Nirmatrelvir plus ritonavir (Paxlovid) a potent SARS-CoV-2 3CLpro protease inhibitor combination

Abstract

All coronavirus, including SARS-CoV-2, encode two proteases needed for the processing of PP1A and PP1AB polyproteins. The main protease 3CL (chemotripsine-like) gives rise to the formation of NSP11/16 proteins. The 3CL protease has been constituted as one of the possible therapeutic targets for the development of antiviral drugs against SARS-COV-2 due to its highly conserved sequence and structure among all coronaviruses. During the SARS-COV-1 pandemic, a hydroxymethyl ketone derivative (PF-00835231) was identified with an intense inhibitory activity against the 3CL protease. Subsequent chemical modifications gave rise to derivative PF-07321332 (nirmatrelvir) which has shown a high antiviral efficacy against SARS-COV-2. The company’s data indicate that it is capable of reducing 89% the risk of hospitalization and death of patients infected with hardly adverse effects. Its effectiveness improves if it is administered orally in the first 24-48 hours and the duration of treatment has been established between 3-5 days. The commercial form has been associated with the antiviral ritonavir that has shown the metabolism of nirmatrelvir, lengthening its average life. This antiviral would be effective against current and future viral variants, since 3CL is not modified in them. The FDA approved this antiviral in November 2021 and EMA is in the final evaluation phase.