Safety and Tolerability Study of Switching From Emicizumab to Fitusiran Injection in Males 12 Years and Older With Severe Hemophilia A

What this Trial Is About

Researchers are evaluating the safety and tolerability of switching male participants aged 12 years and older with severe hemophilia A, with or without inhibitors, from emicizumab prophylaxis to fitusiran prophylaxis. This Phase 4 exploratory study focuses on participants who were previously receiving emicizumab and aims to monitor adverse events and other health outcomes during and after the switch. Participants will first undergo a screening period of about 2 months, followed by a pre-fitusiran treatment period of approximately 2 months where they continue with intravenous clotting factor concentrates or bypassing agents as needed. Then, participants will receive subcutaneous fitusiran prophylaxis either once every two months or monthly for up to 18 months. After the fitusiran treatment, there is a follow-up period of about 6 months to monitor antithrombin activity levels until they return to at least 60%. During the study, intravenous antithrombin concentrate may be given if judged necessary by the investigator, and bleeding events will be managed with intravenous clotting factors or bypassing agents. Throughout the study, participants will have regular clinic visits scheduled monthly or every two months during the fitusiran treatment period. Researchers will assess adverse events, thrombin generation, antithrombin levels, emicizumab concentrations, treatment satisfaction, pain intensity, physical activity, joint health, and annualized bleeding rate. Antithrombin activity will be closely monitored during follow-up until recovery. The study duration can be up to approximately 28 months, including all periods from screening to follow-up.

A Study to Test a Medicine (Fitusiran) for Preventing Bleeds in People With Severe Hemophilia Who Previously Received Preventive Treatment With Emicizumab