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Headline
Dual Therapy With Ixekizumab and Tirzepatide Superior to Biologic Monotherapy for Psoriatic Disease and Weight Reduction at 52 Weeks: Topline Results From TOGETHER-PsO and TOGETHER-PsA
1-Minute Summary
Topline 52-week data from the phase 3b TOGETHER-PsO and TOGETHER-PsA randomized clinical trials demonstrate that adding tirzepatideโa dual glucose-dependent insulinotropic polypeptide (GIP) and glucagon-like peptide-1 (GLP-1) receptor agonistโto ixekizumab (an interleukin-17A inhibitor) significantly outperforms ixekizumab monotherapy in adults with moderate to severe psoriatic disease and co-occurring overweight or obesity. Co-administration produced marked improvements in composite endpoints combining clinical disease control (PASI 100 or ACR50) with significant weight reduction ($\ge$10%), while also yielding superior standalone skin clearance, joint symptom reduction, and broad cardiometabolic benefits compared with biologic monotherapy.
Why This Matters
Obesity is a highly prevalent comorbidity in psoriatic disease that exacerbates systemic low-grade inflammation, reduces clinical response rates to biologic agents, and increases cardiovascular morbidity. Traditionally, dermatologic and rheumatologic care has focused strictly on immune-targeted therapy, addressing metabolic dysfunction as a separate, secondary concern. These 1-year findings provide randomized trial evidence that simultaneously targeting IL-17A-driven inflammation and incretin-mediated metabolic pathways improves both cutaneous and articular manifestations while mitigating underlying cardiometabolic risk.
Study at a Glance
| Feature | Details |
| Study type | Two multicenter, phase 3b, randomized clinical trials (TOGETHER-PsO and TOGETHER-PsA) |
| Participants | TOGETHER-PsO: 274 adults with moderate to severe plaque psoriasis and overweight or obesity (BMI $\ge$27 kg/mยฒ with $\ge$1 weight-related comorbidity or BMI $\ge$30 kg/mยฒ). TOGETHER-PsA: 271 adults with active psoriatic arthritis and overweight or obesity. |
| Intervention | Ixekizumab (Taltz) plus tirzepatide (Zepbound) alongside lifestyle counseling (diet and physical activity) |
| Comparator | Ixekizumab monotherapy alongside lifestyle counseling |
| Primary outcome | TOGETHER-PsO: Proportion of patients achieving both complete skin clearance (PASI 100) and $\ge$10% body weight reduction at week 52. TOGETHER-PsA: Proportion of patients achieving both $\ge$50% improvement in arthritis activity (ACR50) and $\ge$10% body weight reduction at week 52. |
| Main finding | Combination therapy achieved significantly higher rates of both primary composite endpoints: 30.6% vs 4.4% in plaque psoriasis, and 39.2% vs 1.7% in psoriatic arthritis. Standalone joint and skin clearance rates were also substantially higher with dual therapy. |
| Follow-up | 52 weeks (1 year) |
What the Researchers Found
In both trials, participants were randomized 1:1 to receive combination therapy with ixekizumab and tirzepatide or ixekizumab monotherapy. The primary multicomponent endpoints, as well as standalone skin and joint efficacy measures, favored combination therapy through 52 weeks.
Week 52 Primary and Key Secondary Efficacy Outcomes
| Trial & Outcome Measure | Combination Therapy (Ixekizumab + Tirzepatide) | Monotherapy (Ixekizumab Alone) |
| TOGETHER-PsO (Plaque Psoriasis, N = 274) | ||
| Primary Composite: PASI 100 + $\ge$10% Body Weight Loss | 30.6% | 4.4% |
| Complete Skin Clearance Alone (PASI 100) | >40.0% | 29.1% |
| TOGETHER-PsA (Psoriatic Arthritis, N = 271) | ||
| Primary Composite: ACR50 + $\ge$10% Body Weight Loss | 39.2% | 1.7% |
| Arthritis Response Alone (ACR50 without weight criterion) | 43.7% | 15.7% |
Cardiometabolic and Inflammatory Biomarkers
Across both trials, patients in the combination therapy cohorts demonstrated sustained improvements through week 52 in multiple systemic parameters:
- Systemic inflammation: Reductions in high-sensitivity C-reactive protein (hs-CRP)
- Anthropometric & Hemodynamic: Reductions in body mass index (BMI) and blood pressure
- Glycemic & Lipid Profiles: Decreases in fasting glucose, glycated hemoglobin (HbA1c), serum triglycerides, and total cholesterol
Safety Profile
Adverse events documented through 52 weeks were generally mild to moderate in severity and aligned with the established safety profiles of each individual drug class. Adverse events occurring with an incidence $\ge$5% in the combination therapy arms included:
- Nausea
- Diarrhea
- Constipation
- Vomiting
- Injection site reactions
- Dizziness
- Headache
Joseph F. Merola, MD, MMSc, FAAD, professor and chair of dermatology and professor of internal medicine at UT Southwestern Medical Center, observed:
โPsoriatic disease is often accompanied by obesity or overweight, which can make treatment goals related to the skin and joints harder to reach. In psoriatic arthritis, the greater improvements in disease activity seen with Taltz and Zepbound in the first month, before clinically meaningful weight loss occurred, continued through 1 year. In psoriasis, the durability of complete skin clearance at 1 year represents real, lasting progress for patients. Paired with continued metabolic improvements, these findings show what may be possible when treating psoriatic disease and obesity concurrently.โ
Clinical Significance
These data show that incretin receptor agonists do not merely serve as adjunctive therapies for mechanical or cosmetic weight reduction, but actively enhance musculoskeletal and cutaneous therapeutic targets.
Notably, Dr. Merola observed that joint disease responses in TOGETHER-PsA separated early (within the first month of therapy)โprior to significant weight reductionโsuggesting that GIP/GLP-1 receptor agonism may exert independent, direct immunomodulatory or anti-inflammatory effects that complement IL-17A inhibition. Furthermore, sustained weight reduction decreases mechanical stress on entheses and downregulates adipokine-mediated pro-inflammatory signaling (e.g., TNF-ฮฑ, IL-6), leading to durable joint and skin control.
Limitations
- Topline Report: These data derive from an initial pharmaceutical company topline press release; final peer-reviewed publication of complete data tables, subgroup analyses, and exact P values is still pending.
- Population Selectivity: The study cohorts specifically enrolled patients with obesity or overweight with associated metabolic comorbidities; results cannot be generalized to normal-weight individuals with psoriatic disease.
- Duration: While 52-week data confirm medium-term durability, lifelong management is typical for psoriatic disease and obesity, requiring longer observational windows to assess durability post-discontinuation.
- Treatment Complexity & Access: Dual biologic/incretin regimens introduce practical barriers related to insurance coverage, patient adherence to multiple injectable therapies, and cumulative costs.
What Doctors Should Know
- Adopt Holistic Management: When treating psoriatic disease in patients with excess adiposity, clinicians should address obesity as an active driver of inflammatory pathology rather than an unrelated comorbidity.
Joel M. Gelfand, MD, MSCE, FAAD, professor of dermatology and epidemiology at the University of Pennsylvania, emphasized:
โThe 52-week topline data from these trials adds more evidence that in patients who are overweight or obese treating psoriatic disease holistically by adding a GLP-1 agonist to a biologic results in not only better metabolic outcomes, but also better outcomes in the skin and the joints. I routinely recommend GLP-1 agonists when indicated to my patients with psoriatic disease with the goal of not just improving their skin and joint disease, but also their overall cardiometabolic health.โ
- Anticipate Gastrointestinal Adverse Effects: Counsel patients regarding transient gastrointestinal side effects (e.g., nausea, diarrhea, vomiting, constipation) typical of incretin mimetics during dose titration.
- Monitor Comprehensive Biomarkers: Track metabolic indices (HbA1c, lipid panels, blood pressure) alongside standard rheumatology and dermatology metrics (PASI, swollen/tender joint counts).
Bottom Line
In patients with moderate to severe psoriatic disease and overweight or obesity, combining the IL-17A inhibitor ixekizumab with the dual GIP/GLP-1 receptor agonist tirzepatide produces superior 1-year outcomes across skin clearance, articular disease activity, body weight, and cardiometabolic biomarkers compared with biologic monotherapy.
Original Research / Source
Topline 52-week results from the Phase 3b TOGETHER-PsO and TOGETHER-PsA clinical trials (Eli Lilly and Company). Peer-reviewed presentation and publication pending.
