Animal testing is still frequently used to test the safety and effectiveness of medicines and other chemical substances. Alternative methods can reduce the need for such testing, for instance, because they are based on cultured human cells (in vitro). VITO designed a test platform specifically for inhaled substances. Together with the Rega Institute at KU Leuven, the platform was used to investigate whether remdesivir, used to treat Covid-19, can also be administered through the airways.