Current difficulties and recent advances in bypass therapy for the management of hemophilia with inhibitors: a new and practical formulation of recombinant factor VIIa

Real-World Early Treatment with Room Temperature-Stable Recombinant Factor VIIa in Hemophilia A/B and Inhibitors: SMART-7™ Post Hoc Analyses

Treating hemophilia A or B patients with inhibitors is particularly challenging, as they do not respond to replacement therapy with factor VIII or factor IX concentrates. A room temperature–stable formulation of recombinant activated factor VII (rFVIIa; NovoSeven ^® ), which provides improved convenience and treatment access to patients compared with the earlier formulation of rFVIIa, was shown to be safe and effective in a post-authorization, multinational, observational study (Study Monitoring Antibodies against Room Temperature–stable factor 7 [SMART-7™]). In post hoc, subgroup analyses of SMART-7™ data, the hemostatic response following rFVIIa monotherapy in patients with hemophilia A or B with inhibitors by time to first treatment and in different age cohorts was assessed. A total of 482/618 bleeding episodes treated with rFVIIa monotherapy and with (1) valid efficacy assessment, (2) no missing time for bleed start, (3) no missing time for any dose administration, and (4) valid time to first treatment were included in the analyses. Data on the type and location of bleeding episodes treated with rFVIIa monotherapy were also collected. The majority of bleeding episodes treated with rFVIIa monotherapy were treated within 1 hour after bleeding onset (318/482 [66%]) and, among them, 96.5% (307/318) were effectively treated (i.e., bleeding stopped). Hemostatic efficacy remained high for bleeding episodes treated >1 to ≤4 hours after the onset, with 94/101 (93.1%) treated effectively. Cause and location of bleeding varied across the different age groups assessed. Real-world evidence from post hoc, subgroup analyses of SMART-7™ data confirmed that patients were able to treat themselves quickly and that early treatment with rFVIIa was associated with high efficacy.

Factor VIII associated with lipidic nanoparticles retains efficacy in the presence of anti-factor VIII antibodies in hemophilia A mice

The development of inhibitory antibodies against factor VIII (FVIII) is a major challenge in hemophilia A (HA) therapy. Such antibodies develop in nearly 30% of patients receiving replacement FVIII, abrogating therapeutic efficacy. This work evaluated whether B-domain deleted FVIII encapsulated in phosphatidylinositol containing lipid nanoparticles (PI-BDD FVIII) could serve as an efficacious FVIII replacement therapy in the presence of inhibitors. The HA mice were given clinically relevant doses of FVIII to develop inhibitors. The efficacy of free and PI-BDD FVIII was studied in inhibitor-positive HA mice using a tail clip assay. Mathematical modeling of these data was conducted to evaluate the hypothesis that lipid association sterically shields the protein from inhibitor binding. The immunization protocol resulted in a mean inhibitory titer level of 198 ± 52 BU/ml. Free BDD FVIII was ineffective at controlling blood loss in inhibitor-positive HA mice as early as 2 h post dose. In contrast, PI-BDD FVIII treated animals retained partial hemostatic efficacy as long as 18 h post dose. Mathematical modeling supports the hypotheses that a greater fraction of lipid-associated FVIII remains unbound to inhibitors and that PI-BDD FVIII has lower binding affinity to inhibitors than does the free protein. In addition, the modeling approaches extend current efforts to model the impact of immunogenicity on PK and the therapeutically meaningful endpoint of efficacy, thereby addressing an important knowledge gap, particularly in the FVIII scientific literature. Clinical translation of these findings could result in a significant improvement in the quality of care of inhibitor-positive HA patients. Copyright © 2016 John Wiley & Sons, Ltd.