Emicizumab (MC-Ab) is a humanized bispecific antibody which binds to factors IX-activated and X, speeding up the activation of factor X. It solved some unmet needs in hemophilia A (HA) treatment, such as regimen (once weekly up to once monthly infusion) and route of administration (subcutaneous). Although it is an effective non-replacement alternative in the prophylaxis of people with HA and inhibitor (PwHAi), its safety has not been clarified yet. Since 2018, it has been approved for prophylaxis of children and adults with HA in Brazil, despite inhibitor status. In 2019, the Brazilian Ministry of Health started the process to incorporate it in the national protocol of PwHAi who failed immune tolerance induction (ITI). Herein we report the first PwHAi included in the “Brazilian registry of persons with hemophilia A receiving emicizumab” (Emicizumab Cases, EMCase Project). The patient is a 28-years-old white man who was diagnosed as severe HA (factor VIII [FVIII] activity 0.9%) when he was born. He had been treated exclusively on demand (only during bleeding episodes), even after developing a high response inhibitor at the age of 20 years. Three years later, immune tolerance induction (ITI) was prescribed for 32 months. He received plasma-derived FVIII 50 IU/kg 3x/week. Treatment was not increased due to a difficult peripheral venous access and a central line was not implanted due to social barriers about caring of the device. Bypassing agent prophylaxis was prescribed during ITI; however, he had bleeding 11 episodes requiring treatment (annualized bleeding rate [ABR] 4.1 episodes/y). ITI failure was reported on Feb/27/2018, and prophylaxis with activated recombinant factor VII (rFVIIa) 250 kIU 3x/week was maintained. Between Feb/27/2018 and Jul/24/2019 (pre-MC-Ab period), the ABR was 2.1 episodes/y. Mean consumption of intravenous rFVIIa was 2,771±772 kIU/month. After withholding rFVIIa prophylaxis, MC-Ab attack was administered at 3.0mg/kg once weekly for 4 weeks, starting on Jul/25/2020. He kept MC-Ab 1.5mg/kg. Mean consumption of subcutaneous Mc-Ab from Jul/25/2019 to Jul/24/2020 (MC-Ab period) was 366.92±93.40mg/month, with no bleeding episode requiring factor concentrate infusion. The mean monthly cost of the treatment reduced from US$ 34,590.00±8,903.00/month (US$ 11.53/kIU, in 2018), in the pre-MC-Ab period, to US$ 27,446.00±7,120.62/month (US$ 76.25/mg, in 2020), during the MC-Ab period. Currently, he self-infuses MC-Ab at home. He did not report any puncture site event. No thrombotic event has been reported. Prophylaxis with MC-Ab for PwHA with inhibitor who failed ITI was safe and effective. The annualized direct costs reduced about 20% switching from prophylaxis with rFVIIa to MC-Ab.