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In the 68-week TRIUMPH-4 trial, the investigational drug retatrutide reduced knee osteoarthritis pain and improved physical function among participants with obesity. Participants also lost substantial weight, while adverse-event withdrawals were more frequent than with placebo; the study does not establish that retatrutide changes the course of osteoarthritis.
The investigational drug retatrutide reduced knee osteoarthritis pain and improved physical function in adults with obesity in the 68-week TRIUMPH-4 trial, according to results presented at the American College of Rheumatology annual meeting. Participants assigned retatrutide also lost more than one-quarter of their body weight on average, but the findings do not show that the drug slows or reverses joint damage.
The trial randomized 445 adults with obesity and knee osteoarthritis to weekly injections of placebo or retatrutide at 9 mg or 12 mg. The study defined obesity as a body mass index above 27. Participants were recruited in the United States, Canada, Mexico, Australia and Spain. Average starting BMI was 40.4, and average weight was 113 kilograms (249 pounds).
At week 68, average WOMAC pain scores had fallen by 4.48 points with 9 mg and 4.41 points with 12 mg, compared with a 2.43-point decline with placebo. WOMAC is a questionnaire-based measure of osteoarthritis pain and function. Physical-function scores also improved: by 4.14 and 4.20 points in the two retatrutide groups, compared with 2.06 points with placebo. The source report says lower scores indicate less pain or disability.
Weight loss was another primary outcome. Retatrutide participants’ average losses continued through the 68-week study and exceeded one-quarter of body weight, the report said. The placebo group also improved, with pain scores declining and weight falling, in a trial where all participants received individualized dietary counseling and encouragement to do at least 150 minutes of physical activity weekly. The published material also reported improvements in triglycerides, non-HDL cholesterol and high-sensitivity C-reactive protein, a marker of systemic inflammation.
Pain Relief Alongside Weight Loss
The results add evidence that substantial weight loss may coincide with less knee pain for people with obesity and osteoarthritis. That matters because excess body weight can increase the load on knee joints, while pain and reduced mobility can make physical activity harder. The trial tested a drug alongside lifestyle support, rather than as a replacement for it.
However, the size of the pain-score changes does not establish what caused the improvement. The study authors proposed that lower body weight could reduce knee loading and that changes in adipose tissue might affect inflammatory signals. Those are possible explanations, not proof that retatrutide directly treats joint disease. Whether the drug alters cartilage loss or other structural damage remains an open research question.
Tolerability is also relevant to any future use. The MedPage Today report said adverse events led to withdrawal for about 13% of the 9-mg group and 18% of the 12-mg group, versus 4% of placebo participants. Serious adverse events were reported in about 10% of each retatrutide group and 2% of the placebo group. Gastrointestinal problems were the most common adverse events, according to the report.
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How TRIUMPH-4 Was Conducted
Retatrutide is an investigational medicine that acts on three receptor targets: GLP-1, GIP and glucagon. It is not the same as a medicine that targets GLP-1 alone, and its trial results do not establish that it is approved for routine treatment of obesity or osteoarthritis. The report describes the findings as part of a growing research interest in weight-loss medicines and osteoarthritis.
TRIUMPH-4 follows the TRIUMPH-1 study, which was also discussed in a publication appearing alongside the new results, according to MedPage Today. The trial enrolled people with substantial obesity on average, and 64% were reported to have Kellgren-Lawrence grade 3 osteoarthritis, a classification reflecting considerable joint changes. All three groups received lifestyle counseling, a factor that may help explain why the placebo group also lost weight and reported less pain.
At the meeting, investigator Thomas Conaghan of the University of Leeds presented the results. The report says the TRIUMPH-4 findings and a recap of TRIUMPH-1 were published simultaneously in the New England Journal of Medicine. The American College of Rheumatology had also recently issued updated osteoarthritis guidance placing greater emphasis on weight loss, according to the source report.
“Weight reduction leads to decreased loading on the knee, and the level of load reduction appears to be a multiple of the actual weight lost.”
— TRIUMPH-4 authors, as quoted in the MedPage Today report
Joint Effects Still Unproven
The reported findings do not establish whether pain relief came mainly from weight loss, another effect of the drug, lifestyle changes, or a combination. The trial also does not show that retatrutide prevents or reverses structural joint damage. The authors called for further studies on both the mechanisms of pain reduction and the drug’s potential as a disease-modifying osteoarthritis therapy.
The source report does not provide detailed breakdowns of every adverse event, the reasons for serious events, or long-term outcomes after treatment ends. It also notes that some participants left because they considered their weight loss excessive. How common that experience may be beyond this trial, and how benefits and risks compare with established treatments, remain unclear. Results in this population may not apply to people with osteoarthritis who do not have obesity.
Further Trials Must Test Durability
The immediate next step is further study of how long pain and function improvements last, how they relate to weight loss, and what happens when treatment is stopped. Longer follow-up and analysis of joint structure would be needed to assess a disease-modifying effect rather than symptom improvement alone. Researchers would also need to clarify the safety profile and the significance of treatment-related withdrawals.
Retatrutide remains investigational in the source material, which does not report an approval for osteoarthritis. Until additional evidence and regulatory decisions are available, the TRIUMPH-4 results are trial findings, not a basis for assuming the drug is an established knee-osteoarthritis treatment.
Key Questions
What did the TRIUMPH-4 trial find?
Over 68 weeks, participants with obesity and knee osteoarthritis assigned retatrutide had larger average reductions in WOMAC pain and disability scores than those assigned placebo. They also lost substantially more weight, according to the reported results.
Does retatrutide cure knee osteoarthritis?
No. The trial reported improvements in symptoms and weight, but did not establish that retatrutide reverses joint damage or changes the long-term course of osteoarthritis.
How was retatrutide given in the study?
Participants received a weekly injection of placebo or one of two retatrutide doses, 9 mg or 12 mg. All participants also received dietary counseling and encouragement to be physically active.
What side effects were reported?
Gastrointestinal events were the most common, the MedPage Today report said. Withdrawals because of adverse events and serious adverse events were more frequent in the retatrutide groups than in the placebo group.
Is retatrutide approved for osteoarthritis?
The source report describes retatrutide as investigational and does not report approval for osteoarthritis. The trial findings alone do not establish it as a routine treatment.
Source: medpagetoday.com
