PO041 | VARIABLE CLINICAL RESPONSE TO RECOMBINANT PORCINE FVIII IN ACQUIRED HAEMOPHILIA A: A TWO CASE EXPERIENCE WITH LABORATORY SUPPORTED MONITORING
Abstract
Background. Recombinant porcine factor VIII (rpFVIII, Susoctocog α – Obizur®) is used to treat bleeding in patients with Acquired Haemophilia A (AHA). rpFVIII may represent a valid alternative for bleeding control, especially in case of bypassing agents (BPAs) failure. Disadvantages to BPAs include the inability to monitor response with standard laboratory assays, inconsistent haemostatic efficacy and increased thrombotic risk. Susoctocog α allows laboratory monitoring of FVIII activity with calibrated one-stage assays, which may reduce thrombotic risk. However, the response is variable and depends not only on the inhibitor titre (human or porcine), but also on poorly defined pharmacokinetic variables. Materials and Methods. We collected two cases treated with rpFVIII in June 2025 and January 2026. In the first case, rpFVIII was used for bleeding control in a patient with coronary artery disease and AHA (FVIII 0%, Inhibitor 4.07 BU/mL) who developed severe thrombocytopenia during sepsis (platelets 20 000/mmc). In the second case, rpFVIII was used after BPAs failure to stop femoral arterial bleeding following removal of the embolization introducer in a recently diagnosed AHA patient (FVIII 0.8%, Inhibitor 27.98 BU/mL). Clinical and laboratory findings are summarized in the Table. FVIII activity was measured using three assays: one-stage FVIII:C with Actin® (Siemens) calibrated with human plasma; chromogenic FVIII assay (Siemens) calibrated with human plasma; and the reference method for rpFVIII, a one-stage FVIII assay with Actin® FS (Siemens) calibrated with a dedicated Obizur® curve. The anti-porcine FVIII inhibitor was quantified using a mixing Bethesda assay adapted for rpFVIII: patient plasma was heat-inactivated at 56 °C for 45 minutes, mixed 1:1 with Obizur-spiked normal plasma, incubated for 2 hours at 37 °C, and residual FVIII activity measured using the Actin® FS Obizur-calibrated assay. Results. Bleeding control was achieved in both cases and no adverse events related to rpFVIII were observed. The initial bolus of Susoctocog α was 100 U/kg in both cases with a variable response. In the first case the response was less long-lasting and additional doses were required in the first 24 hours to maintain FVIII >50% (another 100 U/kg in boluses 50–30–20 U/kg). In the second case the response was more prolonged (over 24 hours), without further doses to maintain FVIII >50% and bleeding stop. This difference may be partially explained by the increase in human inhibitor titre (15 BU/mL) during sepsis in the first patient. However, since neither patient developed rpFVIII inhibitors, other factors may underlie these differences (age? pharmacokinetic variables?). The calibrated one-stage FVIII assay (Actin® FS with Obizur calibration) correlated with FVIII:C measured using Actin®, while the chromogenic assay underestimated rpFVIII recovery. Conclusions. Susoctocog α proved effective and safe in AHA, also at lower than recommended dosage. However, rpFVIII pharmacokinetics can be highly variable and require active laboratory monitoring. Plasma FVIII:C provides an alternative estimation of rpFVIII recovery. A larger case collection could help clarify the heterogeneous response and the factors influencing it (age? rpFVIII inhibitors? pharmacokinetic variables?).
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BibTeX
@article{pizzini2026po041,
title = {{PO041 | VARIABLE CLINICAL RESPONSE TO RECOMBINANT PORCINE FVIII IN ACQUIRED HAEMOPHILIA A: A TWO CASE EXPERIENCE WITH LABORATORY SUPPORTED MONITORING}},
author = {Attilia Maria Pizzini},
journal = {Bleeding, Thrombosis and Vascular Biology},
year = {2026},
month = oct,
url = {https://www.btvb.org/btvb/article/view/857},
note = {CC BY-NC},
}
RIS
TY - JOUR
TI - PO041 | VARIABLE CLINICAL RESPONSE TO RECOMBINANT PORCINE FVIII IN ACQUIRED HAEMOPHILIA A: A TWO CASE EXPERIENCE WITH LABORATORY SUPPORTED MONITORING
AU - Attilia Maria Pizzini
PY - 2026
DA - 2026/10/26
JO - Bleeding, Thrombosis and Vascular Biology
UR - https://www.btvb.org/btvb/article/view/857
AB - Background. Recombinant porcine factor VIII (rpFVIII, Susoctocog α – Obizur®) is used to treat bleeding in patients with Acquired Haemophilia A (AHA). rpFVIII may represent a valid alternative for bleeding control, especially in case of bypassing agents (BPAs) failure. Disadvantages to BPAs include the inability to monitor response with standard laboratory assays, inconsistent haemostatic efficacy and increased thrombotic risk. Susoctocog α allows laboratory monitoring of FVIII activity with calibrated one-stage assays, which may reduce thrombotic risk. However, the response is variable and depends not only on the inhibitor titre (human or porcine), but also on poorly defined pharmacokinetic variables. Materials and Methods. We collected two cases treated with rpFVIII in June 2025 and January 2026. In the first case, rpFVIII was used for bleeding control in a patient with coronary artery disease and AHA (FVIII 0%, Inhibitor 4.07 BU/mL) who developed severe thrombocytopenia during sepsis (platelets 20 000/mmc). In the second case, rpFVIII was used after BPAs failure to stop femoral arterial bleeding following removal of the embolization introducer in a recently diagnosed AHA patient (FVIII 0.8%, Inhibitor 27.98 BU/mL). Clinical and laboratory findings are summarized in the Table. FVIII activity was measured using three assays: one-stage FVIII:C with Actin® (Siemens) calibrated with human plasma; chromogenic FVIII assay (Siemens) calibrated with human plasma; and the reference method for rpFVIII, a one-stage FVIII assay with Actin® FS (Siemens) calibrated with a dedicated Obizur® curve. The anti-porcine FVIII inhibitor was quantified using a mixing Bethesda assay adapted for rpFVIII: patient plasma was heat-inactivated at 56 °C for 45 minutes, mixed 1:1 with Obizur-spiked normal plasma, incubated for 2 hours at 37 °C, and residual FVIII activity measured using the Actin® FS Obizur-calibrated assay. Results. Bleeding control was achieved in both cases and no adverse events related to rpFVIII were observed. The initial bolus of Susoctocog α was 100 U/kg in both cases with a variable response. In the first case the response was less long-lasting and additional doses were required in the first 24 hours to maintain FVIII >50% (another 100 U/kg in boluses 50–30–20 U/kg). In the second case the response was more prolonged (over 24 hours), without further doses to maintain FVIII >50% and bleeding stop. This difference may be partially explained by the increase in human inhibitor titre (15 BU/mL) during sepsis in the first patient. However, since neither patient developed rpFVIII inhibitors, other factors may underlie these differences (age? pharmacokinetic variables?). The calibrated one-stage FVIII assay (Actin® FS with Obizur calibration) correlated with FVIII:C measured using Actin®, while the chromogenic assay underestimated rpFVIII recovery. Conclusions. Susoctocog α proved effective and safe in AHA, also at lower than recommended dosage. However, rpFVIII pharmacokinetics can be highly variable and require active laboratory monitoring. Plasma FVIII:C provides an alternative estimation of rpFVIII recovery. A larger case collection could help clarify the heterogeneous response and the factors influencing it (age? rpFVIII inhibitors? pharmacokinetic variables?).
SN - 2785-5309
ER -