PK-guided switch between standard half-life and extended half-life factor VII products

P117 Introduction: Extended half-life (EHL) factor VIII (FVIII) requires improvements in half-life (t1/2) & area under the curve (AUC) of 1.3 & 1.25 times compared to standard half-life (SHL) products. The aim of this study is compare pharmacokinetics (PK) after the switch from SHL to EHL in patients with hemophilia A (HA). Methods: Multicenter comparative, cross-sectional, prospective study analyzing PK differences after switch from SHL to EHL (ef-moroctocog alfa [rFVIII-Fc] & 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 & 72 hours (TL24, TL48, TL72); & time to reach FVIII levels of 1, 2, 5% (T1%, T2%, T5%). Ratio of t1/2 & AUC, the number of weekly doses & the dose/kg/week before & after the switch were compared. Wilcoxon & Kruskal-Wallis tests (SPSS®) were used to compare the PK parameters. Results: Eightythree patients from 8 Spanish hospitals were analyzed (62 rFVIII-Fc; 21 PEG-rFVIII), 79 had severe HA & 4 moderate HA. Median age was 30 years (range = 3-64) & no differences in weight were observed between both periods.Dose/kg/week & weekly infusion frequency were reduced after the switch to EHL, & significant improvements were observed in all PK parameters after the change from SHL to EHL (Table 1). The median ratios of t1/2 & AUC were 1.3 (IQR:1.2-1.6) and 1.6 (IQR:1.3-2.2) in the entire cohort. In patients with =12 years ratios of t1/2 & AUC were 1.4 (IQR:1.3-1.6) & 1.7 (IQR:1.3-2.3), and in the cohort of 16 patients <12 years treated with rFVIII-Fc were 1.3 (IQR:0.9-1.5) and 1.4 (IQR:1.1- 2.1).After the switch to EHL, median weekly dose frequency (30%, IQR:0-33.3%) & dose/kg/week (16.9%, IQR:8.7-32.8%) were reduced. In a small subset of 15 younger patients the dose/kg/week was increased a median of 28.6% (IQR:11.7-40-7%). No differences were observed in any of the PK parameters & median ratios of t1/2 & AUC in patients aged =12 years treated with rFVIII-Fc vs. PEG-rFVIII (46 rFVIII-Fc; 21 PEG-rFVIII). Discussion/Conclusion: EHL FVIII have shown significant PK improvements in clinical real practice, allowing to reduce weekly infusion number & dose/kg/week. Outside the clinical trial setting, we have observed an increase in t1/2 & AUC ratios accordingly to EHL definition. Comparisons regarding clinical outcomes (bleeding rate after switch) will be performed after a follow-up of 1 year with EHL for the full cohort