Lilly’s Taltz (ixekizumab) and Mounjaro▼ (tirzepatide) used together demonstrated significant efficacy in adults with active psoriatic arthritis and obesity or overweight

Lilly’s Taltz (ixekizumab) and Mounjaro▼ (tirzepatide) used together demonstrated significant efficacy in adults with active psoriatic arthritis and obesity or overweight 

In a first-of-its-kind Phase 3b 52 week trial, the TOGETHER-PsA study, at 36 weeks, met its primary endpoint of 50% improvement in psoriatic arthritis (PsA) activity based on ACR50 in addition to ≥10% weight reduction with concomitant ixekizumab and tirzepatide compared to ixekizumab monotherapy    

Ixekizumab is now the first and only biologic for PsA with data supporting its potential use alongside an incretin therapy for patients who also have obesity  (BMI ≥30kg/m²) or overweight (BMI 27-29.9 kg/m²) with at least one weight-related condition 

BASINGSTOKE, January 9, 2026 – Eli Lilly and Company (NYSE: LLY) has announced positive topline results from the TOGETHER-PsA open-label Phase 3b trial evaluating the concomitant use of ixekizumab and tirzepatide compared to ixekizumab alone in adults with active psoriatic arthritis (PsA) and obesity or overweight with at least one weight-related condition. At 36 weeks, treatment with concomitant ixekizumab and tirzepatide met the primary and all key secondary endpoints for superiority to ixekizumab monotherapy. TOGETHER-PsA is the first controlled study to evaluate an incretin therapy used with a PsA biologic.  
 

In the study, 31.7% of patients in the ixekizumab plus tirzepatide treatment arm achieved a 50% improvement in PsA activity, based on American College of Rheumatology 50 (ACR50), and weight reduction of at least 10%, compared to 0.8% of patients on ixekizumab monotherapy, meeting the primary endpoint (p<.001). In a key secondary endpoint, 33.5% of patients on ixekizumab plus tirzepatide achieved ACR50 vs. 20.4% on ixekizumab alone.^1,2 The study population included patients with a high disease burden at baseline and an average BMI of 37.6 kg/m² across both arms. Patients had high disease activity and meaningful functional impairment.³ More than 60% had prior experience with one or more advanced therapies for PsA. 

“This is the first controlled pharmacologic study to demonstrate that treatment of obesity improved PsA disease measures,” said Mark Genovese, M.D., senior vice president of Lilly Immunology development. “These results demonstrate how an integrated treatment approach has the potential to improve the standard of care.” 

Adverse events in participants treated with concomitant administration of ixekizumab and tirzepatide were generally mild to moderate, and consistent with the known safety profile of each medicine. The most common adverse events were nausea, diarrhoea, constipation and injection site reactions in the concomitant treatment arm, and injection site reactions and upper respiratory tract infections in the ixekizumab monotherapy arm. 

“While treatment guidelines for psoriatic arthritis recommend management of obesity, the reality is these two chronic diseases are often addressed separately and moving the needle in psoriatic arthritis has remained challenging,” said Joseph F. Merola, M.D., Professor and Chair, Department of Dermatology and Professor of Internal Medicine in the Division of Rheumatic Diseases, UT Southwestern Medical Centre. “The observed benefit with treatment using ixekizumab and tirzepatide appears to meaningfully impact psoriatic disease activity.”  

Detailed 36-week results from the TOGETHER-PsA trial will be presented at an upcoming medical meeting and discussed with regulators.  

About the TOGETHER-PsA Trial 

TOGETHER-PsA (NCT06588296) is a 52-week Phase 3b, randomised, multicentre, assessor-blinded, open-label study assessing the efficacy and safety of concomitant administration of ixekizumab and tirzepatide compared with ixekizumab alone in adult participants with active psoriatic arthritis and obesity or overweight. A total of 271 participants were randomised 1:1 to receive either ixekizumab alone or concomitantly with tirzepatide, both administered subcutaneously. Patients in both arms received counselling on a reduced-calorie diet and increased physical activity. The primary endpoint of the study is to assess the proportion of participants achieving both an ACR50 response and ≥10% weight reduction at Week 36. Participants must have a BMI ≥30 kg/m², or ≥27 to <30 kg/m² with at least one weight-related comorbidity.  

About ixekizumab⁴ 

Ixekizumab is a monoclonal antibody that selectively binds with interleukin 17A (IL-17A) cytokine and inhibits its interaction with the IL-17 receptor. IL-17A is a naturally occurring cytokine that is involved in normal inflammatory and immune responses. Ixekizumab inhibits the release of pro-inflammatory cytokines and chemokines. Ixekizumab is approved to treat adults with active psoriatic arthritis. Ixekizumab, alone or in combination with methotrexate, is indicated for the treatment of active psoriatic arthritis in adult patients who have responded inadequately to, or who are intolerant to one or more disease-modifying anti-rheumatic drug (DMARD) therapies.   

About tirzepatide⁵ 
Tirzepatide is a once-weekly dual GIP (glucose-dependent insulinotropic polypeptide) receptor and GLP-1 (glucagon-like peptide-1) receptor agonist. Tirzepatide is a single molecule that activates the body's receptors for GIP and GLP-1, which are natural incretin hormones. Both GIP and GLP-1 receptors are found in areas of the human brain important for appetite regulation. Tirzepatide decreases calorie intake, and the effects are likely mediated by affecting appetite. Tirzepatide is indicated for weight management, including weight loss and weight maintenance, as an adjunct to a reduced-calorie diet and increased physical activity in adults with an initial Body Mass Index (BMI) of 

• ≥ 30 kg/ m² (obesity) or
• ≥ 27 kg/m² to < 30 kg/m²(overweight) in the presence of at least one weight-related comorbid condition (e.g., hypertension, dyslipidaemia, obstructive sleep apnoea, cardiovascular disease, prediabetes, or type 2 diabetes mellitus).

Endnotes and References 

¹ Hypothetical efficacy estimand in the modified intent-to-treat (mITT) population is used. The hypothetical efficacy estimand represents efficacy in all mITT participants who remained on study intervention without initiating prohibited medication.  

² ACR50 is a composite measure requiring at least a 50% improvement in the number of tender joints (TJC) and swollen joints (SJC), plus at least a 50% improvement in three of the five other core disease activity measures (patient pain assessment, patient global assessment of disease activity, physician global assessment of disease activity, patient assessment of physical function by health assessment questionnaire, and an acute phase reactant as measured by High-Sensitivity C-Reactive Protein [hsCRP])  

³ High disease activity was defined as a mean Disease Activity Index for Psoriatic Arthritis (DAPSA) score of 58.65 at baseline. Functional impairment was defined as a mean Health Assessment Questionnaire – Disability Index (HAQ-DI) score of 1.3 at baseline.  

⁴Taltz 80 mg solution for injection in pre-filled pen - Summary of Product Characteristics (SmPC) - (emc) | 8199. Available at: https://www.medicines.org.uk/emc/product/8199/smpc 

⁵Mounjaro ▼ KwikPen 5mg solution for injection in pre-filled pen - Summary of Product Characteristics (SmPC). Available at:  

https://www.medicines.org.uk/emc/product/15482/smpc 

About Lilly  
Lilly is a medicine company turning science into therapies to make life better for people around the world. We’ve been pioneering life-changing discoveries for nearly 150 years, and today our medicines help tens of millions of people across the globe. Harnessing the power of biotechnology, chemistry and genetic medicine, our scientists are  advancing new discoveries to address some of the world’s most significant health challenges: redefining diabetes and obesity care; advancing the fight against Alzheimer’s disease; providing options for debilitating immune system disorders; and transforming the management of difficult-to-treat cancers. With each step toward a healthier world, we’re motivated by one thing: making life better for millions more people. That includes delivering innovative clinical trials that reflect the diversity of our world and working to ensure our medicines are accessible and affordable. To learn more visit Lilly.com/uk or follow us on LinkedIn 

▼ This medicinal product is subject to additional monitoring. This will allow quick identification of new safety information. Reporting suspected adverse reactions after authorisation of the medicinal product is important. It allows continued monitoring of the benefit/risk balance of the medicinal product. Healthcare professionals are asked to report any suspected adverse reactions via the Yellow Card Scheme: www.mhra.gov.uk/yellowcard or search for MHRA Yellow Card in the Google Play or Apple App Store.   

For further information, contact:  
Lorna May, Lilly Press Office    
Phone: +44 20 3162 0046    
Email: ukpublicaffairs@lilly.com    

 
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