The New England Journal of Medicine, Journal Watch, reports on phase 2/3 clinical trial results of combination treatment with two oral drugs against SARS-CoV-2 (COVID 19). Nirmatrelvir functions to inhibit a SARS-CoV-2 protease which is critically important to viral replication. Ritonavir, is an antiviral used to treat HIV infections. When ritonavir is given in combination with nirmatrelvir it increases levels of this drug to a therapeutic range by inhibiting CYP3A4.
The study found that in patients at high risk, a combination of the oral antiviral drugs nirmatrelvir and ritonavir (Paxlovid), resulted in nearly a 90% reduction in hospitalization or death. This clinical trial led to the authorization of the combination drug therapy (Paxlovid) by the FDA.