On-demand treatment of bleeds in haemophilia patients with inhibitors: strategies for securing and maintaining predictable efficacy with recombinant activated factor VII

Intracranial Hemorrhages in Neonates: Incidence, Risk Factors and Treatment

Hemostasis is a dynamic process that starts in utero. Neonates, especially those who are born preterm, are at high risk of bleeding. The coagulation system evolves with age, and the decreased levels of coagulation factors along with hypo-reactive platelets are counterbalanced with increased activity of von Willebrand factor, high hematocrit and mean corpuscular volume as well as low levels of coagulation inhibitors that promote hemostasis. Neonates with congenital bleeding disorders such as hemophilia are at even higher risk of bleeding complications. This review will focus upon one of the most devastating complications associated with neonatal bleeding: intracranial hemorrhages (ICH). While etiology may be multifactorial and impacted by maternal as well as fetal risk factors, the mode of delivery certainly plays an important role in the pathogenesis of ICH. We will address prematurity and congenital bleeding disorders such as hemophilia A and B and other rare bleeding disorders as risk factors and present an updated approach for treatment and possible prevention.

Barriers and challenges for the fast treatment of bleeds in the non-haemophilia treatment centre hospital setting

INTRODUCTION

Early treatment for acute bleeds in patients with haemophilia and inhibitors is feasible when patients are managed in haemophilia treatment centres (HTCs). Patients may need to attend non-HTCs for out-of-hours emergency care, especially if HTCs are not local and/or transport is difficult.

AIM

We evaluated the barriers to the fast treatment of bleeds in patients with haemophilia and inhibitors presenting at non-HTCs.

METHODS

Healthcare professionals (HCPs) from non-HTCs in the United States (n = 218) and Germany (n = 98) were selected from validated online panels and invited to participate in a survey (October-November 2017).

RESULTS

A mean of 6 (US) and 5 (German) patients with haemophilia and inhibitors were managed for bleeds by these HCPs over 12 months; patient characteristics were similar in both countries. The main HCPs involved in treating bleeds were emergency room specialists (94%) and haematologists (91%) (US); haematologists (79%) and anaesthesiologists (59%) (Germany). Only 26% (US) and 28% (Germany) of HCPs had access to treatment guidelines for these patients; access to bypassing agents was similarly limited: 44% (US) and 38% (Germany) of HCPs reported their institution did not stock these agents. In both countries, key reasons for delaying treatment were lack of bypassing agent availability, HCP experience/education of bleed disorders and internal process time.

CONCLUSION

Barriers to fast treatment of bleeds in patients with haemophilia and inhibitors were identified in non-HTCs in the United States and Germany. These could be reduced by improving the availability of treatment guidelines, bypassing agents and HCP education/training.

The evolution of factor VIIa in the treatment of bleeding in haemophilia with inhibitors

The use of activated factor VII (FVIIa) for the treatment of bleeding events in haemophilia patients with inhibitors was first reported over 30 years ago. Since then clinical trials, registries, case series, real‐world experience and an understanding of its mechanism of action have transformed what was originally a scientific curiosity into one of the major treatments for inhibitor patients, with innovative therapeutic regimens, dose optimization and individualized care now widely practiced. Given current understanding and use, it might be easy to forget the years of clinical research that led up to this point; in this review, we lay out changes based on broad eras of rFVIIa use. These eras cover the original uncertainty associated with dosing, efficacy and safety; the transformation of care ushered in with its widespread use; and the optimization and individualization of patient care and the importance of specialized support provided by haemophilia treatment centres. Today with the introduction of novel prophylactic agents such as emicizumab, we once again find ourselves dealing with the uncertainties of how best to utilize rFVIIa and newer investigational variants such as marzeptacog alfa and eptacog beta; we hope that the experiences of the past three decades will serve as a guide for this new era of care.

The future of bypassing agents for hemophilia with inhibitors in the era of novel agents

Bypassing agents are presently the standard of care for the treatment of bleeding episodes in patients with hemophilia and high-titer inhibitors and are also used for bleed prevention. Only two bypassing agents are available to patients, and these products trace their lineage to the 1970s (activated prothrombin complex concentrates) and the 1980s (recombinant factor VIIa). Given the limited repertoire of available products, clinicians have relied on experience, empirical observation, registry data and individualized care to improve clinical outcomes on a case-by-case basis. Research over the past two decades has culminated in a greatly improved understanding of human coagulation; resulting from this, new products have been developed that offer treatment options and mechanisms of actions that differ from current bypassing agents. The most advanced in clinical development is emicizumab, a bispecific antibody that mimics the function of FVIIIa in the intrinsic Xase complex and is indicated for once-weekly or every-other-week prophylactic dosing in inhibitor patients. Other non-traditional products in clinical development include fitusiran and antibodies directed against tissue factor pathway inhibitor. As non-factor-based therapies become more widely utilized over time, the use of bypassing agents may be expected to decrease; however, bypassing agents will remain essential for the foreseeable future. As such, clinical development of bypassing agents continues, with some products (e.g. eptacog beta) under regulatory review. In this review we examine the optimal use of bypassing agents and their mechanism of action. We also discuss newer products and how these might theoretically be administered in conjunction with traditional bypassing agents.

Sustained pro-haemostatic activity of rFVIIa in plasma and platelets in non-bleeding pigs may explain the efficacy of a once-daily prophylaxis in humans

Recombinant factor VIIa (rFVIIa) is registered for treatment of inhibitor-complicated haemophilia, and a once-daily prophylactic administration of rFVIIa is successful in reducing the number of bleeding events. This suggests that a single rFVIIa dose has a pro-haemostatic effect up to 24 hours (h), which is difficult to explain given its half-life of 2 h. In this study, six pigs received a 90 µg/kg rFVIIa bolus. Plasma was collected and platelets were isolated at various time points up to 48 h, and analysed for FVIIa levels and associated haemostatic activity. Elevated plasma FVIIa levels were detected up to 24 h post-administration (36 (32–56) mU/ml [median (interquartile range [IQR]), 24 h] vs 2 (2–14) mU/ml [baseline]). Corresponding prothrombin time (PT) values remained shortened compared to baseline until 24 h post-administration (9.4 (9.3–9.9) seconds (s) [24 h] vs 10.5 (10.2–11.0) s [baseline], p ≤0.01). The lag time in thrombin generation testing as well as clotting times in plasma-based assays were shortened up to 12 or 24 h post-administration, respectively (lag times 1.8 (1.7–2.1) minutes (min) [12 h] vs 2.3 (2.3–2.6) min [baseline], p ≤0.01 and clotting times 3.8 (3.2–3.9) min [24 h] vs 5.2 (4.6–5.5) min [baseline], p ≤0.001). Platelet FVIIa levels were elevated up to 48 h (7.7 (3.4–9.0) ng VIIa/mg actin [48 h] vs 2.5 (0.7–4.8) ng VIIa/mg actin [baseline]). In conclusion, elevated and haemostatically active plasma and platelet FVIIa levels are detectable up to 24–48 h following rFVIIa administration in pigs. This prolonged pro-haemostatic effect of FVIIa may explain the prophylactic efficacy of a once-daily rFVIIa treatment.

Rapid rFVIIa enhanced on-demand dosing in haemophilia inhibitor patients

Recombinant factor VII activated (rFVIIa) is a bypassing agent widely used in haemophilia A and B patients with antibodies against coagulation factors VIII or IX. When used according to the correct doses, rFVIIa may control bleeding, subclinical bleeding and rebleeding, avoiding the effect of neutralising inhibitors. Because of the fast action of the rFVIIa, haemostasis occurs promptly and enables a fast bleeding control with on-demand treatment in home or in surgical setting. Rapidity is also a distinguishing feature in preparation and injection of rFVIIa to cope the restraining times of busy patients and parents. The effective haemostatic activity of rFVIIa enables a sustained bleeding control, which is implemented with every other day (eod) administration and suited for enhanced on-demand therapy and short-term repeated infusions use of rFVIIa to prevent microhaemorrhages or rebleeding. Comprehensive appreciation of these pharmacological and pharmacodynamic' characteristics will likely be a further stimulus to the wider enhanced on-demand use of rFVIIa.

Combination of FVIII and low-dose rFVIIa improves haemostasis in acquired haemophilia A patients: a collaborative controlled study

INTRODUCTION

Acquired haemophilia A (AHA) is an autoimmune disease that potentially leads to severe bleeding and has a high rate of mortality. This collaborative study aimed to assess the efficacy of the co-administration of FVIII and low-dose rFVIIa in patients with AHA.

MATERIALS AND METHODS

This study retrospectively compared the combined FVIII/low-dose rFVIIa therapy (initial dose range of 25-55μg/Kg) with the combined FVIII/PCC therapy and low-dose rFVIIa monotherapy. Adverse drug reactions and recurrent bleeding episodes were also monitored. Crude comparisons and the exact conditional logistic regression were performed to compare the outcomes between three treatment groups.

RESULTS

First bleeding episodes of 56 consecutive patients from 5 centres were analyzed, and 37 bleeding episodes (66.1%) were determined to be severe. Specifically, the rate of bleeding control was significantly higher with the FVIII/low-dose rFVIIa therapy compared to that of the low-dose rFVIIa alone therapy or the FVIII/PCC therapy (58.3% vs. 41.7% vs. 95.0%, respectively). Analyzing of total 236 bleeding episodes showed a clear positive association between the early initiation of haemostatic treatment and efficacy. No therapy-related adverse events in which thrombosis predominated were reported.

CONCLUSIONS

The combination of FVIII and low-dose rFVIIa offers an ideal haemostatic cover and may be promoted as a feasible and safe therapy protocol for patients with AHA.

Safety and pharmacokinetics of a recombinant fusion protein linking coagulation factor VIIa with albumin in healthy volunteers

BACKGROUND

Development of neutralizing antibodies remains the most problematic complication in treating congenital hemophilia. Control and prevention of bleeding events in such patients with recombinant factor VIIa (rFVIIa) is limited by the short half-life of the available product. Here, we report on the pharmacokinetics and safety of a novel, recombinant fusion protein linking coagulation FVIIa with albumin (rVIIa-FP) in a first-in-human study in healthy male subjects.

METHODS

Forty healthy male subjects between 18 and 35 years of age were included and dosed in five consecutive cohorts. In each cohort, six subjects were randomized to a single dose of rVIIa-FP (140, 300, 500, 750, or 1000 μg kg(-1) ) and two to placebo. All subjects received anticoagulation with an oral vitamin K antagonist to reach an international normalized ratio between 2 and 3 prior to dosing with rVIIa-FP/placebo. Dosing with oral vitamin K antagonist was continued at a fixed dose for 6 days after injection of rFVIIa.

RESULTS AND CONCLUSIONS

Tolerance of rVIIa-FP was good at all dose levels. No serious adverse events were observed. None of the subjects developed anti-drug antibodies. The maximum baseline-corrected mean (SD) FVIIa plasma activity increased in a dose-proportional manner. Across the dose range, the median half-life was consistent, ranging from 6.1 to 9.7 h. At the highest dose of 1000 μg kg(-1) , the median FVIIa activity-based half-life was 8.5 h. Clearance ranged from 7.62 to 12.74 mL h(-1) kg(-1) . Compared with the commercially available rFVIIa product, rVIIa-FP had a reduced clearance resulting in an approximately 3- to 4-fold increase in half-life.

Barriers and perceived limitations to early treatment of hemophilia

Early treatment of bleeds in hemophilia patients, both with and without inhibitors, has been shown to be of immense benefit in the overall clinical outcome. Despite the advantages of treating the bleeding episodes early, significant barriers and limitations remain. The aim of this review is to highlight the various barriers and perceived limitations to early therapy of bleeding episodes, especially in patients who have developed inhibitors to factor VIII. The peer-reviewed literature was searched for articles on hemophilia patients, with and without inhibitors, and early treatment, to identify the barriers to early treatment and potential impact on patient outcomes. The most important barrier is the educational barrier, which involves lack of awareness among patients regarding the signs of a bleed, as well as importance of early therapy. It is also common for parents or caregivers of school-age children to exhibit inconvenience and scheduling barriers. Distance to the treatment center can also play a role here. Some patients experience financial barriers related to cost of clotting factor products, insurance coverage, or insurance caps and out-of-pocket costs. Rarely, there can also be problems related to venous access or home infusion. Lastly, multiple psychosocial barriers can prevent adherence to treatment regimens. Identification and addressing these individual barriers will result in improved compliance rates, prevent joint damage, be more cost-effective, and lead to better overall health of these patients.

Successful management of total knee replacement in a high responder hemophilia patient with a history of inhibitor

The development of inhibitors against administered clotting factors may render replacement therapy ineffective for some hemophilia patients. Such patients are therefore at the highest risk of developing arthropathy. Elective orthopedic surgery (EOS) in hemophilic patients having such inhibitors remains a rare, expensive, and difficult surgery, whose management represents a significant challenge. We report the case of a 35-year-old man with a severe form of hemophilia A (factor VIII < 1%), who was suffering from repetitive spontaneous hemarthrosis, especially in his knee joints that had consequently become more susceptible to bleeding. The patient had a history of high levels of factor VIII inhibitor (> 5.0 Bethesda Unit [BU]/ml) as shown by the factor VIII inhibitor assay; therefore, we began treatment with factor VIIa for his mild-to-moderate bleeding (90 µg/kg intravenous bolus injections). The interval between injections varied with the severity of the hemorrhage in each bleeding episode. The inhibitor level reduced to 3.1 BU/ml after three months, to 1.6 BU/ml after six months, and disappeared completely after one year of treatment. We administered factor VIII at a dose of 50 IU/kg every eight hours during the first three post-operative days, then continued administration with a dose of 40 IU/kg every 12 hours for another four days, and observed a very good response to treatment with no bleeding. Recombinant activated factor VII (rFVIIa) is not an inhibitor-removal strategy, but an inhibitor-bypassing product. However, in our patient, the treatment of mild-to-moderate bleeding with short-term use of rFVIIa and no exposure to factor VIII caused a gradual reduction in the inhibitor level over a period of 1 year.