International comparative field study evaluating the assay performance of AFSTYLA in plasma samples at clinical hemostasis laboratories.

Essentials AFSTYLA exhibits ≈50% underestimation in activity when the one-stage (OS) assay is utilized. A field study compared the performance of AFSTYLA with Advate in factor VIII activity assays. AFSTYLA activity can be monitored with both the chromogenic substrate and the OS assay. The consistent OS underestimation allows for a conversion factor to be applied to OS results. SUMMARY: Introduction AFSTYLA (antihemophilic factor [recombinant] single chain) is a novel B-domain truncated recombinant factor VIII (rFVIII). For AFSTYLA, an approximate 50% discrepancy was observed between results of the one-stage (OS) and chromogenic substrate (ChS) FVIII activity assays. An investigation was undertaken to test whether there is a linear relationship between ChS and OS assay results that would allow reliable clinical interpretation of results independent of the assay method used. Aims To provide confidence in future clinical monitoring, this field study investigated the performance of AFSTYLA and a full-length rFVIII (Advate® ) in FVIII activity assays routinely performed in clinical laboratories. Methods The comparison of AFSTYLA and Advate was performed in an international, multicenter and blinded field study of simulated post-infusion samples. The study documented the extent of variability between methods and laboratories and characterized the relationship between the ChS and OS assays. Results Results from 23 laboratories demonstrate that intra and interlaboratory variability in OS assays were similar for both products. When comparing within the OS assay format, there was a similar and reagent-correlated variability in response to different activators for both AFSTYLA and Advate. The OS underestimation was highly predictable and consistent across the complete range of FVIII plasma concentrations. Conclusion Post-infusion plasma AFSTYLA levels can be monitored in patients by the OS and ChS assays. The consistent and predictable difference between the two assay formats provides clinicians with adequate guidance on how to interpret the results of the OS assay using a single conversion factor.

Population pharmacokinetics of recombinant coagulation factor VIII-SingleChain in patients with severe hemophilia A.

Essentials rVIII-SingleChain is a unique recombinant factor VIII (FVIII) molecule. A population pharmacokinetic model was based on FVIII activity of severe hemophilia A patients. The model was used to simulate factor VIII activity-time profiles for various dosing scenarios. The model supports prolonged dosing of rVIII-SingleChain with intervals of up to twice per week. SUMMARY: Background Single-chain recombinant coagulation factor VIII (rVIII-SingleChain) is a unique recombinant coagulation factor VIII molecule. Objectives To: (i) characterize the population pharmacokinetics (PK) of rVIII-SingleChain in patients with severe hemophilia A; (ii) identify correlates of variability in rVIII-SingleChain PK; and (iii) simulate various dosing scenarios of rVIII-SingleChain. Patients/Methods A population PK model was developed, based on FVIII activity levels of 130 patients with severe hemophilia A (n = 91 for ≥ 12-65 years; n = 39 for < 12 years) who had participated in a single-dose PK investigation with rVIII-SingleChain 50 IU kg-1 . PK sampling was performed for up to 96 h. Results A two-compartment population PK model with first-order elimination adequately described FVIII activity. Body weight and predose level of von Willebrand factor were significant covariates on clearance, and body weight was a significant covariate on the central distribution volume. Simulations using the model with various dosing scenarios estimated that > 85% and > 93% of patients were predicted to maintain FVIII activity level above 1 IU dL-1 , at all times with three-times-weekly dosing (given on days 0, 2, and 4.5) at the lowest (20 IU kg-1 ) and highest (50 IU kg-1 ) doses, respectively. For twice weekly dosing (days 0 and 3.5) of 50 IU kg-1 rVIII-SingleChain, 62-80% of patients across all ages were predicted to maintain a FVIII activity level above 1 IU dL-1 at day 7. Conclusions The population PK model adequately characterized rVIII-SingleChain PK, and the model can be utilized to simulate FVIII activity-time profiles for various dosing scenarios.

Safety, efficacy and pharmacokinetics of rVIII-SingleChain in children with severe hemophilia A: results of a multicenter clinical trial.

Essentials rVIII-SingleChain is a novel recombinant factor VIII with covalently bonded heavy and light chains. Efficacy, safety and pharmacokinetics were studied in pediatric patients with severe hemophilia A. Across all prophylaxis regimens, the median annualized spontaneous bleeding rate was 0.00. rVIII-SingleChain showed excellent hemostatic efficacy and a favorable safety profile. SUMMARY: Background rVIII-SingleChain is a novel B-domain truncated recombinant factor VIII (rFVIII) comprised of covalently bonded FVIII heavy and light chains, demonstrating a high binding affinity to von Willebrand factor. Objectives This phase III study investigated the safety, efficacy and pharmacokinetics of rVIII-SingleChain in previously treated pediatric patients < 12 years of age with severe hemophilia A. Patients/Methods Patients could be assigned to prophylaxis or on-demand therapy by the investigator. For patients assigned to prophylaxis, the treatment regimen and dose were based on the bleeding phenotype. For patients receiving on-demand therapy, dosing was guided by World Federation of Hemophilia recommendations. The primary endpoint was treatment success, defined as a rating of 'excellent' or 'good' on the investigator's clinical assessment of hemostatic efficacy for all treated bleeding events. Results The study enrolled 84 patients (0 to < 6 years, n = 35; ≥ 6 to < 12 years, n = 49); 81 were assigned to prophylaxis and three to an on-demand regimen. Patients accumulated a total of 5239 exposure days (EDs), with 65 participants reaching > 50 EDs. In the 347 bleeds treated and evaluated by the investigator, hemostatic efficacy was rated as excellent or good in 96.3%. The median annualized spontaneous bleeding rate was 0.00 (Q1, Q3: 0.00, 2.20), and the median annualized bleeding rate was 3.69 (Q1, Q3: 0.00, 7.20) across all prophylaxis regimens. No participant developed an inhibitor. Conclusions rVIII-SingleChain is a novel rFVIII molecule showing excellent hemostatic efficacy and a favorable safety profile in a clinical study in children < 12 years of age with severe hemophilia A.

Comparative pharmacokinetics of rVIII-SingleChain and octocog alfa (Advate(®) ) in patients with severe haemophilia A.

BACKGROUND: rVIII-SingleChain, a novel recombinant factor VIII (rFVIII), has been designed as a B-domain truncated construct with covalently bonded heavy and light chains, aiming to increase binding affinity to von Willebrand factor (VWF). Preclinical studies confirmed greater affinity for VWF, giving improved pharmacokinetic and pharmacodynamic properties compared with full-length rFVIII. AIM: To investigate the pharmacokinetics of rVIII-SingleChain and compare them against those of full-length rFVIII. METHODS: This study enrolled 27 patients with severe haemophilia A in the AFFINITY clinical trial programme. After a 4-day washout period, all patients received a single infusion of 50 IU kg(-1) octocog alfa (Advate(®) ); after a ≥4-day postinfusion washout period, they received a single infusion of 50 IU kg(-1) rVIII-SingleChain. Blood samples for pharmacokinetic assessments of each product were collected before infusion (predose) and at 0.5, 1, 4, 8, 10, 24, 32, 48 and 72 h postinfusion for both products. RESULTS: rVIII-SingleChain had a longer mean half-life (t1/2 ) (14.5 vs. 13.3 h), lower mean clearance (CL) (2.64 vs. 3.68 mL h(-1) kg(-1) ), higher mean residence time (20.4 vs. 17.1 h) and larger mean AUCinf (2090 vs. 1550 IU?h dL(-1) ) than octocog alfa, respectively. The mean AUCinf after rVIII-SingleChain infusion was ~35% larger than after octocog alfa. A similar pattern was observed for AUC0-last . No serious adverse events or inhibitors were reported. CONCLUSIONS: rVIII-SingleChain has a favourable pharmacokinetic profile compared with octocog alfa and was well tolerated. The prolonged t1/2 , larger AUC and reduced CL of rVIII-SingleChain may permit longer dosing intervals, thereby improving patient adherence to prophylactic treatment.