Last month, scientists at the The Scripps Research Institute (TSRI) announced a breakthrough in their efforts to develop a vaccine to block the addictive effects of heroin and other opiates.
In research published in the Journal of the American Chemical Society, scientists at the Skaggs Institute for Chemical Biology at TSRI reported their vaccine has proven effective in non-human primates. It is the first vaccine against an opioid to pass this stage of preclinical testing.
“This validates our previous rodent data and positions our vaccine in a favorable light for anticipated clinical evaluation,” said study leader Kim Janda, the Ely R. Callaway Jr. Professor of Chemistry and member of the Skaggs Institute.
The vaccine works by exposing the immune system to a part of the heroin molecule’s telltale structure. This teaches the immune system to produce antibodies against heroin and its psychoactive products. The antibodies neutralize heroin molecules, blocking them from reaching the brain to cause a feeling of euphoria.
The Janda Laboratory at TSRI has been working on the heroin vaccine for more than eight years. The researchers had previously succeeded in neutralizing heroin in rodents.
For the new study in rhesus monkeys, the researchers redesigned their vaccine candidate to more closely resemble heroin, with the goal of better stimulating the immune system to attack this opioid.
The researchers found that the four primates that were given three doses of this vaccine showed an effective immune response and could neutralize varying doses of heroin. This effect was most acute in the first month after vaccination but lasted for over eight months. The researchers also found no negative side effects from the vaccine.
“We believe this vaccine candidate will prove safe for human trials,” Janda said. Components of the vaccine have either already been approved by the FDA or have passed safety tests in previous clinical trials, he noted.
Two of the four primates tested had been pre-vaccinated with the same vaccine candidate for a more basic pilot study seven months prior to the experiment in this study. The researchers found that these two primates showed a much higher response to the vaccine in the second round of experiments, indicating that their antibody-producing cells held a “memory” of the vaccine.
If this effect can be replicated in humans, a recovering addict would have long-term immunity to heroin.
This is the first vaccine against heroin to succeed in primate models. Vaccines against other drugs of abuse have been tested in humans without first completing non-human primate trials—and failed.
In their current effort, the Janda team focused on the chemistry of the vaccine, studying how well antibodies elicited by the vaccine could bind to drug molecules.
The researchers said their vaccine candidate works only against heroin and not other opioid-based painkillers or medications for treating opioid addiction or overdose.
The researchers’ next step will be to license the vaccine to a pharmaceutical company for partnering in clinical trials.