Nelfinavir Mesylate hydrate is primarily used as an antiretroviral medication in the treatment of HIV infection. It functions as a protease inhibitor, effectively blocking the activity of the HIV-1 protease enzyme, which is crucial for the virus to replicate and produce infectious particles. By inhibiting this enzyme, the drug prevents the maturation of the virus, thereby reducing the viral load in the body and slowing the progression of the disease. It is often prescribed as part of combination therapy, known as highly active antiretroviral therapy (HAART), to enhance its efficacy and minimize the risk of developing drug resistance. Additionally, it has been explored in research for potential applications in treating other viral infections and certain cancers, leveraging its mechanism of action to inhibit protease activity in various contexts.