Annual Bleeding Rates: Pitfalls of Clinical Trial Outcomes in Hemophilia Patients.

Emerging treatment options for hemophilia, including gene therapy, modified factor products, antibody-based products, and other nonreplacement therapies, are in development or on their way to marketing authorization. For proof of efficacy, annual bleeding rates (ABRs) have become an increasingly important endpoint in hemophilia trials. We hypothesized that ABR analyses differ substantially between and within medicinal product classes and that the ABR observation period constitutes a major bias. For ABR characterization, an internal factor VIII (FVIII) treatment database has been built based on confidential clinical trial data submitted to the Paul-Ehrlich-Institut (PEI). Furthermore, anonymized data from 46 trial protocols submitted for review to the PEI were analyzed (FVIII replacement, n = 27; antibody-based, n = 12; and gene therapy, n = 7) for methodology. Definitions of bleeding episodes and ABR observational periods differed substantially in clinical trials. In the initial observation phase, individual ABRs of patients, treated prophylactically for 1 year, vary by about 40% (P < 0.001), which finally led to a significant reduction of the ABR group mean by 20% (P < 0.05). Furthermore, the high variance in ABRs constitutes a major challenge in statistical analyses. In conclusion, considerable heterogeneity and bias in the ABR estimation in clinical trials was identified, which makes it substantially more difficult to compare the efficacy of different treatment regimens and products. Thus, awareness of the important pitfalls when using ABR as a clinical outcome is needed in the evaluation of hemophilia therapies for patients, physicians, regulators, and health technology assessment agencies.

Immediate allergic reactions after vaccinations--a post-marketing surveillance review.

UNLABELLED: Immediate systemic allergic reactions after vaccination with commonly used vaccines are very rare. Consequently, the risk of these reactions cannot be verified before widespread use. A data analysis of spontaneously reported suspected adverse drug reactions following the administration of 15 marketed vaccines, from 1994 to 1998, shows an average reporting rate for "allergic" reactions of one case report per 450,000 vaccine doses sold. Of these, potentially life-threatening events are extremely rare. In 31% of our case reports the reaction was reported after the first vaccination. In these cases a pre-sensitisation or a pseudo-allergic reaction can be assumed. There was no evidence for an increased risk of "allergic" reactions for patients with atopy. CONCLUSION: our data support a high level of safety for the vaccines included in the analysis. They also emphasise the importance of a careful vaccination management after occurrence of "allergic" reactions and the necessity of a post-marketing surveillance system for recording adverse drug reactions.