The development of new therapeutic agents to combat COVID-19 pandemic requires years. Repurposing of existing drugs offers a faster access to an efficient therapy. However, the already existing drugs are not ideally suited for the treatment of COVID-19. We have identified two classes of approved drugs suitable for repurposing: iminosugars and chloroquine derivatives. Through an interdisciplinary approach, which includes iterative application of computational modeling, organic synthesis, and biological testing, we will elucidate mechanisms of antiviral action of two privileged classes of pharmaceutical compounds and propose new structures with enhanced antiviral activity and diminished side effects. Thus, the existing drugs – migalastat and chloroquine – will serve as starting points for the development of new drug candidates, whose preclinical examination should be considerably shortened. This approach could be used to combat other viral infections. Our study of the mechanism of action of chloroquine derivatives (whose use caused controversies and public debate) should contribute to treating this issue exclusively on scientific grounds.