Integrase inhibitors have a novel antiretroviral mechanism which prevents proviral DNA integration into the CD4+ cell chromosome. Promising results have been seen in clinical trials in treatment-naïve and -experienced infected individuals. CCR5 antagonists bind to CCR5, one of the second receptors of HIV-1, and inhibit HIV-1 entry into CD4+ cells. However, they cannot prevent the cell entry of HIV-1s which can use another second receptor, CXCR4. Fusion inhibitors are synthetic peptides which mimic a fragment of HIV-1 gp41. They can bind a counterpart portion of HIV-1 gp41 and prevent the fusion of viral and cellular membranes, one of the critical steps of HIV-1 entry into CD4+ cells.