CO-33 | REAL-WORLD EXPERIENCE WITH MARSTACIMAB PROPHYLAXIS IN SEVERE HEMOPHILIA A WITHOUT INHIBITORS AND ADVANCED HEMOPHILIC ARTHROPATHY

A. Casson¹, I. Ricca¹, A. Barchieri¹, G. Guido¹, M. Tucciarone¹, P. Ocello¹, C. Francisco², P. Abrate², G. Delios¹ | ¹Centro Malattie Trombotiche ed Emorragiche - SC Servizio Trasfusionale ASL TO4, Ivrea, Torino, Italy; ²SC Farmacia Ospedaliera ASL TO4, Ivrea, Torino, Italy

Background. Marstacimab is a novel subcutaneous anti-TFPI monoclonal antibody approved as non-replacement prophylaxis for hemophilia without inhibitors. Real-world data are still limited, particularly in patients with severe hemophilia A and advanced arthropathy.
Case Report. A 47-year-old man with severe hemophilia A (FVIII <1%), no history of inhibitors and advanced hemophilic arthropathy was followed at our Centre. His history included resolved HCV infection, bilateral knee and ankle prostheses, previous bleeding duodenal ulcer, prior pulmonary hemorrhagic parenchymal suffusion. Treatment history included on-demand cryoprecipitate and plasma-derived FVIII, then recombinant FVIII prophylaxis, followed by emicizumab from January 2021 to February 2024. Because of persistent joint disease with effusion and synovitis, prophylaxis was then switched to extended half-life recombinant FVIII (Efmoroctocog alfa 3000 IU twice weekly). In October 2025, treatment was changed to Marstacimab, with a 300 mg loading dose followed by 150 mg subcutaneously once weekly; thrombophilia screening performed before treatment initiation was reported as normal. During follow-up, reduced bleeding tendency and good hemostatic coverage were documented. In February 2026 the patient reported paresthesias, headache, diarrhea and lower-limb pain: clinical evaluation and labaoratory assessment were negative for thrombotic complications, and weekly Marstacimab was continued. At April 2026 follow-up, the patient reported subjective well-being on weekly Marstacimab prophylaxis.
Conclusions. In this adult with severe hemophilia A without inhibitors, advanced arthropathy and multiple comorbidities, Marstacimab prophylaxis proved feasible in routine practice and was associated with favorable short-term clinical perception of bleeding control. Careful surveillance remains warranted, and further real-world evidence is needed to define safety and effectiveness in complex patients.