A Clinical Trial to Evaluate Prophylactic Emicizumab Versus no Prophylaxis in Hemophilia A Participants Without Inhibitors

Inclusion Criteria:

- Body weight >/= 40 kilogram (kg) at the time of screening

- Diagnosis of severe congenital hemophilia A

- Documentation of the details of prophylactic or episodic FVIII treatment and of number
of bleeding episodes for at least the last 24 weeks

- Adequate hematologic function

- Adequate hepatic function

- Adequate renal function

- For women of childbearing potential: agreement to remain abstinent (refrain from
heterosexual intercourse) or use contraceptive methods that result in a failure rate
of less than (<) 1 percent (%) per year during the treatment period and for at least 5
elimination half-lives (24 weeks) after the last dose of study drug

Exclusion Criteria:

- Inherited or acquired bleeding disorder other than hemophilia A

- Previous or current treatment for thromboembolic disease or signs of thromboembolic
disease

- 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

- Known human immunodeficiency virus (HIV) infection with cluster of differentiation
(CD) 4 count <200 cells per microliter (cells/mcL) within 24 weeks prior to screening.
Participants with HIV infection who has CD4 greater than (>) 200 and meet all other
criteria are eligible

- Use of systemic immunomodulators at enrollment or planned use during the study, with
the exception of anti-retroviral therapy

- Participants who are at high risk for thrombotic microangiopathy (TMA) (for example,
have a previous medical or family history of TMA), in the investigator's judgment

- 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

- Planned surgery (excluding minor procedures) 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

- Pregnant or lactating, or intending to become pregnant during the study