September 15, 2021 – Opioid-related drug overdose deaths in the United States have skyrocketed to an estimated 69,031 people in 2020, surpassing the 49,860 deaths recorded in 2019, according to a new CDC report. Most of the deaths involved synthetic opioids such as fentanyl.
President Joe Biden has pledged more than $ 10 billion to expand access to prevention, treatment and recovery services. Money is important because people receiving treatment for an opioid use disorder have a high risk of relapse, which means a high risk of opioid overdose.
Now, researchers are studying a possible bridge to a successful cure: a vaccine that could blunt the ability of drugs to cause harm.
The first vaccines of this type are now entering clinical trials, raising hopes of adding another tool to the anti-addiction arsenal. But even if vaccines prove to be safe and effective, their success could create new problems to be solved.
One advantage of vaccines is that their effects can last for several months, says Susan Comer, trial researcher, professor of neurobiology and psychiatry at Columbia University Irving Medical Center. Drop-out rates from existing medical treatments for opioid use disorders can be as high as 50% at 6 months, and a vaccine could protect people from overdoses and give them time to return to treatment.
“It serves as a bit of a safety net,” she says.
The first vaccine to enter a trial targets oxycodone. Volunteers are recruited who have been diagnosed with an opioid use disorder, but are not being treated medically and are still using opioids. One third of them will receive a placebo vaccine, one third will receive a low dose vaccine injection and the other third will receive a high dose vaccine.
A hit against oxycodone
The researchers mainly monitor the safety of the vaccine, but they are also looking to see if the vaccination prevents the euphoria that opioids usually produce. They plan to enroll 24 people initially, but will increase to 45 if the results look promising.
In response to the injection, the body produces antibodies, proteins that mark oxycodone and prevent it from reaching the brain. If the drug cannot reach the brain cells, it cannot produce euphoria. And more important for vital effects, it cannot block signals from the brain to the body to breathe. The vaccine has already shown good results in animal studies.
Previous trials of cocaine and nicotine vaccines have failed. These vaccines have reached the final stage of clinical trials, but have not been shown to be effective overall. So this time, investigators plan to track the antibody levels in the participants, examining blood samples for signs of a good immune response to the vaccine.
But even though the early cocaine and nicotine vaccines didn’t work for everyone, there were some people they seemed to help. That’s why investigators involved in opioid vaccine trials want to track immune responses, says Marco Pravetoni, associate professor of pharmacology and medicine at the University of Minnesota School of Medicine, whose team will be evaluating samples of blood. Ultimately, he says, a doctor might even be able to use that information to tailor vaccine selection to a specific person.
Pravetoni also says that oxycodone is one of three vaccine targets – the other two are heroin and fentanyl – that researchers hope to combine into a single injection. Recipients may need one injection per month for the first 3 to 4 months and then receive annual boosters.
Stop the pain
Vaccines also raise issues that require special attention, says Cody Wenthur, an assistant professor of pharmacy at the University of Wisconsin, who is not involved in vaccine trials.
“If you are vaccinated against oxycodone, you might not have access to adequate pain control if you have a car accident, for example,” he says.
Clinicians could use other opioids for pain management, but limiting the opioids targeted by the vaccine is a “double-edged sword,” Wenthur explains, because vaccinated people could simply replace the opioid of their choice with one. other than a vaccine does not inhibit.
While these issues need to be addressed, vaccines, if they are effective, will play an important role. Wenthur notes a survey of pharmacists and pharmacy students he and his group conducted, showing that respondents “overwhelmingly” viewed a potential vaccine as useful.
If the vaccines become available, their application could expand beyond people with opioid use disorders, Pravetoni explains. He mentions the 2002 incident when terrorists took over a theater in Moscow and Russian special forces allegedly used some form of fentanyl spray to incapacitate everyone in the room. More than 100 of the hostages have died and the episode has raised the specter of opioid use in chemical attacks. Pravetoni says the vaccination could offer protection to first responders, law enforcement or others whose professions put them at risk of inhalation, accidentally or through such attacks.
These or other real applications for those at risk of exposure are several years away. Pravetoni says it took 10 years to get to this phase and estimates that in about 5 years, a vaccine that targets multiple opioid drugs could enter the first clinical trial.