What are Fusion Inhibitors?

Fusion inhibitors are drugs which are designed to prevent the Human Immunodeficiency Virus (HIV) from entering cells. The goal of this class of drugs is essentially to head the virus off at the pass, attacking it before it gets a chance to attack the body. These drugs, also known as entry inhibitors, are designed to be used as part of HIV combination therapy, which means that they must be used with other antiretroviral drugs in order to be effective.

The way in which fusion inhibitors work is fairly simple. In order to replicate in the body, HIV needs to attach itself to human cells and hijack their normal routine, forcing them to produce clones of the virus instead of performing their normal function. In order to attach to the cells, HIV must form bonds with the proteins in the cells. The virus has a number of proteins which target specific spots on potential host cells. Fusion inhibitors interfere with these proteins, making it impossible for the virus to attach to another cell.

Some fusion inhibitors simply attach to the proteins, blocking the potential for bonding with human cells. Others mutate the proteins, making them different enough that they become nonfunctional. Development of this class of drugs was only made possible by extensive research on HIV, which allowed drug companies to identify the proteins involved in the attachment process. By preventing attachment, fusion inhibitors reduce the overall viral load, making it difficult for HIV to develop into full-blown AIDS.

As of 2008, two fusion inhibitors had been approved for use in patients. Both drugs were recommended for use in patients who had already tried other drugs in combination therapy, providing some hope for patients who were finding other drugs ineffective against the virus. Fusion inhibitors are not currently recommended for patients just starting combination therapy for HIV treatment, although this may change as more fusion inhibitors enter the market.

Like other drugs used in HIV treatment, fusion inhibitors represent a life-long commitment. Patients must take combination therapy consistently in order to suppress HIV in their bodies. Long-term combination therapy can get extremely expensive, especially with newer drugs, which tend to be treated as “experimental” by insurance companies, allowing them to exclude coverage. For the most part, combination therapy with new classes of HIV/AIDS drugs is only available in the industrialized world, as the cost of such drugs and the need for a consistent regimen is prohibitive in developing nations.