Disease-modifying therapies are treatments that can change the natural course of the disease. Four treatments for people with relapsing MS (MS attacks) are approved for lifelong use by the FDA: Avonex®, Betaseron®, and Rebif® (beta interferons), and Copaxone® (glatiramer acetate). These treatments are all given by injection and work by influencing the activity of the immune system. All of these drugs reduce the frequency of MS attacks, and may slow down the rate of physical disability.