Clinical Outcomes of Low Dose PK-guided EHL FVIII Concentrates Versus Standard Prophylaxis in Severe Haemophilia A

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Individualised pharmacokinetic (PK)-guided dosing of extended half-life (EHL) FVIII concentrates prophylaxis may reduce hemophilia A bleeding events than previous prophylactic regimen. Methods A single-centre prospective cohort study, the investigators recruited consecutive eligible patients aged 5-25 years with clinically severe haemophilia A (FVIII:C ≤3%), no inhibitor, on low-dose weight-based prophylaxis at King Chulalongkorn Memorial Hospital (KCMH) from July 2021 to February 2022. All of patients with clinically severe haemophilia A received low dose weight-based standard half-life FVIII concentrates replacement prophylaxis for ≥ 1 year prior to enrolment in the study. The data of annual bleeding rate (ABR), annual joint bleeding rate (AJBR), annual FVIII use (prophylactic and breakthrough bleeding dosing) in the last 6 months before the study and number of target joints were collected at the beginning of the study. Baseline variables, including age and weight, were recorded before performing the analyses using online medical device (www.mypkfit.com). Wash-out period for 72 hours, each participant subsequently received a dose of 20 IU/kg FVIII by intravenous injection. Blood samples were collected and the concentration of FVIII was measured two times at 3 h and 48 h or 72 h after injection by one-stage technique. Desired FVIII trough levels were selected in this study as 1%. Individually proper regimen were selected by discussion with patients and families. All of participant individually underwent dose calculation of EHL factor VIII concentrates and received low dose PK-guided regimen (10-20u/kg, 2-3times/week) with EHL FVIII concentrates for 6 months. If breakthrough bleeding occurs, FVIII concentrates 500 U intravenous injection immediately. ABR, AJBR, HJHS and annual FVIII concentrates use were again prospectively recorded during intervention period after PK adjustment for 6 months. Primary objectives To compare clinical outcomes including annual bleeding rate (ABR), annual joint bleeding rate (AJBR) and Haemophilia joint health score (HJHS) before and after switching from standard half-life (SHL) to Extended half-life (EHL) factor VIII concentrates with adjusted dosing by PK-guided program (MyPKFiT®) in severe haemophilia A patients Secondary objectives To compare factor VIII concentrates consumption before and after using PK-guided program (MyPKFiT®) adjusting dose of factor VIII infusion in severe HA patients.

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