Recombinant porcine factor VIII for high-risk surgery in paediatric congenital haemophilia A with high-titre inhibitor

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.

Clot formation and fibrinolysis assays reveal functional differences among hemostatic agents in hemophilia A plasma

Background

Measuring the activity of hemostatic agents used to treat hemophilia A often requires drug-specific assays. In vitro assays show hemophilic clots have abnormal characteristics, including prolonged clotting time and decreased resistance to fibrinolysis. The ability of certain agents to correct these parameters in vitro is associated with hemostatic efficacy in vivo.

Objectives

To compare effects of established and emerging hemostatic agents on clot formation and fibrinolysis in hemophilia A plasma.

Methods

Pooled and individual hemophilia A platelet-poor plasmas were spiked with replacement (recombinant factor VIII [rFVIII], PEGylated rFVIII, polysialylated rFVIII, and porcine rFVIII) or bypassing (emicizumab, rFVIIa, and activated prothrombin complex concentrate) products. Effects on tissue factor-initiated clot formation and fibrinolysis were measured by turbidity.

Results

Compared to normal pooled plasma, hemophilia-pooled plasma showed reduced clot formation and increased fibrinolysis, and all replacement agents improved these characteristics. rFVIII and PEGylated rFVIII produced similar effects at similar concentrations, whereas polysialylated rFVIII produced slightly higher and porcine rFVIII slightly lower effects at these concentrations. Bypassing agents enhanced clot formation and stability, but patterns differed from replacement agents. The clotting rate showed a concentration-response relationship for all agents. High concentrations of all products produced effects that exceeded the normal range in at least some parameters. Responses of individual donors varied, but all agents improved clot formation and stability in all donors tested.

Conclusion

Clotting and fibrinolysis assays reveal hemostatic effects of replacement and bypassing therapies at clinically relevant concentrations. These assays may help characterize hemostatic agents and optimize dosing.

Trends in prescribing practices for management of haemophilia: 1999-2021

INTRODUCTION

People with haemophilia rely on specialists for their care, yet the specific dosing regimens of treatments prescribed by these specialists have not been widely studied.

AIM

The objective of this study is to describe trends in clinician prescribing practices for the management of haemophilia in the United States (US).

METHODS

We administered surveys to members of the Hemostasis and Thrombosis Research Society via paper surveys at its in-person annual symposia in 1999 and 2015, and an online survey in 2021. The surveys collected information on haemophilia treatments including factor dosing, inhibitor therapy and gene therapy.

RESULTS

Clinicians treating haemophilia for more than 50% of their practice time have increased from 37.5% of respondents in 1999 to 46.3% in 2021. Clinicians prescribing factor concentrates at >40 units/kg for routine bleeding events increased from 0% in 1999 to 29.3% in 2021 in haemophilia A (HA) and from 22.5% to 87.8% in haemophilia B (HB). In 2021, the clinicians reported prescribing emicizumab to treat HA patients (>89.5% paediatric, >85.7% adult) with or without inhibitors at least some of the time. Approximately 78.0% of respondents reported that they expected to recommend gene therapy at least some of time.

CONCLUSION

These data indicate changing trends in prescribing practices among US haemophilia specialists during the past 22 years. Preference for high doses of factor (>40 units/kg) has increased during this period. Emicizumab prophylaxis has been prescribed for patients with and without HA inhibitors. Clinicians expect gene therapy to have value for some haemophilia patients.

Platelet-targeted hyperfunctional FIX gene therapy for hemophilia B mice even with preexisting anti-FIX immunity

Gene therapy may lead to a cure for hemophilia B (HB) if it is successful. Data from clinical trials using adeno-associated virus (AAV)-mediated liver-targeted FIX gene therapy are very encouraging. However, this protocol can be applied only to adults who do not have liver disease or anti-AAV antibodies, which occur in 30% to 50% of individuals. Thus, developing a protocol that can be applied to all HB patients is desired. Our previous studies have demonstrated that lentivirus-mediated platelet-specific FIX (2bF9) gene therapy can rescue bleeding diathesis and induce immune tolerance in FIXnull mice, but FIX expression was only ∼2% to 3% in whole blood. To improve the efficacy, we used a codon-optimized hyperfunctional FIX-Padua (2bCoF9R338L) to replace the 2bF9 cassette, resulting in 70% to 122% (35.08-60.77 mU/108 platelets) activity levels in 2bCoF9R338L-transduced FIXnull mice. Importantly, sustained hyperfunctional platelet-FIX expression was achieved in all 2bCoF9R338L-transduced highly immunized recipients with activity levels of 18.00 ± 9.11 and 9.36 ± 12.23 mU/108 platelets in the groups treated with 11 Gy and 6.6 Gy, respectively. The anti-FIX antibody titers declined with time, and immune tolerance was established after 2bCoF9R338L gene therapy. We found that incorporating the proteasome inhibitor bortezomib into preconditioning can help eliminate anti-FIX antibodies. The bleeding phenotype in 2bCoF9R338L-transduced recipients was completely rescued in a tail bleeding test and a needle-induced knee joint injury model once inhibitors dropped to undetectable. The hemostatic efficacy in 2bCoF9R338L-transduced recipients was further confirmed by ROTEM and thrombin generation assay (TGA). Together, our studies suggest that 2bCoF9R338L gene therapy can be a promising protocol for all HB patients, including patients with inhibitors.

Acquired haemophilia A, concomitant acute myocardial infarction and urgent major surgery: How to successfully treat a critical patient with rpFVIII (Obizur®)

Association of acute myocardial infarction (AMI) and acquired haemophilia A (AHA) is extremely rare, and very difficult to treat, if the patient then presents several serious comorbidities and must undergo an urgent major surgery, the correct choice of haemostatic therapy is essential to avoid potentially life-threatening adverse events for the patient. The recombinant porcine FVIII (rpFVIII) is considered, together with the bypassing agents, as first-line therapy for the AHA, but compared to these it presents a reduced thromboembolic risk which makes it safer in patients who already present at the onset of haemorrhagic event an underlying cardiovascular disease. Haemorrhagic and thrombotic events are always to be taken into consideration in the case of surgery, but in the case of patients with concomitant acquired haemophilia the risk of having serious bleeding has further increase. Today there have been no reports of surgeries carried out under Obizur® coverage. We are reporting the successful case of an elderly critical patient with acquired haemophilia A and concomitant myocardial infarction, treated with rpFVIII and in which an urgent major surgery under coverage of this dug was performed for the first time.

Perioperative Management of Hemophilia A Patients Undergoing Cardiac Surgery: A Literature Review of Published Cases

OBJECTIVE

To investigate the perioperative management of patients with hemophilia A (HA) who undergo cardiac surgery.

DESIGN

Retrospective analysis of the published literature.

SETTING

University hospital.

PARTICIPANTS

HA patients undergoing cardiac surgery.

INTERVENTIONS

The PubMed, Embase, Web of Science Core Collection, CNKI, VIP, and WANFANG databases were searched with the terms "hemophilia A," "cardiac surgery," "cardiopulmonary bypass," "coronary artery bypass graft," "valve disease," and "congenital heart disease" to identify relevant articles. Data regarding patient characteristics, perioperative management protocols, and clinical outcomes were extracted and analyzed.

MEASUREMENTS AND MAIN RESULTS

Fifty articles, with 72 patients aging from 12 days to 80 years, were included. The analyzed population consisted of 36 (50%) mild HA, 10 (14%) moderate HA, and 25 (35%) severe HA patients. Factor VIII inhibitors were detected in 7 cases. Surgical procedures included 27 coronary artery bypass grafting procedures, 15 valve surgeries, 8 combined coronary artery bypass grafting with valve surgery procedures (1 with left ventricular assist device), 1 ventricular aneurysm resection with valve surgery, 11 corrections of congenital heart disease, 7 adult aortic surgeries, 3 heart transplantations, and 1 repair of heart injury. Factor VIII concentrates were used as a substitution therapy to ensure normalization of perioperative coagulation function. Although an uneventful clinical outcome was achieved in the majority of cases, 20% of patients developed complications with different severities.

CONCLUSIONS

Execution of a perioperative management strategy with a multidisciplinary approach, a thorough factor replacement protocol, and careful monitoring of factor levels facilitate an optimal outcome for HA patients undergoing cardiac surgery.

Surfing the Blood Coagulation Cascade: Insight into the Vital Factor Xa

Factor Xa (FXa) plays a key role in haemostasis, it is a central part of the blood coagulation cascade which catalyzes the production of thrombin and leads to clot formation and wound closure. Therefore, FXa is an attractive target for the development of new anticoagulant agents. In this review, we will first describe the molecular features of this fundamental protein in order to understand its mechanism of action, an essential background for the design of novel inhibitors by means of synthetic organic chemistry or using peptides obtained from recombinant methodologies. Then, we will review the current state of the synthesis of novel direct FXa inhibitors along with their mechanisms of action. Finally, approved reversal agents that aid in maintaining blood haemostasis by using these commercial drugs will also be discussed.

Clinical utility of viscoelastic testing (TEG and ROTEM analyzers) in the management of old and new therapies for hemophilia

Hemophilia A and B are rare inherited bleeding disorders resulting from deficiency of coagulation factors VIII and IX respectively. In the past few decades, the field of hemophilia has witnessed pivotal management challenges and therapeutic advances. Routine coagulation and factor assays, while useful in the classification of severity and treatment monitoring in hemophilia patients, have been shown to be of limited use in managing clinical presentations and outcomes. This prompted the investigation of viscoelastic studies in hemophilia care, which have established their utility in various bleeding and thrombotic states. In this review, we will discuss and critically assess the current literature highlighting the use of viscoelastic studies in various aspects of hemophilia including the determination of clinical phenotype, management of patients with inhibitors, perioperative management, and monitoring of novel agents.

Protein-Engineered Coagulation Factors for Hemophilia Gene Therapy

Hemophilia A (HA) and hemophilia B (HB) are X-linked bleeding disorders due to inheritable deficiencies in either coagulation factor VIII (FVIII) or factor IX (FIX), respectively. Recently, gene therapy clinical trials with adeno-associated virus (AAV) vectors and protein-engineered transgenes, B-domain deleted (BDD) FVIII and FIX-Padua, have reported near-phenotypic cures in subjects with HA and HB, respectively. Here, we review the biology and the clinical development of FVIII-BDD and FIX-Padua as transgenes. We also examine alternative bioengineering strategies for FVIII and FIX, as well as the immunological challenges of these approaches. Other engineered proteins and their potential use in gene therapy for hemophilia with inhibitors are also discussed. Continued advancement of gene therapy for HA and HB using protein-engineered transgenes has the potential to alleviate the substantial medical and psychosocial burdens of the disease.

Evolving Complexity in Hemophilia Management

Rapid expansion of therapeutic options have increased the complexity of hemophilia care. Previously, on-demand therapy aimed to reduce morbidity and early mortality; however, now aggressive prophylaxis, particularly in children, encourages an active lifestyle. Accurate diagnosis, recognition of early threats to musculoskeletal health, and optimization of therapy are critical for both males and females affected by hemophilia. The diversity of emerging hemophilia therapies, from modified factor protein concentrates, to gene therapy, to nonfactor hemostatic strategies, provide an exciting opportunity to target unmet needs in the bleeding disorder community.

Factor XIII cotreatment with hemostatic agents in hemophilia A increases fibrin α-chain crosslinking

Essentials Factor XIII (FXIII)-mediated fibrin crosslinking is delayed in hemophilia. We determined effects of FXIII cotreatment with hemostatic agents on clot parameters. FXIII cotreatment accelerated FXIII activation and crosslinking of fibrin and α2 -antiplasmin. These data provide biochemical rationale for FXIII cotreatment in hemophilia.

SUMMARY

Background Hemophilia A results from the absence, deficiency or inhibition of factor VIII. Bleeding is treated with hemostatic agents (FVIII, recombinant activated FVII [rFVIIa], anti-inhibitor coagulation complex [FEIBA], or recombinant porcine FVIII [rpFVIII]). Despite treatment, some patients have prolonged bleeding. FXIII-A2 B2 (FXIII) is a protransglutaminase. During clot contraction, thrombin-activated FXIII (FXIIIa) crosslinks fibrin and α2 -antiplasmin, which promotes red blood cell retention and increases clot stability and weight. We hypothesized that FXIII cotreatment in hemophilia would accelerate FXIII activation, leading to increased fibrin crosslinking. Methods FVIII-deficient plasma and whole blood were clotted with or without hemostatic agents (FVIII, rFVIIa, FEIBA, or recombinant B-domain-deleted porcine FVIII [rpFVIII]) and/or FXIII. The effects on FXIII activation, thrombin generation, fibrin and α2 -antiplasmin crosslinking, clot formation and clot weight were measured by western blotting, calibrated automated thrombography, thromboelastography, and clot contraction assays. Results As compared with FVIII-treated hemophilic plasma, FVIII + FXIII cotreatment accelerated FXIIIa formation without increasing thrombin generation. As compared with buffer-treated or FXIII-treated hemophilic plasma, FVIII treatment and FVIII + FXIII cotreatment increased the generation and amount of crosslinked fibrin, including α-chain-rich high molecular weight species and crosslinked α2 -antiplasmin. In the presence of FVIII inhibitors, as compared with hemostatic treatments (rFVIIa, FEIBA, or rpFVIII) alone, FXIII cotreatment increased whole blood clot weight. Conclusion In hemophilia A plasma and whole blood, FXIII cotreatment with hemostatic agents accelerated FXIIIa formation, increased the generation and amount of fibrin α-chain crosslinked species, accelerated α2 -antiplasmin crosslinking, and increased clot weight. FXIII cotreatment with hemostatic therapy may augment hemostasis through increased crosslinking of fibrin and α2 -antiplasmin.