Daily injections of GS-5734, a small-molecule antiviral agent, protected 100% of infected Rhesus monkeys against lethal disease when administered three days after exposure, with markedly decreased symptoms even where viraemia (spread of the virus into the blood) had already occurred. “It inhibits Ebola virus by blocking the virus’s ability to replicate its own genetic material [so that] the virus can’t make copies of itself,” Dr Travis Warren of the US Army Medical Research Institute of Infectious Diseases (USAMRIID) explained. “Additionally, we saw no evidence… that the virus was able to generate resistance to GS-5734.”
These findings come as the result of collaboration between USAMRIID, Gilead Sciences, and the CDC. As Warren et al. stated in their report in Nature, the recent Ebola outbreak in Sierra Leone, Guinea and Liberia has been “unprecedented in the number of cases and fatalities, geographic distribution, and number of nations affected,” with nearly 30,000 cases and more than 11,000 deaths since late 2013. Though the epidemic has been been among the top priorities in global public health, with countless researchers seeking a cure and more than 4,000 technical experts deployed by the World Health Organisation in 70 field sites, “no antiviral therapeutics have yet received regulatory approval.”
Dr Thomas Cihlar of Gilead Sciences has expressed the hope of invoking the US Food and Drug Administration’s Animal Efficacy Rule to speed the development of the drug. Provided the FDA deems the findings from these animal studies sufficient to indicate the safety and effectiveness of the drug in humans, the researchers may be able to forgo human efficacy trials. As of now, the company is conducting Phase I clinical studies with the help of healthy volunteers to determine the safety and fate of GS-5734 within the body once administered.
While much remains to be investigated, the compound shows great promise: it has also displayed antiviral activity against filoviruses, arenaviruses, and coronaviruses, so clinical applications could extend beyond the treatment and prevention of Ebola.