How Lilly’s Psoriasis Trial Validates an Integrated Immunometabolic Treatment Approach

Growing recognition that inflammatory and metabolic diseases share overlapping biological drivers is reshaping treatment strategies across immunology and chronic disease care, as demonstrated by data in a new Phase IIIb trial (TOGETHER-PsO) by Eli Lilly and Company (Lilly). The data, which Lilly announced in February 2026, suggest that simultaneously targeting immune-mediated skin inflammation and obesity may significantly improve clinical outcomes in patients with moderate-to-severe psoriasis, supporting an emerging multidisease treatment paradigm.¹

Results from the trial evaluating concomitant treatment with Lilly’s ixekizumab (brand name Taltz) and tirzepatide (brand name Zepbound) demonstrated superior efficacy compared with biologic therapy alone, highlighting the potential of integrated immunometabolic intervention strategies.

Can treating metabolic disease improve psoriasis outcomes?

Psoriasis and obesity frequently coexist, with approximately 61% of patients living with psoriasis also affected by overweight or obesity alongside related comorbidities.² Increasing body mass index (BMI) has been associated with reduced response rates to biologic therapies, creating persistent treatment challenges in high-burden patient populations.

At 36 weeks, patients receiving concomitant ixekizumab and tirzepatide achieved the study’s primary endpoint, demonstrating superiority over ixekizumab monotherapy in reaching both complete skin clearance (Psoriasis Area Severity Index [PASI] 100) and at least 10% weight reduction.¹

A total of 27.1% of patients receiving combination therapy met this dual endpoint compared with 5.8% receiving biologic treatment alone (p<0.001). In a key secondary endpoint, combination therapy produced a 40% relative increase in PASI 100 achievement versus monotherapy (40.6% vs. 29.0%, p<0.05).¹

The enrolled population represented one of the highest BMI cohorts studied in psoriasis biologic trials, with mean BMI exceeding 39 kg/m², which is approximately 9–10 kg/m² higher than populations evaluated in prior Phase III registrational studies using psoriasis biologic therapies.^1,3

What does dual pathway targeting reveal about disease biology?

The findings reinforce growing evidence that psoriasis and obesity share interconnected inflammatory pathways rather than representing independent clinical conditions.

“Psoriasis and obesity can profoundly impact how people feel, how they are seen, and how they live,” said Adrienne Brown, executive vice president and president, Lilly Immunology, in a company press release.¹ “For people living at the intersection of these chronic inflammatory diseases, these PASI 100 results represent far more than a clinical milestone—they demonstrate what becomes possible when we address both simultaneously.”

Ixekizumab selectively inhibits interleukin-17A, a cytokine central to inflammatory signaling in psoriatic disease. Tirzepatide, a dual glucose-dependent insulinotropic polypeptide (GIP) and glucagon-like peptide-1 receptor agonist, reduces body weight through metabolic regulation and appetite suppression. Together, the therapies appear to address both immune activation and metabolic dysfunction contributing to disease persistence.

Mark Lebwohl, MD, dean for Clinical Therapeutics and professor and chairman emeritus of the Department of Dermatology at the Icahn School of Medicine at Mount Sinai and principal investigator of the Phase IIIb trial, noted that the results support a shift away from treating psoriasis and obesity independently. “Psoriasis and obesity share underlying inflammatory pathways, yet they are too often treated in silos despite psoriasis treatment guidelines calling for obesity management,” he said in the release.¹

Could immunometabolic combinations redefine chronic disease management?

Safety findings were consistent with established profiles for both agents, with adverse events generally mild to moderate. According to the company, the most commonly reported events included gastrointestinal symptoms and injection-site reactions.

Beyond dermatology, the results may signal broader implications for drug development strategies targeting interconnected chronic diseases. As incretin therapies expand beyond metabolic indications, combination approaches pairing immune modulators with metabolic agents may represent a new avenue for improving therapeutic response in complex inflammatory conditions.⁴

Detailed Phase IIIb study results are expected to be published in a peer-reviewed journal and discussed with regulatory authorities, according to Lilly. The results could potentially inform future clinical development strategies focused on integrated disease management.

References

1. Eli Lilly and Company. Lilly's Taltz (ixekizumab) and Zepbound (tirzepatide) used together delivered superior efficacy in first-of-its-kind Phase 3b trial for adults with psoriasis and obesity or overweight. Press Release. Feb. 18, 2025.
2. Armstrong, et al. Addressing the Obesity-Psoriasis Connection: Prevalence, Incidence, and Comorbidity Insights from a Large US Population of 19.9 Million (2018-2024). Presented at: Maui Derm; Jan. 25–29, 2026; Maui, Hawaii.
3. Lebwohl M, Strober B, Menter A, et al. Phase 3 studies comparing brodalumab with ustekinumab in psoriasis. N. Engl. J. Med. 2015;373(14):1318–1328. doi: 10.1056/NEJMoa1503824
4. Haran K, Johnson CE, Smith P, et al. Impact of GLP-1 Receptor Agonists on Psoriasis and Cardiovascular Comorbidities: A Narrative Review. Psoriasis (Auckl). 2024;14:143–152. doi: 10.2147/PTT.S485061