HIV entry into a CD4+ cell is a multi-step process. Entry begins when the HIV envelope glycoprotein gp-120 attaches to a CD4 receptor. The HIV glycoprotein gp-120 undergoes a confirmational change when it contacts the CD4 receptor allowing it to be secured to a coreceptor, CCR5 or CXCR4.
Maraviroc is the first of a new class of medications targeting the CCR5 co-receptor on a CD4+ cell. Maraviroc binds to the CCR5 co-receptor stopping CCR5 tropic HIV-1 from securely attaching to the CD4+ cell.
Co-receptor binding is believed to be essential for HIV-1 replication. Antiretroviral therapy that includes maraviroc is indicated only for treatment experienced adult patients who have evidence of viral replication of CCR5-tropic HIV-1. An HIV-1 tropism test such as a trofile assay must be done to verify that maraviroc will be effective.