Taltz and Zepbound are about to share a podium again.
On Wednesday, November 11, Eli Lilly will present detailed 52-week results from TOGETHER-PsA, a Phase 3b trial that paired its IL-17A antibody Taltz (ixekizumab) with its GIP and GLP-1 receptor agonist Zepbound (tirzepatide) in adults with active psoriatic arthritis and obesity or overweight with a weight-related condition.
The headline is striking: 43.7% of patients receiving the combination achieved an ACR50 response at week 52, compared with 15.7% receiving Taltz alone.
That is nearly 2.8 times the response rate.
The numbers are not entirely new. Lilly first disclosed its one-year results on August 31, 2026, and repeated the central findings in a November 5 preview of ACR Convergence. The November 11 oral presentation, abstract 2942, will provide the scientific meeting discussion of those findings.
The result is meaningful, but it comes with an important qualification. The week-52 analyses were prespecified but exploratory, with no statistical adjustment for multiple comparisons. The trial was also open-label, although outcome assessors were blinded.
And its original primary endpoint, assessed at week 36, combined improvement in arthritis with a weight-loss requirement that strongly favored the group receiving a weight-loss medicine.
Understanding what TOGETHER-PsA actually demonstrated requires separating the arthritis response from the weight-loss result and reading the statistical details.
What TOGETHER-PsA Tested
TOGETHER-PsA, registered as NCT06588296, was a randomized, multicenter Phase 3b trial comparing Taltz alone with Taltz administered alongside Zepbound over 52 weeks.
The study enrolled 271 adults with active psoriatic arthritis.
Participants were randomly assigned in a 1:1 ratio. The combination group contained 138 participants, while the Taltz-only group contained 133.
Eligibility required obesity, defined as a body mass index of at least 30, or overweight with a BMI of at least 27 but below 30 alongside at least one weight-related condition.
The average baseline BMI was 37.6 kg/m². The mean participant age was 55 years, and approximately 70% were women.
Participants had active inflammatory joint disease. More than 60% had previously received at least one advanced treatment, making this a population with substantial existing disease burden.
Both treatment groups received individualized counseling on reduced-calorie diets and increased physical activity.
The study used approved U.S. dosing regimens for both medicines.
Its design was open-label. Participants and treating clinicians knew whether Zepbound had been added, although assessors evaluating outcomes were blinded to treatment assignment.
That distinction matters because psoriatic arthritis assessments combine objective measures, including joint examinations and inflammatory markers, with patient-reported pain and function.
Knowledge of treatment assignment can influence some subjective assessments even when the clinical examination is performed by a blinded assessor.
The central question was whether treating obesity alongside established inflammatory arthritis treatment could improve disease control beyond what Taltz achieved alone.
Taltz and Zepbound: Reading the Primary Endpoint
The trial’s primary endpoint was evaluated at week 36.
To meet it, a participant needed to achieve both an ACR50 response and at least 10% bodyweight reduction.
ACR50 represents at least a 50% improvement in tender and swollen joint counts, together with improvement in at least three additional measures of arthritis activity.
The combined outcome was achieved by 31.7% of participants receiving Taltz plus Zepbound, compared with only 0.8% receiving Taltz alone.
The difference was statistically significant, with a reported p value below 0.001.
But the endpoint requires careful interpretation.
Zepbound is an effective weight-management medicine. Adding it to Taltz would be expected to substantially increase the number of participants reaching the trial’s weight-loss threshold.
That is exactly what happened.
At week 36, 84.5% of patients receiving the combination achieved at least 10% weight reduction, compared with 4.5% receiving Taltz alone.
A composite endpoint that requires substantial weight loss will therefore strongly disadvantage a comparison group that does not receive the additional weight-loss medicine.
This does not make the primary endpoint invalid. It means the composite result answers a specific question about achieving both arthritis improvement and weight reduction, rather than isolating the incremental benefit for arthritis.
The more informative arthritis-specific comparison was ACR50 on its own.
At week 36, 33.5% of combination patients achieved ACR50, compared with 20.4% receiving Taltz alone.
That was an absolute difference of 13.1 percentage points, with a reported p value of 0.020.
Importantly, the week-36 ACR50 comparison was a key secondary endpoint included in the study’s multiplicity-controlled statistical testing.
Minimal disease activity was reached by 26.3% of combination patients versus 15.3% of those on Taltz alone, although that additional comparison was not part of the same confirmatory testing hierarchy.
These findings show that the combination’s benefit was not confined to the composite measure requiring weight loss.
The weight-loss composite produced the largest headline gap. The arthritis-only ACR50 result provided the more useful evidence of additional disease control.
=== ADD ONE INLINE IMAGE HERE — UPLOADED IMAGE 2: MONUMENTAL SKELETAL HAND SCULPTURE AND LARGE WEIGHING SCALE DISPLAYED IN A DARK HALL, WITH AN ATHLETIC ADULT VIEWING THE INSTALLATION. CONCEPTUAL ILLUSTRATION OF THE RELATIONSHIP BETWEEN JOINT DISEASE AND BODYWEIGHT MANAGEMENT. NOT AN ACTUAL TOGETHER-PsA PARTICIPANT, CLINICAL STUDY IMAGE OR DEMONSTRATION OF A DRUG EFFECT. ===
The 52-Week Arthritis Result and Its Asterisk
At week 52, the difference in ACR50 response was larger.
Among patients receiving Taltz plus Zepbound, 43.7% achieved an ACR50 response. Among patients receiving Taltz alone, 15.7% achieved the same response.
The adjusted between-group difference was 28.0 percentage points, with a 95% confidence interval from 17.1 to 38.9 percentage points.
The reported p value was below 0.001.
That is a substantial separation between treatment groups, and it is the central finding Lilly is highlighting in its November 11 presentation.
However, unlike the confirmatory week-36 testing, the week-52 analyses were prespecified exploratory outcomes without multiplicity control.
That means the reported p values are nominal. They describe statistical evidence for individual comparisons but do not account for the increased chance of false-positive findings when numerous outcomes are tested.
It is also important not to confuse the change in percentages across time with a formally tested difference in treatment trajectories.
The combination group’s ACR50 response increased numerically from 33.5% at week 36 to 43.7% at week 52, while the Taltz-only group’s response was 20.4% and then 15.7%.
Those timepoint comparisons are descriptive. They should not be presented as proof that the combination continued accelerating in efficacy after week 36.
At week 52, the composite of ACR50 plus at least 10% weight reduction was achieved by 39.2% of combination patients compared with 1.7% receiving Taltz alone.
Additional exploratory comparisons favored the combination for several measures, including minimal disease activity, the Disease Activity Index for Psoriatic Arthritis, physical function and high-sensitivity C-reactive protein.
Metabolic outcomes, including bodyweight, systolic blood pressure, triglycerides and total cholesterol, also showed favorable differences.
Those outcomes reinforce the broader pattern, but they belong in the exploratory category.
One-year results are valuable in a chronic disease, but they do not establish permanent treatment benefit or demonstrate what happens when patients discontinue either medicine.
Why Weight Treatment Might Affect Inflamed Joints
The biological rationale behind TOGETHER-PsA is not that obesity and psoriatic arthritis are identical conditions.
It is that they interact in ways that may make inflammatory joint disease harder to control.
Excess bodyweight can increase mechanical stress on joints. Adipose tissue is also metabolically active and participates in signaling pathways associated with chronic inflammation.
People living with psoriatic arthritis and obesity may therefore face overlapping mechanical, metabolic and inflammatory burdens.
Taltz selectively blocks interleukin-17A, a cytokine involved in inflammatory disease.
Zepbound activates GIP and GLP-1 receptors, reducing appetite and supporting weight reduction. Research continues into whether incretin-based treatments also influence inflammatory pathways independently of weight loss.
The combination produced differences in arthritis response as early as week 4, before substantial weight loss had occurred.
That early separation is scientifically interesting because it raises the possibility that some additional benefit may not depend entirely on later weight reduction.
But the study does not establish that tirzepatide has a direct anti-inflammatory effect in psoriatic joints.
There are several possible explanations for the observed findings.
Weight reduction may improve symptoms or disease activity. Tirzepatide may affect metabolic or inflammatory pathways beyond its weight-loss effects. Differences in expectations and reporting may also influence some patient-reported components because treatment was open-label.
The trial was not designed to isolate the contribution of each mechanism.
A study that compared comparable levels of weight reduction achieved through different methods, or included appropriately blinded treatment groups, could provide additional information.
For now, the evidence supports the clinical value of evaluating obesity and inflammatory arthritis together. It does not fully explain why the combination performed better.
TOGETHER-PsA shows a stronger arthritis response with two treatments. It does not reveal how much of the improvement came from weight loss itself.
The Safety Picture and the Limits of the Trial
Lilly has reported that adverse events were generally consistent with the established safety profiles of Taltz and Zepbound.
In the combination group, commonly reported adverse events included nausea, diarrhea, constipation and injection-site reactions.
The company’s broader one-year announcement also identified vomiting, dizziness and headache among events reported by at least 5% of patients receiving the combination across the TOGETHER psoriasis and psoriatic arthritis trials.
The ACR abstract states that adverse-event-related treatment discontinuations were comparable between the two TOGETHER-PsA groups and that no new safety concerns were identified.
That is reassuring as a general summary. It is not a substitute for examining complete adverse-event counts, serious events, exposure duration and discontinuation patterns.
Another detail deserves attention.
According to the 52-week ACR abstract, 71.6% of participants completed study treatment.
In other words, more than one-quarter did not complete the full assigned treatment period.
The efficacy analyses used a hypothetical estimand with statistical imputation for certain intercurrent events, including treatment discontinuation or use of prohibited medication.
That approach attempts to estimate treatment effects under defined assumptions rather than simply reporting outcomes observed among everyone who remained on their medication for a full year.
The distinction matters because treatment persistence and tolerability are especially important for medicines intended to manage chronic conditions.
Other limitations remain.
The trial was open-label, and its week-52 analyses were exploratory. The study also did not compare the combination against a blinded placebo injection added to Taltz.
Nor did it establish whether the same arthritis benefit would be achieved through substantial weight loss without tirzepatide.
These limitations do not invalidate the positive findings, but they restrict how confidently the results can be interpreted as evidence of a specific biological mechanism or an enduring benefit after treatment ends.
The Business Logic and What Still Needs Answering
For Eli Lilly, TOGETHER-PsA also supports a commercial strategy that connects two major areas of its pharmaceutical business.
Taltz is an established treatment for psoriatic arthritis. Zepbound is an approved obesity medicine.
Evidence that the two can be used together with favorable clinical outcomes gives Lilly an opportunity to position obesity management as part of broader care for people with inflammatory disease and excess weight.
At ACR Convergence, Lilly is also presenting research involving patients recruited through a Zepbound Savings for Taltz customer support program.
That program demonstrates the company’s commercial interest in supporting concurrent treatment, although a patient support initiative is not evidence that such a combination is appropriate for every patient.
The commercial opportunity is distinctive because Lilly owns both products involved in the trial.
Other manufacturers of arthritis biologics may not have an approved obesity medicine within the same portfolio.
If obesity treatment becomes more closely integrated into routine rheumatology care, Lilly may be positioned to benefit from prescriptions in both therapeutic categories.
The company has been expanding the broader market for Zepbound, including through distribution and telehealth relationships, while navigating the pricing and competition issues described in Grey Pepper’s coverage of Lilly’s third-quarter 2026 results.
There is nothing inherently improper about studying two medicines from the same company. But the sponsor’s commercial interest makes transparent trial design and careful interpretation especially important.
Three scientific questions remain unresolved.
First, would the difference in arthritis outcomes remain as large in a blinded comparison, with equivalent injection procedures and expectations across treatment groups?
Second, how much of the additional disease control is explained by weight reduction, and how much might reflect other physiological effects of tirzepatide?
Third, what happens after patients stop treatment, experience weight regain or switch to another obesity therapy?
These questions matter because psoriatic arthritis is a chronic disease. Meaningful improvements over one year are valuable, but clinicians must also understand treatment persistence, safety and outcomes over longer periods.
TOGETHER-PsA makes a credible case that treating obesity alongside inflammatory arthritis can improve outcomes in some patients.
The week-36 confirmatory ACR50 result provides stronger statistical support than the trial’s more dramatic weight-loss composite alone.
The exploratory week-52 findings extend that signal, showing a 43.7% ACR50 response with the combination against 15.7% with Taltz alone.
That is worth paying attention to.
But it is not evidence that every patient will benefit, that the drugs work synergistically through a proven anti-inflammatory mechanism, or that the same improvement will persist indefinitely.
The November 11 presentation will feature a striking difference between two bars. The more important scientific story is what the trial can establish about those bars—and what remains outside them.
Sources and Further Reading
- Merola J, et al. Ixekizumab Plus Tirzepatide Demonstrated Greater Disease Control at 52 Weeks Versus Ixekizumab Alone. ACR Convergence 2026, abstract #2942. Presentation scheduled November 11, 2026.
- Merola JF, et al. Ixekizumab With Tirzepatide Achieved Greater Disease Control Than Ixekizumab Alone in Adults With Psoriatic Arthritis and Overweight or Obesity: Results From a Randomized Clinical Trial. Arthritis & Rheumatology, 2026. DOI: 10.1002/art.70134.
- Eli Lilly and Company. TOGETHER-PsA Week-36 Topline Results. January 8, 2026.
- Eli Lilly and Company. Phase 3b Results Presented at the AAD Annual Meeting. March 28, 2026.
- Eli Lilly and Company. One-Year Results From TOGETHER-PsO and TOGETHER-PsA. August 31, 2026.
- Eli Lilly and Company. Lilly to Showcase New Retatrutide, Taltz and Zepbound Data at ACR Convergence 2026. November 5, 2026.
- ClinicalTrials.gov. TOGETHER-PsA: Ixekizumab Concomitantly Administered With Tirzepatide. NCT06588296.
