Abstract Number: PB1151
Meeting: ISTH 2020 Congress
Theme: Hemophilia and Rare Bleeding Disorders » Novel Biotherapeutics in Hemophilia
Background: Emicizumab(Hemlibra®), an antibody that bridges factor IXa(FIX) and factor X(FX), is approved as prophylactic treatment in patients with haemophilia A.
Aims: The first aim was to confirm that a one stage clotting assay(OSCA) and chromogenic assay(CA) modified with emicizumab calibrator is suited for quantification of emicizumab. Secondly, we evaluated a OSCA and a CA for the measurement of FVIII:C and anti-FVIII in patient samples with emicizumab.
Methods: Both the OSCA(C.K.PREST® reagent) and CA(BIOPHEN FVIII:C reagent) modified with emicizumab calibrator were applied on STA-R EVO for quantification of emicizumab(µg/mL) in a severe hemophilia patient before and during treatment with emicizumab, normal pooled plasma(NPP), FVIII deficient plasma and control samples. To explore potential interference of FVIII in the emicizumab assay, dilutions of normal pool plasma in FVIII deficient plasma(0-100%FVIII) were measured. FVIII:C and anti-FVIII were measured with OSCA(C.K.PREST reagent) and CA(TriniCHROM Factor VIII:C reagent) in the same patient before and during treatment with emicizumab.
Results: %CV for emicizumab control samples(n=6) was 1.8-2.1% for OSCA and 8.7-9.7% for CA. Emicizumab levels(16-24µg/ml) in samples from the treated patient(n=3)(FVIII< 0.3%) were similar(difference 2-17%) between both methods. A positive linear correlation was observed between FVIII:C and emicizumab for both assays. In patients under emicizumab therapy, a large overestimation of FVIII was observed using the OSCA(FVIII:C 121.0-175.8%) compared to the CA with BIOPHEN reagent(FVIII:C 9.3-13.6%). CA with TriniCHROM reagent measured <1.6% FVIII and 2.8-3.5BE anti-FVIII as measured with OSCA before treatment.
Conclusions: The OSCA(C.K.PREST® reagent) modified with emicizumab calibrator is more accurate compared to CA(BIOPHEN reagent) for the quantification of emicizumab. Prior denaturation of FVIII is necessary in samples that contain native FVIII due to interference with both emicizumab assays. The CA(TriniCHROM reagent) is the preferred method for the quantification of FVIII:C and anti-FVIII in patients treated with emicizumab, explained by the use of bovine instead of human coagulation factors.
To cite this abstract in AMA style:
Heireman L, Devreese K. Optimization of Measurement of Emicizumab, FVIII and Anti-FVIII Activity in Patients Treated with Emicizumab [abstract]. Res Pract Thromb Haemost. 2020; 4 (Suppl 1). https://abstracts.isth.org/abstract/optimization-of-measurement-of-emicizumab-fviii-and-anti-fviii-activity-in-patients-treated-with-emicizumab/. Accessed January 28, 2022.« Back to ISTH 2020 Congress
ISTH Congress Abstracts - https://abstracts.isth.org/abstract/optimization-of-measurement-of-emicizumab-fviii-and-anti-fviii-activity-in-patients-treated-with-emicizumab/