J&J's Guselkumab (Tremfya) Meets Endpoints in Axial PsA Trial

Johnson & Johnson (J&J) announced September 25, 2026, that guselkumab (Tremfya) met the primary and major secondary endpoints of the phase 4 STAR study, making it the first interleukin-23 (IL-23) inhibitor to demonstrate significant improvement in spinal pain and stiffness in psoriatic arthritis (PsA) with axial involvement (axial PsA), as confirmed by magnetic resonance imaging (MRI).¹ The company said STAR is also the first study to use objective MRI assessments both to confirm axial involvement at enrollment and to demonstrate a reduction in axial inflammation in PsA.¹

"Axial PsA involves inflammation of the spine and sacroiliac joints, often leading to debilitating pain, stiffness, and fatigue," said David M. Lee, MD, PhD, global immunology therapeutic area head at Johnson & Johnson, in a company press release.¹ "As the first phase 4 study of an IL-23 inhibitor in this patient population, STAR further strengthens the growing body of evidence supporting guselkumab as a first-line treatment option proven to help stop further joint damage."

What did the STAR study evaluate?

STAR (NCT04929210) is a phase 4, multicenter, randomized, double-blind, placebo-controlled trial evaluating guselkumab in 411 biologic-naive adults worldwide with active PsA and axial involvement.¹^,² Eligible participants had objective evidence of axial inflammation confirmed by centrally read MRI and elevated C-reactive protein despite prior treatment with non-biologic disease-modifying antirheumatic drugs, apremilast, or nonsteroidal anti-inflammatory drugs.¹^,³

The trial included a 24-week placebo-controlled period followed by a 24-week active-treatment period.¹^,³ The primary endpoint measured change from baseline in the Bath Ankylosing Spondylitis Disease Activity Index, a composite patient-reported score covering spinal pain, stiffness, fatigue, and joint symptoms, at week 24 versus placebo.¹ Major secondary endpoints assessed axial symptoms using the Ankylosing Spondylitis Disease Activity Score with C-reactive protein and MRI-measured sacroiliac joint inflammation; guselkumab met both.¹ Johnson & Johnson reported no new safety signals, consistent with guselkumab's established safety profile in PsA.¹

Why does axial involvement matter in psoriatic arthritis?

Axial involvement is a clinical domain of PsA in which inflammation affects the spine and sacroiliac joints, causing back pain, morning stiffness, fatigue, and impaired mobility. It is associated with worse quality of life than PsA without axial involvement.¹ It may affect approximately 5% to 28% of patients with early PsA and 25% to 70% of those with longer-standing disease.¹ There are no universally accepted classification criteria for axial PsA, and few prospective trials have focused on this population, according to J&J.¹

What makes the trial's design significant?

Philip J. Mease, MD, MACR, FRCP, director of rheumatology research at Providence Swedish Medical Center and clinical professor at the University of Washington School of Medicine in Seattle, Wash., acting as a paid consultant to J&J, said in the release that STAR is the first prospective, randomized, double-blind, placebo-controlled PsA trial to use MRI assessments for enrollment and to provide an objective measure of inflammation alongside clinical outcomes.¹ "Together, these findings contribute to a more comprehensive understanding of disease activity and treatment effects," he added.¹

How does this fit into guselkumab's broader evidence base in PsA?

J&J recently received FDA approval in May 2026 of a label expansion for inhibition of structural joint damage progression in adults with active PsA, which the company said makes guselkumab the only IL-23 inhibitor proven to help stop further joint damage.¹^,4 Detailed STAR efficacy and safety results, including MRI findings, will be presented at an upcoming scientific congress.

What are the limitations?

The results announced are topline only, and detailed efficacy and safety data, including MRI findings, have not been peer-reviewed or independently verified. Axial PsA lacks universally accepted classification criteria, so how the population is defined may vary across studies. J&J sponsored and reported the results ahead of external publication.

References

1. Johnson & Johnson. Johnson & Johnson announces Tremfya (guselkumab) is the first and only IL-23 inhibitor to show significant improvement in spinal pain and stiffness in landmark axial psoriatic arthritis (PsA) study. Press release. Published September 25, 2026. Accessed September 25, 2026. https://www.jnj.com/media-center/press-releases/johnson-johnson-announces-tremfya-guselkumab-is-the-first-and-only-il-23-inhibitor-to-show-significant-improvement-in-spinal-pain-and-stiffness-in-landmark-axial-psoriatic-arthritis-psa-study
2. A study of guselkumab administered subcutaneously in bio-naive participants with active psoriatic arthritis axial disease (STAR). ClinicalTrials.gov; NCT04929210. Updated September 25, 2026. Accessed September 25, 2026. https://clinicaltrials.gov/study/NCT04929210
3. Gladman DD, Mease PJ, Bird P, et al. Efficacy and safety of guselkumab in biologic-naïve patients with active axial psoriatic arthritis: study protocol for STAR, a phase 4, randomized, double-blinded, placebo-controlled trial. Trials. 2022;23(1):743. doi:10.1186/s13063-022-06589-y
4. Johnson & Johnson. FDA approves label expansion, cementing TREMFYA as the only IL‑23 inhibitor proven to help stop further joint damage. Press Release. Published May 28, 2026. Accessed September 25, 2026. https://www.jnj.com/media-center/press-releases/fda-approves-label-expansion-cementing-tremfya-as-the-only-il-23-inhibitor-proven-to-help-stop-further-joint-damage