Enfuvirtide is primarily used in the treatment of HIV-1 infection, particularly in patients who have developed resistance to other antiretroviral therapies. It functions as a fusion inhibitor, preventing the virus from entering human immune cells by blocking the fusion of the viral envelope with the cell membrane. This mechanism is crucial in halting the progression of HIV, as it stops the virus from infecting new cells and replicating. Enfuvirtide is often administered as part of a combination therapy, enhancing the effectiveness of other antiretroviral drugs. It is typically prescribed for advanced HIV cases or when other treatments have failed, offering a critical option for managing the disease in complex scenarios. The drug is administered via subcutaneous injection, requiring careful adherence to dosing schedules to maintain its therapeutic benefits.