Retatrutide trials report less knee osteoarthritis pain; ixekizumab plus tirzepatide shows exploratory ACR50 benefits in psoriatic arthritis.
“For many people living with knee osteoarthritis pain or psoriatic arthritis, obesity can compound the challenges of managing their condition, affecting how they feel and function every day,” Adrienne Brown, executive vice president and president of Lilly Immunology, said in the announcement.¹
The randomized phase 3 TRIUMPH-4 trial evaluated once-weekly retatrutide over 68 weeks. Lilly reported a mean reduction of up to 4.5 points on the Western Ontario and McMaster Universities Osteoarthritis Index (WOMAC) pain subscale, from an average baseline score of 6.0. More than 1 in 8 retatrutide-treated participants reported no knee pain at trial completion.¹
In the 80-week, randomized phase 3 TRIUMPH-1 trial, which evaluated 3 retatrutide doses, WOMAC pain scores decreased by up to 4.3 points from a baseline of 6.0. More than 1 in 6 retatrutide-treated participants reported no knee pain at completion.¹
The corresponding relative pain reductions—75.8% and 73.1%—were calculated in post hoc analyses, rather than prespecified analyses. The announcement did not provide comparator-group pain results, sample sizes, confidence intervals, or numerical weight-loss outcomes. Consequently, the reported within-group changes do not establish the magnitude of benefit relative to the trial comparators.¹
Retatrutide activates glucose-dependent insulinotropic polypeptide (GIP), glucagon-like peptide-1 (GLP-1), and glucagon receptors. It remains investigational; the announcement describes no regulatory approval or submission for knee osteoarthritis.¹
The randomized phase 3b TOGETHER-PsA study compared ixekizumab plus tirzepatide with ixekizumab alone in adults with psoriatic arthritis and obesity, or overweight with at least 1 weight-related comorbidity. At week 52, ACR50 responses were reported in 43.7% and 15.7%, respectively. Lilly also reported favorable disease activity, patient-reported, and metabolic outcomes without supplying detailed numerical results for those measures.¹
Importantly, the week 52 analyses were prespecified exploratory objectives without multiplicity control. Comparisons between time points were descriptive. These results therefore warrant cautious interpretation rather than being treated as confirmatory evidence of superiority across outcomes.¹
Ixekizumab inhibits interleukin-17A and is approved for active psoriatic arthritis, among other inflammatory conditions. Tirzepatide activates GIP and GLP-1 receptors; its US indications include weight management in eligible adults and moderate-to-severe obstructive sleep apnea in adults with obesity. The announcement reports no new indication for concomitant treatment.¹
According to Lilly, guidelines for both rheumatologic conditions recommend weight loss, although obesity and joint disease are often managed separately. The studies examine integrated treatment, but the summarized results do not establish how much joint improvement reflects weight reduction versus other treatment effects.¹
Trial-specific adverse-event and discontinuation rates were not supplied. The included prescribing summaries identify infection and inflammatory bowel disease risks with ixekizumab, and gastrointestinal adverse effects, pancreatitis, gallbladder disease, and thyroid tumor warnings with tirzepatide. These established warnings should not be mistaken for safety findings from the reported trials. Full efficacy and safety results are needed to assess benefit-risk and clinical applicability.¹
