Efficacy, Safety, and Pharmacokinetic Study of Prophylactic Emicizumab Versus No Prophylaxis in Hemophilia A Participants

Inclusion Criteria: Inclusion Criteria for Arms A, B, and C: * Diagnosis of severe congenital hemophilia A or hemophilia A with FVIII inhibitors * Aged 12 years or older at the time of informed consent * Body weight ≥40 kilograms (kg) at the time of screening * Participants without FVIII inhibitors (\<0.6 Bethesda unit per milliliter \[BU/mL\]) who completed successful immune tolerance induction (ITI) must have done so at least 5 years before screening and have no evidence of inhibitor recurrence (permanent or temporary) * Documentation of the details of episodic therapy (FVIII or bypassing agents) and of number of bleeding episodes for at least the last 24 weeks and ≥5 bleeds in the last 24 weeks prior to study entry * Adequate hematologic, hepatic, and renal function * For women of child bearing potential: agreement to remain abstinent or use a protocol defined contraceptive measure during the treatment period and for at least 5 elimination half-lives (24 weeks) after the last dose of study drug Inclusion Criteria for Arm D: * Diagnosis of congenital hemophilia A of any severity and documented history of high-titer inhibitor (i.e., ≥5 BU/mL) * Children \<12 years old at time of informed consent * Body weight \>3 kg at time of informed consent * Requires treatment with bypassing agents * Adequate hematologic, hepatic, and renal function * For female participants who are of childbearing potential, follow the same contraception criteria as listed above for Arms A, B, and C…