Lilly reports one-year results for Taltz plus Zepbound in psoriatic disease

Eli Lilly said on Aug. 31, 2026 that adults with psoriatic disease and obesity who received Taltz (ixekizumab) and Zepbound (tirzepatide) together maintained or further improved their results at one year in two Phase 3b trials ^[1]. The improvements seen at Week 36, when the combination was statistically superior to Taltz alone, held through Week 52 across disease activity, systemic inflammation and metabolic measures, with no new safety concerns identified, the company said ^[1].

The studies, TOGETHER-PsO and TOGETHER-PsA, are randomized, multicenter, open-label and assessor-blinded ^[1]. TOGETHER-PsO enrolled 274 adults with moderate-to-severe plaque psoriasis and TOGETHER-PsA enrolled 271 adults with active psoriatic arthritis. Everyone in both trials also had obesity or overweight with at least one weight-related condition; the average baseline body mass index was 39.2 in TOGETHER-PsO and 37.6 in TOGETHER-PsA ^[1]. Participants were assigned 1:1 to Taltz alone or Taltz plus Zepbound, all given as injections under the skin, and all received counseling on a reduced-calorie diet and increased physical activity ^[1].

At Week 52, the primary outcome in TOGETHER-PsO — complete skin clearance on the Psoriasis Area Severity Index (PASI 100) plus at least 10% weight loss — was reached by 30.6% of patients on Taltz plus Zepbound versus 4.4% on Taltz alone ^[1]. In TOGETHER-PsA, the primary outcome — at least a 50% reduction in arthritis disease activity (ACR50) plus at least 10% weight loss — was reached by 39.2% versus 1.7% ^[1].

On the key secondary measures, PASI 100 by itself was maintained at 40.5% with the combination versus 29.1% with Taltz alone, and ACR50 by itself rose to 43.7% versus 15.7% ^[1]. Lilly said ACR50 improvements with the combination appeared as early as Week 4, before clinically meaningful weight loss occurred ^[1].

Systemic inflammation, measured by high-sensitivity C-reactive protein, showed deeper improvements over time in both trials, and changes in BMI, blood pressure, glucose, HbA1c, triglycerides and total cholesterol were sustained or further improved compared with Taltz alone ^[1].

The company flagged a limit on the evidence: the Week 52 analyses were pre-specified but exploratory, without statistical control for multiple comparisons, and comparisons between timepoints were descriptive rather than formally tested ^[1]. The trials' primary endpoints were measured at Week 36.

Adverse events in the combination arms were generally mild to moderate and consistent with the known safety profile of each medicine, Lilly said. Events reported in 5% or more of participants in the combination arms of both trials were nausea, diarrhea, constipation, injection site reactions, vomiting, dizziness and headache ^[1].

"People living with the cumulative burden of psoriatic disease and obesity are too often treated with separate, disconnected approaches," said Mark Genovese, M.D., Lilly's senior vice president of immunology development ^[1]. Joseph F. Merola, M.D., a dermatologist and rheumatologist who leads the Rheumatology-Dermatology Society, said the psoriasis finding shows durability of complete skin clearance at one year and that the arthritis improvements began before meaningful weight loss ^[1].

Why it matters for patients

In the U.S., about 61% of people with psoriasis and 65% of people with psoriatic arthritis also have obesity or overweight with at least one weight-related condition, and that is often linked to poorer treatment outcomes ^[1]. For patients whose skin or joint symptoms have been hard to control, these results point to a possible benefit from treating the inflammatory disease and the weight condition at the same time rather than in separate tracks ^[1].

The practical picture is still unsettled. Taltz is approved for adults with active psoriatic arthritis and for adults and children 6 and older with moderate-to-severe plaque psoriasis, and Zepbound is approved for adults with obesity or overweight plus at least one weight-related medical problem ^[1]. Using them together in the way these trials did has not been established as an approved regimen, and Lilly did not say whether it plans to seek regulatory review of the combination ^[1]. Nothing in the announcement addresses what the two drugs would cost together or whether insurers would cover them for this purpose ^[1].

What happens next

The detailed 52-week results from TOGETHER-PsO (NCT06588283) and TOGETHER-PsA (NCT06588296) are scheduled to be presented at future medical meetings and published in peer-reviewed journals, according to Lilly ^[1]. No dates for those presentations or publications were given, and regulatory plans for the combination have not been announced ^[1].