Study of the Efficacy and Safety PF-06741086 in Adult and Teenage Participants With Severe Hemophilia A or Moderately Severe to Severe Hemophilia B

Inclusion Criteria * Participants with a diagnosis of severe hemophilia A or moderately severe to severe hemophilia B with a minimum weight of 35 kg at screening. * Participant or legally authorized representative, or participant's caregiver capable of giving signed informed consent (or minor assent, when applicable). Participants who are enrolled into the Non-Inhibitor Cohort must also meet the following criteria: * No detectable or documented history of inhibitors * Participants on FVIII/FIX routine prophylaxis who have demonstrated at least 80% compliance with scheduled prophylaxis regimen during 6 months prior to enrollment and are willing to continue to receive routine prophylaxis treatment with FVIII/FIX replacement during the Observational Phase. * Participants with on-demand treatment regimen with ≥6 acute bleeding episodes (spontaneous or traumatic) that required coagulation factor infusion during the 6 months period prior to enrollment and willing to continue to receive on demand treatment during the Observational Phase. Participants who are enrolled into the Inhibitor Cohort must also meet the following criteria: * Documentation of current high titer inhibitor (≥5 BU/mL) or current low titer inhibitor (\<5 BU/mL) refractory to FVIII or FIX replacement and with FVIII or FIX recovery \<60% of expected within previous 6 months prior to enrolment into the Observational Phase * Hemophilia A participants with on-demand treatment regimen with ≥6 bleeding episodes or …