Prescription opioid drugs have become such an epidemic in the United States they now cause more fatalities than heroin each year, leaving addiction scientists scrambling. Two of these highly addictive drugs, oxycodone and hydrocodone, are the most commonly associated with emergency department visits, according to the Drug Abuse Warning Network (DAWN), and fatalities linked to these two drugs alone have increased four-fold between 2000 and 2014. Recently, however, researchers at The Scripps Research Institute (TSRI) have developed vaccines that decrease the risk of fatal opioid overdose with these two drugs.
If the idea of a vaccination for a drug addiction sounds odd, researcher Kim D. Janda, professor of chemistry at TSRI, who ran the recent study, tells mental_floss, “There are ways to stimulate the immune response against different molecules besides bacterial pathogens or a virus.” One way is vaccine-mediated pharmacokinetic strategy: In the treatment, a small molecule known as an “immunogenic protein conjugate” stimulates the immune system to make drug-specific antibodies. These antibodies then “bind the drug molecule so it doesn’t reach the opioid receptors,” Janda says.
Because the vaccines are drug-specific, scientists must make a unique vaccine for each drug in order for them to be effective. In the current study, published in ACS Chemical Biology, the researchers made one vaccine for hydrocodone, dubbed Hydro-TT, and one for oxycodone, Oxy-TT. They administered these vaccines to mice via injections into their abdomens two to three times over an eight-week period. “The vaccine has to build up over time," Janda explains. "It doesn’t kick in all at once.”
Once the mice had built up their vaccine levels, researchers then administered potentially lethal doses of either hydrocodone or oxycodone, depending on which vaccine the mice had been given. They found that survival rate in the Oxy-TT vaccinated mice increased from 14.2 percent to 37.5 percent. In Hydro-TT vaccinated mice, the results were even more dramatic, with the survival rate jumping from 25 percent to 62.5 percent.
This vaccine has several advantages to current treatment, Janda and his co-authors write in their paper: “Such a vaccine could effectively suppress the addiction liability and overdose potential of the target drug over an extended time period without placing excessive compliance demands on the patient.”
The vaccines would last several months and require monthly boosters to maintain their efficacy. Janda’s research does not show any significant side effects, and he believes them to be no more taxing to the immune system than vaccines for diseases like polio and smallpox.
Of course, these trials have so far only been done in rodents and non-human primates, but Janda is hopeful they will eventually move to human trials.
Even once they prove effective in humans, unlike typical vaccines for diseases and viruses, opioid vaccines are not preventative, and Janda stresses that they are not a cure for addiction. “You’re not going to be giving these to kids or people who don’t do drugs,” he says. “This is for people who have problems getting off the drugs, [who] have issues with abstinence, which all addicts have."
The vaccines will most likely only be given to people who have either had a previous overdose or are unsuccessfully attempting to quit. Phil Skolnick, director of the Division of Therapeutics and Medical Consequences at the National Institute on Drug Abuse, which funded Janda’s work (as well as other similar research), believes that opioid vaccines could be especially helpful with compliance. In other words, it will hopefully help addicts do what they need to do to keep off opiates, whether that’s suboxone treatment, a drug detoxification method for opiates; the medication naltrexone, which prevents the drug from binding to the opiate receptors; or simply staying away from their drugs of choice.
“Getting [addicts] to make one good decision every day not to take opiates is a very tough thing to do,” Skolnick tells mental_floss. However, by taking a biologic vaccine targeted to the drug they're addicted to, an addicted—and now immunized—person “would have an enduring protection. That’s one of the strongest arguments for developing biologics against drugs of abuse,” he says.
There are some downsides to the vaccines. For one thing, they block the pain-relieving effects of the opiates, so a person who was taking an opiate for pain would need to find an alternative. Likewise, because there is no global vaccine for all opiates, if a person has been abusing more than one opiate, they would need more than one vaccine.
Other vaccines are in development for drugs including heroin, fentanyl, cocaine, and methamphetamines. Skolnick thinks that if all goes smoothly in further trials, the first available opioid vaccines for humans could hit clinics in the next five years or so.
Meanwhile, Janda’s team views the vaccines “as a crutch to assist people who are undergoing abstinence programs and have relapse problems.” Either way, biologic vaccines offer a promising addition to drug treatment programs and a potential new way to curb fatal opioid overdoses.