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Recombinant factor VIII Fc fusion protein for first-time immune tolerance induction: final results of the verITI-8 study.

ABSTRACT: Inhibitor development remains a major challenge in factor VIII (FVIII) replacement therapy. verITI-8 is the first prospective study of a recombinant FVIII Fc fusion protein (rFVIIIFc; efmoroctocog alfa) for first-time immune tolerance induction (ITI) in males with severe hemophilia A and high-titer inhibitors (historical peak ≥5 Bethesda units [BU]/mL). In this single-arm, open-label, multicenter study, screening was followed by ITI (rFVIIIFc 200 IU/kg per day until tolerization or maximum of 48 weeks). Those who achieved ITI success entered a tapering period, returning to standard prophylaxis, and then entered follow-up. Primary end point was time to tolerization with rFVIIIFc defined by inhibitor titer <0.6 BU/mL, incremental recovery (IR) ≥66% of expected IR (IR ≥1.32 IU/dL per IU/kg), and half-life (t½) ≥7 hours within 48 weeks. Sixteen patients received ≥1 rFVIIIFc dose. Twelve (75%), 11 (69%), and 10 patients (63%), respectively, achieved negative inhibitor titers, an IR ≥66%, and a t½ ≥7 hours (ie, tolerance) within 48 weeks. Median times in weeks to achieve these markers of success were 7.4 (interquartile range [IQR], 2.2-17.8), 6.8 (IQR, 5.4-22.4), and 11.7 (IQR, 9.8-26.2), respectively. All patients experienced ≥1 treatment-emergent adverse event (TEAE), and 1 reported ≥1 related TEAE (injection site pain). Nine patients experienced ≥1 treatment-emergent serious AE. No thrombotic events, discontinuations because of AEs, or deaths were reported during the study. As the first extended half-life rFVIII with prospective data in ITI, rFVIIIFc offered short time to tolerization with durable responses in almost two-thirds of patients and was well tolerated. This trial was registered at www.clinicaltrials.gov as #NCT03093480.

SUBMITTER: Malec L

PROVIDER: S-EPMC10646781 | biostudies-literature | 2023 Apr

REPOSITORIES: biostudies-literature

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Recombinant factor VIII Fc fusion protein for first-time immune tolerance induction: final results of the verITI-8 study.

Malec Lynn L Van Damme An A Chan Anthony K C AKC Spasova Mariya M Jain Nisha N Sensinger Charlotte C Dumont Jennifer J Lethagen Stefan S Carcao Manuel M Peyvandi Flora F

Blood 20230401 16

Inhibitor development remains a major challenge in factor VIII (FVIII) replacement therapy. verITI-8 is the first prospective study of a recombinant FVIII Fc fusion protein (rFVIIIFc; efmoroctocog alfa) for first-time immune tolerance induction (ITI) in males with severe hemophilia A and high-titer inhibitors (historical peak ≥5 Bethesda units [BU]/mL). In this single-arm, open-label, multicenter study, screening was followed by ITI (rFVIIIFc 200 IU/kg per day until tolerization or maximum of 48 ...[more]

PMID: 36735911

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Project description:BackgroundImmune tolerance induction (ITI) is the gold standard for inhibitor eradication to restore the clinical efficacy of factor replacement therapy in haemophilia. However, as ITI often requires frequent administration over extended periods, it can be considered burdensome for patients and healthcare resources. Therefore, there is a need to optimise ITI treatment, particularly in patients who failed previous ITI attempts.ObjectivesThe ReITIrate study aimed to prospectively evaluate rescue ITI with efmoroctocog alfa, an extended half-life recombinant FVIII Fc fusion protein (herein rFVIIIFc), within a limited 60-week timeframe in patients with severe haemophilia A and inhibitors who failed previous ITI attempts.DesignReITIrate was a phase IV, open-label, single-arm, interventional, multicentre study.MethodsPrimary endpoint was ITI success (negative titre, <0.6 BU/mL; incremental recovery >66%; elimination half-life ⩾7 hours) within 60 weeks. Exploratory immunophenotype analyses were performed to characterise anti-drug antibodies (ADA) and cellular immune responses.ResultsNine of 16 enrolled subjects completed the ITI period during ReITIrate, of which one subject attained all 3 ITI success criteria after 46 weeks with no relapse. Two subjects achieved partial success (one subject met 2/3 success criteria; one met all criteria, but not simultaneously, with inhibitor recurrence). One additional subject (ITI failure) achieved negative inhibitor titre. Across these four subjects, median (range) time to negative titre was 19 (11-60) weeks. No new safety concerns were identified. IgG4 was the major contributor to the ADA IgG response. Subjects with partial/complete ITI success had fewer IgG subclasses involved than those who failed/withdrew. Immunophenotyping indicated an increase in regulatory T-cells (CD4+CD25+CD127low), supporting the ability to perform sensitive blood sampling to identify immune tolerance markers.ConclusionThis study demonstrates that ITI with rFVIIIFc given within a limited timeframe has potential benefit in a difficult-to-treat inhibitor haemophilia population who failed previous ITI attempts.Trial registrationNCT03103542.

Project description:Essentials Recombinant factor VIII (rFVIII) Fc fusion protein has a 1.5-fold longer half-life than rFVIII. Five orthogonal methods were used to characterize the structure of rFVIIIFc compared to rFVIII. The C-terminal Fc fusion does not perturb the structure of FVIII in rFVIIIFc. The FVIII and Fc components of rFVIIIFc are flexibly tethered and functionally independent.SummaryBackground Fusion of the human IgG1 Fc domain to the C-terminal C2 domain of B-domain-deleted (BDD) factor VIII (FVIII) results in the recombinant FVIII Fc (rFVIIIFc) fusion protein, which has a 1.5-fold longer half-life in humans. Objective To assess the structural properties of rFVIIIFc by comparing its constituent FVIII and Fc elements with their respective isolated components, and evaluating their structural independence within rFVIIIFc. Methods rFVIIIFc and its isolated FVIII and Fc components were compared by the use of hydrogen-deuterium exchange mass spectrometry (HDX-MS). The structure of rFVIIIFc was also evaluated by the use of X-ray crystallography, small-angle X-ray scattering (SAXS), and electron microscopy (EM). The degree of steric interference by the appended Fc domain was assessed by EM and surface plasmon resonance (SPR). Results HDX-MS analysis of rFVIIIFc revealed that fusion caused no structural perturbations in FVIII or Fc. The rFVIIIFc crystal structure showed that the FVIII component is indistinguishable from published BDD FVIII structures. The Fc domain was not observed, indicating high mobility. SAXS analysis was consistent with an ensemble of rigid-body models in which the Fc domain exists in a largely extended orientation relative to FVIII. Binding of Fab fragments of anti-C2 domain antibodies to BDD FVIII was visualized by EM, and the affinities of the corresponding intact antibodies for BDD FVIII and rFVIIIFc were comparable by SPR analysis. Conclusions The FVIII and Fc components of rFVIIIFc are structurally indistinguishable from their isolated constituents, and show a high degree of structural independence, consistent with the functional comparability of rFVIIIFc and unmodified FVIII.

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Recombinant factor VIII Fc fusion protein for first-time immune tolerance induction: final results of the verITI-8 study.

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Recombinant factor VIII Fc fusion protein for first-time immune tolerance induction: final results of the verITI-8 study.

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