ritonavir brands

Molecular formula: C37H48N6O5S2

Ritonavic inhibits the HIV viral proteinase enzyme that normally cleaves the structural and replicative proteins that arise from major HIV genes, such as *gag* and *pol*. *Gag* encodes proteins involved in the core and the nucleocapsid, while *pol* encodes the the HIV reverse transcriptase, ribonuclease H, integrase, and protease. The *pol*-encoded proteins are initially translated in the form of a larger precursoe polypeptide, *gag-pol*, and needs to be cleaved by HIV protease to form other complement proteins. Ritonavir prevents the cleavage of the *gag-pol* polyprotein, which results in noninfectious, immature viral particles. Ritonavir is a potent inhibitor of cytochrome P450 CYP3A4 isoenzyme present both in the intestinal tract and liver. It is a type II ligand that perfectly fits into the CYP3A4 active site cavity and irreversibly binds to the heme iron via the thiazole nitrogen, which decreases the redox potential of the protein and precludes its reduction with the redox partner, cytochrome P450 reductase. Ritonavir may also play a role in limiting cellular transport and efflux of other protease inhibitors via the P-glycoprotein and MRP efflux channels. Unlike nucleoside antiretroviral agents, the antiviral activity of ritonavir does not depend on intracellular conversion to an active metabolite. Ritonavir and other HIV protease inhibitors (e.g., amprenavir, indinavir, lopinavir, nelfinavir, saquinavir) act at a different stage of the HIV replication cycle than nucleoside and nonnucleoside reverse transcriptase inhibitors, and results of in vitro studies indicate that the antiretroviral effects of HIV protease inhibitors and some nucleoside or nonnucleoside antiretroviral agents may be additive or synergistic. Ritonavir is a selective, competitive, reversible inhibitor of HIV protease. HIV protease, an aspartic endopeptidase that functions as a homodimer, plays an essential role in the HIV replication cycle and the formation of infectious virus. During HIV replication, HIV protease cleaves viral polypeptide products of the gag and gag-pol genes (i.e., p55 and p160) to form structural proteins of the virion core (i.e., p17, p24, p9, and p7) and essential viral enzymes (i.e., reverse transcriptase, integrase, and protease). By interfering with the formation of these essential proteins and enzymes, ritonavir blocks maturation of the virus and causes formation of nonfunctional, immature, noninfectious virions. Ritonavir is active in both acutely and chronically infected cells since it targets the HIV replication cycle after translation and before assembly. Thus, the drug is active in chronically infected cells (e.g., monocytes and macrophages) that generally are not affected by nucleoside reverse transcriptase inhibitors (e.g., didanosine, lamivudine, stavudine, zalcitabine, zidovudine). Ritonavir does not affect early stages of the HIV replication cycle; however, the drug interferes with production of infectious HIV and limits further infectious spread of the virus. While the complete mechanisms of antiviral activity of ritonavir have not been fully elucidated, ritonavir apparently inhibits replication of retroviruses, including human immunodeficiency virus type 1 (HIV-1) and 2 (HIV-2), by interfering with HIV protease. The drug, therefore, exerts a virustatic effect against retroviruses by acting as an HIV protease inhibitor.

Source: PubChem (NCBI) · compound 392622