Ritonavir is a peptidomimetic inhibitor of the HIV-1 protease. Inhibition of HIV protease renders the enzyme incapable of processing the Gag-Pol polyprotein precursor which leads to production of non-infectious immature HIV particles. Nirmatrelvir plus ritonavir (Paxlovid) has been approved for the treatment and post-exposure prophylaxis of coronavirus disease 2019 (COVID-19).