HemLibra Prophylaxis in Patients With Hemophilic Pseudotumor

Inclusion Criteria: * Signed informed consent form from the subject, parent or guardian * Diagnosis of congenital hemophilia A (baseline FVIII level \<40%) with or without FVIII inhibitor, either high or low responding, regardless of titer * Diagnosis of a hemophilic pseudotumor confirmed by radiologic assessment such as CT or MRI * Any weight or BMI * Medical documentation of prophylactic or episodic treatment (FVIII or bypassing agent) and the number of bleeding episodes for at least 16 weeks, and up to 6 months if available, prior to entry into the study * Medical documentation of any need for PRBC transfusion or hospitalization for 6 months prior to entry into the study * Subjects with a history of an inhibitor should provide documentation of the inhibitor history including date of initial diagnosis of inhibitor, peak titer, and agent utilized for hemostatic control * Subjects with high titer inhibitors or those with low titer inhibitors who do not respond to FVIII must be willing to use rFVIIa as first line therapy for the treatment of breakthrough bleeding events * Medical documentation of ITI therapy for subjects with a history of a FVIII inhibitor and ITI, including current FVIII inhibitor titer * Willingness to discontinue any current prophylactic hemostatic regimen (FVIII or bypassing agent) and/or FVIII ITI therapy for the duration of the study * Subjects receiving FVIII prophylaxis must be willing to discontinue their FVIII prophylactic regimen immediately prior to their second loading dose of Hemlibra (emicizumab) * Subjects receiving bypassing agent prophylaxis must be willing to discontinue their prophylactic regimen at least 24 hours prior to their first loading dose of Hemlibra (emicizumab) * Subjects receiving FVIII ITI therapy must be willing to discontinue ITI immediately prior to their first loading dose of Hemlibra (emicizumab) * Willingness and ability to comply with scheduled visits, treatment plans, laboratory tests, and other study procedures, including the health-related questionnaires, activity tracking, and bleed diaries, using systems provided during the study * Adequate hepatic function, defined as total bilirubin ≤1.5 × age-adapted upper limit of normal (ULN) (excluding Gilbert's syndrome) and both AST and ALT ≤3 × age-adapted ULN at the time of screening, and no clinical signs or known laboratory/radiographic evidence consistent with cirrhosis * Subjects must be willing to be vaccinated against HAV and HBV if not previously vaccinated, exposed or immune to HAV or HBV\* * Adequate hematologic function, defined as a platelet count ≥100,000/μL and a PT≤1.5 times the ULN at the time of screening * Adequate renal function, defined as serum creatinine ≤2.5 × age-adapted ULN and creatinine clearance ≥30 mL/min by Cockcroft-Gault formula * For women with hemophilia of childbearing potential: agreement to remain abstinent (refrain from heterosexual intercourse) or use highly effective contraceptive methods that result in a failure rate of \<1% 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 congenital hemophilia A * Lack of a documented diagnosis of hemophilic pseudotumor * Patients who are at high risk for TMA (eg, have a previous medical or family history of TMA), in the Study Investigator's judgment * History of illicit drug or alcohol abuse within 48 weeks prior to screening, in the Study Investigator's judgment * Previous (within the last 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 * Other conditions (eg, certain autoimmune diseases) that may currently increase the risk of bleeding or thrombosis * History of clinically significant hypersensitivity associated with monoclonal antibody therapies or components of the Emicizumab injection * Planned surgery (excluding minor procedures such as tooth extraction or incision and drainage) during the study * Known HIV infection with CD4 counts \<200 cells/μL. HIV infection with CD4 counts ≥200 cells/μL permitted * Use of systemic immunomodulators (eg, interferon) at enrollment or planned use during the study, with the exception of anti-retroviral therapy * Concomitant disease, condition, significant abnormality on screening evaluations or laboratory tests, or treatment that could interfere with the conduct of the study, or that would, in the opinion of the Study Investigator, pose an additional unacceptable risk in administering study drug to the patient * Receipt of any of the following: * Hemlibra (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 within last 30 days or 5 half-lives, whichever is shorter * Any other investigational drug currently being administered or planned to be administered * Inability to comply with the study protocol in the opinion of the Study Investigator * Pregnancy or lactation or intention to become pregnant during the study * Women with a positive serum pregnancy test result within 10 days prior to initiation of study drug