The Phase 3b TOGETHER‑PsA study, presented at the American Academy of Dermatology Annual Meeting on March 28 2026, evaluated ixekizumab (Taltz) plus tirzepatide (Zepbound) versus ixekizumab alone in adults with active psoriatic arthritis and obesity or overweight. The primary composite endpoint—ACR50 response and ≥10 % weight loss at 36 weeks—was met by 31.7 % of patients receiving the combination, compared with only 0.8 % on ixekizumab monotherapy.
Secondary analyses confirmed the superiority of the combination across all key endpoints. ACR20 and ACR50 responses were higher in the combination arm, and significant reductions were observed in BMI, systolic blood pressure, and HbA1c. These cardiometabolic improvements underscore the dual benefit of treating both psoriatic arthritis and obesity in a single regimen.
The data reinforce Lilly’s obesity‑driven growth strategy by demonstrating that its flagship obesity drug can be paired with an IL‑17A inhibitor to address a high‑risk, high‑need patient population. Payer coverage decisions are likely to be influenced by the dual efficacy, potentially accelerating clinical adoption and expanding Lilly’s market share at the intersection of rheumatology and obesity.
"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, M.D., study author. "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 PsA has remained challenging. The observed benefit with treatment using ixekizumab and tirzepatide appears to meaningfully impact psoriatic disease activity, indicating that for many patients, PsA is an obesity‑related condition," added Joseph F. Merola, MD.
"2025 was an important year for Lilly. We reached millions more patients—launching Inluriyo, expanding Mounjaro and Kisunla globally, and submitting orforglipron for approval. We expanded our manufacturing capacity, and through our U.S. government agreement, opened new access to obesity medicines. Entering our 150th year with a deep pipeline and platforms like LillyDirect, we're positioned to reach more patients than ever and expand our global health impact," said CEO David A. Ricks.
The TOGETHER‑PsA results support Lilly’s broader strategy of leveraging its incretin franchise beyond obesity. By demonstrating clinical benefit in a rheumatologic indication, the company can expand the therapeutic reach of tirzepatide, strengthen its competitive position in both obesity and rheumatology markets, and potentially unlock new payer pathways and revenue streams.
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