New therapies for acute RSV infections: where are we?

Respiratory syncytial virus (RSV) infection is one of the main causes of infant hospitalization and mortality. The single-stranded RNA virus codes for 11 proteins of which the F protein, a surface epitope responsible for RSV fusion, is the most targeted for developing antiviral medicines and vaccines. The peak of symptoms occurs around day 4 to 6 of illness and the airway obstruction is merely caused by the host immune inflammatory response. Risk factors for severe bronchiolitis are prematurity, comorbidity, and/or being immunocompromised. At present, there are no curative therapies available for RSV infections and treatment is supportive only. Development of new antiviral medicines is however promising. The aim of this review is to give a summary of the most important new antiviral therapies in clinical development for RSV infection and to explain their mode of action. We therefore performed a literature search on this topic.Conclusion: There are currently at least eight antivirals being investigated in clinical trials. They all use different approaches to either focus on preventing viral fusion with host cells or inhibiting virus replication. Some target RSV surface epitopes like the F protein to halt fusion, others aim for RNA chain termination, while small interfering RNAs downregulate viral protein production. What is known: • RSV bronchiolitis is a very important pediatric disease as it is one of the main causes of infant hospitalization and mortality. By the age of 2 years, 95% of all the infants worldwide will have been infected. • The only recommended therapy is supportive since there are no existing curative therapies yet. What this study adds: • This review gives an overview of the current progress in the research field of RSV antivirals with background information on their mode of action.