In this 24-month, randomized trial involving patients with relapsing–remitting multiple sclerosis, oral fingolimod reduced the rates of relapse and disability progression, as compared with placebo. Adverse events reported in patients treated with fingolimod included bradycardia, atrioventricular conduction block, macular edema, elevations in liver-enzyme levels, and mild hypertension.

In this 12-month trial involving patients with relapsing–remitting multiple sclerosis, oral fingolimod was more effective than intramuscular interferon beta-1a in reducing relapse rates. Adverse events associated with fingolimod included herpesvirus infections (two fatal infections), atrioventricular block, macular edema, skin cancer, and liver-enzyme elevation.

In this 96-week, placebo-controlled trial, oral cladribine reduced relapse rates and lowered the risk of sustained disability in patients with relapsing–remitting multiple sclerosis. Patients who were treated with cladribine had large reductions in lymphocyte counts and more infections, including herpes zoster and one death from reactivation of tuberculosis.

Suppressive therapy for herpes simplex virus 2 (HSV-2) has also been shown to reduce the levels of human immunodeficiency virus type 1 (HIV-1). However, in this placebo-controlled trial involving 3408 African couples who were discordant in serologic status for these two viruses, daily treatment with acyclovir did not reduce the frequency of HIV-1 transmission, despite a reduction in HIV-1 RNA levels and a 73% reduction in the occurrence of HSV-2–positive genital ulcers.