The prospective Hemophilia Inhibitor PUP Study reveals distinct antibody signatures prior to FVIII inhibitor development.

Preventing factor VIII (FVIII) inhibitors following replacement therapies with FVIII products in patients with hemophilia A remains an unmet medical need. Better understanding of the early events of evolving FVIII inhibitors is essential for risk identification and the design of novel strategies to prevent inhibitor development. The Hemophilia Inhibitor Previously Untreated Patients (PUPs) Study (HIPS; www.clinicaltrials.gov #NCT01652027) is the first prospective cohort study to evaluate comprehensive changes in the immune system during the first 50 exposure days (EDs) to FVIII in patients with severe hemophilia A. HIPS participants were enrolled prior to their first exposure to FVIII or blood products ("true PUPs") and were evaluated for different immunological and clinical parameters at specified time points during their first 50 EDs to a single source of recombinant FVIII. Longitudinal antibody data resulting from this study indicate that there are 4 subgroups of patients expressing distinct signatures of FVIII-binding antibodies. Subgroup 1 did not develop any detectable FVIII-binding immunoglobulin G (IgG) antibodies. Subgroup 2 developed nonneutralizing, FVIII-binding IgG1 antibodies, but other FVIII-binding IgG subclasses were not observed. Subgroup 3 developed transient FVIII inhibitors associated with FVIII-binding IgG1 antibodies, similar to subgroup 2. Subgroup 4 developed persistent FVIII inhibitors associated with an initial development of high-affinity, FVIII-binding IgG1 antibodies, followed by IgG3 and IgG4 antibodies. Appearance of FVIII-binding IgG3 was always associated with persistent FVIII inhibitors and the subsequent development of FVIII-binding IgG4. Some of the antibody signatures identified in HIPS could serve as candidates for early biomarkers of FVIII inhibitor development.

Real-world experience with use of Antihemophilic Factor (Recombinant), PEGylated for prophylaxis in severe haemophilia A.

INTRODUCTION: Prophylaxis with extended half-life factor VIII (FVIII) is approved for haemophilia A, but data regarding routine clinical use are limited. AIM: To assess real-world experience of ADYNOVATE® (Antihemophilic Factor (Recombinant), PEGylated prophylaxis in children and adults with haemophilia A. METHODS: A retrospective chart review was conducted in three US haemophilia treatment centres. Records of all patients who began Adynovate prophylaxis in routine clinical practice were identified. Demographic, clinical and patient-reported information beginning 6 months before initiation of Adynovate until the record review was analysed. RESULTS: Fifteen patients (aged 9 months to 28 years), with median 9 months' use of Adynovate (range 1-15 months), were identified. All had switched from another prophylactic regimen, 13 (87%) from standard half-life recombinant FVIII. Nine (60%) patients had ≥1 bleed within 6 months preswitch. The most frequent reason for switching was to reduce infusion frequency (14 patients). After switching, infusion frequency reduced for 13 patients, and overall weekly factor consumption decreased by 19%. Eight (53%) patients had no bleeds postswitch, three (20%) had spontaneous joint bleeds (vs four pre-switch), and three (20%) had only mild traumatic bleeds. Patient/parental satisfaction with Adynovate was documented as positive in 13 of 15 (87%) cases; 2 patients were not satisfied and discontinued Adynovate. No adverse events were considered related to Adynovate. CONCLUSION: In patients who switched from a standard half-life FVIII to Adynovate prophylaxis in routine clinical practice, bleeding control was generally improved or maintained, with a lower infusion frequency and factor consumption in most patients.

Subcutaneous diphtheria and tetanus vaccines in children with haemophilia: A pilot study and review of the literature.

INTRODUCTION: Subcutaneous (SQ) vaccination has emerged as standard of care in children with severe bleeding disorders to reduce unnecessary factor exposure and avoid provoking an intramuscular bleed, but little is known about comparative immunogenicity to intramuscular (IM) vaccination. AIM: To confirm immunogenicity of Diphtheria Tetanus acellular Pertussis (DTaP) vaccines administered SQ to individuals <6 years old with haemophilia. METHODS: We performed a retrospective and prospective pilot study of tetanus and diphtheria antibody titres among patients evaluated at our Haemophilia Treatment Centre between 2015-2016. Children with haemophilia who had received three to four doses of DTaP containing vaccine administered SQ were eligible. RESULTS: Eight children met inclusion criteria. The mean age at the time of diphtheria and tetanus antibody testing was 21.1±17.8 months. All children who received SQ diphtheria and tetanus developed a positive antibody titre to both antigens. There was no statistically significant difference in distribution of titre values. The average time between the last dose of vaccine and antibody testing was 6.6±3.9 months among SQ vaccinated subjects. Minor injection site reactions were common with SQ vaccines. CONCLUSION: SQ administration of diphtheria and tetanus vaccination appears to be immunogenic in a pilot study of Haemophilia patients and supports this practice as the standard of care for this population.

Extended half-life pegylated, full-length recombinant factor VIII for prophylaxis in children with severe haemophilia A.

INTRODUCTION: Primary factor VIII (FVIII) prophylaxis is the optimal treatment in children with severe haemophilia A. They are expected to benefit from extended half-life (T1/2 ) FVIII coverage by reduced infusion frequency while maintaining haemostatic efficacy. AIMS: To determine immunogenicity, pharmacokinetics (PK), efficacy, safety and quality of life of prophylaxis with a polyethylene glycol (peg)-ylated FVIII (BAX 855) based on full-length recombinant FVIII (ADVATE) in paediatric previously treated patients (PTPs) with severe haemophilia A. METHODS: PTPs <12 years without history of FVIII inhibitors received twice-weekly infusions of 50 ± 10 IU kg-1 BAX 855 for ≥50 exposure days. Prophylactic dose increases to ≤80 IU kg-1 were allowed under predefined conditions. PK was evaluated after single infusions of 60 ± 5 IU kg-1 . RESULTS: T1/2 and mean residence time were extended 1.3- to 1.5-fold compared to ADVATE (n = 31), depending on the analysis used. The point estimate for the mean annualized bleeding rate in 66 subjects receiving a median of 1.9 weekly infusions of 51.3 IU kg-1 of BAX 855 each was 3.04 (median 2.0); 1.10 (median 0) for joint and 1.16 (median 0) for spontaneous bleeds. Overall, 38% of subjects had zero bleeds. No bleeds were severe. Haemostatic efficacy was rated excellent or good for 90% of bleeds; 91% were treated with one or two infusions. In 8/14 subjects all target joints resolved. No subject developed FVIII inhibitors or persistent binding antibodies that affected safety or efficacy. No adverse reactions occurred. CONCLUSION: Twice-weekly prophylaxis with BAX 855 was safe and efficacious in paediatric PTPs with severe haemophilia A.