A Phase II trial from Tohoku University found that lubiprostone, a common constipation drug, slowed kidney function decline in patients with chronic kidney disease by reshaping gut bacteria and boosting spermidine production.
A drug long prescribed for constipation may do something its label never promised: help slow the decline of kidney function.
In a Phase II randomized, double-blind, placebo-controlled trial published in Science Advances, researchers reported that lubiprostone, a chloride channel activator used for constipation, appeared to preserve estimated glomerular filtration rate (eGFR) in patients with chronic kidney disease. The effect was strongest in the higher-dose group, where the decline in kidney function was significantly suppressed compared with placebo over 24 weeks.
The study, led by researchers at Tohoku University Graduate School of Medicine, enrolled 150 patients with moderate chronic kidney disease across nine medical institutions in Japan. Patients received placebo or lubiprostone at doses of 8 micrograms or 16 micrograms, while researchers tracked kidney-function markers, uremic toxins, gut microbial activity, and metabolic changes.
The main target of the trial was not actually eGFR. Researchers set out to see whether lubiprostone could lower indoxyl sulfate, a gut-derived uremic toxin linked to kidney stress. On that primary endpoint, the drug did not show a meaningful change. But the kidney-function signal was still notable: patients in the 16-microgram group showed better preservation of eGFR and eGFR slope than those given placebo.
The possible explanation sits in the gut. According to Tohoku University’s summary of the findings, lubiprostone appeared to shift gut microbial pathways in a way that increased spermidine, a polyamine associated with mitochondrial activity. The researchers proposed that this gut-driven change improved mitochondrial function and helped protect kidney tissue from further damage.
That matters because chronic kidney disease is usually treated by targeting the kidneys and the risk factors that damage them. This trial suggests a different route may be possible: treating the gut environment in ways that influence kidney biology.
The idea grew from a simple clinical observation. Constipation is common among people with chronic kidney disease, and the researchers suspected that disrupted gut microbiota might be part of the problem. Lubiprostone does not act like a traditional kidney drug. Its established role is in the intestine, where it increases chloride-rich fluid secretion and helps bowel movement.
The drug is already approved in the United States for constipation-related indications, including chronic idiopathic constipation in adults, opioid-induced constipation in adults with chronic non-cancer pain, and irritable bowel syndrome with constipation in adult women. It is not approved as a kidney-disease treatment.
That distinction is important. A Phase II result is not enough to change clinical practice, and the researchers said larger Phase III trials are needed to confirm whether the effect holds in a broader population. Patients should not interpret the findings as a reason to take lubiprostone for kidney disease outside medical supervision.
Still, the finding is intriguing because it points to a larger shift in how researchers think about chronic disease. The microbiome is no longer being treated as a digestive sideshow. In this case, the gut appeared to influence kidney decline through a chain involving bacteria, spermidine, mitochondria, and inflammation.
If future trials confirm the result, the most important part of the discovery may not be that one constipation drug helped one group of kidney patients. It may be that old drugs can reveal new control panels inside the body.
The cheapest medical breakthroughs do not always begin with new chemistry. Sometimes they begin with an old drug being asked a better question.
