The United States is in the grip of prescription painkiller addiction. In 2014, 28,000 Americans died of narcotic overdoses, four times more than in 1999. More than half of these deaths involved prescription drugs, such as the narcotic oxycodone.

In response, President Obama this year signed into law a bill providing $1.1 billion for opioid addiction treatment. Researchers, meanwhile, are trying to design an effective painkiller that doesn’t trigger addiction.

According to a new study published in the journal Nature, scientists are one step closer to a safer pill. A team of researchers led by scientists at the University of California San Francisco, Stanford University, the University of North Carolina and the Friedrich-Alexander University in Germany have engineered a new opioid drug that eases pain without common side effects, such as breathing difficulties and constipation. In early tests with mice, the drug also dodged the area of the brain that causes addiction, making the drug safer than those currently on the market.

To develop the new drug, the research team started from scratch and used computational techniques that allowed them to try more than four million different chemical interactions. They also used the recently discovered atomic structure of the brain’s morphine receptor to ensure the drug blocks pain in the same way as morphine but without the debilitating side effects.

The authors note that clinical trials are needed to determine if the drug is as effective in humans as it is in mice. The team’s hope is that once this new drug is on the market, it will help turn the tide against America’s painkiller addiction.