Factor VIII products: key aspects of development, clinical research and use (part 2)

Continuous replacement therapy with clotting factor products can lead to serious complications in haemophilia A patients. One of potential reasons of such complications is an undesirable immune response to a blood clotting factor VIII (FVIII) product, which undermines the treatment effectiveness. The aim of the study was to systematise and summarise data on undesirable immunogenicity of plasma-derived and recombinant FVIII products, formation of immunological tolerance, and modern approaches to the development of clinical trial programmes for such products. The analysis was based on scientific literature, as well as Russian and international guidelines, including the updated document of the European Medicines Agency. The paper presents clinical trial data on pharmacokinetics, efficacy, and safety of FVIII products, including data on manifestations of unwanted immunogenicity. It highlights molecular mechanisms of interaction between inhibitors and FVIII, and analyses the main factors (genetic characteristics, immune status of patients, dosage regimen, etc.) affecting the frequency and intensity of the immune response to the product. The authors summarised approaches to the clinical trial design, including selection of patients and studied parameters. They substantiate the need for post-authorisation studies to collect additional clinical data on both efficacy and safety of the routine use of the product, including additional assessment of immunogenicity and other adverse reactions. It is concluded that the successful use of high-quality FVIII products ensures by harmonisation of requirements of Russian and international regulatory documents.