Certain forms of HIV viruses (R5 tropic viruses) require the CCR5 receptor as a “co-receptor” to gain entry to the cell. However, when the CCR5 antagonist is bound to the receptor, the virus cannot interact with the receptor and thus viral entry is blocked.
This is the first antiretroviral drug that targets the hosts cells rather than targeting the virus directly. CCR5 antagonists block the mechanistic pathway the virus uses to gain entry to the host.
Four possible effects of co-receptor antagonists on the tropism of HIV-1 population in patients with R5 HIV-1 are described below.