Shapiro A.D.Angchaisuksiri P.Astermark J.Benson G.Castaman G.Eichler H.Jiménez-Yuste V.Kavakli K.Matsushita T.Poulsen L.H.Wheeler A.P.Young G.Zupančić-Šalek S.Oldenburg J.Chowdary P.Mahidol University2023-06-182023-06-182022-06-14Blood Advances Vol.6 No.11 (2022) , 3422-343224739529https://repository.li.mahidol.ac.th/handle/20.500.14594/85795Despite current therapies, there remains an unmet need for treatment for patients with hemophilia. The main parts of two phase 2 trials established clinical proof-of-concept for once-daily, subcutaneous concizumab prophylaxis in patients with hemophilia A/B with inhibitors (HAwI/HBwI; explorer4) and severe hemophilia A without inhibitors (HA; explorer5). Here, we present results from extension parts of these trials, included to evaluate longer term safety and efficacy. Both trials included main ($24 weeks) and extension (52-102 weeks) parts, with patients receiving concizumab 0.15 mg/kg with potential dose escalation to concizumab 0.20 or 0.25 mg/kg if they experienced $3 treated spontaneous bleeding episodes within 12 weeks. Endpoints included annualized bleeding rate (ABR), adverse events (AEs), and occurrence of antidrug antibodies. Thromboembolic events were AEs of special interest. Thirty-six patients with HA, 15 with HAwI, and 10 with HBwI were exposed to concizumab. Estimated ABRs during the main 1 extension parts at last dose level were 4.8 (95% confidence interval [CI], 3.2-7.2) and 6.4 (95% CI, 4.1-9.9) in explorer4 and explorer5, respectively (spontaneous ABRs were 1.8 [95% CI, 1.2-2.6] and 2.1 [95% CI, 1.3-3.3]). Most AEs were mild, with no deaths, events leading to withdrawal, or thromboembolic events. Anti-drug antibodies developed in 25% of patients and were low titer and transient, with no observed clinical effect in most cases. Results of the main 1 extension parts of these trials were consistent with results of the main parts. Ongoing phase 3 trials will further evaluate concizumab as a once-daily, subcutaneous treatment across hemophilia subtypes.MedicineArticleSCOPUS10.1182/bloodadvances.20210064032-s2.0-851323374512473953735290453