Nelfinavir is an oral antiretroviral agent. Nelfinavir is a protease inhibitor, belongs to the group that includes indinavir , ritonavir and saquinavir. Nelfinavir is used in conjunction with nucleoside reverse transcriptase inhibitors , for the treatment of HIV infection. Nelfinavir is a competitive inhibitor of HIV protease, an enzyme involved in the replication of HIV. Protease is responsible for cleaving precursor molecules (immuture budding particles) to produce the final structural proteins of a mature virion core and to activate reverse transcriptase for a new round of infection. Thus, protease is necessary for the production of mature virions. Protease inhibition renders the virus noninfectious. Because they inhibit the HIV replication cycle after translation and before assembly, HIV protease inhibitors are active in acutely and chronically infected cells, as well as in cells (e.g., monocytes and macrophages) not normally affected by dideoxynucleoside reverse transcriptase inhibitors.