The trial was revised to be two protocols, one Prevention, one Eradication Trials.

This study will evaluate if Eloctate is superior to Emicizumab in reducing inhibitors in children with severe hemophilia when given before the first bleed (preemptive) and continued weekly to prevent bleeds (prophylaxis); and whether Eloctate immune tolerance induction (ITI) plus emicizumab is superior to Eloctate ITI alone in eradicating inhibitor formation in children and adults with severe hemophilia A.

This is a multi-center, randomized Phase III Clinical Trials Platform (INHIBIT) in which hemostatic agents will be compared using adaptive design to prevent and eradicate inhibitors in patients with severe hemophilia A. This adaptive design is necessary as randomized trials in rare diseases are otherwise not possible. The INHIBIT Trial Platform includes one Inhibitor Prevention Trial and one Inhibitor Eradication Trial that will be conducted at up to 41 U.S. hemophilia treatment centers (HTCs) affiliated with universities. The Inhibitor Prevention Trial is a 48-week randomized phase III trial in which 66 previously untreated patients (PUPs) (children < 6 yr) with severe hemophilia A will be enrolled and randomized to preemptive weekly Eloctate vs. Emicizumab to prevent inhibitor formation, defined as anti-FVIII > 5.0 BU. The Inhibitor Eradication Trial is a 48-week randomized phase III trial in which 90 previously-treated patients (PTPs) with severe hemophilia A and high-responding inhibitors (anti-VIII >5.0 B.U.), including subjects developing inhibitors during the Prevention Trials and adults or children of any age at the same HTCs refractory to or never previously tolerated, will be enrolled and randomized to Eloctate ITI god plus weekly Emicizumab vs. Eloctate ITI alone to eradicate inhibitor formation, defined as anti-FVIII<0.6 B.U. Blood draws will be minimized to 6 timepoints, pre, 4, 12, 24, 36, and 48 weeks, and validated for small volumes, 3.8 cc (¾ tsp) each. The Inhibit Trials Platform is considered greater than minimal risk as study drug is given before the first bleed and special inhibitor studies are obtained.

Prevention Trial, Inclusion Criteria:

• Male children >/= 4 months of age.
• Severe hemophilia A (FVIII < 0.01 U/ml)
• No previous bleed or surgery requiring treatment (except circumcision)
• No previous factor VIII product (except for circumcision)
• Willingness to comply with weekly prophylaxis for 48 weeks
• Willingness of parent/caregiver to keep a personal diary of bleeding frequency and factor treatment.
• Willingness to make monthly visits and coagulation testing at weeks 4, 12, 24, 36, and 48 (end of study)

Prevention Trial, Exclusion Criteria:

• Acquired hemophilia.
• Any bleeding disorder other than hemophilia A.
• Treatment with clotting factor previously, other than circumcision.
• Presence of an inhibitor to factor VIII.
• Use of an experimental drug(s).
• Surgery anticipated in the next 48 weeks.
• Life expectancy less than 5 years.
• Inability to comply with study requirements.

Eradication Trial, Inclusion Criteria:

• Male adults or children with no age limitation.
• Severe hemophilia A (FVIII <0.01 U/ml).
• Presence of an inhibitor to FVIII (anti-FVIII > 5.0 B.U.)
• Willingness to comply with study drugs for up to 48 weeks.
• Willingness to keep a personal diary of bleed frequency and drug treatment.
• Willingness to make monthly visits and coagulation testing at weeks 4, 12, 24, 36, and 48 (end of study).

Eradication Trial, Exclusion Criteria:

• Acquired hemophilia.
• Any bleeding disorder other than hemophilia A.
• Current use of Emicizumab, or if used, > 8 weeks since last treatment.
• Use of an experimental drug(s).
• Surgery anticipated in the next 48 weeks.
• Life expectancy less than 5 years.
• Inability to copy with study requirements.

A biologic specimen and data repository for this trial will be available, pending NHLBI approval, at BioLINCC https://biolincc.nhlbi.nih.gov, to any research or investigator who makes formal application request and is formally approved by NHLBI.

Within one year of trial completion.

Access will be determined by NHLBI.