Celsentri, known generically as maraviroc, is a medication used in the treatment of human immunodeficiency virus (HIV) infection. It belongs to a class of drugs known as CCR5 antagonists, which work by blocking the CCR5 co-receptor on the surface of certain immune cells. This prevents the HIV virus from entering and infecting these cells. Celsentri is used in combination with other antiretroviral medications as part of an overall treatment regimen for HIV. It is specifically designed for use in patients whose virus uses the CCR5 co-receptor to enter cells, as determined by a specific test. By targeting this entry pathway, Celsentri helps to reduce the viral load in the body, thereby improving the immune system's function and slowing the progression of HIV disease.