Nirmatrelvir/ritonavir, a combination drug comprising a protease inhibitor and a CYP3A inhibitor (pharmacokinetic enhancer), was evaluated for its safety and efficacy among non-hospitalized adults with mild to moderate COVID-19 at high risk for progression to severe disease in the phase II/III Evaluation of Protease Inhibitor for COVID-19 in High-Risk Patients (EPIC-HR) trial.4 Here, CYP3A4 is linked to COVID-19.