JNJ-678 (JNJ-53718678) is primarily investigated for its antiviral properties, particularly in the treatment of respiratory syncytial virus (RSV) infections. It functions as a fusion inhibitor, targeting the RSV fusion protein to prevent the virus from entering host cells. This mechanism makes it a promising candidate for managing severe RSV infections, especially in high-risk populations such as infants, elderly individuals, and immunocompromised patients. Clinical studies have explored its efficacy in reducing viral load and improving respiratory symptoms. Additionally, its potential for prophylactic use is being evaluated to prevent RSV infections in vulnerable groups. Research continues to assess its safety, dosing, and long-term effectiveness in both treatment and prevention contexts.