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

Prior treatment

• History of illicit drug or alcohol abuse within 48 weeks prior to screening, in the investigator's judgment
• Previous (in the past 12 months) or current treatment for thromboembolic disease (with the exception of previous catheter-associated thrombosis for which anti-thrombotic treatment is not currently ongoing) or signs of thromboembolic disease
• Use of systemic immunomodulators at enrollment or planned use during the study, with the exception of anti-retroviral therapy
• Planned surgery (excluding minor procedures such as tooth extraction or incision and drainage) during the study
• Receipt of: Emicizumab in a prior investigational study; An investigational drug to treat or reduce the risk of hemophilic bleeds within 5 half-lives of last drug administration; A non-hemophilia-related investigational drug concurrently, within last 30 days or 5 half-lives, whichever is shorter
• Ongoing (or plan to receive during the study) ITI therapy or prophylaxis treatment with FVIII
• Previous (in the past 12 months) or current treatment for thromboembolic disease (with the exception of previous catheter-associated thrombosis for which anti-thrombotic treatment is not currently ongoing) or signs of thromboembolic disease
• Planned surgery (excluding minor procedures such as tooth extraction or incision and drainage) during the study
• Receipt of: Emicizumab in a prior investigational study; An investigational drug to treat or reduce the risk of hemophilic bleeds within 5 half-lives of last drug administration; A non-hemophilia-related investigational drug concurrently, within last 30 days or 5 half-lives, whichever is shorter

Other illness

• Inherited or acquired bleeding disorder other than hemophilia A
• Other conditions that may increase risk of bleeding or thrombosis
• History of clinically significant hypersensitivity associated with monoclonal antibody therapies or components of the emicizumab injection
• Inherited or acquired bleeding disorder other than hemophilia A
• Other diseases that may increase risk of bleeding or thrombosis
• History of clinically significant hypersensitivity associated with monoclonal antibody therapies or components of the emicizumab injection
• Known infection with HIV, hepatitis B virus (HBV), or hepatitis C virus (HCV)
• Inability (or unwillingness by caregiver) to receive (allow receipt of) blood or blood products (or any standard-of-care treatment for a life-threatening condition)

Lab values

• Known human immuno-deficiency virus (HIV) infection with cluster of differentiation 4 (CD4) count \<200 cells/microliter (cells/mcL) within 24 weeks prior to screening. Participants with HIV infection who have CD4 \>200 cells/mcL and meet all other criteria are eligible
• Concurrent disease, treatment, or abnormality in clinical laboratory tests that could interfere with the conduct of the study, may pose additional risk, or would, in the opinion of the investigator, preclude the participant's safe participation in and completion of the study
• Concurrent disease, treatment, or abnormality in clinical laboratory tests that could interfere with the conduct of the study, may pose additional risk, or would, in the opinion of the investigator, preclude the participant's safe participation in and completion of the study

Other

• At high risk for thrombotic microangiopathy, in the investigator's judgment
• Pregnant or lactating, or intending to become pregnant during the study
• At high risk for thrombotic microangiopathy, in the investigator's judgment
• Use of systemic immunomodulators at enrollment or planned use during the study
• Pregnant or lactating, or intending to become pregnant during the study

• 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
• 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