Introduction: In many countries, there is a shift from standard half-life (SHL) to extended half-life (EHL) clotting factor concentrates (CFCs).Aim: To describe the experience of switching from SHL to an EHL FVIII CFC and the impact of this on frequency of infusions, factor consumption, bleeding rates and HRQoL using the Canadian Hemophilia Kids' Life Assessment Tool (CHO-KLAT).Methods: A retrospective chart review was conducted at a single haemophilia treatment centre in 2018 that included boys (ages: 4-18 years) with moderate/severe haemophilia A, without inhibitors, who switched from a SHL to an EHL FVIII CFC in the previous 2 years and for whom HRQoL data were available. Results:The study cohort comprised 38 boys [mean (SD) age: 11.0 (3.4) years] with moderate (n = 5)/severe (n = 33) haemophilia A. The switch was associated with a 33% reduction in the number of weekly infusions from a median of 3.5 to 2.3 (P < .0001) and a 17% reduction in median FVIII consumption from 103 IU/kg/wk to 85.5 IU/kg/wk (P = .004).There was no significant change in annualized joint bleed rates or in CHO-KLAT scores. Conclusions:Despite documenting several benefits of switching to EHL FVIII (less infusions, lower factor consumption with no increase in bleeding), our study did not demonstrate any improvement in HRQoL. We conclude that either the current CHO-KLAT tool is not optimized to measure burden of treatment administration in boys with low bleed rates switching from SHL to EHL FVIII CFCs or that a reduction of 1.2 infusions/week does not result in a meaningful change in HRQoL. K E Y W O R D SCanadian Hemophilia Outcomes Kids' Life Assessment Tool (CHO-KLAT), EHL FVIII, healthrelated quality of life, pediatrics, prophylaxis, severe haemophilia A | INTRODUC TI ONRecent advances in haemophilia care include the availability of extended half-life (EHL) factor (F)VIII or FIX clotting factor concentrates (CFCs) prepared using pegylation or fusion technologies. 1,2 These new CFCs show an extension of half-life of 1.4-to 1.6-fold for EHL FVIII products and 3->5-fold for EHL FIX products.EHL CFCs were designed to allow persons with haemophilia (PWH)

Standard pharmacokinetic (PK) assessments are demanding for persons with hemophilia A, requiring a 72hr washout and 5-11 timed blood samples. A no-washout, single-clinic visit, sparse sampling population PK (PPK) protocol is an attractive alternative. Here, we compared PK parameters obtained with a traditional washout, 6-sampling time point PPK protocol with a no-washout, single-clinic visit, reverse 2-sampling time point PPK protocol in persons with severe hemophilia A (SHA) receiving ADVATE®. 39 inhibitor-negative males with SHA (FVIII:C<2%) were enrolled in a prospective sequential design PK study. Participants completed a washout, 6-sampling time point PPK protocol as well as a no-washout, reverse 2-sampling time point protocol, with samples taken during a single 3hr clinic visit 24hr-post home infusion of FVIII and then 3hr-post infusion in clinic. FVIII:C levels were analyzed by one-stage and chromogenic assays; blood group and VWF:Ag were determined; and PK parameters were analyzed using the ADVATE® myPKFiT® dosing tool. There was moderate to almost perfect agreement for the PK parameters obtained with the 2- and the 6-point PPK protocols using a one-stage FVIII:C assay and a substantial to almost perfect agreement using a chromogenic FVIII:C assay. Significant associations between specific PK parameters and blood group and VWF:Ag were observed. The no-washout, single-clinic visit, reverse 2-sampling time point PPK protocol can be used in the routine clinical setting since it demonstrates sufficient accuracy compared to the more demanding and less practical washout, 6-sampling time point PPK protocol in persons with SHA receiving ADVATE®.