Heroin needle found in the gutter. Credit: Wikimedia Commons.

An estimated 9.2 million people in the world use heroin, and the United States is one of the hardest hit countries. In the last decade alone, heroin users have grown fivefold with young, white males being the most vulnerable group. Since the year 2000, the number of deaths from heroin overdose has quadrupled. Many blame lax use of prescription opioid painkillers — narcotics such as Oxycontin, Percocet, and Vicodin – which are seen as gate way drugs for smack. Culprits aside, it’s clear that we need solutions to what can only be called double opioid and heroin epidemic.

It might sound odd to call heroin addiction an epidemic but really no other medical term captures the rapid spread and health consequences that we see in heroin use today. And if indeed heroin addiction is an epidemic that perhaps we can treat it like we would the measles or polio: with a vaccine. American researchers at the Scripps Research Institute are working on just that and according to a recent report, progress is encouraging enough to warrant a clinical trial soon.

Immunizing against heroin, now seemingly possible

The idea is to develop a shot that nullifies heroin’s high. Minutes after heroin’s morphine chemicals enter the blood stream and bind to opioid receptors in the brain, users report an intense feeling of euphoria as if a ‘warm blanket snuggled the brain’. A vaccine, however, would block the morphine from binding to receptors and hence cancel its effects. Taken long enough and devoid of any physical high, the cycle of addiction could be broken in some cases or at least that’s what doctors hope.

Of course, there are already some drugs that block heroin’s psychoactive effects (such as Naltrexone). However, these drugs, taken orally as a pill, need to be administered regularly whereas a vaccine is given once and provides long-term protection. A vaccine is much more desirable in the case of heroin drug abuse since users battling with withdrawal most often than not can’t muster the required discipline to take their pills.

A notion of a vaccine for various drug addictions isn’t novel at all. Scientists in the 1970s investigated vaccines for all sorts of addictions from cocaine to nicotine to amphetamines. These early attempts have been unsuccessful and interest was lost though somewhat renewed by some research groups in the 1990s.

One big problem that has made research difficult is the fact that drugs like amphetamine or heroin have small molecules. In order to set off an immune response like any vaccine would do, it then becomes necessary to bind these molecules with larger ones, such as a protein. The hapten-carrier can then train the body to fight off real heroin once it enters the blood stream, an effect which can be amplified by secondary chemicals called adjuvants in the vaccine.

Credit: Scripps.

The Scripps vaccine is carefully crafted with the right mix of hapten, carrier, and adjuvant. Specifically, the vaccine has tetanus toxoid core — the same as in the better-known tetanus vaccine — formulated with adjuvants alum and CpG oligodeoxynucleotide (ODN).

Tests on mice and rhesus monkeys suggest the researchers’ vaccine blocks heroin effects for at least eight months if injected every three months. What’s more, other tests suggest the vaccine can also protect users from overdoses, which often result in death.

“[…] [The vaccine] generated heroin “immunoantagonism”, reducing heroin potency by >15-fold.”

“Following a series of heroin challenges over six months in vaccinated monkeys, drug-sequestering antibodies caused marked attenuation of heroin potency (>4-fold) in a schedule-controlled responding (SCR) behavioral assay. Overall, these preclinical results provide an empirical foundation supporting the further evaluation and potential clinical utility of an effective heroin vaccine in treating opioid use disorders,” the authors wrote.

These are all extremely encouraging results, which is why many are so keen to start a clinical trial as a soon as possible, within a few years.

Critics caution, however, that a heroin vaccine isn’t a magic fix for our growing heroin abuse epidemic. For one, such a vaccine can only work in those cases where users wish to stop or where existing treatment such as those involving methadone are inadequate. People end up abusing heroin for a variety of reasons and there’s only so much a vaccine can do.