A postmarketing surveillance study of the safety and efficacy of ReFactoR (St Louis-derived active substance) in patients with haemophilia A

Outcomes for studies assessing the efficacy of hemostatic therapies in persons with congenital bleeding disorders

INTRODUCTION

Management strategies and hemostatic treatments to achieve control of bleeding are relevant across many disease areas. Identification of primary outcomes for studies assessing hemostatic intervention was the objective of a National Heart, Lung and Blood Institute (NHLBI) sponsored multidisciplinary initiative. The aim of this report is to summarize the evidence reviewed, and the outcomes identified by the subgroup tasked to assess outcomes for inherited bleeding disorders.

METHODS

The subgroup decided to focus on haemophilia, the prototypal congenital bleeding disorder and the one with the largest available body of evidence. MEDLINE, EMBASE and PsycINFO, The Cochrane Review, CINAHL, and Web of Science were searched for systematic and narrative reviews on outcomes used in haemophilia clinical trials. Three different clinical goals were identified as typical objectives of future research.

RESULTS

Out of 1322 unique citations, 24 reviews published in the period 2002-2019 were included. We identified 113 outcome measures, categorized in 6 domains: health-related quality of life (HRQoL), comorbidities and mortality, overall physical functioning and participation, bleeding and hemostasis, joint health, and costs and resource use. Three different clinical goals were identified as typical objectives of future research: Episodic 'on demand' replacement therapy, prevention of bleeding (Prophylaxis), and long-term and overall impact of bleeding. For each of these scenarios, specific outcomes were recommended.

CONCLUSIONS

Primary outcomes for clinical trials assessing the efficacy of hemostatic treatment in achieving control, prevention and limiting long-term consequences of bleeding in inherited bleeding disorders are suggested, and their strength and limitations discussed.

Natural history and clinical characteristics of inhibitors in previously treated haemophilia A patients: a case series

BACKGROUND

Development of inhibitors is the most serious complication in haemophilia A treatment. The assessment of risk for inhibitor formation in new or modified factor concentrates is traditionally performed in previously treated patients (PTPs). However, evidence on risk factors for and natural history of inhibitors has been generated mostly in previously untreated patients (PUPs). The purpose of this study was to examine cases of de novo inhibitors in PTPs reported in the scientific literature and to the EUropean HAemophilia Safety Surveillance (EUHASS) programme, and explore determinants and course of inhibitor development.

METHODS

We used a case series study design and developed a case report form to collect patient level data; including detection, inhibitor course, treatment, factor VIII products used and events that may trigger inhibitor development (surgery, vaccination, immune disorders, malignancy, product switch).

RESULTS

We identified 19 publications that reported 38 inhibitor cases and 45 cases from 31 EUHASS centres. Individual patient data were collected for 55/83 (66%) inhibitor cases out of 12 330 patients. The median (range) peak inhibitor titre was 4.4 (0.5-135.0), the proportion of transient inhibitors was 33% and only two cases of 12 undergoing immune tolerance induction failed this treatment. In the two months before inhibitor development, surgery was reported in nine (22%) cases, and high intensity treatment periods reported in seven (17%) cases.

CONCLUSIONS

By studying the largest cohort of inhibitor development in PTPs assembled to date, we showed that inhibitor development in PTPs, is on average, a milder event than in PUPs.

Results from a large multinational clinical trial (guardian™1) using prophylactic treatment with turoctocog alfa in adolescent and adult patients with severe haemophilia A: safety and efficacy

Recombinant factor VIII (rFVIII) products provide a safe and efficacious replacement therapy for prophylaxis and treatment of bleeding episodes in patients with severe haemophilia A. This multinational, open-label, non-controlled trial investigated the safety and efficacy of turoctocog alfa, a new rFVIII product. The primary objective was to evaluate safety. A total of 150 patients (24 adolescents and 126 adults) with severe haemophilia A (FVIII activity ≤ 1%), with at least 150 exposure days (EDs) to any FVIII product and no history of inhibitors were enrolled, and 146 patients (97%) completed the trial. All patients received prophylaxis with turoctocog alfa for approximately 6 months and had a mean of 85 EDs during the trial. None of the patients developed FVIII inhibitors, there were no indications of early FVIII inhibitor development and no safety concerns were identified. A total of 225 adverse events were reported in 100 (67%) patients, with the most common being events associated with dosing procedures, headaches, and nasopharyngitis. A total of 499 bleeding episodes were reported during the trial, the majority (89%) were controlled with 1-2 infusions of turoctocog alfa. Based on patient reports, the success rate (defined as 'excellent' or 'good' haemostatic response) for treatment of bleeding episodes was 81%. The overall median annualized bleeding rate was 3.7 (interquartile range: 8.7) bleeds/patient/year. In conclusion, turoctocog alfa provides a new, safe and effective alternative for prophylaxis and treatment of bleeding episodes in patients with haemophilia A.

Can B-domain deletion alter the immunogenicity of recombinant factor VIII? A meta-analysis of prospective clinical studies

BACKGROUND

As a result of the infrequency of inhibitors in previously treated patients (PTPs) with hemophilia A and the small size of available clinical studies, the immunogenicity of factor (F)VIII products has been difficult to assess.

OBJECTIVES

A meta-analysis of prospective clinical studies was conducted to test the hypothesis that de novo inhibitor incidence differs between PTPs receiving full-length recombinant FVIII (FL-rFVIII) and B-domain deleted recombinant FVIII (BDD-rFVIII).

METHODS

Prospective studies with data on inhibitors in PTPs receiving FL-rFVIII or BDD-rFVIII were sought using systematic methods including bibliographic database searches. Data were secured from published study reports and inquiries to investigators. Between-group differences in inhibitor incidence rates were evaluated using mixed effects Cox regression.

RESULTS

Twenty-nine studies with 3012 total PTPs were included. Patients were at risk of de novo inhibitor development for a median of 79 exposure days. A total of 35 de novo inhibitors were observed. The cumulative hazard for all de novo inhibitors was 1.25% with a 95% confidence interval (CI) of 0.63-1.88%. The corresponding rate for high-titer de novo inhibitors [> 5 Bethesda units (BU)] was 0.29% (CI, 0.01-0.57%). Exposure to BDD-rFVIII was associated with an increased risk of all de novo inhibitors (hazard ratio, 7.26; CI, 2.12-24.9; P = 0.0016) and of high-titer de novo inhibitors (hazard ratio, 10.8; CI, 2.17-53.7; P = 0.0037), compared with FL-rFVIII.

CONCLUSIONS

This meta-analysis of prospective clinical studies suggests that recombinant FVIII products may differ in immunogenicity.

Functional roles of the factor VIII B domain

Unravelling the structure, function and molecular interactions of factor VIII (FVIII) throughout its life cycle from biosynthesis to clearance has advanced our understanding of the molecular mechanisms of haemophilia and the development of effective treatment strategies including recombinant replacement therapy. These insights are now influencing bioengineering strategies toward novel therapeutics. Whereas available molecular models and crystal structures have helped elucidate the structure and function of the A and C domains of FVIII, these models have not included detailed structural information of the B domain. Therefore, insights into the role of the FVIII B domain have come primarily from expression studies in heterologous systems, biochemical studies on bioengineered FVIII variants and clinical studies with B domain-deleted FVIII. This manuscript reviews the available data on the potential functional roles of the FVIII B domain. A detailed literature search was performed, and the data extracted were qualitatively summarized. Intriguing emerging evidence suggests that the FVIII B domain is involved in intracellular interactions that regulate quality control and secretion, as well as potential regulatory roles within plasma during activation, platelet binding, inactivation and clearance.

Haemophilia in the first years of life

Surgery in infants and young children with haemophilia, when preceded by accurate diagnosis and accompanied by safe and effective factor prophylaxis, is not associated with a significant risk of haemorrhage. Haemophilic newborns undergoing circumcision or major surgery prior to diagnosis and in the absence of appropriate haemostatic prophylaxis remain as a concern. Inhibitor development has replaced haemorrhage as the major surgical complication in the developed world, largely because of the intensity of treatment used to secure haemostasis. For that reason only, essential surgery should be performed. Intracranial haemorrhage (ICH) during the neonatal period affects 3.5-4.0% of all haemophilia boys in countries with a good standard of health care, which is considerably (40-80 times) higher than expected in the normal population. Because of the high frequency of sporadic cases, ICH in the neonatal period can only be partially prevented by improved carrier diagnosis and counselling. Infections and thrombosis are the major serious complications of central venous lines. Large differences are seen in the frequency of these complications, the most plausible explanations are probably related to the protocol used for device care, the quality of education and the compliance of the users, an issue addressed in an on-going study.

Factor VIII recovery after a single infusion of recalibrated ReFacto�in 14 severe haemophilia A patients

A recent multicentre collaborative study showed higher estimates of ReFacto potency when assayed with ReFacto Laboratory Standard(TM) (RLS) in comparison when standards consisting of full-length factor VIII (FVIII) were used. The RLS was hence recalibrated, leading to a 20% increase in the amount of ReFacto per vial without change in the labelled potency. The primary objective of this study was to determine the incremental and in vivo recovery of the recalibrated ReFacto in patients with severe haemophilia A. Fourteen male severe haemophilia A patients (FVIII < 1 IU dL(-1)) with a cumulative previous exposure days to any FVIII product >150 were administered an intravenous infusion 50 +/- 5 IU kg(-1) of ReFacto over a 5-min period. Blood samples were collected before infusion and after 15, 30 and 60 min. FVIII clotting activity (FVIII:C) was assessed in a central laboratory by the chromogenic substrate assay. After ReFacto infusion, peak FVIII:C was obtained within 15 min for 10 patients and within 30 min for the remaining four. Mean FVIII:C at peak was 117.7 +/- 17.3 IU dL(-1). Mean incremental recovery was 2.22 +/- 0.27 IU dL(-1) per IU kg(-1) while mean in vivo recovery was 105.9 +/- 14.6%. One patient reported three mild adverse events rated as 'unrelated' to the study drug. FVIII recovery after recalibrated ReFacto infusion falls within the expected range and is similar to the values reported for other FVIII concentrates.

Efficacy, safety and tolerability of recombinant factor VIII (REFACTO�) in patients with haemophilia A: interim data from a postmarketing surveillance study in Germany and Austria

An open-label, multicentre, postmarketing surveillance study conducted in Germany and Austria with recombinant factor VIII (REFACTO) has enrolled 217 patients (mean age 26.3 years) from 38 haemophilia centres during the first 4.8 years. Most patients (188/217; 86.6%) had severe to moderately severe haemophilia A, of whom 153 completed sufficient diary information for the main efficacy analysis. These 153 patients experienced a median of 6.6 (interquartile range 1.4-18.6) bleeding episodes per year. Patients treated with prophylaxis experienced a median of 4.4 (1.1-9.3) bleeds per year, while patients treated on-demand experienced a median of 22.8 (11.3-29.0) bleeds per year. Overall, most physicians (41/43 [95.3%]) were 'very satisfied' or 'satisfied' with the efficacy of REFACTO in the treatment of bleeding episodes. A total of 137 non-serious adverse events have been reported in 52/217 patients (24.0%) to date. In addition, 129 serious adverse events in 87 patients (40%) were reported, including 41 cases of 'less than expected therapeutic effect' (LETE). Of these, 39 LETE cases were reported in one centre; however, patients in this centre experienced considerably fewer bleeding episodes per year than patients outside this centre. Overall, six patients (2.8%) have developed de novo inhibitors, three of which were considered high titre. Four of these patients were at high risk (0-50 exposure days [ED]) of inhibitor formation, one was at intermediate risk (51-100 ED) and one was at low risk (>100 ED). These results emphasize the benefit of postmarketing surveillance and, overall, this study confirms the efficacy, safety and tolerability of REFACTO in the treatment of patients with haemophilia A.

Clinical Evaluation of Recombinant Factor VIII Preparation (Kogenate) in Previously Treated Patients with Hemophilia A: Descriptive Meta-Analysis of Post-Marketing Study Data

The safety and efficacy of Kogenate, a recombinant factor VIII (rFVIII) preparation for the treatment of bleeding episodes, were studied in a 123-patient meta-analysis population of previously treated patients (PTPs), including 15 enrolled in the registration Phase III trial (PTP-I group), 93 from the post-marketing special investigation (PTP-II group), and 15 from short-term special investigations in surgery or tooth extraction (SI group). These patients (82 severe, 31 moderate, 9 mild, and 1 unknown), aged 11 months to 72 years, were enrolled in 28 centers in Japan. Blood samples taken at the baseline and at 3, 6, 9, 12, 18, and 24 months after the introduction of Kogenate were evaluated for FVIII inhibitor antibodies, antibodies formed against trace proteins derived from the rFVIII production process, and for general changes in laboratory test results. Mean exposure to Kogenate was 1103 days in PTP-I, 86 days in PTP-II, 27 days in patients in surgery, and 2 days in patients with tooth extraction. Assessment of FVIII inhibitor activity was conducted in 115 of the 123 patients by means of the Bethesda assay. Twelve patients were found to have a low titer of FVIII inhibitor (0.5-3.0 BU/mL) prior to any administration of Kogenate, and 103 were inhibitor-negative at the baseline. Among this latter group, 3 patients (2.9%) tested inhibitor-positive, with titers ranging from 1.2 to 2.1 BU/mL, with 4 patients below 1.0 BU/mL. One patient in the 11 PTPs investigated (PTP-I) developed antibodies against baby hamster kidney protein and mouse immunoglobulin G, but these findings were transient and asymptomatic. Hemostasis was achieved (markedly effective or effective) in 3666 of the 3855 bleeding episodes (95.1%) observed in 108 patients. Only 1 infusion was necessary in 3790 (98.3%) of these episodes. These data indicate that Kogenate is safe and very effective for the treatment of bleeding in PTPs with hemophilia A.