The 2014 outbreak of Ebola virus, which caused more than 11,000 deaths in West Africa, has been brought to heel, but the need for effective Ebola treatments remains urgent. The drugmaker Gilead Sciences just launched a mid-stage study of GS-5734, an antiviral, that, if proven effective, could be a crucial weapon against future flare-ups of Ebola.
The Phase II clinical trial in Liberia will test whether the Gilead compound can clear viral RNA that has hunkered down in areas of the body—the eyes, testes, and spinal column, for example—that immune cells have trouble reaching. In rare cases, that reservoir of genetic material causes the Ebola virus to come roaring back months after a person is believed to be cured. It also can be passed on to sexual partners.
The National Institute of Allergy & Infectious Diseases, a sponsor of the trial, will recruit 60 to 120 men who are already enrolled in a study of the long-term health of Ebola survivors. The volunteers will be given either GS-5734 or a placebo once daily for five days and then monitored over the next six months to measure the compound’s effect on the viral load.
GS-5734 is a monophosphoramidate prodrug of an adenosine analog that was discovered through a collaboration among Gilead, the Centers for Disease Control & Prevention, and the U.S. Army Medical Research Institute of Infectious Diseases. Discovered in 2014, the compound already has been shown to wipe out signs of the virus in monkeys. It also has been tested for safety in healthy humans.
Gilead previously stated that the combination of the Phase II study, monkey data, and healthy human data could be enough to ask for U.S. regulatory approval for GS-5734.
Given the urgency with which GS-5734 is moving forward, Gilead has made a major investment in manufacturing. According to Tomas Cihlar, vice president of biology, the company has made enough of the drug to treat 1,000 people infected with Ebola for up to two weeks and is in the process of making thousands more doses.
GS-5734 also has shown activity against the Zika virus, but it is far more effective against Ebola, Cihlar notes. As such, Gilead is currently screening its library of antivirals for potential Zika treatments.