Determination of the Biological Activity of Insulin and Its Analogues in Animals

Abstract

In recent years, there has been a tendency to equate the results of insulin testing by physicochemical methods with its biological activity. However, it should be emphasised that the effectiveness of insulin preparations can be judged only by the reaction of the whole organism, i.e. by the hypoglycaemic action, which is a composite indicator. The determination of the biological activity of insulin has become especially relevant with the pharmaceutical market entry of insulin biosimilars, which are practically not analogous to the original medicinal products. The effectiveness of insulin products cannot be adequately evaluated using only physicochemical testing. At present, the biological activity of insulin is tested in rabbits. Additionally, the State Pharmacopoeia of the Russian Federation includes an alternative method to determine this parameter using mice. Owing to the physiological characteristics of mice, an adequate test would require special attention to the selection of test concentrations of insulin. The aim of the study was to offer recommendations for choosing the range of insulin concentrations for determining its biological activity in mice with due consideration of changes in their sensitivity depending on the season. Materials and methods: the authors analysed the results of testing the biological activity of insulin in female mice, bearing in mind the analytical range of the method specified in the State Pharmacopoeia of the Russian Federation. Test concentrations of insulin were selected taking into account seasonal shifts in insulin sensitivity of the animals. Results: the study demonstrated significant dose dependence and linearity of the responses of female mice to insulin in the concentration range of 0.03–0.3 IU/mL. Therefore, this range can be recommended as a guideline for determining the biological activity of insulin in female mice. The selection of test concentrations is illustrated with specific examples. Conclusions: the authors offer a methodological approach to the selection of insulin concentrations and the assessment of the validity of test results during biological activity determination using twin-crossover tests in female mice.