Gilead Sciences has moved a stage closer to bringing the first antiviral drug for respiratory syncytial virus (RSV) infection to market after reporting encouraging data in a phase II trial.
The company presented the results of a study of GS-5806, an orally-active RSV fusion inhibitor, showing that it was able to limit RSV infection in adult patients who were given an intranasal dose of the virus.
The drug met its objectives of lowering viral load – achieving a 99.9 per cent decline in 54 patients – as well as improving total mucus weight (54 per cent less than placebo) and symptom diary scores compared to the control group.
Healthy patients who contract RSV generally recover with no long-term ill effects, but the infection can be hazardous in the elderly, infants and people with compromised immune systems, causing bronchiolitis and pneumonia.
At the moment there are few treatments for RSV, which is similar in incidence to influenza, so patients can really only be managed with supportive care such as oxygen and fluid replacement, with bronchodilators and ribavirin used in some severe cases.
As the first RSV-specific antiviral therapy GS-508 would be an important addition to the armamentarium of drugs for severe respiratory infections if reaches the market.
“Based on the reductions in RSV viral load and clinical symptoms, as well as the safety profile observed in this adult challenge study, clinical trials in naturally infected patients should now be explored,” commented the study’s lead investigator, John DeVincenzo of the University of Tennessee’s School of Medicine.
Gilead is in the planning stages for a placebo-controlled phase II study that will look at GS-5806’s safety and efficacy in patients naturally infected with RSV who have been hospitalised with acute respiratory symptoms. The study will deploy an initial loading dose of Gilead’s drug and follow patients for 28 days, with daily nasal swabs to record viral load.
Other companies developing therapeutics for RSV include ADMA Biologics, which recently completed enrolment in a phase III trial of its RI-002 immunoglobulin candidate, Teva’s MicroDoseTherapeutx, whose inhalable fusion inhibitor MDT-637 recently completed phase I trials, and Ablynx with its anti-RSV antibody ALX-0171 entering mid-stage development.
AstraZeneca was developing an RSV-preventing antibody called motavizumab but discontinued its development in 2010 and is now focusing on a vaccine candidate (MEDI-559).