Current approaches to assessing the biological activity of immunocytokines <i>in vitro</i>

Abstract

The use of cytokines as anticancer drugs is limited due to their toxicity. It is possible to reduce toxicity and to increase the therapeutic index by using cytokines in the form of conjugates with antibodies – immunocytokines. The results of preclinical studies have shown increased efficacy and reduced toxicity of various immunocytokines compared to the original, unconjugated cytokines. The potential of immunocytokines as anticancer agents is currently being studied in clinical trials. The therapeutic efficacy of immunocytokines depends on their physicochemical parameters, which determine the in vivo biodistribution, and biological activity as a result of the mechanisms of the antibody action and cytokine sites incorporated in the design. There is a need for methods that allow to assess the biological activity of both individual sites and the entire immunocytokine molecule when characterizing immunocytokines at an early stage of research.This review considers the existing approaches for assessing the biological activity of immunocytokines in vitro in the course of preclinical studies, such as monolayer cultures, reporter cell lines, co-cultures, three-dimensional (3D) tumor models. Monolayer cultures are sufficient to confirm the mechanism of action of separate sites of immunocytokines used in the design, and the “gold standard” test systems for determining the specific biological activity of the cytokine and the effector functions of the antibody site remain in demand. Commercial reporter cell lines remain an alternative option for assessing the biological activity of cytokine and antibody sites at the level of activation of signaling pathways. Co-cultures of tumor and effector cells make it possible to evaluate the cytotoxic and immunomodulatory effects of antibody and cytokine sites without using 3D cultivation methods. The use of 3D tumor models makes it possible to replace several tests for the biological activity of separate sites of immunocytokines conducted on monolayer cultures and co-cultures with one comprehensive study, however, such models require significant time and material costs.