The first strategy offers a shorter path to the public, which is important. In fact, most of the immediate drug discovery efforts in the early stages of the pandemic were focused on drug repurposing of known clinically approved drugs and virtual screening for the molecules available from chemical libraries. However, this method proved to be of limited efficiency. For example, the IC50 of lopinavir, an HIV protease inhibitor, against the 3C-like protease was found to be approximately 50 micromolar, which was far from ideal.
The second strategy, de novo drug design, is a more complex process, but it can provide a much better eventual solution -- an efficient first-in-class or best-in-class antiviral that can save lives of COVID-19 patients with severe forms of the disease. In an attempt to come up with a bold solution for both the current pandemic and for future pandemics, Insilico Medicine chose to pursue this route. On January 28, 2020, Insilico utilized part of its generative chemistry pipeline Chemistry42 to design novel drug-like inhibitors of COVID-19 and began generation on January 30.