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
Key facts
- Drug: guselkumab (Tremfya; Johnson & Johnson/Janssen Biotech)
- Class: IL-23 inhibitor; dual-acting monoclonal antibody (blocks IL-23, binds CD64)
- Indication studied: Active psoriatic arthritis with axial involvement (axial PsA) in biologic-naive adults
- Trial: STAR (NCT04929210); phase 4
- Primary endpoint met: Change from baseline in BASDAI score at week 24 vs placebo
- Secondary endpoints met: ASDAS-CRP reduction; MRI-confirmed reduction in sacroiliac joint inflammation
- Safety: Consistent with guselkumab's established PsA safety profile; no new signals
- Regulatory status: Topline data announced September 25, 2026; full results pending presentation at a scientific congress
- Current approval: plaque psoriasis, active PsA, ulcerative colitis, Crohn disease in US; also approved in Europe, Canada, Japan, and other countries
- Geography: 411 participants enrolled worldwide
"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
