While the Ebola epidemic in West Africa and beyond has begun to wane, the race to find a drug to help fight, or prevent, another outbreak continues. Since there is no cure or vaccine for the virus, any progress on finding a treatment is a welcome sign. On Wednesday, a new study, while far from being conclusive, gave reason for optimism, as an experimental drug saved the lives of monkeys infected with the same strain of the virus that has led to the current outbreak.

The treatment, known as TKM-Ebola-Makona, is in the preliminary testing stage, and has not been proven to work on humans. During the trial, six rhesus monkeys were given a high dose of the virus and the half that were then administered TKM-Ebola-Makona survived. “All three treated monkeys survived despite fevers and enormous blood levels of virus,” according to Reuters. “Three untreated monkeys became so ill they were euthanized within nine days.”