In human tests, painkiller abusers found the investigational opioid “boring,” says Nektar Therapeutics’ chief medical officer, Rob Medve. “There is no joy or euphoria associated with the drug,” he says. And yet human trials show that the compound increases pain tolerance.

 

Opioids, which include morphine, remain the top choice for treating severe pain because they offer potent relief, but they also boost dopamine pathways in the brain, which causes an intensely rewarding high that can trigger repeated, chronic use and eventually addiction.