Efanesoctocog Alfa Prophylaxis for Children with Severe Hemophilia A.

BACKGROUND: Once-weekly efanesoctocog alfa provides high sustained factor VIII activity with superior bleeding prevention as compared with prestudy factor VIII prophylaxis in previously treated patients 12 years of age or older with severe hemophilia A. Data on outcomes of efanesoctocog alfa treatment in children younger than 12 years of age with severe hemophilia A are limited. METHODS: We conducted a phase 3, open-label study involving previously treated patients younger than 12 years of age with severe hemophilia A. Patients received prophylaxis with once-weekly efanesoctocog alfa (50 IU per kilogram of body weight) for 52 weeks. The primary end point was the occurrence of factor VIII inhibitors (neutralizing antibodies against factor VIII). Secondary end points included annualized rates of treated bleeding episodes, bleeding treatment, safety, and pharmacokinetics. RESULTS: A total of 74 male patients were enrolled (38 with an age of <6 years and 36 with an age of 6 to <12 years). No factor VIII inhibitors developed. Most adverse events were nonserious. No serious adverse events that were assessed by the investigator as being related to efanesoctocog alfa were reported. In the 73 patients treated according to the protocol, the median and model-based mean annualized bleeding rates were 0.00 (interquartile range, 0.00 to 1.02) and 0.61 (95% confidence interval, 0.42 to 0.90), respectively. A total of 47 patients (64%) had no treated bleeding episodes, 65 (88%) had no spontaneous bleeding episodes, and 61 (82%) had no episodes of bleeding into joints. A total of 41 of 43 bleeding episodes (95%) resolved with one injection of efanesoctocog alfa. Mean factor VIII activity at steady state was more than 40 IU per deciliter for 3 days and more than 10 IU per deciliter for almost 7 days after dose administration. The geometric mean terminal half-life was 40.0 hours. CONCLUSIONS: In children with severe hemophilia A, once-weekly prophylaxis with efanesoctocog alfa provided high sustained factor VIII activity in the normal to near-normal range (>40 IU per deciliter) for 3 days and more than 10 IU per deciliter for almost 7 days after administration, leading to effective bleeding prevention. Efanesoctocog alfa was associated with mainly nonserious adverse events. (Funded by Sanofi and Sobi; XTEND-Kids ClinicalTrials.gov number, NCT04759131.).

A global comparative field study to evaluate the factor VIII activity of efanesoctocog alfa by one-stage clotting and chromogenic substrate assays at clinical haemostasis laboratories.

INTRODUCTION: Structural and chemical modifications of factor VIII (FVIII) products may influence their behaviour in FVIII activity assays. Hence, it is important to assess the performance of FVIII products in these assays. Efanesoctocog alfa is a new class of FVIII replacement therapy designed to provide both high sustained factor activity levels and prolonged plasma half-life. AIM: Evaluate the accuracy of measuring efanesoctocog alfa FVIII activity in one-stage clotting assays (OSAs) and chromogenic substrate assays (CSAs). METHODS: Human plasma with no detectable FVIII activity was spiked with efanesoctocog alfa or a full-length recombinant FVIII product comparator, octocog alfa, at nominal concentrations of 0.80 IU/mL, 0.20 IU/mL, or 0.05 IU/mL, based on labelled potency. Clinical haemostasis laboratories (N = 35) tested blinded samples using in-house assays. Data from 51 OSAs (14 activated partial thromboplastin time [aPTT] reagents) and 42 CSAs (eight kits) were analyzed. RESULTS: Efanesoctocog alfa activity was reliably (±25% of nominal activity) measured across all concentrations using OSAs with Actin FSL and multiple other aPTT reagents. Under- and overestimation of FVIII activity occurred with some reagents. No specific trend was observed for any class of aPTT activators. A two- to three-fold overestimation was consistently observed using CSAs and the OSA with Actin FS as the aPTT reagent across evaluated concentrations. CONCLUSION: Under- or overestimation occurred with some specific OSAs and most CSAs, which has been previously observed with other modified FVIII replacement products. Efanesoctocog alfa FVIII activity was measured with acceptable accuracy and reliability using several OSA methods and commercial plasma standards.

Efficacy of rFVIIIFc versus Emicizumab for the Treatment of Patients with Hemophilia A without Inhibitors: Matching-Adjusted Indirect Comparison of A-LONG and HAVEN Trials.

PURPOSE: Primary prophylaxis, using factor VIII replacement, is the recognized standard of care for severe hemophilia A. Recombinant factor VIII-Fc fusion protein (rFVIIIFc) and emicizumab, a humanized, bispecific antibody, are approved for routine prophylaxis of bleeding episodes in severe hemophilia A. These products have different mechanisms of action, methods of administration and treatment schedules. In the absence of head-to-head trials, indirect treatment comparisons can provide informative evidence on the relative efficacy of the two treatments. The aim of the study was to compare the approved dosing regimens for each product, rFVIIIFc individualized prophylaxis and emicizumab administered once every week (Q1W), every 2 weeks (Q2W) or every 4 weeks (Q4W), based on clinical trial evidence. PATIENTS AND METHODS: The comparison was conducted using matching-adjusted indirect comparison since clinical evidence did not form a connected network. Individual patient data for rFVIIIFc (A-LONG) were compared with data for emicizumab (HAVEN trial program) for mean annualized bleeding rate (ABR) and proportion of patients with zero bleeds. Safety data reported across the analyzed treatment arms were tabularized but not formally compared. RESULTS: After matching, no significant differences were observed between mean ABR for rFVIIIFc and emicizumab administered Q1W, Q2W or Q4W. The proportion of patients with zero bleeds was significantly higher with rFVIIIFc compared with emicizumab administered Q4W (51.2% versus 29.3%, respectively; odds ratio 2.53; 95% confidence interval 1.09-5.89); no significant differences noted when rFVIIIFc was compared with emicizumab administered Q1W or Q2W. The mean number of adverse events expressed per participant was 1.9 for individualized prophylaxis with rFVIIIFc and 3.7-4.0, 4.1 and 3.6 for emicizumab administered Q1W, Q2W or Q4W, respectively. CONCLUSION: This indirect treatment comparison suggests that rFVIIIFc individualized prophylaxis is more efficacious than emicizumab Q4W, and at least as effective as more frequent emicizumab regimens, for the management of hemophilia A.