rFVIIIFc over 5±2 mins at a dose of 50 IU/kg for PK assessment. The first prophylactic dose of rFVIIIFc is administered at a starting dose of 25 IU/kg IV injection on Day 1 and 50 IU/kg on Day 4. Dose increases to a maximum of 80 IU/kg, and frequency of administration to a minimum interval of once every 2 days, are allowed as indicated. Non-PK subgroup: On Day 1, a first prophylactic dose of rFVIIIFc of 25 IU/kg IV injection is given, followed by a dose of 50 IU/kg on Day 4. Dose increases to a maximum of 80 IU/kg, and frequency of administration to a minimum interval of once every 2 days, are allowed as indicated.	Participants 6 to < 12 Years Old PK subgroup: After a Washout Period of ≥72 hours, at the Baseline Visit (28±7 days prior to Day 1), participants receive a single IV injection of prestudy FVIII over 5 (±2) minutes at a dose of 50 IU/kg, rounded up to the nearest 250 IU increment, for a PK assessment. Following a second Washout Period of ≥72 hours, participants receive a single IV injection of rFVIIIFc over 5 (±2) minutes at a dose of 50 IU/kg for PK assessment. The first prophylactic dose of rFVIIIFc is administered at a starting dose of 25 IU/kg IV injection on Day 1 and 50 IU/kg on Day 4. Dose increases to a maximum of 80 IU/kg, and frequency of administration to a minimum interval of once every 2 days, are allowed as indicated. Non-PK subgroup: On Day 1, a first prophylactic dose of rFVIIIFc of 25 IU/kg IV injection is given, followed by a dose of 50 IU/kg on Day 4. Dose increases to a maximum of 80 IU/kg, and frequency of administration to a minimum interval of once every 2 days, are allowed as indicated.
Overall Study Withdrawal by Subject	2	0
Overall Study Pre-rFVIIIFc Adverse Event	1	0
Overall Study Withdrawn Per Protocol	0	1

Baseline Characteristics

Study to Evaluate the Safety, Efficacy, and Pharmacokinetics of Recombinant Coagulation Factor VIII Fc Fusion Protein (rFVIIIFc) in Previously Treated Pediatric Subjects With Hemophilia A

Baseline characteristics by cohort

Baseline characteristics by cohort
Measure	Participants < 6 Years Old n=36 Participants PK subgroup: After a Washout Period of ≥72 hours, at the Baseline Visit (28±7 days prior to Day 1), participants receive a single IV injection of prestudy FVIII over 5 (±2) minutes at a dose of 50 IU/kg, rounded up to the nearest 250 IU increment, for a PK assessment. Following a second Washout Period of ≥72 hours, participants receive a single IV injection of rFVIIIFc over 5 (±2) minutes at a dose of 50 IU/kg for PK assessment. The first prophylactic dose of rFVIIIFc is administered at a starting dose of 25 IU/kg IV injection on Day 1 and 50 IU/kg on Day 4. Dose increases to a maximum of 80 IU/kg, and frequency of administration to a minimum interval of once every 2 days, are allowed as indicated. Non-PK subgroup: On Day 1, a first prophylactic dose of rFVIIIFc of 25 IU/kg IV injection is given, followed by a dose of 50 IU/kg on Day 4. Dose increases to a maximum of 80 IU/kg, and frequency of administration to a minimum interval of once every 2 days, are allowed as indicated.	Participants 6 to < 12 Years Old n=35 Participants PK subgroup: After a Washout Period of ≥72 hours, at the Baseline Visit (28±7 days prior to Day 1), participants receive a single IV injection of prestudy FVIII over 5 (±2) minutes at a dose of 50 IU/kg, rounded up to the nearest 250 IU increment, for a PK assessment. Following a second Washout Period of ≥72 hours, participants receive a single IV injection of rFVIIIFc over 5 (±2) minutes at a dose of 50 IU/kg for PK assessment. The first prophylactic dose of rFVIIIFc is administered at a starting dose of 25 IU/kg IV injection on Day 1 and 50 IU/kg on Day 4. Dose increases to a maximum of 80 IU/kg, and frequency of administration to a minimum interval of once every 2 days, are allowed as indicated. Non-PK subgroup: On Day 1, a first prophylactic dose of rFVIIIFc of 25 IU/kg IV injection is given, followed by a dose of 50 IU/kg on Day 4. Dose increases to a maximum of 80 IU/kg, and frequency of administration to a minimum interval of once every 2 days, are allowed as indicated.	Total n=71 Participants Total of all reporting groups
Age, Continuous	4.0 years n=5 Participants	8.0 years n=7 Participants	5.0 years n=5 Participants
Sex: Female, Male Female	0 Participants n=5 Participants	0 Participants n=7 Participants	0 Participants n=5 Participants
Sex: Female, Male Male	36 Participants n=5 Participants	35 Participants n=7 Participants	71 Participants n=5 Participants

PRIMARY outcome

Timeframe: Up to Week 26 +/- 7 days, or up to 50 exposure days (EDs) if reached prior to Week 26

Population: Safety Analysis Set: participants who received at least 1 dose of prestudy FVIII, or at least 1 dose of rFVIIIFc; n=number of participants with given number of exposure days who had a valid inhibitor test.

An inhibitor test result ≥0.6 Bethesda units (BU)/mL, confirmed on 2 separate samples drawn 2 to 4 weeks apart, was considered positive. Both tests were to be performed by the central laboratory using the Nijmegen-modified Bethesda Assay. Incidences were summarized for any positive inhibitor for participants with ≥50 EDs to rFVIIIFc. In addition, the incidence for all participants, regardless of their EDs to rFVIIIFc, was also summarized. An exact 95% CI for the proportion of participants with a confirmed inhibitor was calculated using the Clopper-Pearson exact method for a binomial proportion.

Outcome measures

Outcome measures
Measure	Participants < 6 Years Old n=36 Participants PK subgroup: After a Washout Period of ≥72 hours, at the Baseline Visit (28±7 days prior to Day 1), participants receive a single IV injection of prestudy FVIII over 5 (±2) minutes at a dose of 50 IU/kg, rounded up to the nearest 250 IU increment, for a PK assessment. Following a second Washout Period of ≥72 hours, participants receive a single IV injection of rFVIIIFc over 5 (±2) minutes at a dose of 50 IU/kg for PK assessment. The first prophylactic dose of rFVIIIFc is administered at a starting dose of 25 IU/kg IV injection on Day 1 and 50 IU/kg on Day 4. Dose increases to a maximum of 80 IU/kg, and frequency of administration to a minimum interval of once every 2 days, are allowed as indicated. Non-PK subgroup: On Day 1, a first prophylactic dose of rFVIIIFc of 25 IU/kg IV injection is given, followed by a dose of 50 IU/kg on Day 4. Dose increases to a maximum of 80 IU/kg, and frequency of administration to a minimum interval of once every 2 days, are allowed as indicated.	Participants 6 to < 12 Years Old n=35 Participants PK subgroup: After a Washout Period of ≥72 hours, at the Baseline Visit (28±7 days prior to Day 1), participants receive a single IV injection of prestudy FVIII over 5 (±2) minutes at a dose of 50 IU/kg, rounded up to the nearest 250 IU increment, for a PK assessment. Following a second Washout Period of ≥72 hours, participants receive a single IV injection of rFVIIIFc over 5 (±2) minutes at a dose of 50 IU/kg for PK assessment. The first prophylactic dose of rFVIIIFc is administered at a starting dose of 25 IU/kg IV injection on Day 1 and 50 IU/kg on Day 4. Dose increases to a maximum of 80 IU/kg, and frequency of administration to a minimum interval of once every 2 days, are allowed as indicated. Non-PK subgroup: On Day 1, a first prophylactic dose of rFVIIIFc of 25 IU/kg IV injection is given, followed by a dose of 50 IU/kg on Day 4. Dose increases to a maximum of 80 IU/kg, and frequency of administration to a minimum interval of once every 2 days, are allowed as indicated.	All Arms: Total n=71 Participants
Occurrence of FVIII Inhibitor Development Participants with ≥50 EDs; n=27, 34, 61	0 percentage of participants Interval 0.0 to 12.77	0 percentage of participants Interval 0.0 to 10.28	0 percentage of participants Interval 0.0 to 5.87
Occurrence of FVIII Inhibitor Development All participants; n=36, 35, 71	0 percentage of participants Interval 0.0 to 9.74	0 percentage of participants Interval 0.0 to 10.0	0 percentage of participants Interval 0.0 to 5.06

SECONDARY outcome

Timeframe: Up to Week 26 +/- 7 days (efficacy period as defined in description)

Population: Full Analysis Set: participants who received at least 1 dose of rFVIIIFc; based on the number of participants whose efficacy period was of at least 1 day in duration.

Annualized bleeding rate = (number of bleeding episodes during the efficacy period / total number of days during the efficacy period)\*365.25. The efficacy period begins with the first prophylactic dose of rFVIIIFc and ends with the last dose (for prophylaxis or a bleed). Surgery/rehabilitation periods and PK evaluation periods are not included in the efficacy period. A bleeding episode started from the first sign of a bleed and ended no more than 72 hours after the last treatment for the bleed, within which any symptoms of bleeding at the same location or injections less than or equal to 72 hours apart were considered the same bleeding episode. Any injection to treat the bleeding episode taken more than 72 hours after the preceding one was considered the first injection to treat a new bleeding episode at the same location. Any bleeding at a different location was considered a separate bleeding episode, regardless of time from last injection.

Outcome measures

Outcome measures
Measure	Participants < 6 Years Old n=35 Participants PK subgroup: After a Washout Period of ≥72 hours, at the Baseline Visit (28±7 days prior to Day 1), participants receive a single IV injection of prestudy FVIII over 5 (±2) minutes at a dose of 50 IU/kg, rounded up to the nearest 250 IU increment, for a PK assessment. Following a second Washout Period of ≥72 hours, participants receive a single IV injection of rFVIIIFc over 5 (±2) minutes at a dose of 50 IU/kg for PK assessment. The first prophylactic dose of rFVIIIFc is administered at a starting dose of 25 IU/kg IV injection on Day 1 and 50 IU/kg on Day 4. Dose increases to a maximum of 80 IU/kg, and frequency of administration to a minimum interval of once every 2 days, are allowed as indicated. Non-PK subgroup: On Day 1, a first prophylactic dose of rFVIIIFc of 25 IU/kg IV injection is given, followed by a dose of 50 IU/kg on Day 4. Dose increases to a maximum of 80 IU/kg, and frequency of administration to a minimum interval of once every 2 days, are allowed as indicated.	Participants 6 to < 12 Years Old n=34 Participants PK subgroup: After a Washout Period of ≥72 hours, at the Baseline Visit (28±7 days prior to Day 1), participants receive a single IV injection of prestudy FVIII over 5 (±2) minutes at a dose of 50 IU/kg, rounded up to the nearest 250 IU increment, for a PK assessment. Following a second Washout Period of ≥72 hours, participants receive a single IV injection of rFVIIIFc over 5 (±2) minutes at a dose of 50 IU/kg for PK assessment. The first prophylactic dose of rFVIIIFc is administered at a starting dose of 25 IU/kg IV injection on Day 1 and 50 IU/kg on Day 4. Dose increases to a maximum of 80 IU/kg, and frequency of administration to a minimum interval of once every 2 days, are allowed as indicated. Non-PK subgroup: On Day 1, a first prophylactic dose of rFVIIIFc of 25 IU/kg IV injection is given, followed by a dose of 50 IU/kg on Day 4. Dose increases to a maximum of 80 IU/kg, and frequency of administration to a minimum interval of once every 2 days, are allowed as indicated.	All Arms: Total
Annualized Bleeding Rate	0.00 bleeding episodes per participant per yr Interval 0.0 to 3.96	2.01 bleeding episodes per participant per yr Interval 0.0 to 4.04	—

SECONDARY outcome

Timeframe: Up to Week 26 +/- 7 days (efficacy period as defined in description)

Population: Full Analysis Set: participants who received at least 1 dose of rFVIIIFc; based on the number of participants whose efficacy period is of at least 1 day in duration.

Annualized bleeding rate for spontaneous joint bleed=(number of bleeding episodes meeting those criteria during the efficacy period/total number of days during the efficacy period)\*365.25. The efficacy period begins with the first prophylactic dose of rFVIIIFc and ends with the last dose (for prophylaxis or a bleed). Surgery/rehabilitation periods and PK evaluation periods are not included in the efficacy period. A bleeding episode started from the first sign of a bleed and ended no more than 72 hours after the last treatment for the bleed, within which any symptoms of bleeding at the same location or injections less than or equal to 72 hours apart were considered the same bleeding episode. Any injection to treat the bleeding episode taken more than 72 hours after the preceding one was considered the first injection to treat a new bleeding episode at the same location. Any bleeding at a different location was considered a separate bleeding episode, regardless of time from last inject

Outcome measures

Outcome measures
Measure	Participants < 6 Years Old n=35 Participants PK subgroup: After a Washout Period of ≥72 hours, at the Baseline Visit (28±7 days prior to Day 1), participants receive a single IV injection of prestudy FVIII over 5 (±2) minutes at a dose of 50 IU/kg, rounded up to the nearest 250 IU increment, for a PK assessment. Following a second Washout Period of ≥72 hours, participants receive a single IV injection of rFVIIIFc over 5 (±2) minutes at a dose of 50 IU/kg for PK assessment. The first prophylactic dose of rFVIIIFc is administered at a starting dose of 25 IU/kg IV injection on Day 1 and 50 IU/kg on Day 4. Dose increases to a maximum of 80 IU/kg, and frequency of administration to a minimum interval of once every 2 days, are allowed as indicated. Non-PK subgroup: On Day 1, a first prophylactic dose of rFVIIIFc of 25 IU/kg IV injection is given, followed by a dose of 50 IU/kg on Day 4. Dose increases to a maximum of 80 IU/kg, and frequency of administration to a minimum interval of once every 2 days, are allowed as indicated.	Participants 6 to < 12 Years Old n=34 Participants PK subgroup: After a Washout Period of ≥72 hours, at the Baseline Visit (28±7 days prior to Day 1), participants receive a single IV injection of prestudy FVIII over 5 (±2) minutes at a dose of 50 IU/kg, rounded up to the nearest 250 IU increment, for a PK assessment. Following a second Washout Period of ≥72 hours, participants receive a single IV injection of rFVIIIFc over 5 (±2) minutes at a dose of 50 IU/kg for PK assessment. The first prophylactic dose of rFVIIIFc is administered at a starting dose of 25 IU/kg IV injection on Day 1 and 50 IU/kg on Day 4. Dose increases to a maximum of 80 IU/kg, and frequency of administration to a minimum interval of once every 2 days, are allowed as indicated. Non-PK subgroup: On Day 1, a first prophylactic dose of rFVIIIFc of 25 IU/kg IV injection is given, followed by a dose of 50 IU/kg on Day 4. Dose increases to a maximum of 80 IU/kg, and frequency of administration to a minimum interval of once every 2 days, are allowed as indicated.	All Arms: Total
Annualized Joint Bleeding Rate (Spontaneous)	0.00 bleeding episodes per participant per yr Interval 0.0 to 0.0	0.00 bleeding episodes per participant per yr Interval 0.0 to 0.0	—

SECONDARY outcome

Timeframe: Up to Week 26 +/- 7 days

Population: Full Analysis Set: participants who received at least 1 dose of rFVIIIFc and had a bleeding episode; participants with a non-evaluable bleed are counted in the number of participants analyzed, but not the percentages.

Participant's assessment (provided by the caregiver) of the response to the first rFVIIIFc injection for each bleeding episode. Percentages were based on the number of first injections for which a response was provided, using the following 4-point scale: excellent=abrupt pain relief and/or improvement in signs of bleeding within approximately 8 hours after the initial injection; good=definite pain relief and/or improvement in signs of bleeding within approximately 8 hours after a single injection, but possibly requiring more than one injection after 24 to 48 hours for complete resolution; moderate=probable or slight beneficial effect within approximately 8 hours after the initial injection and requiring more than one injection; no response=no improvement, or condition worsened, within approximately 8 hours after the initial injection.

Outcome measures

Outcome measures
Measure	Participants < 6 Years Old n=35 Injections PK subgroup: After a Washout Period of ≥72 hours, at the Baseline Visit (28±7 days prior to Day 1), participants receive a single IV injection of prestudy FVIII over 5 (±2) minutes at a dose of 50 IU/kg, rounded up to the nearest 250 IU increment, for a PK assessment. Following a second Washout Period of ≥72 hours, participants receive a single IV injection of rFVIIIFc over 5 (±2) minutes at a dose of 50 IU/kg for PK assessment. The first prophylactic dose of rFVIIIFc is administered at a starting dose of 25 IU/kg IV injection on Day 1 and 50 IU/kg on Day 4. Dose increases to a maximum of 80 IU/kg, and frequency of administration to a minimum interval of once every 2 days, are allowed as indicated. Non-PK subgroup: On Day 1, a first prophylactic dose of rFVIIIFc of 25 IU/kg IV injection is given, followed by a dose of 50 IU/kg on Day 4. Dose increases to a maximum of 80 IU/kg, and frequency of administration to a minimum interval of once every 2 days, are allowed as indicated.	Participants 6 to < 12 Years Old n=46 Injections PK subgroup: After a Washout Period of ≥72 hours, at the Baseline Visit (28±7 days prior to Day 1), participants receive a single IV injection of prestudy FVIII over 5 (±2) minutes at a dose of 50 IU/kg, rounded up to the nearest 250 IU increment, for a PK assessment. Following a second Washout Period of ≥72 hours, participants receive a single IV injection of rFVIIIFc over 5 (±2) minutes at a dose of 50 IU/kg for PK assessment. The first prophylactic dose of rFVIIIFc is administered at a starting dose of 25 IU/kg IV injection on Day 1 and 50 IU/kg on Day 4. Dose increases to a maximum of 80 IU/kg, and frequency of administration to a minimum interval of once every 2 days, are allowed as indicated. Non-PK subgroup: On Day 1, a first prophylactic dose of rFVIIIFc of 25 IU/kg IV injection is given, followed by a dose of 50 IU/kg on Day 4. Dose increases to a maximum of 80 IU/kg, and frequency of administration to a minimum interval of once every 2 days, are allowed as indicated.	All Arms: Total
Participant Assessment of Response to Injections to Treat a Bleeding Episode Excellent or Good	91.4 percent of 1st injections w/ a response	93.5 percent of 1st injections w/ a response	—
Participant Assessment of Response to Injections to Treat a Bleeding Episode Excellent	65.7 percent of 1st injections w/ a response	47.8 percent of 1st injections w/ a response	—
Participant Assessment of Response to Injections to Treat a Bleeding Episode Good	25.7 percent of 1st injections w/ a response	45.7 percent of 1st injections w/ a response	—
Participant Assessment of Response to Injections to Treat a Bleeding Episode Moderate	8.6 percent of 1st injections w/ a response	2.2 percent of 1st injections w/ a response	—
Participant Assessment of Response to Injections to Treat a Bleeding Episode No Response	0 percent of 1st injections w/ a response	4.3 percent of 1st injections w/ a response	—

SECONDARY outcome

Timeframe: Up to Week 26 +/- 7 days

Population: Full Analysis Set: participants who received at least 1 dose of rFVIIIFc; based on the number of responses.

Investigators assessed each participant's response to his rFVIIIFc regimen using a 4-point scale: excellent=bleeding episodes responded to ≤ the usual number of injections or ≤ the usual dose of rFVIIIFc or the rate of breakthrough bleeding during prophylaxis was ≤ that usually observed; effective=most bleeding episodes responded to the same number of injections and dose, but some required more injections or higher doses, or there was a minor increase in the rate of breakthrough bleeding; partially effective=bleeding episodes most often required more injections and/or higher doses than expected, or adequate breakthrough bleeding prevention during prophylaxis required more frequent injections and/or higher doses; ineffective=routine failure to control hemostasis, or hemostatic control required additional agents. Percentages are based on the total number of responses; multiple responses per participant are counted.

Outcome measures

Outcome measures
Measure	Participants < 6 Years Old n=141 Responses PK subgroup: After a Washout Period of ≥72 hours, at the Baseline Visit (28±7 days prior to Day 1), participants receive a single IV injection of prestudy FVIII over 5 (±2) minutes at a dose of 50 IU/kg, rounded up to the nearest 250 IU increment, for a PK assessment. Following a second Washout Period of ≥72 hours, participants receive a single IV injection of rFVIIIFc over 5 (±2) minutes at a dose of 50 IU/kg for PK assessment. The first prophylactic dose of rFVIIIFc is administered at a starting dose of 25 IU/kg IV injection on Day 1 and 50 IU/kg on Day 4. Dose increases to a maximum of 80 IU/kg, and frequency of administration to a minimum interval of once every 2 days, are allowed as indicated. Non-PK subgroup: On Day 1, a first prophylactic dose of rFVIIIFc of 25 IU/kg IV injection is given, followed by a dose of 50 IU/kg on Day 4. Dose increases to a maximum of 80 IU/kg, and frequency of administration to a minimum interval of once every 2 days, are allowed as indicated.	Participants 6 to < 12 Years Old n=165 Responses PK subgroup: After a Washout Period of ≥72 hours, at the Baseline Visit (28±7 days prior to Day 1), participants receive a single IV injection of prestudy FVIII over 5 (±2) minutes at a dose of 50 IU/kg, rounded up to the nearest 250 IU increment, for a PK assessment. Following a second Washout Period of ≥72 hours, participants receive a single IV injection of rFVIIIFc over 5 (±2) minutes at a dose of 50 IU/kg for PK assessment. The first prophylactic dose of rFVIIIFc is administered at a starting dose of 25 IU/kg IV injection on Day 1 and 50 IU/kg on Day 4. Dose increases to a maximum of 80 IU/kg, and frequency of administration to a minimum interval of once every 2 days, are allowed as indicated. Non-PK subgroup: On Day 1, a first prophylactic dose of rFVIIIFc of 25 IU/kg IV injection is given, followed by a dose of 50 IU/kg on Day 4. Dose increases to a maximum of 80 IU/kg, and frequency of administration to a minimum interval of once every 2 days, are allowed as indicated.	All Arms: Total
Physician's Global Assessment of the Participant's Response to His rFVIIIFc Regimen Excellent	96.5 percentage of responses	89.7 percentage of responses	—
Physician's Global Assessment of the Participant's Response to His rFVIIIFc Regimen Effective	3.5 percentage of responses	9.1 percentage of responses	—
Physician's Global Assessment of the Participant's Response to His rFVIIIFc Regimen Partially Effective	0 percentage of responses	1.2 percentage of responses	—
Physician's Global Assessment of the Participant's Response to His rFVIIIFc Regimen Ineffective	0 percentage of responses	0 percentage of responses	—

SECONDARY outcome

Timeframe: Up to Week 26 +/- 7 days (efficacy period as defined in description)

Population: Full Analysis Set: participants who received at least 1 dose of rFVIIIFc. 'Overall' n=participants in the Full Analysis Set with evaluable data in the efficacy period; 'Last 3 Months on Study' n=participants in the Full Analysis Set with evaluable data and ≥ 24 weeks on study.

Consumption is calculated for the efficacy period. The efficacy period begins with the first prophylactic dose of rFVIIIFc and ends with the last dose (for prophylaxis or a bleed). Surgery/rehabilitation periods and PK evaluation periods are not included in the efficacy period. Annualized consumption = (total IU/kg of study treatment received during the efficacy period / total number of days during the efficacy period)\*365.25. Consumption was calculated overall for all participants and for the last 3 months (91 days) on study, counted backwards from the end of the efficacy period, for participants with at least 24 weeks on study.

Outcome measures

Outcome measures
Measure	Participants < 6 Years Old n=35 Participants PK subgroup: After a Washout Period of ≥72 hours, at the Baseline Visit (28±7 days prior to Day 1), participants receive a single IV injection of prestudy FVIII over 5 (±2) minutes at a dose of 50 IU/kg, rounded up to the nearest 250 IU increment, for a PK assessment. Following a second Washout Period of ≥72 hours, participants receive a single IV injection of rFVIIIFc over 5 (±2) minutes at a dose of 50 IU/kg for PK assessment. The first prophylactic dose of rFVIIIFc is administered at a starting dose of 25 IU/kg IV injection on Day 1 and 50 IU/kg on Day 4. Dose increases to a maximum of 80 IU/kg, and frequency of administration to a minimum interval of once every 2 days, are allowed as indicated. Non-PK subgroup: On Day 1, a first prophylactic dose of rFVIIIFc of 25 IU/kg IV injection is given, followed by a dose of 50 IU/kg on Day 4. Dose increases to a maximum of 80 IU/kg, and frequency of administration to a minimum interval of once every 2 days, are allowed as indicated.	Participants 6 to < 12 Years Old n=34 Participants PK subgroup: After a Washout Period of ≥72 hours, at the Baseline Visit (28±7 days prior to Day 1), participants receive a single IV injection of prestudy FVIII over 5 (±2) minutes at a dose of 50 IU/kg, rounded up to the nearest 250 IU increment, for a PK assessment. Following a second Washout Period of ≥72 hours, participants receive a single IV injection of rFVIIIFc over 5 (±2) minutes at a dose of 50 IU/kg for PK assessment. The first prophylactic dose of rFVIIIFc is administered at a starting dose of 25 IU/kg IV injection on Day 1 and 50 IU/kg on Day 4. Dose increases to a maximum of 80 IU/kg, and frequency of administration to a minimum interval of once every 2 days, are allowed as indicated. Non-PK subgroup: On Day 1, a first prophylactic dose of rFVIIIFc of 25 IU/kg IV injection is given, followed by a dose of 50 IU/kg on Day 4. Dose increases to a maximum of 80 IU/kg, and frequency of administration to a minimum interval of once every 2 days, are allowed as indicated.	All Arms: Total
Annualized rFVIIIFc Consumption Per Participant Overall (n=35, 34)	5331.8 IU/kg rFVIIIFc per participant per year Standard Deviation 1106.68	4973.5 IU/kg rFVIIIFc per participant per year Standard Deviation 976.06	—
Annualized rFVIIIFc Consumption Per Participant Last 3 months on study (n=26, 33)	5562.1 IU/kg rFVIIIFc per participant per year Standard Deviation 1474.42	5092.6 IU/kg rFVIIIFc per participant per year Standard Deviation 1013.01	—

SECONDARY outcome

Timeframe: Up to Week 26 +/- 7 days (efficacy period as defined in description)

Population: Full Analysis Set: participants who received at least 1 dose of rFVIIIFc; number of participants and number of episodes were determined for participants with at least 1 evaluable spontaneous bleeding episode.

The number of days from the last prophylaxis injection to the onset of a new spontaneous bleeding episode, analyzed across all evaluable bleeding episodes per participant and per episode, based on the efficacy period. Evaluable bleeding episodes are those for which both a date and time are available for both the onset of the bleeding episode and the previous prophylactic injection. The efficacy period begins with the first prophylactic dose of rFVIIIFc and ends with the last dose (for prophylaxis or a bleed). Surgery/rehabilitation periods and PK evaluation periods are not included in the efficacy period. For 'Per participant' values, the number of days from the last prophylactic injection to a spontaneous bleeding episode is averaged across all evaluable spontaneous bleeding episodes per participant.

Outcome measures

Outcome measures
Measure	Participants < 6 Years Old n=17 Evaluable Spontaneous Bleeding Episodes PK subgroup: After a Washout Period of ≥72 hours, at the Baseline Visit (28±7 days prior to Day 1), participants receive a single IV injection of prestudy FVIII over 5 (±2) minutes at a dose of 50 IU/kg, rounded up to the nearest 250 IU increment, for a PK assessment. Following a second Washout Period of ≥72 hours, participants receive a single IV injection of rFVIIIFc over 5 (±2) minutes at a dose of 50 IU/kg for PK assessment. The first prophylactic dose of rFVIIIFc is administered at a starting dose of 25 IU/kg IV injection on Day 1 and 50 IU/kg on Day 4. Dose increases to a maximum of 80 IU/kg, and frequency of administration to a minimum interval of once every 2 days, are allowed as indicated. Non-PK subgroup: On Day 1, a first prophylactic dose of rFVIIIFc of 25 IU/kg IV injection is given, followed by a dose of 50 IU/kg on Day 4. Dose increases to a maximum of 80 IU/kg, and frequency of administration to a minimum interval of once every 2 days, are allowed as indicated.	Participants 6 to < 12 Years Old n=19 Evaluable Spontaneous Bleeding Episodes PK subgroup: After a Washout Period of ≥72 hours, at the Baseline Visit (28±7 days prior to Day 1), participants receive a single IV injection of prestudy FVIII over 5 (±2) minutes at a dose of 50 IU/kg, rounded up to the nearest 250 IU increment, for a PK assessment. Following a second Washout Period of ≥72 hours, participants receive a single IV injection of rFVIIIFc over 5 (±2) minutes at a dose of 50 IU/kg for PK assessment. The first prophylactic dose of rFVIIIFc is administered at a starting dose of 25 IU/kg IV injection on Day 1 and 50 IU/kg on Day 4. Dose increases to a maximum of 80 IU/kg, and frequency of administration to a minimum interval of once every 2 days, are allowed as indicated. Non-PK subgroup: On Day 1, a first prophylactic dose of rFVIIIFc of 25 IU/kg IV injection is given, followed by a dose of 50 IU/kg on Day 4. Dose increases to a maximum of 80 IU/kg, and frequency of administration to a minimum interval of once every 2 days, are allowed as indicated.	All Arms: Total
Number of Days From Last Treatment Injection to a Spontaneous Bleeding Episode Per Participant	2.17 days Interval 1.51 to 2.84	2.55 days Interval 1.58 to 3.04	—
Number of Days From Last Treatment Injection to a Spontaneous Bleeding Episode Per Spontaneous Bleeding Episode	2.16 days Interval 1.35 to 2.87	2.77 days Interval 1.58 to 3.29	—

SECONDARY outcome

Timeframe: Up to Week 26 +/- 7 days (efficacy period as defined in description)

Population: Full Analysis Set: participants who received at least 1 dose of rFVIIIFc; number of participants and number of episodes were determined for participants with at least 1 evaluable bleeding episode.

The number of injections required to resolve a bleeding episode per participant and per episode, based on the efficacy period. The efficacy period begins with the first prophylactic dose of rFVIIIFc and ends with the last dose (for prophylaxis or a bleed). Surgery/rehabilitation periods and PK evaluation periods are not included in the efficacy period. All injections given from the initial sign of a bleed, until the last date/time within the bleed window are counted. The resolution of a bleed is defined as no sign of bleeding following injection for the bleed. For 'Per participant' values, the number of injections required to resolve each bleed is averaged across all bleeding episodes per participant.

Outcome measures

Outcome measures
Measure	Participants < 6 Years Old n=38 Bleeding Episodes PK subgroup: After a Washout Period of ≥72 hours, at the Baseline Visit (28±7 days prior to Day 1), participants receive a single IV injection of prestudy FVIII over 5 (±2) minutes at a dose of 50 IU/kg, rounded up to the nearest 250 IU increment, for a PK assessment. Following a second Washout Period of ≥72 hours, participants receive a single IV injection of rFVIIIFc over 5 (±2) minutes at a dose of 50 IU/kg for PK assessment. The first prophylactic dose of rFVIIIFc is administered at a starting dose of 25 IU/kg IV injection on Day 1 and 50 IU/kg on Day 4. Dose increases to a maximum of 80 IU/kg, and frequency of administration to a minimum interval of once every 2 days, are allowed as indicated. Non-PK subgroup: On Day 1, a first prophylactic dose of rFVIIIFc of 25 IU/kg IV injection is given, followed by a dose of 50 IU/kg on Day 4. Dose increases to a maximum of 80 IU/kg, and frequency of administration to a minimum interval of once every 2 days, are allowed as indicated.	Participants 6 to < 12 Years Old n=48 Bleeding Episodes PK subgroup: After a Washout Period of ≥72 hours, at the Baseline Visit (28±7 days prior to Day 1), participants receive a single IV injection of prestudy FVIII over 5 (±2) minutes at a dose of 50 IU/kg, rounded up to the nearest 250 IU increment, for a PK assessment. Following a second Washout Period of ≥72 hours, participants receive a single IV injection of rFVIIIFc over 5 (±2) minutes at a dose of 50 IU/kg for PK assessment. The first prophylactic dose of rFVIIIFc is administered at a starting dose of 25 IU/kg IV injection on Day 1 and 50 IU/kg on Day 4. Dose increases to a maximum of 80 IU/kg, and frequency of administration to a minimum interval of once every 2 days, are allowed as indicated. Non-PK subgroup: On Day 1, a first prophylactic dose of rFVIIIFc of 25 IU/kg IV injection is given, followed by a dose of 50 IU/kg on Day 4. Dose increases to a maximum of 80 IU/kg, and frequency of administration to a minimum interval of once every 2 days, are allowed as indicated.	All Arms: Total
Number of Injections Required for Resolution of a Bleeding Episode Per Participant	1.0 injections Interval 1.0 to 1.2	1.0 injections Interval 1.0 to 1.2	—
Number of Injections Required for Resolution of a Bleeding Episode Per Bleeding Episode	1.0 injections Interval 1.0 to 1.0	1.0 injections Interval 1.0 to 1.0	—

SECONDARY outcome

Timeframe: Up to Week 26 +/- 7 days (efficacy period as defined in description)

Population: Full Analysis Set: participants who received at least 1 dose of rFVIIIFc; number of participants and number of episodes were determined for participants who had complete information on the dose administered to treat a bleeding episode.

The total dose required to resolve a bleeding episode per participant and per episode, based on the efficacy period. The efficacy period begins with the first prophylactic dose of rFVIIIFc and ends with the last dose (for prophylaxis or a bleed). Surgery/rehabilitation periods and PK evaluation periods are not included in the efficacy period. For 'Per bleeding episode' values, for each bleeding episode, the total dose is the sum of the doses (IU/kg) administered across all injections given to treat that bleeding episode. For 'Per participant' values, the total dose (IU/kg) used to resolve each bleed is averaged across all bleeding episodes per participant.