A new clinical trial demonstrates that treating psoriatic arthritis and obesity together with two medications delivers better results than treating the arthritis alone. The TOGETHER-PsA study, presented at the 2026 American Academy of Dermatology Annual Meeting, found that 33.5% of patients receiving both Taltz (ixekizumab) and Zepbound (tirzepatide) achieved significant improvement in joint symptoms, compared to 20.4% receiving Taltz alone .

Why Do Psoriatic Arthritis and Weight Often Go Hand in Hand?

Psoriatic arthritis (PsA) is an autoimmune condition that causes joint inflammation and pain, often accompanied by skin symptoms. What many people don't realize is that approximately 65% of adults with PsA in the United States also struggle with obesity or being overweight with at least one additional weight-related health concern . This combination creates a particularly challenging disease burden that's difficult to manage with traditional approaches.

The connection between these two conditions isn't coincidental. Both involve inflammation in the body, and carrying extra weight can worsen joint symptoms and make arthritis harder to control. Major treatment guidelines now recommend managing weight as part of comprehensive PsA care, yet most treatments address only one condition at a time.

What Did the TOGETHER-PsA Study Actually Test?

Researchers enrolled 271 participants with active psoriatic arthritis and obesity or overweight status in this 52-week trial . The study population was notably challenging: participants had an average body mass index (BMI) of 37.6 (roughly equivalent to 260 pounds for someone 5'10"), high disease activity at baseline, and more than 60% had already tried one or more advanced therapies without adequate relief .

Half the participants received Taltz alone, while the other half received Taltz combined with Zepbound. Both groups also received counseling on reduced-calorie diets and increased physical activity. Taltz works by blocking a specific immune protein called interleukin 17A (IL-17A), while Zepbound is a dual GIP and GLP-1 receptor agonist, meaning it activates two different pathways to help regulate appetite and blood sugar .

How to Understand the Key Results from This Trial

• Joint Improvement (ACR50): 33.5% of patients on combined therapy achieved at least 50% improvement in tender and swollen joints, plus improvement in three other disease measures, compared to 20.4% on Taltz alone
• Weight Loss Achievement: 84.5% of patients on combined therapy lost at least 10% of their body weight, a clinically meaningful reduction that typically improves overall health
• Low Disease Activity Target: 26.3% of patients on combined therapy reached Minimal Disease Activity (MDA), a high treatment goal indicating well-controlled arthritis, compared to 15.3% on Taltz alone
• Quality of Life Improvements: Patients reported significant reductions in fatigue, better physical function, and improved mental health-related quality of life with combined treatment
• Cardiometabolic Benefits: Combined therapy led to improvements in blood pressure, glucose levels, HbA1c (a marker of long-term blood sugar control), triglycerides, and total cholesterol

One particularly striking finding was that patients showed greater reduction in arthritis disease activity as early as week 4 in the combined treatment group, before clinically meaningful weight loss had even occurred . This suggests the medications may work through complementary mechanisms rather than weight loss alone driving the arthritis improvement.

"In TOGETHER-PsA, treating PsA and obesity concurrently with Taltz and Zepbound yielded meaningful, broad improvements in PsA disease activity, inflammation, and outcomes that can impact patients' daily lives, such as fatigue, disability and quality of life," said Philip Mease, Director of Rheumatology Research at Swedish Medical Center and Clinical Professor at the University of Washington, Seattle.

Philip Mease, Director of Rheumatology Research, Swedish Medical Center

The inflammation marker hsCRP (high-sensitivity C-reactive protein), which indicates systemic inflammation throughout the body, also showed greater improvement with combined therapy . Additionally, patients reported better physical function using the HAQ-DI (Health Assessment Questionnaire-Disability Index), meaning they could perform daily activities more easily.

What About Safety and Side Effects?

The adverse events reported were generally mild to moderate and consistent with what's known about each medication individually . In the combined treatment group, the most common side effects occurring in at least 5% of participants included nausea, diarrhea, constipation, and injection site reactions. In the Taltz-alone group, injection site reactions and upper respiratory tract infections were most common. No unexpected safety concerns emerged from combining these two medications.

"Living with psoriatic arthritis and obesity can deeply affect every part of a person's day, from how they feel physically to what they're able to do. The TOGETHER-PsA results show that when Taltz and Zepbound were used together, people saw meaningful improvements in their psoriatic arthritis and felt better in their daily lives," explained Adrienne Brown, Executive Vice President and President of Lilly Immunology.

Adrienne Brown, Executive Vice President and President, Lilly Immunology

Why This Approach Represents a Shift in Autoimmune Treatment

This trial highlights an important evolution in how doctors think about treating autoimmune conditions. Rather than managing each disease separately with different specialists and medication regimens, the TOGETHER-PsA results suggest that addressing multiple interconnected health problems simultaneously may yield better outcomes. For patients juggling both arthritis and weight management, this integrated approach could simplify treatment and improve quality of life more comprehensively.

The study was specifically designed for a real-world patient population: people with difficult-to-treat disease who had already failed other therapies. This makes the results particularly relevant for patients struggling with both conditions despite existing treatments. The findings were published simultaneously in the journal Arthritis & Rheumatology, adding to the scientific evidence base .

Taltz is now the only biologic medication with clinical evidence supporting this comprehensive treatment approach alongside an incretin therapy like Zepbound for people with psoriatic arthritis who also have obesity or overweight . As these results are discussed with regulatory agencies, they may influence how treatment guidelines evolve for this patient population.