Introduction: The physicochemical and biological stability of therapeutic proteins is influenced by several environmental stress factors and agents. Therapeutic proteins should be evaluated using the appropriate techniques to establish their biological stability, which refers to their resistance to changes in biological activity, potency, toxicity, and immunogenicity in response to diverse environmental conditions. The biological activity of therapeutic proteins necessitates physicochemical stabilities that cannot ensure their efficacy and safety. There have only been a few experiments on both physicochemical and biological stability. Therefore, therapeutic proteins usually lack well-documented stability studies. This article aims to offer an overview of the effects of different environmental conditions on the bioactivity of therapeutic proteins.
Methods: A literature search was conducted on Scopus, PubMed, and Web of Science up to August 2022 for this purpose. We performed a title/abstract/keywords search for "Therapeutic proteins," "stability," "therapeutic proteins," and "stress parameters."
Results: The findings showed that several stress characteristics, including elevated temperature, pH, freeze-thaw, oxidative agents, light, mechanical stress, metal ions, and oxygen, have a detrimental influence on the stability of therapeutic proteins and result in unique degradation processes. Bioassays play an essential role in the stability studies of therapeutic proteins and may detect any change in their structure and bioactivity that standard physicochemical approaches cannot discern. Although physicochemical techniques are useful for identifying a product's purity, identity, and integrity, they are incapable of assessing the higher-order structure of therapeutic proteins; hence, the findings cannot be attributed to bioactivity. Therefore, bioassays based on the MoA are commonly necessary to investigate the bioactivity of therapeutic proteins. At least one functional bioassay is needed to assess bioactivity, however, more bioassays may be required if the product's mechanism of action is not entirely understood. Cell-based potency test, which employs a live cell-based system to generate a physiological response from interaction with therapeutic proteins, is the most widely used method for evaluating bioactivity. Activation of the receptor, cell signaling, receptor binding, and internalization of product molecules often occur due to the interaction between living cells and therapeutic protein products. Using living cells, tissues, or creatures makes bioassays more variable, less exact, and more robust than physicochemical methods.
Conclusion: Even while physicochemical stability alone cannot ensure the safety and effectiveness of biologic products, it is essential for the bioactivity of therapeutic proteins. To evaluate therapeutic protein stability comprehensively, it is required to examine both biological and physicochemical stability using the proper analytical methods.