The cellular machinery of exercise, firing without the exercise
In a laboratory in St. Louis, scientists are attempting something that has long occupied the edges of medical imagination: capturing the cellular essence of physical exertion and delivering it as a pill. Bahaa Elgendy and his team at Washington University have developed compounds that activate the same molecular switches exercise triggers — offering potential relief to those for whom movement is no longer possible, or never was enough. The work is still in its early chapters, confined to animals and lab dishes, but it points toward a future where the boundary between effort and its benefits may be redrawn.
- Millions of people — the elderly, the chronically ill, those losing muscle to weight-loss drugs like Ozempic — have no reliable way to preserve muscle health when exercise is out of reach.
- The molecular targets, called estrogen-related receptors, were long considered undruggable, making every prior attempt to replicate exercise at the cellular level incomplete.
- Elgendy's team cracked the hardest receptor of the three, publishing a compound that activates all of them and demonstrably improved endurance and muscle fiber composition in mice.
- A newer, more potent generation of compounds is now being tested in animals engineered to model heart failure, obesity, and kidney disease — with Alzheimer's research waiting in the wings.
- Human trials remain at least two years away, and the risk of unintended effects in cancer-prone cells means precision, not just potency, will determine whether this science becomes medicine.
Bahaa Elgendy works on a problem that sounds deceptively simple: how to give someone the cellular benefits of exercise without requiring them to move. At Washington University School of Medicine in St. Louis, he and his team have developed drug compounds that activate the same metabolic switches inside human cells that normally fire during a run or a weightlifting session.
The need is real and wide. Older adults too fragile for physical activity, patients with muscle-wasting diseases, and people taking appetite-suppressing drugs like Ozempic — which also strips away muscle mass — all stand to benefit. Elgendy, who co-founded a startup called Pelagos Pharmaceuticals around this research, was candid enough to include the simply sedentary among the potential market.
The science centers on three cellular structures called estrogen-related receptors, or ERRs — orphan receptors with no known natural activator, found densely in energy-hungry tissues like muscle, heart, and brain. Exercise wakes them up, prompting mitochondria to produce more fuel, cells to burn fat over sugar, and muscles to build endurance. Earlier researchers had activated two of the three receptor types, but the most abundant one, alpha, was widely considered undruggable. Elgendy's team proved otherwise, publishing a molecule in 2023 that activated all three, with striking results in mice: better endurance, more fatigue-resistant muscle fibers, elevated skeletal metabolism.
Now a newer generation of more precisely fitted compounds is being tested in animals modeled after human heart failure, obesity, and kidney dysfunction. The complexity is significant — ERRs are involved in dozens of cellular processes, including some active in cancer cells, meaning the team must isolate only the exercise-mimicking effects. There is also early interest in Alzheimer's, where activating ERR alpha may reduce the protein buildup associated with neurodegeneration.
Human trials, if animal testing succeeds, could begin within two years. Elgendy is careful to note that nothing has been tested in humans yet, and the road from lab to clinic is long. But the destination is coming into focus: the biological signature of a workout, distilled into something you can swallow.
Bahaa Elgendy sits in a lab at Washington University School of Medicine in St. Louis with a problem that sounds simple but has eluded scientists for years: how to give someone the cellular benefits of exercise without them having to move. He and his team think they're getting close. In March, they presented new drug compounds that can flip the metabolic switches inside human cells—the same ones that normally activate when you run or lift weights. If the work holds, it could reshape medicine for millions of people who can't exercise at all.
The appeal is obvious. There are older adults whose bodies have grown too fragile for the treadmill. There are people with muscle-wasting diseases that steal strength no matter what they do. There are those taking weight-loss drugs like Ozempic, which work by suppressing appetite but also strip away muscle mass as a side effect. And then there are the rest of us—busy, sedentary, or simply unmotivated—who could theoretically benefit from a pill that does the work our bodies won't. Elgendy, who co-founded a startup called Pelagos Pharmaceuticals to pursue this exact goal, doesn't shy away from the last category. In describing the potential market, he included people who are "lazy, like myself."
The science hinges on three cellular structures called estrogen-related receptors, or ERRs. Despite their name, these receptors have nothing to do with the hormone estrogen. They're orphan receptors—meaning scientists still don't fully understand what naturally activates them in the body. But they're scattered throughout tissues that demand a lot of energy: skeletal muscle, the heart, the brain. When you exercise, these receptors wake up. They tell your mitochondria to produce more fuel. They coax your cells to burn fat instead of sugar. They build endurance and fatigue-resistant muscle fibers. The question Elgendy's team asked was whether you could activate these receptors without the exercise.
Previous researchers had managed to activate two of the three ERR types—beta and gamma—using synthetic compounds. But alpha, the most abundant in muscle and brain tissue, seemed impossible to target. "There was a claim that it was not druggable," Elgendy said. His team proved otherwise. In 2023, they published a molecule called SLU-PP-332 that could activate all three receptor types, with particular potency for alpha. In mice, the compound improved running endurance and increased the proportion of fatigue-resistant muscle fibers. In lab dishes, it boosted skeletal muscle metabolism. The cellular machinery of exercise was firing without the exercise.
But a single working molecule is not a drug. The team has now designed a new generation of compounds that fit more snugly into the receptors and pack greater potency. They're testing these in animals right now—specifically in mice engineered to mimic human heart failure, obesity, and kidney dysfunction. The challenge ahead is immense. ERRs don't just handle exercise responses. They're involved in dozens of cellular functions, and they're active in cancer cells as well as healthy ones. As Elgendy and his colleagues refine their compounds, they have to ensure they're triggering only the exercise-like effects while leaving everything else alone.
There's another potential avenue: Alzheimer's disease. Some evidence suggests that activating ERR alpha reduces the buildup of misfolded proteins in the brain, the hallmark of neurodegeneration. Elgendy's team is interested in exploring whether exercise mimetics could help there too. For now, though, the work remains in the animal phase. Human trials, if all goes well, might begin in a couple of years. "This is not a drug," Elgendy emphasized. "It's never been tested in humans." Translation from lab to clinic, he said, takes time. But the direction is clear: the cellular machinery of a workout, bottled and ready to swallow.
Citações Notáveis
There was a claim that it was not druggable—referring to the alpha receptor, which the team proved could be targeted— Bahaa Elgendy, associate professor at Washington University School of Medicine
This is not a drug. It's never been tested in humans.— Bahaa Elgendy
A Conversa do Hearth Outra perspectiva sobre a história
Why target these particular receptors—ERRs—instead of trying to mimic exercise some other way?
Because they're the actual switches. When you exercise, your body doesn't just feel tired and build muscle by accident. These receptors flip on in response to the physical stress, and that's what tells your cells to adapt. If you can activate them directly, you're not fooling the body—you're speaking its language.
But you said ERRs are involved in lots of cellular functions, not just exercise. Isn't that dangerous?
It's the central problem, honestly. You could activate these receptors and inadvertently trigger something in cancer cells, or mess with some other system you didn't intend to touch. That's why they're testing in animals first, and why they're being so careful about potency and specificity. One wrong move and you've created a different problem.
For someone taking Ozempic, would this drug actually replace exercise, or just slow the muscle loss?
That's the real question nobody can answer yet. The compounds show they can activate the same cellular pathways exercise does. But exercise does a thousand things at once—cardiovascular adaptation, bone density, mental health, balance. A pill might handle the muscle metabolism piece without touching the rest. It's not a replacement. It's a tool for people who have no other option.
What happens if this works and gets approved? Who gets it first?
Probably the people with the clearest medical need—the elderly, people with muscle-wasting diseases, maybe those on weight-loss drugs. The "lazy" people like Elgendy joked about? That's a much longer conversation, and probably not one medicine should be having alone.