Credit: ZME Science.
The idea of getting some of exercise’s benefits from a pill has hovered somewhere between serious medicine and science fiction. Now, one such drug has made it through its first test in people.
Enveda, a biotechnology company, reported this week that its experimental pill ENV-308 was well tolerated in a Phase I trial involving 88 healthy adults. The drug is designed to imitate Lac-Phe, a molecule that surges in the bloodstream during strenuous exercise and appears to suppress appetite.
But this is not, despite the irresistible shorthand, exercise in a pill. The trial did not show that ENV-308 causes weight loss, builds muscle, improves fitness or reproduces the sweeping effects of physical activity. It was primarily a safety study, and its top-line results have not yet appeared in a peer-reviewed scientific journal.
Nevertheless, this is the first human test of an intriguing idea: instead of copying the gut-hormone biology exploited by now popular weight loss drugs such as Wegovy and Zepbound, researchers might borrow one of the chemical signals the body produces during exercise.
“ENV-308 is our attempt to put the chemistry of exercise into a daily tablet, and to offer a sustainable and convenient solution that synergizes with people’s daily habits and supports them on the path to long-term health,” Viswa Colluru, Enveda’s founder and chief executive, said in a company statement.
The Molecule Your Body Makes After a Hard Workout
Lac-Phe — short for N-lactoyl-phenylalanine — entered the obesity conversation only recently.
In a 2022 Nature study, Jonathan Long of Stanford University and his colleagues found that exercise sharply increased Lac-Phe in mice, racehorses and humans. When researchers gave the molecule to mice with diet-induced obesity, the animals ate less and lost fat without moving more or burning more energy. Mice genetically impaired in their ability to produce Lac-Phe, meanwhile, ate more after exercise.
That made Lac-Phe interesting as an appetite-control signal. It also fitted into a much older effort to develop “exercise mimetics” — drugs that reproduce specific molecular effects of physical activity. Researchers have pursued this goal through metabolic, inflammatory and neurological pathways for years, although a 2021 review in Nature Reviews Drug Discovery inflated expectations after showing the staggering number of biological systems exercise changes at once.
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Lac-Phe itself makes a poor medicine because the body clears it rapidly. Enveda says it engineered ENV-308 to reproduce its effects in a longer-lasting small molecule that can be swallowed once a day.
In the Phase I trial, participants received different doses of ENV-308. According to Enveda, there were no serious adverse events or treatment discontinuations, and the drug produced no notable nausea, vomiting or other gastrointestinal problems — symptoms that commonly accompany GLP-1 drugs. For now, these findings remain company-reported until full trial data undergo scientific review.
A Strange Signal from Leptin
The trial also produced a biological clue that Enveda considers important: circulating leptin levels fell.
Leptin is made largely by fat cells and helps tell the brain how much stored energy the body has available. The obvious assumption might be that more leptin means less hunger. But obesity often comes with unusually high leptin levels because the brain becomes less responsive to the signal — a phenomenon known as leptin resistance.
Scientists have tried to exploit leptin for obesity treatment for roughly three decades, mostly without success. More recently, researchers have started revisiting the hormone alongside GLP-1, on which Wegovy is based. A 2024 Science Translational Medicine study identified mouse brain neurons carrying receptors for both leptin and GLP-1 and showed that a compound targeting both systems could suppress food intake and body weight.
Enveda argues that the rapid decline in leptin seen with ENV-308 could indicate that the body is becoming more sensitive to leptin again, though that remains a hypothesis.
Francisco Lopez-Jimenez, a preventive cardiologist at Mayo Clinic who was not involved in the trial, told STAT that he would want to see broader safety measurements, including liver function, as well as direct measurements of appetite, calorie consumption, glucose and metabolism.
“The ultimate trial will be: Can people with obesity lose weight?” he told STAT.
Can You Lose Weight?
Curiously, Enveda is not positioning ENV-308 primarily as another drug for producing spectacular initial weight loss. It wants to know whether the pill can stop weight from coming back.
That is becoming one of the central problems of the GLP-1 era.
In the STEP 1 trial extension, participants who stopped semaglutide (the most common GLP-1 drug) regained roughly two-thirds of the weight they had lost during treatment over the following year. And a 2026 BMJ systematic review and meta-analysis of 37 studies involving more than 9,000 people found rapid weight regain after weight-management drugs were discontinued.
In animals, Enveda says ENV-308 prevented rebound weight gain after another weight-loss treatment was withdrawn and helped preserve lean tissue. Those results have not yet been demonstrated in humans.
The planned Phase II trial will therefore recruit people stopping, or hoping to stop, GLP-1 drugs and test whether ENV-308 can slow or prevent their weight from returning.
Calling the drug an exercise pill would still be a considerable stretch. Exercise changes the heart, blood vessels, muscles, bones, brain, immune system and metabolism through an enormous web of signals. Lac-Phe represents just one strand.
“It’s an interesting thought, but it’s an oversimplification because certainly it’s not the only thing that is produced with exercise,” Lopez-Jimenez told STAT.
