A disease registry may serve as a more suitable data source for evaluation of factor VIII inhibitors in pediatric patients receiving orphan drug treatment for hemophilia A compared with a single-arm clinical trial.
While several new factor VIII products have been developed in recent years, the rarity of hemophilia A makes it difficult to recruit sufficient numbers of patients to clinical studies. The Patient Registry Initiative of the European Medicines Agency has explored the use of disease registries instead of small clinical studies to evaluate inhibitor development.
In this study, investigators questioned whether disease registries could serve as a suitable alternative to clinical studies in order to evaluate safety of orphan drugs in children with hemophilia A. They used data from previously untreated patients with severe hemophilia A from the factor VIII (rAHF-PFM) clinical study (ClinicalTrials.gov Identifier: NCT00243386) and the PedNet registry (ClinicalTrials.gov Identifier: NCT02979119), both of which took place between 2000 and 2009. The primary outcomes were baseline patient characteristics and the difference in inhibitor development at 50 exposure days between the 2 studies.
The present study included patients from the clinical study (55 patients) and the registry-based study (168 patients) who were administered the same factor VIII product. Median age at first exposure was similar in both groups. More patients in the clinical study had a positive family history of inhibitors (31% vs 10%) and a high-risk F8 genotype (82% vs 63%) compared with the registry-based study.
The registry-based study was more complete with more patients reaching 50 exposure days than in the clinical study (96% vs 75%). More patients in the clinical study developed inhibitors than in the registry-based study (39% vs 27%); however, the percentage of patients who developed high-titer inhibitors was equal in both studies (17%).
In a Cox regression analysis adjusted for family history of inhibitors, treatment intensity, and F8 genotype, the risk of developing an inhibitor during the first 50 days of exposure was similar (hazard ratio, 1.04; 95% CI, 0.56-1.94).
The major limitations of this study were that only 1 clinical study and 1 registry-based study were compared and that both studies had varying small samples sizes. Other limiting aspects of the 2 studies included duration of follow up and intralaboratory variation.
“This study indicates that registries like PedNet are potentially useful in assessing the inhibitor developments in treatments for haemophilia and may serve as an alternative to uncontrolled clinical studies for evaluation of high-titre inhibitors,” concluded the authors. “Although the sample size of this study was too small to conclude on differences in high- or low-titre inhibitors, this paper contributes to the discussion for the use of registry-based studies to assess long-term safety data.”
Jonker CJ, Oude Rengerink K, Hoes AW, Mol PGM, van den Berg HM. Inhibitor development in previously untreated patients with severe haemophilia: a comparison of included patients and outcomes between a clinical study and a registry‐based study [published online July 6, 2020]. Haemophilia. doi: 10.1111/hae.14100