GLP-1 Agonist plus IL-17 Inhibition in Obese Psoriatic Arthritis

Jack Cush, MD

Jan 08, 2026 6:51 pm

Lilly announced the topline results from its phase 3b "TOGETHER PsA" trial, showing that the combination use of ixekizumab (Taltz) and tirzepatide (Zepbound) was superior to IXE alone, yielding both significant weight loss and ACR50 disease control in adults with active psoriatic arthritis (PsA).

TOGETHER-PsA was a 36 week, phase 3b trial that enrolled adults with active PsA who were also obese (BMI ≥30 kg/m²) or overweight (BMI 27-29.9 kg/m²) and had one other weight related comorbidity.

A total of 271 obese PsA pts were randomized to receive either concomitant ixekizumab (IXE) and tirzepatide (TIR) vs. IXE alone. The primary co-endpoints were an ACR50 improvement in PsA activity with a ≥10% weight reduction. An important secondary endpoint, was the effect of combination IXR and TIR on ACR50 responses compared to IXE alone - attempting to answering the question if GLP-1 agonists have a rheumatic benefit beyond weight loss anticipated with GLP-1 use.

At 36 weeks, concomitant IXE plus TIR met the primary and all key secondary endpoints for superiority against IXE monotherapy. The primary endpoint (ACR50 plus >10% weight loss) favored combination therapy (31.7%) compared to IXE alone (0.8%).

Moreover, ACR 50 responses were significantly better with IXE-TIR (33.5%) compared to IXE alone (20.4%); p<.05.

This is the first controlled study to evaluate the combined use of an incretin therapy (GLP-1 agonist) used with a PsA biologic, and show benefit.

Detailed 36-week results from the TOGETHER-PsA trial will be presented at an upcoming medical meeting and discussed with regulators.

Lilly's Taltz (ixekizumab) and Zepbound (tirzepatide) used together delivered superior efficacy in first-of-its-kind Phase 3b trial for adults with active psoriatic arthritis and obesity or overweight