In a new study, the drug, called AT-121, relieved pain in monkeys without making them dependent on it. Most pain drugs work by activating a receptor in neurons called the mu-opiate receptor. “Oxycodone, morphine, fentanyl, heroin–they all work through the mu receptor,” says Mei-Chuan Ko, a professor of physiology and pharmacology at the Wake Forest School of Medicine and one of the authors of the study. “This receptor provides pain relief, but at the same time, also produces euphoria.”

The new compound activates the same receptor, but also activates a second receptor that blocks dependence on opioids. When monkeys took the new drug, it treated pain, but didn’t make them high. The monkeys in the study dosed themselves with oxycodone when given the opportunity, but they didn’t take any extra AT-121.

When AT-121 was given to animals that had become dependent on oxycodone, it also helped reduce their level of addiction. This aspect of the drug is similar to suboxone, a drug that can be used to treat pain or opiate abuse. But suboxone still has some risk of abuse itself.

By working with both receptors, AT-121 can treat pain more powerfully. In the recent study, monkeys showed the same level of pain relief at a tiny dose compared to current drugs. The small dose also helps the drug avoid other side effects that are common with opioids, including the shallow breathing that can lead to an overdose.

All of this suggests that the drug might eventually be able to help address the opioid epidemic. In what was the worst year ever for drug overdoses–more than 72,000 people died in 2017, according to preliminary data from the Centers for Disease Control and Prevention. That’s more than the combined number of people killed in the Vietnam and Iraq wars, and more than the combined number of Americans ever killed in a single year by car crashes, guns, and AIDS. At least two-thirds of the deaths were linked to opioids. More than 2 million Americans also regularly abuse opioids, by some estimates.

The new drug is far from being ready for use. Astraea Therapeutics, a Bay Area biotech startup that also worked on the study, will need to gather more data to get FDA approval to begin a clinical trial. If the trial is successful, it could still take six years before the drug is on the market. But the early results are promising, says Ko, and the new drug is the first of its kind, to his knowledge, that has been successfully tested in monkeys. It’s possible that this could be the next generation of opiate painkillers.