Successful perioperative prophylaxis with susoctocog alfa in a patient with acquired haemophilia A: A case study

Recombinant porcine factor VIII in patients with congenital haemophilia A with inhibitors undergoing surgery: Phase 3, single-arm, open-label study

INTRODUCTION

Recombinant porcine factor VIII (rpFVIII; susoctocog alfa) is predicted to provide functional FVIII activity in patients with congenital haemophilia A with inhibitors (CHAWI).

AIMS

To evaluate the efficacy and safety of rpFVIII in patients with CHAWI undergoing invasive procedures.

METHODS

This phase 3, multicentre, single-arm, open-label study (NCT02895945) enrolled males aged 12-75 years with severe/moderately severe CHAWI who required surgical/invasive procedures. Patients received a loading dose of rpFVIII 1-2 h before surgery. The primary outcome was the proportion of all procedures with a 'good' or 'excellent' response (treatment success) on the global haemostatic efficacy assessment score.

RESULTS

Of the eight dosed patients, five completed the study. Six of seven surgeries (85.7%; 95% confidence interval, 42.1-99.6) achieved treatment success; five were rated 'excellent', one was rated 'good'. Seven surgery-related bleeding episodes occurred in three patients during the study, with none requiring additional surgical intervention. Overall, six of eight patients experienced 17 treatment-emergent adverse events. Three patients developed de novo inhibitors to rpFVIII. Five patients reported anamnestic reactions, three to both human (h) FVIII (i.e., alloantibodies to exogenous FVIII detected with anti-hFVIII assays) and rpFVIII, and two to hFVIII only. Four serious adverse events were considered related to rpFVIII (three anti-rpFVIII antibody positive; one anamnestic reaction to hFVIII and rpFVIII).

CONCLUSION

Good haemostasis was achieved with rpFVIII during the immediate perioperative period. The study was terminated early because the study sponsor and health authorities determined that the risk of anamnestic reactions outweighs the benefits in this study population.

Surgery and Prophylaxis with Susoctocog-Alfa in Acquired Hemophilia: Case Series and Literature Review

BACKGROUND

Acquired hemophilia A (AHA) is a rare bleeding disease due to autoantibodies directed against clotting factor VIII (FVIII). Treatment of AHA consists of inhibitor eradication with immunosuppressive therapy (IST) and prompt control of bleeding obtained with bypassing agents or recombinant porcine FVIII (rpFVIII). The latter has recently been licensed for management of acute bleeding in AHA. Unlike treatment with bypassing agents, rpFVIII can be monitored to provide a successful hemostatic effect and avoid overtreatment. Correlation between rpFVIII inhibitor titers and efficacy of rpFVIII treatment remains a matter of debate.

METHODS

We report three cases of AHA in which rpFVIII was successfully used with an unconventional schedule despite the presence of medium-high titers of the rpFVIII. The modified Nijmegen-Bethesda inhibitor assay (NBA) was used to dose porcine FVIII inhibitors.

RESULT

The presence of rpFVIII inhibitors prior to the exposition to susoctocog-alfa, that may suggest a cross-reactivity with human FVIII inhibitors, did not affect hemostasis.

CONCLUSION

In our experience, rpFVIII demonstrates safety and efficacy in the presence of rpFVIII inhibitors and using an unconventional schedule in both the perioperative and outpatient settings. Laboratory measurement of inhibitors against rpFVIII during treatment is described for the first time.

Analytical Performance of Different Laboratory Methods for Measuring Susoctocog-Alfa

Recombinant porcine factor VIII (rpFVIII) is indicated for treating bleeding episodes in acquired haemophilia A, but there are few data regarding laboratory methods to adequately monitor treatment. This study involving three Italian laboratories aimed to evaluate the analytical performance of different assays for measuring rpFVIII. Five spiked rpFVIII samples (0.5–1.5 IU/mL) were analysed on three days, in triplicate, with eleven combinations of reagents (Werfen, Boston, MA, USA: SynthasIL and SynthaFax for one-stage assay, Chromogenix Coamatic FVIII for chromogenic assay), FVIII depleted plasmas (with or without von Willebrand factor—VWF) and calibrators (HemosIL human calibrator plasma, porcine calibrator diluted in FVIII deficient plasma with or without VWF). The assays were performed on ACL TOP analysers (Werfen, Boston, MA, USA). Intra- and inter-assay and inter-laboratory Coefficient of Variation (CV%) were calculated together with percentage of recovery (% recovery) on the expected value. The results showed that the reagent combinations reaching satisfactory analytical performance are: SynthasIL/human calibrator/deficient plasma+VWF (total recovery 99.4%, inter-laboratory CV 4.04%), SynthasIL/porcine calibrator/deficient plasma+VWF (total recovery 111%, inter-laboratory CV 2.75%) and Chromogenic/ porcine calibrator/deficient plasma+VWF (total recovery 96.6%, inter-laboratory CV 8.32%). This study highlights that the use of porcine standard (when available) and FVIII deficient plasma with VWF should be recommended.