**8. Fusion and entry inhibitors**

Fusion inhibitors are also known as entry inhibitors is a class of antiviral drugs which prevent the entry of virus to host cell by blocking the receptors. They are used in combination therapy for the treatment of HIV infections by blocking the steps

involved in HIV replication cycle. Once virus enters into the host cell the viral surface protein gp120 form complex with CD4 receptor with co-receptors like CCR5 and CXCR4 which is necessary step for viral entry into the host cell.

Enfuvirtide, the first approved drug of this class which interfere with viral attachment with host cell membrane by inhibiting the necessary conformational change in particular viral envelop protein (gp41) which trigger the formation of transmembrane pore through which virus would enter the host cell. Maraviroc is also a new chemokine co-receptor antagonist (CCR5 antagonist) drugs that blocks the binding of HIV to CCR5 co-receptor in HIV infection [29, 30].
