Fig. 2.
Pharmacology, pharmacokinetics and toxicology of nirmatrelvir. Nirmatrelvir and its metabolite M4 inhibit severe acute respiratory syndrome coronavirus 2 (SARS-CoV-2) replication by suppressing the SARS-CoV-2 main protease (Mpro). Nirmatrelvir is metabolized by liver cytochrome P450 3A4 (CYP3A4) into M1−M4 and m/z 498 and is excreted in the urine. Ritonavir inhibits the metabolism of nirmatrelvir by suppressing CYP3A4 expression. Nirmatrelvir causes fetal developmental toxicity in rats and rabbits.