OC 50.1 - First interim analysis of clinical outcomes in adults and adolescents with severe hemophilia A receiving efanesoctocog alfa prophylaxis in XTEND-ed, a phase 3 long-term extension study

Tuesday, June 25, 2024

09:30 – 09:45 ICT

Room: Plenary Hall

Presenting Author(s)

SS

Sophie Susen, PhD,MD

Professor of Haematology
Centre Hospitalier Universitaire de Lille, Université de Lille, Lille, France
Lille, Nord-Pas-de-Calais, France

Co-Author(s)

SP

Stephanie P'ng

Haematologist
The Haemophilia and Haemostasis Centre, Fiona Stanley Hospital, Murdoch, Australia
Murdoch, Western Australia, Australia
TL

Toshko Lissitchkov

Professor
Specialized Hospital for Active Treatment of Hematological Diseases, Department of Chemotherapy, Hemotherapy and Hereditary Blood Diseases at Clinical Hematology Clinic, Sofia, Bulgaria
Sofia, Sofiya, Bulgaria
Davide Matino

Assistant Professor
Division of Hematology & Thromboembolism, Department of Medicine, McMaster University, Ontario, Canada
Hamilton, Ontario, Canada
Pratima Chowdary, MD

Professor of Haemophilia, Centre Director
Katharine Dormandy Haemophilia and Thrombosis Centre, Royal Free Hospital
London, England, United Kingdom
Angela Weyand, MD

Associate Professor
Division of Hematology/Oncology, Department of Pediatrics, University of Michigan Medical School, Ann Arbor, MI, USA
Ann Arbor, Michigan, United States
Robert Klamroth, MD

Head of Department
Vivantes Klinikum, Friedrichshain, Berlin, Germany
Berlin, Berlin, Germany
YP

Young-Shil Park

Professor
Department of Pediatrics, Kyung Hee University Hospital at Gangdong, School of Medicine, Kyung Hee University, Seoul, Korea
Seoul, Seoul-t'ukpyolsi, Republic of Korea
María Teresa Alvarez-Román, MD, PhD

Head of the Haemostasis Unit
Department of Hematology, University Hospital La Paz, Autonoma University of Madrid, Madrid, Spain
Madrid, Madrid, Spain
LF

Liqi Feng

Senior Biostatistician
Sanofi, Shanghai, China
Shanghai, Shanghai, China (People's Republic)
HP

Helena Palmborg

Associate Director Scientific Communications
Sobi, Stockholm, Sweden
Stockholm, Stockholms Lan, Sweden
JD

Jennifer Dumont

Senior Medical Director, Global Medical Affairs
Sanofi, Cambridge, MA, USA
Cambridge, Massachusetts, United States
ES

Elena Santagostino

VP, Medicine Development Lead Haemophilia
Sobi, Basel, Switzerland
Basel, Basel-Stadt, Switzerland
LF

Lila-Sabrina Fetita

Clinical Research Director
Sanofi, Paris, France
Paris, Ile-de-France, France
KN

Keiji Nogami

Professor
Nara Medical University, Nara, Japan
Nara, Nara, Japan

Background: Efanesoctocog alfa (formerly BIVV001) is a first-in-class high-sustained factor VIII (FVIII) replacement therapy designed to decouple FVIII from endogenous von Willebrand factor. In the Phase 3 XTEND-1 study (NCT04161495), once-weekly efanesoctocog alfa demonstrated superior bleed protection over prior prophylaxis, was well tolerated, and provided FVIII activity within the normal to near-normal (>40%) range for most of the week.

Aims: Evaluate long-term safety and efficacy of efanesoctocog alfa in adults/adolescents with severe hemophilia A from XTEND-ed (NCT04644575; first interim analysis).

Methods: Previously treated patients (≥12 years old) who completed XTEND-1 (Arm A/B) could continue once-weekly efanesoctocog alfa (50 IU/kg) prophylaxis in the multicenter, open-label, long-term XTEND-ed study. The primary endpoint is incidence of FVIII inhibitor development. Secondary endpoints include annualized bleed rates (ABRs), efficacy for bleed treatment, and safety. XTEND-ed was approved by local ethics committees; participants provided informed consent. Data cut: June 8, 2023.

Results: A total of 146 patients (including 1 female) rolled over from XTEND-1 to XTEND-ed (12–17 years, n=21; 18–64 years, n=120; ≥65 years, n=5). Mean (range) treatment duration in XTEND-ed was 82.5 (14.1–103.6) weeks. FVIII inhibitors were not detected. Mean (standard deviation) ABR during XTEND-ed for patients from XTEND-1 Arms A and B was 0.72 (1.26) and 0.42 (0.89), respectively (6-monthly data: Table 1), thus maintaining the low mean ABRs observed in the parent study (Arm A: 0.71; Arm B: 0.69). Most (94%; 142/151) bleeding episodes resolved with 1 injection of efanesoctocog alfa; response was rated by participants as excellent/good for 88% (108/123) of bleeds. Overall, 108 (74%) participants experienced ≥1 treatment-emergent adverse event (TEAE) and 17 (12%) experienced ≥1 serious TEAE (Table 2).

Conclusion(s): Long-term results in adults/adolescents in XTEND-ed show that once-weekly efanesoctocog alfa continues to be well tolerated and highly effective. No inhibitors were detected and ABRs remained low.

Funded by Sanofi and Sobi.