Emicizumab is a bispecific monoclonal antibody that bridges activated factor IX and factor X to replace the function of missing activated factor VIII, thereby restoring hemostasis. In a phase 3, multicenter trial, we investigated its use as prophylaxis in persons who have hemophilia A without factor VIII inhibitors.

Patients require different warfarin dosages to achieve the target therapeutic anticoagulation. The variability is largely genetically determined, and it can be only partly explained by genetic variability in the cytochrome CYP2C9 locus. In 147 patients followed from the start of anticoagulation with warfarin, we have investigated whether VKORC1 gene mutations have affected doses of drug prescribed to acquire the target anticoagulation intensity. Two synonymous mutations, 129C>T at Cys43 and 3462C>T at Leu120, and 2 missense mutations, Asp38Tyr and Arg151Gln, were identified. None of these mutations was found to affect the interindividual variability of warfarin prescribed. Finally, 2 common polymorphisms were found, 1173C>T in the intron 1 and 3730G>A transition in the 3′ untranslated region (UTR). Regardless of the presence of confounding variables, the mean adjusted dose required of warfarin was higher (6.2 mg) among patients with the VKORC1 1173CC genotype than those of patients carrying the CT (4.8 mg; P = .002) or the TT genotype (3.5 mg; P < .001). In the present setting, VKORC1 and CYP2C9 genetic variants investigated accounted for about a third (r2, 0.353) of the interindividual variability. Genetic variants of the VKORC1 gene locus modulate the mean daily dose of drug prescribed to acquire the target anticoagulation intensity.

The development of neutralizing anti–factor VIII alloantibodies (inhibitors) in patients with severe hemophilia A may depend on the concentrate used for replacement therapy. We conducted a randomized trial to assess the incidence of factor VIII inhibitors among patients treated with plasma-derived factor VIII containing von Willebrand factor or recombinant factor VIII. Patients who met the eligibility criteria (male sex, age <6 years, severe hemophilia A, and no previous treatment with any factor VIII concentrate or only minimal treatment with blood components) were included from 42 sites. Of 303 patients screened, 264 underwent randomization and 251 were analyzed. Inhibitors developed in 76 patients, 50 of whom had high-titer inhibitors (≥5 Bethesda units). Inhibitors developed in 29 of the 125 patients treated with plasma-derived factor VIII (20 patients had high-titer inhibitors) and in 47 of the 126 patients treated with recombinant factor VIII (30 patients had high-titer inhibitors). The cumulative incidence of all inhibitors was 26.8% (95% confidence interval [CI], 18.4 to 35.2) with plasma-derived factor VIII and 44.5% (95% CI, 34.7 to 54.3) with recombinant factor VIII; the cumulative incidence of high-titer inhibitors was 18.6% (95% CI, 11.2 to 26.0) and 28.4% (95% CI, 19.6 to 37.2), respectively. In Cox regression models for the primary end point of all inhibitors, recombinant factor VIII was associated with an 87% higher incidence than plasma-derived factor VIII (hazard ratio, 1.87; 95% CI, 1.17 to 2.96). This association did not change in multivariable analysis. For high-titer inhibitors, the hazard ratio was 1.69 (95% CI, 0.96 to 2.98). When the analysis was restricted to recombinant factor VIII products other than second-generation full-length recombinant factor VIII, effect estimates remained similar for all inhibitors (hazard ratio, 1.98; 95% CI, 0.99 to 3.97) and high-titer inhibitors (hazard ratio, 2.59; 95% CI, 1.11 to 6.00). Patients treated with plasma-derived factor VIII containing von Willebrand factor had a lower incidence of inhibitors than those treated with recombinant factor VIII. (Funded by the Angelo Bianchi Bonomi Foundation and others; ClinicalTrials.gov number, NCT01064284; EudraCT number, 2009-011186-88.)

In a Plenary Paper, Young et al describe impressive favorable outcomes of emicizumab prophylaxis in children with hemophilia A and factor VIII inhibitors, reporting a 99% reduction in annualized bleeding, with 77% of patients having no treated bleeding events.

Acquired hemophilia A (AHA) is a rare bleeding disorder characterized by autoantibodies directed against circulating coagulation factor (F) VIII. Typically, patients with no prior history of a bleeding disorder present with spontaneous bleeding and an isolated prolonged aPTT. AHA may, however, present without any bleeding symptoms, therefore an isolated prolonged aPTT should always be investigated further irrespective of the clinical findings. Control of acute bleeding is the first priority, and we recommend first-line therapy with bypassing agents such as recombinant activated FVII or activated prothrombin complex concentrate. Once the diagnosis has been achieved, immediate autoantibody eradication to reduce subsequent bleeding risk should be performed. We recommend initial treatment with corticosteroids or combination therapy with corticosteroids and cyclophosphamide and suggest second-line therapy with rituximab if first-line therapy fails or is contraindicated. In contrast to congenital hemophilia, no comparative studies exist to support treatment recommendations for patients with AHA, therefore treatment guidance must rely on the expertise and clinical experience of specialists in the field. The aim of this document is to provide a set of international practice guidelines based on our collective clinical experience in treating patients with AHA and contribute to improved care for this patient group.