Gilead Halts RSV Trials for Obeldesivir Amid Low Infection Rates

Gilead Sciences has announced the termination of two mid-stage clinical trials for its antiviral drug obeldesivir in respiratory syncytial virus (RSV) indications. The company cited unexpectedly low RSV infection rates during the most recent Northern Hemisphere season as the primary reason for the decision.

Trial Termination and Implications

The two studies, which were evaluating obeldesivir in both adult and pediatric populations, were ended due to difficulties in determining meaningful rates of symptom reduction—a primary endpoint of the studies. Gilead emphasized that the decision to halt the trials was not related to any safety or efficacy concerns.

This setback for obeldesivir in RSV follows a similar situation in 2023 when Gilead terminated a phase 3 study of the drug for COVID-19, also due to lower-than-expected incidence rates and related hospitalizations.

Obeldesivir's Future and Ongoing Research

Despite the setbacks in RSV and COVID-19, Gilead continues to explore obeldesivir's potential in other indications. A clinical trial investigating the drug's efficacy against Marburg virus, a severe disease with a high mortality rate, is currently ongoing. Preclinical research has suggested that obeldesivir could be effective against this virus.

RSV Market Landscape

The RSV market is currently dominated by vaccines and prophylactic antibodies. Key players include:

• Pfizer's Abrysvo
• GSK's Arexvy
• Moderna's mRESVIA
• Sanofi and AstraZeneca's Beyfortus
• Merck's recently approved Enflonsia

Despite the prevalence of vaccines, there remains ongoing interest in antiviral treatments for RSV. Companies such as Shionogi and Enanta Pharmaceuticals have demonstrated clinical success with their respective antiviral candidates, S-337395 and zelicapavir. Enanta has noted that there is still a need for antivirals in both pediatric and adult populations, particularly as vaccine protection wanes and uptake remains low among adults.