R R esearchers have developed a heroin vaccine that blocks users from feeling the drug’s characteristic high. As the first anti-opioid vaccine to pass preclinical testing, they have hopes that it could provide a path out of dependency for recovering heroin addicts.
“We’ve optimized a vaccine against heroin,” said Kim Janda, a professor in the chemistry and immunology department at The Scripps Research Institute (TSRI) and a senior member of the research team. “Our hope is that this can be used in the fight against the opioid epidemic.”
The vaccine, which has proven effective in trials on rodents and monkeys, works by mimicking the unique structure of the heroin molecule and its key metabolite, 6-acetylmorphine. The vaccine, administered by way of a carrier protein, trains the body to produce antibodies that intersect and neutralize heroin, preventing it from reaching the brain and having an effect. In trials, the vaccine reduced the potency of heroin by more than 15-fold.
Authors on the research, published in the Journal of the American Chemical Society, hope that the vaccine could eliminate the motivation for relapse among recovering heroin addicts. Current pharmacological remedies for heroin addiction have shown some effectiveness, but in-patient rehab remains costly, treatments have shown adverse side effects, and the potential for relapse remains.
The announcement comes as opioid abuse in the United States reaches epidemic levels. Between 2005 and 2015, according to the study, the number of people over the age of 12 that had used heroin in the country doubled, from 379,000 to 828,000. Heroin use in the country is at a 20-year high, according to the UN Office on Drugs and Crime. Other data suggest drug overdoses are now the leading cause of death among Americans under 50 years of age.
The anti-heroin vaccine being developed by TSRI is the first to show effectiveness in non-human primates, in addition to rodents, a fact that researchers in the lab believe make it more likely to succeed in human applications.
“We wanted to see if a lot of the research we had done in rodents correlated, and we saw a good correlation,” Janda said. “Working with non-human primates, that’s as close as you’re going to get to humans.”
In trials on rhesus monkeys, Janda and his team found that the four primates given three doses of the vaccine showed an effective immune response. Antibodies deployed by the body were able to neutralize varying doses of heroin. While the effect was strongest in the month following vaccination, it proved to be durable, with some effect seen for as many as eight months after the treatment.
In fact, two primates that had received an earlier version of the vaccine showed a much higher response rate in the second round of experiments than first-time recipients. This, according to authors, indicates a certain level of “immunological memory” among their antibody-producing cells — a carry over from the previous vaccine.
“We were really encouraged to see the vaccine produce such lasting effects in non-human primate models,” lead author Paul Bremer said in a statement.
Thus far, there have been no adverse effects reported among subjects tested with the vaccine. Scientists believed that one possible limitation would be the use of a tetanus toxoid vaccination as the basis for the conjugate heroin vaccine — a preexisting immunity to tetanus might exist in patients due to the prevalence of publicly administered DTaP vaccine. But Janda said that the hurdle was more or less discarded in testing.
Another possible limitation was the potential for the vaccine to interfere with other opioid-based painkillers or medications currently used to treat opioid addiction or overdose in emergency situations. In trials, however, the team demonstrated that no such interference existed.
Last year, members of the same team developed a vaccine that proved effective in tests against fentanyl, a potent so-called designer opioid that is often used to cut heroin.
While Janda reiterated that a combination vaccine to counter both opioids would be worth investigating, for now his team is focused on what is needed to take the heroin vaccine to market. The first step will be to license the vaccine to a third-party company that would act as their partner in clinical trials.
“At this point, I don’t see any research hurdles,” Janda said. “The bigger hurdle will be getting money to do all this stuff.”
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