Phase 3b data presented at AAD Annual Meeting show Lilly's Taltz (ixekizumab) plus Zepbound (tirzepatide) delivered superior efficacy for adults with psoriatic arthritis and obesity

Phase 3b results from the TOGETHER-PsA trial were presented at the American Academy of Dermatology Annual Meeting in Denver (March 27–31, 2026), and the headline number doesn’t require statistical training to understand. In patients with active psoriatic arthritis and obesity, the combination of Taltz (ixekizumab, an IL-17A biologic) plus Zepbound (tirzepatide) achieved both a 50% improvement in arthritis activity score (ACR50) and at least 10% body weight loss in 31.7% of participants at 36 weeks. The same endpoint on Taltz monotherapy: 0.8%. That’s roughly a 40-fold difference. For ACR50 alone, the combination reached 33.5% versus 20.4% on Taltz monotherapy — a 64% relative improvement. These results were simultaneously published in Arthritis & Rheumatology, giving them the peer-reviewed standing insurers need to evaluate a prior authorization request.

The biological explanation for the overlap matters. Adipose tissue generates pro-inflammatory cytokines — IL-6, TNF-alpha, leptin — that sustain joint inflammation independently of whatever biologic a patient is on. You can suppress IL-17A with ixekizumab effectively, but if the underlying inflammatory burden from obesity persists, the joint disease doesn’t fully resolve. TOGETHER-PsA also found that ACR50 improvements separated between treatment arms as early as Week 4 — before meaningful weight loss had occurred. That early separation implies tirzepatide’s metabolic effects operate through mechanisms beyond simple fat-loss-driven inflammation reduction. The trial’s sister study, TOGETHER-PsO (plaque psoriasis and obesity), showed the same pattern: 27.1% of combination patients achieved complete skin clearance plus 10% weight loss at 36 weeks, versus 5.8% on Taltz monotherapy alone.

What Lilly has built here is a systematic, multi-indication evidence base positioning tirzepatide as a treatment multiplier for inflammatory diseases that co-occur with obesity. Approximately 1 million Americans have psoriatic arthritis, and a meaningful subset are both obese and already on expensive biologics. These patients are being treated for their inflammatory disease but not for the obesity that’s amplifying the disease burden. TOGETHER-PsA makes the clinical argument that leaving obesity untreated while prescribing a biologic is an incomplete treatment plan — and that adding tirzepatide produces outcomes neither drug achieves independently.

If you have PsA, psoriasis, or another inflammatory condition alongside obesity, bring the TOGETHER-PsA paper to your next rheumatology or dermatology appointment. Insurance will require prior authorization, and coverage decisions vary widely by plan. But the peer-reviewed publication in Arthritis & Rheumatology is exactly the document an appeals reviewer looks for when evaluating combination therapy requests. The clinical argument is solid enough to push for authorization — and if you’re denied initially, it’s solid enough to appeal.

Frequently Asked Questions

Can I take Zepbound alongside my current biologic — Humira, Cosentyx, or Skyrizi?

The TOGETHER-PsA trial specifically studied Zepbound combined with Taltz (ixekizumab), not other biologics. That doesn’t make other combinations unsafe — the safety profile in TOGETHER-PsA was favorable — but controlled Phase 3 data for tirzepatide combined with adalimumab, secukinumab, or risankizumab doesn’t yet exist. Your rheumatologist needs to evaluate your specific disease activity, current biologic, and whether adding tirzepatide makes clinical sense for your situation. The TOGETHER-PsA data supports having that conversation now.

Does Zepbound now treat psoriatic arthritis as a standalone therapy?

No. Tirzepatide is FDA-approved for chronic weight management, not PsA as a standalone indication. What TOGETHER-PsA shows is that treating obesity with Zepbound — when combined with an established anti-inflammatory biologic — produces outcomes neither drug achieves alone. The trial makes the case that leaving obesity untreated while on a biologic is an incomplete treatment plan. The mechanism operating through Week 4 ACR50 improvements (before weight loss occurs) also suggests tirzepatide may have direct anti-inflammatory effects independent of fat mass reduction.

Will insurance cover Zepbound for patients with psoriatic arthritis?

Zepbound’s FDA approval covers chronic weight management in adults with obesity (BMI ≥30) or overweight (BMI ≥27) with at least one weight-related comorbidity. Psoriatic arthritis qualifies as a weight-related condition for many payers. Coverage requires prior authorization and is decided case by case. Bring your PsA diagnosis, current biologic prescription, BMI documentation, and the TOGETHER-PsA publication from Arthritis & Rheumatology to support the request. The peer-reviewed data significantly strengthens your prior auth appeal if you’re initially denied.

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