Two milligrams of fentanyl, about the weight of five grains of salt, is enough to cause an overdose. Around 200 Americans were dying from the drug every day when researchers at the University of Houston reported a vaccine that kept it out of rats’ brains.
Dr Colin Haile, who led the work, told DailyMail.com that most vaccines protect people against viruses. This one is aimed at a chemical.
The shot is built on a fentanyl conjugate, an altered form of the drug’s molecule, and it goes after the part of the molecule that forms the opioid’s backbone. It trains the body to make antibodies that grab fentanyl in the bloodstream. The drug is then processed in the kidney and flushed out. A compound called dmLT is added as an adjuvant to strengthen the immune response.
“The antibodies will bind to the drug and keep it from getting to the brain,” Haile said. “If you prevent fentanyl from entering the brain you prevent it from producing euphoric effects and effects that lead to overdose deaths.”
What the rat tests showed
The team, whose results appeared in the journal Pharmaceuticals, tested the vaccine on 60 rats. Twenty-eight of them got the shots: three doses, one every three weeks, before any exposure to fentanyl. Blood samples after each dose tracked antibody levels, which jumped between weeks four and six. Protection then held from week four to week ten, the last week of the study.
To check whether the drug was still working, the researchers used two pain tests. In the first, heat was applied to a rat’s tail, and a rat that pulled its tail away could feel the heat. In the second, rats stood on a plate that was slowly warmed, and lifting a paw counted as pain. Unvaccinated rats did not react, because fentanyl had numbed them. Vaccinated rats did.
Brain samples told the same story. They showed no trace of the drug. “It’s as if they never got fentanyl at all. Complete blockade,” Haile said.
The antibodies were narrow in what they recognized. “The anti-fentanyl antibodies were specific to fentanyl and a fentanyl derivative and did not cross-react with other opioids, such as morphine,” Haile explained. A vaccinated person could therefore still be given other opioids for pain.
Who might use it
Haile pointed to people addicted to illicit drugs who risk taking fentanyl by accident. He also offered the example of a parent who has a child vaccinated before college, in case the student experiments.
Naloxone, sold as Narcan, is the main tool doctors and first responders have against an overdose, and it can only be used in the time right after one. A vaccine would act earlier, before the drug reaches the brain.
The researchers told DailyMail.com they aimed to begin phase 1 human trials the following year. Consult your doctor for medical advice.
