Brian M. Wicklund

A Randomized Trial of Factor VIII and Neutralizing Antibodies in Hemophilia A.

BACKGROUND The development of neutralizing anti-factor VIII alloantibodies (inhibitors) in patients with severe hemophilia A may depend on the concentrate used for replacement therapy. METHODS We conducted a randomized trial to assess the incidence of factor VIII inhibitors among patients treated with plasma-derived factor VIII containing von Willebrand factor or recombinant factor VIII. Patients who met the eligibility criteria (male sex, age <6 years, severe hemophilia A, and no previous treatment with any factor VIII concentrate or only minimal treatment with blood components) were included from 42 sites. RESULTS Of 303 patients screened, 264 underwent randomization and 251 were analyzed. Inhibitors developed in 76 patients, 50 of whom had high-titer inhibitors (≥5 Bethesda units). Inhibitors developed in 29 of the 125 patients treated with plasma-derived factor VIII (20 patients had high-titer inhibitors) and in 47 of the 126 patients treated with recombinant factor VIII (30 patients had high-titer inhibitors). The cumulative incidence of all inhibitors was 26.8% (95% confidence interval [CI], 18.4 to 35.2) with plasma-derived factor VIII and 44.5% (95% CI, 34.7 to 54.3) with recombinant factor VIII; the cumulative incidence of high-titer inhibitors was 18.6% (95% CI, 11.2 to 26.0) and 28.4% (95% CI, 19.6 to 37.2), respectively. In Cox regression models for the primary end point of all inhibitors, recombinant factor VIII was associated with an 87% higher incidence than plasma-derived factor VIII (hazard ratio, 1.87; 95% CI, 1.17 to 2.96). This association did not change in multivariable analysis. For high-titer inhibitors, the hazard ratio was 1.69 (95% CI, 0.96 to 2.98). When the analysis was restricted to recombinant factor VIII products other than second-generation full-length recombinant factor VIII, effect estimates remained similar for all inhibitors (hazard ratio, 1.98; 95% CI, 0.99 to 3.97) and high-titer inhibitors (hazard ratio, 2.59; 95% CI, 1.11 to 6.00). CONCLUSIONS Patients treated with plasma-derived factor VIII containing von Willebrand factor had a lower incidence of inhibitors than those treated with recombinant factor VIII. (Funded by the Angelo Bianchi Bonomi Foundation and others; ClinicalTrials.gov number, NCT01064284; EudraCT number, 2009-011186-88.).

The use of a single von Willebrand factor-containing, plasma-derived FVIII product in hemophilia A immune tolerance induction: the US experience.

Summary.  Background: Inhibitors are a serious complication for patients with severe hemophilia A. Immune tolerance induction (ITI) is the primary method for eradicating these inhibitors. The role of type of concentrate and in particular the use of von Willebrand factor‐containing, plasma‐derived factor VIII (VWF/pd‐FVIII) concentrate in primary or rescue ITI remains unclear. Objectives: To report retrospective collection of data on the use of a single VWF/pd‐FVIII concentrate in primary and rescue ITI. Methods: Retrospective chart review of hemophilia A inhibitor patients at 11 US institutions who received VWF/pd‐FVIII concentrate in primary or rescue ITI. Results: Primary ITI was carried out in eight inhibitor patients with a 75% complete and partial success. Secondary ITI was carried out in 25 inhibitor patients, with 52% attaining complete or partial success. Conclusions: This report represents the largest group of primarily pediatric, high‐titer inhibitor patients treated with a single VWF/pd‐FVIII concentrate. It adds retrospective data to the use of VWF‐containing plasma‐derived factor VIII concentrate in primary and rescue ITI, particularly in those patients with characteristics of poor response to ITI.

A study of prospective surveillance for inhibitors among persons with haemophilia in the united states

Inhibitors are a rare but serious complication of treatment of patients with haemophilia. Phase III clinical trials enrol too few patients to adequately assess new product inhibitor risk. This project explores the feasibility of using a public health surveillance system to conduct national surveillance for inhibitors. Staff at 17 U.S. haemophilia treatment centres (HTC) enrolled patients with haemophilia A and B into this prospective study. HTC staff provided detailed historic data on product use and inhibitors at baseline, and postenrolment patients provided monthly detailed infusion logs. A central laboratory performed inhibitor tests on blood specimens that were collected at baseline, annually, prior to any planned product switch or when clinically indicated. The central laboratory also performed genotyping of all enrolled patients. From January 2006 through June 2012, 1163 patients were enrolled and followed up for 3329 person‐years. A total of 3048 inhibitor tests were performed and 23 new factor VIII inhibitors were identified, 61% of which were not clinically apparent. Infusion logs were submitted for 113 205 exposure days. Genotyping revealed 431 distinct mutations causing haemophilia, 151 of which had not previously been reported elsewhere in the world. This study provided critical information about the practical issues that must be addressed to successfully implement national inhibitor surveillance. Centralized testing with routine monitoring and confirmation of locally identified inhibitors will provide valid and representative data with which to evaluate inhibitor incidence and prevalence, monitor trends in occurrence rates and identify potential inhibitor outbreaks associated with products.

Off-label use of rFVIIa in children with excessive bleeding: A consecutive study of 153 off-label uses in 139 children

Recombinant factor VIIa is a general hemostatic agent. Randomized trials have demonstrated effectiveness in adults; however, data in children are confined to case reports and series subject to publication bias.

Comparison of clot-based, chromogenic and fluorescence assays for measurement of factor VIII inhibitors in the US Hemophilia Inhibitor Research Study

Detection and validation of inhibitors (antibodies) to hemophilia treatment products are important for clinical care, evaluation of product safety and assessment of population trends.

Prophylactic versus reactive transfusion of thawed plasma in patients undergoing surgical repair of craniosynostosis: a randomized clinical trial

Surgical repair of craniosynostosis in young children is associated with copious bleeding and often coagulopathy. Typically, a reactive transfusion strategy is used to treat coagulopathy whereby fresh frozen plasma (FFP) is given only after clinical manifestation of clotting abnormality. This prospective, randomized clinical trial was designed to test the hypothesis that prophylactic FFP during craniofacial surgery reduces blood loss and blood transfusion requirements compared to a reactive FFP transfusion strategy.

Limit of detection and threshold for positivity of the Centers for Disease Control and Prevention assay for factor VIII inhibitors

Essentials Immunologic methods detect factor VIII (FVIII) antibodies in some inhibitor‐negative specimens. Specimens were tested by modified Nijmegen‐Bethesda assay (NBA) and fluorescence immunoassay. The NBA with preanalytical heat inactivation detects FVIII inhibitors down to 0.2 NBU. IgG4 frequency validates the established threshold for positivity of ≥ 0.5 NBU for this NBA.

Use of pharmacokinetic modelling to individualize FFP dosing in factor V deficiency

Therapy with fresh frozen plasma (FFP) confers serious risks, such as contraction of blood‐borne viruses, allergic reaction, volume overload and development of alloantibodies. The aim of this study was to apply principles of pharmacokinetic (PK) modelling to individual factor content of FFP to optimize individualized dosing, while minimizing potential risks of therapy. We used PK modelling to successfully target individual factor replacement in an 8‐month‐old patient receiving FFP for treatment of a severe congenital factor V (FV) deficiency. The model fit for the FV activity vs. time data was excellent (r = 0.98) and the model accurately predicted FV activity during the intraoperative and postoperative period. Accurate PK modelling of individual factor activity in FFP has the potential to provide better targeted therapy, enabling clinicians to more precisely dose patients requiring coagulation products, while avoiding wasteful and expensive product overtreatment, minimizing potentially life‐threatening complications due to undertreatment and limiting harmful product‐associated risks.

Hepatitis B vaccination is effective by subcutaneous route in children with bleeding disorders: a universal data collection database analysis

Subcutaneous (SQ) vs. intramuscular (IM) vaccination may cause fewer injection site complications in children with bleeding disorders, but little is known about comparative immunogenicity. To compare immunogenicity of hepatitis B virus (HBV) vaccination administered SQ or IM to individuals <2 years old with bleeding disorders, we performed a retrospective analysis of HBV surface antibody titres among patients enrolled in the universal data collection database who had received three doses of HBV vaccine solely by one route (SQ or IM). Data reviewed were from an initial visit before 24 months of age, until time of hepatitis antibody titre testing. The SQ and IM study groups did not differ in demographics, haemophilia type or severity or bleeding history. The mean age at the time of HBV surface antibody (anti‐HBs) testing was 56.9 ± 20.3 months. Eighty‐five of 92 subjects (92.4%) who received vaccine SQ developed a positive antibody titre (>12 IU/L), compared to 101/114 (88.6%) who received IM (P = 0.30). There was no statistically significant difference in distribution of titre values. The average age of the subjects at time of testing was 53 ± 20 months in the SQ group vs. 60 ± 20 months in the IM group (P = 0.02). The average time between the last dose of vaccine and anti‐HBs testing was 47.6 ± 18.5 months among SQ vaccinated subjects vs. 51.6 ± 20.5 months in the IM group (P = 0.2). Immunogenicity to hepatitis B vaccination by the SQ and IM routes is similar.

The impact of thromboelastography on resuscitation in pediatric liver transplantation

Although TEG directs effective resuscitation in adult surgical patients, pediatric data are lacking. We performed a retrospective comparative review of the effect of TEG on blood product utilization and outcomes following pediatric liver transplantation in 38 patients between 2008 and 2014. Diagnoses, laboratory values, fluid and blood product use, and outcomes were examined. Nineteen patients underwent liver transplantation prior to the implementation of TEG, and 19 had perioperative TEG. The most common indications for transplant were BA (n = 14), HB (n = 7), and metabolic disorders (n = 7). Intraoperative blood loss, urine output, fluid and blood product use were similar between groups. However, the use of fresh frozen plasma decreased significantly in TEG patients within the first 24 hours (29 vs 0 mL/kg, P < .01), and between 24 and 48 hours (12 vs 0 mL/kg, P = .01) post‐operatively. The total use of fresh frozen plasma during hospitalization was markedly reduced (111 vs 17 mL/kg, P < .01). Four patients in the TEG group had thromboembolic graft complications, including portal vein or hepatic artery thrombosis, and underwent retransplantation. The decreased use of fresh frozen plasma since implementation of TEG is an important finding for resource utilization and patient safety. However, the increased incidence of thromboembolic complications requires further investigation.