Aims: To describe the hemostatic management of patients with hemophilia A or B who underwent surgical procedures while receiving fitusiran prophylaxis. Methods: Fitusiran was evaluated in a phase 1 dose-escalation study (NCT02035605) followed by a phase 2 open-label extension (OLE) study (NCT02554773) that included patients with hemophilia A or B, with or without inhibitors. Patients who were eligible to continue in the phase 2 Open-Label Extension study received monthly fixed subcutaneous doses of fitusiran 50mg or 80mg. Data on perioperative hemostatic therapies and hemostatic response were collected for patients undergoing surgical procedures who had lowered anti-thrombin (AT) during the study. Results: In addition to 5 previously presented surgical procedures, 1 total knee replacement and 1 total hip replacement were performed. Further details on perioperative treatment regimens and hemostatic responses in all 7 procedures will be presented. Conclusions: Successful perioperative hemostatic management of patients in the context of AT lowering with fitusiran has now been observed in several orthopedic, thoracic, gastrointestinal, maxillofacial, and dental surgical procedures. Data first presented at ISTH 2020, 12th-14th July 2020. Study funded by Alnylam and Sanofi.