Cross-Sectional Comparative Study of PK-Guided Switch between Standard Half-Life and Extended Half-Life Factor VIII Products

Background The high inter-individual variability in pharmacokinetics (PK) of factor VIII (FVIII) justifies the use of PK-guided prophylaxis, especially in switching between different products. A proposed definition of extended half-life (EHL) FVIII requires improvements of at least 1.3 times in half-life (t1/2) and 1.25 times the area under the curve (AUC) compared to standard half-life (SHL) products (Mahlangu et al. Haemophilia. 2018;24(3):348-358). The objective of this multicenter study was to analyze the results of a PK-guided switch from SHL to EHL in patients with hemophilia A (HA). Methods Multicenter comparative, cross-sectional, prospective study in HA severe/moderate patients in prophylaxis analyzing PK differences after switch from SHL to EHL (efmoroctocog alfa [rFVIII-Fc] and rurioctocog alfa pegol [PEG-rFVIII]). WAPPS-Hemo® was used to analyze PK parameters with 2-3 samples: t1/2; AUC, peak level (PL); trough level at 24, 48 and 72 h (TL24, TL48, TL72); and time to reach FVIII levels of 1, 2, 5% (T1%, T2%, T5%). We have also compared the ratio of t1/2 and AUC, the number of weekly doses and the dose/kg/week before and after the switch. Wilcoxon and Kruskal-Wallis tests (SPSS®) were used to compare the PK parameters. Results are expressed with the median and interquartile range (IQR) or range, and mean and standard deviation (SD). Results Eighty-one patients from 8 Spanish hospitals were analyzed (61 rFVIII-Fc; 20 PEG-rFVIII), 78 had severe HA and 3 moderate HA. Mean age was 30 years (range=3-64) and no differences in weight were observed between both periods [70 (range=12-116) vs 70 (13.7-116) kg; p=0,141]. Dose/kg/week and weekly infusion frequency were reduced after the switch to EHL, and significant improvements were observed in all PK parameters after the change from SHL to EHL (Table 1). These results were similar in adult and pediatric patients switching to rFVIII-Fc. The median ratios of t1/2 and AUC were 1.3 (IQR:1.2-1.6) and 1.5 (IQR:1.3-2.3) in the entire cohort. These results were reproduced in the subset of patients with ≥12 years treated with rFVIII-Fc and PEG-rFVIII (ratio t1/2: 1.4 [IQR:1.3-1.6]; ratio AUC: 1.6 [IQR:1.3-2.3]), and were slightly in the cohort of 15 patients