Maria Kuzikov

• This thesis focuses on the role of drug repurposing in containment of an emerging disease, taking SARSCoV‐2 as a case study. The severe acute respiratory syndrome coronavirus 2 (SARS‐CoV‐2) emerged in2019 causing a deadly respiratory disease: COVID‐19. The increasing knowledge about SARS‐CoV‐2allowed the expansion of multiple approaches to contain the spread of infection. Eventually the rapid development of anti‐SARS‐CoV‐2 vaccines allowed a control of the pandemic. Effective antiviral pharmacological treatments are still rare and viral evolution allowed a fast adaptation and escape from available containment methods. Since the beginning of the SARS‐CoV‐2 pandemic drug repurposing was considered as a valuable source for identification of new antivirals, due to the advantage of available clinical safety data and activity profiles. To interfere with SARS‐CoV‐2 infection and to identify new antiviral compounds, key steps of the virus replication cycle and their corresponding targets were selected for assay development. The screening approaches not only identified new molecules, that can act as starting points to develop new antiviral therapies, but also revealed critical steps and pitfalls in developing assays, that will help to optimize the translation of compound effects from biochemical to cell‐based state. The study also adresses the misconception that repurposed drug cannot interfere with assay, by showing examples of compound‐reactivity through generation of reactive oxygen species, and readout interference. In addition, a drug‐combination approach for entry‐inhibitors aiming at a synergistic response is shown as an option to overcome difficulties in reaching necessary intracellular target‐doses without increasing cytotoxicity. In conclusion, this research highlights the potential of drug repurposing in antiviral drug discovery. The generated results contribute to the publicly available data on drug repurposing against SARS‐CoV‐2, which may be used for research.