Comparing In Vitro and In Vivo Models as Part of Pre-Clinical Studies for COVID-19 Medicines

The emergence of SARS-CoV-2 (the aetiological agent of COVID-19) has called for the need to develop robust in vitro and in vivo models as part of the pre-clinical testing of novel therapeutics and treatments. In vitro studies used to study SARS-CoV-2 have included use of cell lines and organoids, which have the advantage of being manipulated to retain high viral loads using the ACE2 receptor. However, despite some drugs having similar data readouts during in vitro studies, as demonstrated by the conflicting approvals of remdesivir and hydroxychloroquine, these studies alone are not entirely reflective of the physiology of human tissue. Therefore, in vivo studies have been used small and large mammals to better understand how COVID-19 interact systematically in the body. This review compares different models of COVID-19 pathogenesis, considering their advantages and limitations to developing candidate drugs or testing existing drugs. Whilst both in vitro and in vivo methods have their advantages and disadvantages, together they allow for the expedition of therapies through clinical trials and reduce the risk of clinical failure. As highlighted during the COVID-19 pandemic, reflective and meaningful models have been crucial in tackling one of the biggest healthcare challenges in recent history.