What the one-year combination trials revealed
- In the TOGETHER-PsO trial, 30.6% of adult participants taking ixekizumab combined with tirzepatide achieved complete skin clearance and lost at least 10% of their body weight at 52 weeks, compared to 4.4% of those receiving ixekizumab alone.
- In the TOGETHER-PsA trial, 39.2% of patients taking both drugs reached a 50% improvement in joint disease markers alongside a minimum 10% weight reduction at one year, compared to 1.7% in the monotherapy group.
- Standalone skin clearance (PASI 100) at 52 weeks reached 40.5% in the combination therapy arm versus 29.1% in the monotherapy arm.
- Standalone joint disease reduction (ACR50) at 52 weeks reached 43.7% in the combination arm versus 15.7% for ixekizumab monotherapy.
- The two Phase 3b trials, sponsored by Eli Lilly, enrolled 274 and 271 participants respectively across US study sites.
| Finding | Plain-English meaning |
|---|---|
| 30.6% achieved PASI 100 and >=10% weight loss in TOGETHER-PsO | Roughly three in ten adults with psoriasis and obesity cleared all skin plaques and lost over a tenth of their body weight on dual therapy. |
| 39.2% achieved ACR50 and >=10% weight loss in TOGETHER-PsA | Nearly four in ten patients with joint inflammation halved their joint symptoms while losing significant weight when combining both medications. |
| 43.7% reached ACR50 joint response on combination therapy | Patients taking both drugs were almost three times as likely to cut joint pain and swelling in half compared to taking the skin drug alone. |
Understanding psoriatic conditions and metabolic drivers
Psoriasis is a chronic inflammatory condition that causes itchy, red, scaly patches on the skin. A related condition, psoriatic arthritis, causes painful swelling, stiffness, and structural inflammation inside the joints. These autoimmune conditions do not exist in isolation. Epidemiological data indicates that between 60% and 78% of people diagnosed with psoriasis also live with overweight or obesity. In the United States, roughly 61% of psoriasis patients and 65% of psoriatic arthritis patients fall into these weight categories while managing at least one additional metabolic issue such as high blood pressure, type 2 diabetes, or altered lipid levels.
Excess adipose tissue is not passive storage mass. Fat tissue actively secretes biochemical signaling proteins called cytokines that drive systemic inflammation throughout the vascular system, skin tissue, and joint linings. For decades, clinicians observed that high body weight reduced the effectiveness of standard biologic therapies, leading to lower remission rates and persistent joint pain. Adding weight management directly into autoimmune care addresses both mechanical load on joints and the systemic chemical signals generated by excess body fat.
Dual targeting of skin joints and body weight
The clinical trials evaluated two separate therapeutic mechanisms administered together over a 52-week period. Ixekizumab, sold under the brand name Taltz, is a targeted humanized monoclonal antibody that blocks interleukin-17A (IL-17A), a key signaling protein responsible for driving skin plaque formation and joint swelling. Tirzepatide, sold under the brand names Zepbound and Mounjaro, acts as a dual receptor agonist for glucose-dependent insulinotropic polypeptide (GIP) and glucagon-like peptide-1 (GLP-1). Tirzepatide regulates blood glucose, slows gastric emptying, and reduces body mass.
During the trials, participants receiving ixekizumab were given an initial dose of 180 mg, followed by regular monthly doses of 80 mg. Participants in the combination treatment group also received weekly tirzepatide injections, starting at 2.5 mg and escalating over time to a maximum dose of 15 mg weekly. All trial participants across both treatment arms received standard counseling on reduced-calorie nutritional planning and increased physical activity.
Summary of trial parameters and main outcomes
| Trial Metric | TOGETHER-PsO (Plaque Psoriasis) | TOGETHER-PsA (Psoriatic Arthritis) |
|---|---|---|
| Total Enrolled Participants | 274 adults | 271 adults |
| Mean Baseline Body Mass Index | 39.2 | 37.6 |
| Composite Endpoint (Drug Combo) | 30.6% (PASI 100 + >=10% weight loss) | 39.2% (ACR50 + >=10% weight loss) |
| Composite Endpoint (Monotherapy) | 4.4% (PASI 100 + >=10% weight loss) | 1.7% (ACR50 + >=10% weight loss) |
| Primary Symptom Outcome Alone | 40.5% (PASI 100 at 52 weeks) | 43.7% (ACR50 at 52 weeks) |
Comparing one-year treatment outcomes across trial arms
On August 31, 2026, Eli Lilly announced top-line 52-week data from the two Phase 3b studies, showing that combining metabolic treatment with biologic therapy yielded superior disease control compared to biologic therapy alone. In the TOGETHER-PsO trial, 40.5% of participants on dual therapy maintained 100% skin clearance (PASI 100) at one year, compared to 29.1% of participants receiving ixekizumab alone.
An earlier 36-week analysis of the TOGETHER-PsO trial, published in JAMA Dermatology on July 1, 2026, examined 274 adults with a mean age of 45.6 years and a baseline Psoriasis Area and Severity Index (PASI) score of 19.7. At 36 weeks, 27.1% of the combination group hit the dual target of complete skin clearance and >=10% weight loss, compared to 5.8% in the monotherapy group. That represented a risk difference of 21.2% (95% CI, 12.8% to 29.7%; P < .001). Furthermore, 79.9% of combination patients achieved at least 75% skin clearance (PASI 75) combined with a >=5% weight loss at 36 weeks, compared to 17.9% of monotherapy participants.
In the TOGETHER-PsA trial, joint outcomes showed a similar spread. At 52 weeks, 43.7% of patients on the combination regimen achieved an ACR50 response, which measures a 50% reduction in swollen and tender joint counts alongside patient assessment scores. By contrast, only 15.7% of patients taking ixekizumab monotherapy achieved an ACR50 response.
Beyond skin and joint metrics, the dual-therapy groups in both trials demonstrated greater reductions in systemic inflammatory biomarkers, specifically high-sensitivity C-reactive protein (hs-CRP). Participants in the combination arms also showed improvements across blood pressure, fasting blood glucose, glycated hemoglobin (A1c), total cholesterol, and triglyceride levels.
Dr. Joseph F. Merola of UT Southwestern Medical Center, who presented earlier 36-week data at the American Academy of Dermatology meeting in March 2026, observed that historical attempts to combine biologics or add supportive therapies had failed to produce major shifts in ACR50 joint scores. Mark Genovese, MD, senior vice president of Lilly Immunology Development, noted that the one-year results showed that initial improvements were either sustained or deepened over the full 52-week period.
Safety profiles and study limitations
The side effect profile reported across both 52-week trials reflected the known safety parameters of each drug individually, with no unexpected safety signals emerging from concurrent administration. Most reported adverse events were classified as mild to moderate in severity.
Adverse events reported by 5% or more of participants in the combination treatment arms included:
- Nausea
- Diarrhea
- Constipation
- Vomiting
- Injection-site reactions
- Dizziness
- Headache
Several study parameters warrant consideration when evaluating these results. Both TOGETHER-PsO and TOGETHER-PsA were open-label Phase 3b trials, meaning participants and treating clinicians were aware of assigned treatments, though outcome assessors were blinded. Both trials were designed, managed, and funded by Eli Lilly, the manufacturer of both ixekizumab and tirzepatide.
Dr. Joseph F. Merola also disclosed extensive financial relationships with pharmaceutical manufacturers, including Eli Lilly, AbbVie, Amgen, AstraZeneca, Biogen, Boehringer Ingelheim, Bristol Myers Squibb, Dermavant, Galderma, Janssen, Moonlake, Novartis, Oruka, Pfizer, Regeneron, Sanofi, Sun Pharma, and UCB. The press releases and published data focused on 52-week outcomes; long-term data following treatment discontinuation or multi-year continuous use was not reported, so the durability and safety of the combination beyond one year remain unknown.
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Sources:
- Medscape, “1-Year Results Reported for Tirzepatide-Ixekizumab Combo”: https://www.medscape.com/viewarticle/1-year-results-reported-tirzepatide-ixekizumab-combo-2026a1000vf2
- BioPharm International, “Ixekizumab (Taltz) and Tirzepatide (Zepbound) Show One-Year Psoriatic Disease Benefit”: https://www.biopharminternational.com/view/ixekizumab-taltz-tirzepatide-zepbound-1-year-psoriatic-disease
- PubMed (National Library of Medicine), “Combination ixekizumab and tirzepatide in psoriatic disease with obesity”: https://pubmed.ncbi.nlm.nih.gov/42139049/
Disclaimer: This article is for general information only and does not constitute medical advice, diagnosis, or treatment. Always consult a qualified healthcare provider about any medical condition or before making health decisions.