Indianapolis, Indiana, United States, November 11, 2026
Eli Lilly and Company has announced detailed 52-week Phase 3b clinical results from its TOGETHER-PsA study evaluating the combined use of Taltz (ixekizumab) and Zepbound (tirzepatide) in adults with active psoriatic arthritis and obesity or overweight with at least one additional weight-related health condition. The findings showed that improvements in disease activity, physical function, fatigue and metabolic health observed during treatment were maintained or further improved through one year. At Week 52, 43.7% of participants receiving Taltz and Zepbound achieved an ACR50 response, representing at least a 50% reduction in psoriatic arthritis disease activity, compared with 15.7% of participants receiving Taltz alone. The combination also produced greater improvements in body weight and several metabolic measures, including blood pressure, glucose, glycated hemoglobin (HbA1c), triglycerides and total cholesterol. These findings build on the statistically significant results reported at the Week 36 primary endpoint. Lilly presented the detailed one-year findings at ACR Convergence 2026, the annual meeting of the American College of Rheumatology, and simultaneously published them in the journal Arthritis & Rheumatology. The results add clinical evidence to research investigating the relationship between inflammatory diseases and metabolic health.
TOGETHER-PsA Phase 3b Study Evaluates Combination Treatment
The TOGETHER-PsA study is a 52-week, randomized, multicenter, assessor-blinded, open-label Phase 3b clinical trial involving 271 adults with active psoriatic arthritis and obesity or overweight accompanied by at least one additional weight-related comorbidity. Participants were assigned to receive either Taltz alone or Taltz alongside Zepbound. Both medicines were administered by subcutaneous injection, and participants also received counseling on a reduced-calorie diet and increased physical activity. Taltz is an IL-17A-targeting monoclonal antibody that reduces inflammatory activity associated with psoriatic arthritis. Zepbound contains tirzepatide, a dual GIP and GLP-1 receptor agonist that helps regulate appetite and supports chronic weight management in eligible adults. The study investigated whether addressing inflammatory disease and excess body weight together could provide broader benefits than treating psoriatic arthritis alone. At Week 36, the combination demonstrated statistically superior results compared with Taltz monotherapy for the study’s primary and key secondary endpoints. The newly reported Week 52 findings provide additional information about the durability of these outcomes over a longer treatment period.
One-Year Results Demonstrate Improved Joint and Metabolic Outcomes
At Week 52, 39.2% of participants receiving Taltz and Zepbound achieved the combined primary outcome of ACR50 response and at least 10% body-weight reduction, compared with 1.7% receiving Taltz alone. The proportion achieving ACR50 independently was 43.7% in the combination group versus 15.7% in the monotherapy group. Furthermore, 85.7% of participants receiving both medicines achieved at least 10% weight reduction, compared with 6.7% receiving Taltz alone. Improvements were also observed in minimal disease activity, systemic inflammation and patient-reported outcomes. Measures of physical function, assessed using the Health Assessment Questionnaire Disability Index (HAQ-DI), showed greater improvement with combination treatment. Fatigue scores, evaluated through the Functional Assessment of Chronic Illness Therapy-Fatigue (FACIT-F) scale, also improved. The combination group demonstrated favorable changes in body mass index, high-sensitivity C-reactive protein, blood pressure, glucose, HbA1c, triglycerides and total cholesterol. Lilly also reported that a greater proportion of participants achieved ACR50 as early as Week 4, before clinically meaningful weight loss was observed. This finding provides an additional area of interest for understanding the relationship between inflammatory disease activity and metabolic health.
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Safety Findings and Significance for Immunometabolic Health
The safety profile of Taltz and Zepbound used together was generally consistent with the known safety profiles of the individual medicines. The most frequently reported adverse events in the combination treatment groups, each occurring in at least 5% of participants, included nausea, diarrhea, constipation, injection-site reactions, vomiting, dizziness and headache. Most events were generally mild to moderate, and Lilly reported no new safety concerns in the one-year findings. The company emphasized that the results contribute to a growing understanding of immunometabolic health, particularly in people living with both psoriatic arthritis and obesity. However, an important scientific qualification is that the Week 52 analyses were prespecified exploratory objectives without multiplicity control. Comparisons between time points were descriptive and were not adjusted for multiple testing. Therefore, these findings should be interpreted as supportive one-year follow-up data rather than independent confirmatory evidence for every outcome. Overall, the TOGETHER-PsA results highlight the potential value of studying inflammatory and metabolic conditions together. They provide further clinical evidence for this investigational combination approach, while treatment decisions and use of the medicines must continue to follow their respective approved indications and prescribing information.
Source: Eli Lilly and Company press release
