Recommendations for authors of manuscripts reporting inhibitor cases developed in previously treated patients with hemophilia: communication from the SSC of the ISTH

Clinicopathological parameters influencing inhibitor development in patients with hemophilia A receiving on-demand therapy

BACKGROUND

Development of inhibitors to transfused factor VIII in patients with hemophilia A continues to be a challenge for professionals involved in hemophilia care. The majority of patients in India receive 'on-demand' rather than prophylactic therapy. The present study was done to assess the prevalence of factor VIII inhibitors in patients with hemophilia A (PWHA) receiving 'on-demand' therapy in a North Indian population and to study the clinicopathological parameters influencing the development of inhibitors.

METHODS

The study group comprised of 300 PWHA. Detailed clinical parameters, treatment history, bleeding profile including family history were recorded. Diagnosis of hemophilia A was confirmed by relevant coagulation tests. Inhibitors were screened using mixing based studies followed by quantification by Bethesda assay and Nijmegen modified Bethesda assay. Samples were collected from five cities in North India where a free supply of factor VIII was available and effectively used in three of these cities.

RESULTS

In the 300 PWHA, disease phenotype was severe in 219 (73%), moderate in 62 (20.67%) and mild in 19 (6.34%), based on the factor VIII bioassay. Inhibitor prevalence was 9.6% (n = 29) and seen only in the severe phenotype. Inhibitor titers ranged from 0.8 to 108.8 BU/ml. A total of 12 PWHA had low and 17 had high titers. Correlation of various clinicopathological parameters in inhibitor-positive versus negative PWHA showed significant correlation with age at onset of disease, severity of disease, age at first exposure to treatment, annual factor intake (IU/kg/year), intense treatment episodes and bleeding manifestations like central nervous system bleed and hematuria. The total study sample had blood group B in 33.34% PWHA, followed by O (27.34%), A (24.34%) and AB (15%), however, in inhibitor-positive samples, significant inhibitor formation was associated with the ABO subtype A (19/29, 65.51%).

CONCLUSIONS

Factor VIII inhibitor prevalence in PWHA receiving 'on-demand' therapy was 9.6%. Clinicopathological correlates of inhibitor development in such PWHA have been analyzed in this novel study.

Factor VIII products and inhibitor development in previously treated patients with severe or moderately severe hemophilia A: a systematic review

Essentials Data on product-related immunogenicity in previously treated haemophilia A patients is scarce. A systematic review and meta-analysis of all currently available evidence was conducted. The overall incidence rate was 2.06 per 1000 person-years (95% confidence interval: 1.06-4.01). Some recombinant factor VIII products were associated with increased immunogenicity.

SUMMARY

Background Patients with severe hemophilia A who have been treated extensively with factor VIII products have a low but potentially serious risk of inhibitor development. It is unknown why these patients develop inhibitors, and data on product-related immunogenicity are scarce. Aims To summarize the currently available evidence on the relationship between inhibitor development and recombinant FVIII product type in previously treated patients (PTPs) with severe hemophilia A. Methods Longitudinal studies were included that reported on de novo inhibitor formation in patients with baseline FVIII activity levels of < 0.02 IU mL-1 who had been treated with FVIII for at least 50 days. Pooled incidence rates of inhibitor development according to product types were calculated with a random intercept Poisson regression model. Results Forty-one independent cohorts were included; 39 patients developed de novo inhibitors during 19 157 person-years of observation. The overall incidence rate was 2.06 per 1000 person-years, with a 95% confidence interval (CI) of 1.06-4.01. According to product type, the pooled incidence rates were 0.99 (95% CI 0.37-2.70) per 1000 person-years for patients treated with Advate, 5.86 (95% CI 0.25-134.92) per 1000 person-years for those treated with Kogenate/Helixate, 1.35 (95% CI 0.66-2.77) per 1000 person-years for those treated with Kogenate FS/Helixate NexGen, 12.05 (95% CI 1.53-94.78) per 1000 person-years for those treated with Refacto, and 4.64 (95% CI 0.82-26.43) per 1000 person-years for those treated with Refacto AF. Conclusion These results suggest that some products may be associated with increased immunogenicity. However, the low incidence of inhibitors in PTPs and the differences in study design may cause significant variation in estimates of risk.

Safety and Efficacy of B-domain Deleted Third Generation Recombinant Factor VIII (GreenGene F™) in Korean Patients with Hemophilia A: Data from a Post-marketing Surveillance Study

BACKGROUND

New B-domain deleted third generation recombinant factor VIII (FVIII; GreenGene F™, beroctocog alfa) was launched in 2010. We determined safety and efficacy of GreenGene F™ during routine clinical practice in patients with hemophilia A over a period of 12 months.

METHODS

From July 2010 to July 2014, a total of 136 hemophilia A patients were enrolled in a post-marketing surveillance (PMS) study. Among them, 134 patients were assessed for drug safety and 114 patients were analyzed for drug efficacy. Patients with differing hemophilia A severities and medical histories were monitored during 12 months of prophylactic and/or on-demand therapy.

RESULTS

Among 134 patients evaluated, 85 (63.4%) had severe hemophilia. Ninety-two received a total of 1,266,077 units for prophylaxis, and 42 received 516,491 units for bleeding episodes. Three patients developed inhibitors. In 112 previously treated patients, one patient (0.9%) developed inhibitor after intensive FVIII treatment for surgery. Among 22 previously untreated patients, inhibitors were observed in 2 infants (9.1%). Overall, there were a total of 47 adverse events (other than inhibitors) of all types in 30 patients (22.4%), 11 in 10 patients (7.5%) of which were considered showing serious adverse events (SAEs); most of which were hemorrhages at different sites. None of the SAEs were judged as product related. An excellent/good efficacy rate of 91.3% for hemostasis and 89.4% for hemorrhage prevention was recorded.

CONCLUSION

The results of this PMS study support the use of GreenGene F™ as safe and efficacious in hemorrhage prevention and treatment of hemophilia A. These results are consistent with the findings from previously published GreenGene F™ studies.