Saquinavir mesylate is primarily used as an antiretroviral medication in the treatment of HIV infection. It belongs to the protease inhibitor class, which works by blocking the activity of HIV protease, an enzyme essential for the replication of the virus. By inhibiting this enzyme, it prevents the virus from maturing and producing new infectious particles, thereby reducing the viral load in the body. It is often prescribed as part of a combination therapy known as highly active antiretroviral therapy (HAART) to enhance its effectiveness and minimize the risk of drug resistance. This medication is particularly beneficial for patients with advanced HIV or AIDS, helping to improve immune function and slow disease progression. It is typically administered orally in conjunction with other antiretroviral drugs to achieve optimal therapeutic outcomes.