Adding tirzepatide to ixekizumab improved psoriatic arthritis in people with obesity

Design

Phase 3b randomised trial, 52 weeks

Population

271 adults with active psoriatic arthritis and overweight with comorbidity or obesity

Primary outcome

ACR50 plus ≥10% weight loss at week 36

Effect

31.7% vs 0.8%; ACR50 alone 33.5% vs 20.4% (p = 0.02)

TOGETHER-PsA was a 52-week phase 3b randomised trial, published in March 2026, in 271 adults with active psoriatic arthritis and either obesity or overweight with a weight-related comorbidity. Participants received ixekizumab with tirzepatide (138) or ixekizumab alone (133) at standard doses.

The primary endpoint, ACR50 plus at least 10% weight loss at 36 weeks, was met by 31.7% with the combination and 0.8% with ixekizumab alone. More relevant to joints, ACR50 alone was 33.5% versus 20.4% (p = 0.02), with separation from week 4. Minimal disease activity, skin scores, function (HAQ-DI −0.2) and fatigue were also better, though several of these are nominal results. Safety was in line with each drug.

Obesity is present in most people with psoriatic arthritis and blunts response to biologics. This trial suggests that treating weight actively is part of treating the arthritis, not an add-on. The primary endpoint was built to favour the combination, so ACR50 is the fairer measure of joint benefit, and the open question is how long the gain lasts if weight is regained.

• Assess weight and metabolic comorbidity in every patient with psoriatic arthritis.
• Consider adding an incretin-based therapy for weight loss in patients with obesity and active psoriatic arthritis.
• Expect joint benefit within weeks, alongside weight loss.
• Coordinate with diabetes or obesity services for monitoring and gastrointestinal side effects.
• Check local availability and cost before planning combination treatment.

Why it matters

Weight is not a side issue in psoriatic arthritis; treating it improved the arthritis itself.

Don't overread it

The headline endpoint included weight loss by design; joint benefit is better judged by ACR50, and several secondary results are nominal.

The statistics, in plain English

The 31.7% versus 0.8% primary result looks dramatic because it required weight loss, which ixekizumab alone would not produce. ACR50 of 33.5% versus 20.4% is the joint-specific result: about 13 more responders per 100 patients, or one extra responder for every eight treated.

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