Antiviral chemotherapeutic agents against respiratory viruses: where are we now and what's in the pipeline

PURPOSE OF REVIEW: The emergence of severe acute respiratory syndrome in late 2002 and the recent outbreaks of avian influenza in Asia are timely reminders of the ever present risks from respiratory viral diseases. Apart from influenza, there are no vaccines and very few antiviral chemotherapeutic agents available for the prevention and treatment of respiratory viral infections-the most common cause of human illness. If the current H5N1 avian influenza outbreak ever assumes the role of a pandemic, formidable technical difficulties relating to the properties of the agent, itself, will ensure that vaccines will only become available after a significant lead time and then only to a relatively small percentage of the population. The use of existing antivirals could be critical in limiting the initial spread of a pandemic, although their use in the control of epidemics caused by nonpandemic viruses has not been evaluated. It is against this background that a review of recent developments in respiratory antivirals has been undertaken. RECENT FINDINGS: The late 1990s were a period of unprecedented activity in the development of new and much superior antivirals for the treatment of influenza infections. However, during the past 2 to 3 years and largely for commercial reasons, there has been a decline in interest in their further development by major drug companies. This situation may soon change with the possible advent of new pandemic viruses, and moves are afoot in several countries to consider the stockpiling of antivirals.