Cocaine use disorder affects a significant share of the US population and carries serious risks, including a high rate of fatal overdose. Yet as of now, no medication has received regulatory approval specifically for treating it. That gap has pushed addiction researchers toward an unlikely candidate: a class of peptides originally studied for their role in blood sugar and appetite regulation.
A registered randomised controlled trial, described in a published protocol, is now testing whether semaglutide, a glucagon-like peptide-1 (GLP-1) receptor agonist, can reduce cocaine craving, cocaine consumption, and the neurological pull of drug-related cues when added on top of standard cognitive behavioural therapy. The trial is not yet reporting outcomes, but the protocol itself tells a detailed story about where addiction science is heading and why researchers believe this mechanism is worth a rigorous test.
What GLP-1 receptor agonists actually do
GLP-1 is a naturally occurring peptide hormone released in the gut after eating. It signals to the brain and pancreas in ways that influence hunger, food intake, and blood glucose. Synthetic versions of this peptide, engineered to last longer in the body than the natural hormone, have been studied extensively in metabolic research.
What made addiction scientists take notice is that GLP-1 receptors are not found only in the gut and pancreas. They also appear in brain regions closely tied to reward processing, motivation, and the reinforcing effects of substances. Early animal studies showed that activating these receptors reduced the rewarding properties of alcohol, nicotine, and stimulants including cocaine. The working hypothesis, according to the published protocol, is that these peptides modulate reward-related behaviours in a way that might blunt the intense pull that cocaine exerts on people with a use disorder.
Design of the registered trial
The trial is a randomised, double-blind, placebo-controlled study enrolling 75 adults who are actively seeking treatment for cocaine use disorder. Participants are assigned in equal numbers to receive either once-weekly injections of the GLP-1 peptide or matching placebo injections over 14 weeks. Both groups also receive weekly individual sessions of cognitive behavioural therapy, which is considered a first-line behavioural treatment for stimulant use disorders.
The dose of the active peptide starts at 0.25 mg per week and can increase up to 1.0 mg per week across the study period, following a gradual titration schedule. This kind of stepwise dosing is common in GLP-1 research and is intended to help participants adjust while minimising side effects.
Primary outcomes the researchers are measuring
The trial is tracking four primary outcomes, which together aim to capture cocaine-related behaviour from multiple angles. The first is neurophysiological reactivity, measured by a brain-wave signal called the late positive potential. This signal, recorded during exposure to cocaine-related images or cues, reflects how strongly the nervous system responds to drug-associated triggers. The researchers are looking at whether the peptide reduces that reactivity compared to placebo.
The second outcome is a behavioural economics measure called cocaine demand. This captures how much a person values cocaine relative to its cost, essentially how motivated they remain to seek the drug even as obtaining it becomes harder or more expensive. Reductions in cocaine demand would suggest the peptide is dampening the reinforcing value of the drug.
The third and fourth outcomes are more direct. Craving is measured using a validated questionnaire designed for cocaine, and actual cocaine use is tracked through both self-report and urine drug screens collected across the 14-week period. Combining a subjective measure with an objective biological test adds reliability to the self-reported data.
Exploratory aims and broader substance questions
Beyond the four primary outcomes, the trial protocol also describes exploratory aims. One of these examines whether changes in the neurophysiological and behavioural measures are linked to changes in actual cocaine use, which would help clarify the chain of events if the peptide does show an effect.
Another exploratory aim looks at other substances. Because many people with cocaine use disorder also use tobacco, alcohol, or cannabis, the researchers plan to track consumption of those substances as well. This is scientifically interesting given that GLP-1 receptor agonists have shown signals in alcohol and nicotine research too. The trial is also designed to examine dose-response relationships, meaning whether higher doses of the peptide correspond to greater changes in the outcomes.
The statistical approach is Bayesian, which differs from traditional hypothesis testing. Rather than producing a simple pass or fail result, Bayesian analysis continuously updates the probability that the treatment is effective as data accumulate. The researchers will analyse results on an intention-to-treat basis, meaning all enrolled participants count in the analysis regardless of whether they completed every session.
Why this matters for addiction research
The protocol frames this trial within a broader recognition in addiction science that treatment approaches need to be mechanism-based rather than purely behavioural. Cognitive behavioural therapy helps many people, but relapse rates in cocaine use disorder remain high, and the absence of any approved medication leaves clinicians with limited options.
The GLP-1 hypothesis is notable because it connects metabolic biology to reward neuroscience in a way that was not widely appreciated a decade ago. If the brain regions that process food reward and drug reward share important receptor systems, then peptides developed for one purpose might have measurable effects on the other. Early data from animal models and smaller human studies in other substance categories have pointed in this direction, which is the scientific rationale the trial protocol cites.
It is worth being clear about what this trial is not. It is a protocol publication, not a results paper. No outcomes have been reported. The trial is testing a hypothesis, and the hypothesis may or may not be supported when data are collected and analysed. The published protocol represents the researchers' plan, pre-registered so that the scientific community can evaluate their methods before seeing results.
Context around peptide mechanism research
The GLP-1 receptor system is one of several peptide-based pathways researchers are exploring in the context of motivation, reward, and appetite regulation. Related peptides that act on overlapping systems, including compounds that target receptors for amylin or growth hormone releasing hormone, are also under study in various metabolic and neurological contexts. The broader picture that emerges from this literature is that peptide signalling between the gut, metabolic tissues, and the brain is far more complex than early research suggested.
For a consumer-curious reader, the key takeaway from this trial protocol is straightforward. Researchers are taking seriously the possibility that a peptide originally developed for metabolic research could, through its action on reward-related brain circuits, reduce the grip that cocaine exerts on people who are trying to stop using it. The trial is designed rigorously, uses validated measurement tools, and asks mechanistic as well as behavioural questions. The field will be watching for results.
