Antiretroviral Therapy (Treatment of HIV AIDS)
Antiretroviral drugs are medications for the treatment of infection by retroviruses, primarily HIV. Different classes of antiretroviral drugs act at different stages of the HIV life cycle. Combination of several (typically three or four) antiretroviral drugs is known as Highly Active Anti-Retroviral Therapy (HAART).
Antiretroviral drugs are broadly classified by the phase of the retrovirus life-cycle that the drug inhibits. There are thus six broad classifications of antiretroviral drugs in development, though only the first three classes currently have licensed examples:
Reverse transcriptase inhibitors (RTIs) target construction of viral DNA by inhibiting activity of reverse transcriptase.
- Protease inhibitors (PIs) target viral assembly by inhibiting the activity of protease, an enzyme used by HIV to cleave nascent proteins for final assembly of new virons.
- Fusion inhibitors block HIV from fusing with a cell’s membrane to enter and infect it. There is currently only one FDA-approved drug in this class, enfuvirtide, marketed as Fuzeon.
- Integrase inhibitors inhibit the enzyme integrase, which is responsible for integration of viral DNA into the DNA of the infected cell.
- Entry inhibitors block HIV-1 from the host cell by binding CCR5, a molecule on the host membrane termed a co-receptor that HIV-1 normally uses for entry into the cell together with a primary receptor. Only one entry-inhibitor class drug is available, maraviroc.
- Maturation inhibitors inhibit the last step in gag processing in which the viral capsid polyprotein is cleaved, thereby blocking the conversion of the polyprotein into the mature capsid protein (p24). Because these viral particles have a defective core, the virions released consist mainly of non-infectious particles. Bevirimat is the only drug that is currently under investigation.
- Portmanteau inhibitors A new way to combat HIV through the merging of two antiviral agents into one drug, achieving the same effect as when two or more drugs are taken separately.