Researchers have developed a compound that blocks the high from heroin by recruiting the body's immune system to fight the drug—it's essentially a heroin vaccine.
In a study published in the Journal of the American Chemical Society, chemists from The Scripps Research Institute describe how the compound works. They also reveal that it's proven effective in tests on rhesus monkeys, claiming it's the first opioid vaccine to do so.
The results come after eight years of work, including rodent tests using different permutations of the vaccine. When exposed to part of the heroin molecule's structure that's in the vaccine, the immune system responds by producing antibodies tailored to that structure. It's the same process by which, say, a chickenpox vaccine produces antibodies for the varicella virus. And in the same way, when the immune system again encounters what it recognizes as a threat, the antibodies break it down. That prevents heroin from reaching the brain and producing the euphoria that users crave, making it potentially useful in treating addiction: Without the high, the drug could be that much easier to kick.
When researchers moved to testing on monkeys, they redesigned their compound, making it more closely resemble heroin in hopes of improving the immune response. They saw an effective response in four monkeys given three doses of the compound; their immune systems neutralized varying doses of heroin. The strongest response came in the first month, but effects lasted for more than eight months. Two monkeys who'd already received the vaccine in earlier testing showed a much higher response in the second round, suggesting that the compound could produce long-term immunity. There were no apparent side effects.
Because the compound is so specific to heroin, it won't block other opioid-based drugs like painkillers, the researchers say. It won't interfere with medications for treating addiction or preventing overdoses, either—naloxone, often used to reverse overdoses, would still be effective in vaccinated people.
Similar vaccines for drugs that get misused have skipped the primate testing phase, only to fail during human clinical trials. The Scripps researchers think their approach puts them on stronger footing; they've been able to carefully tweak the compound over years of experiments. "We believe this vaccine candidate will prove safe for human trials," Kim Janda, a chemistry professor and the study leader, said in a statement. The vaccine components, he noted, have either already received FDA approval or have been safety tested in earlier trials.
There's no timeline yet for testing the vaccine in humans. Before that can happen, the researchers are looking to license their compound to an outside company that will help shepherd it through the clinical trials process.
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