Tremfya Meets Primary, Major Secondary Endpoints in Phase 4 STAR Study of Axial PsA

Johnson & Johnson announced positive topline results from the phase 4 STAR study evaluating guselkumab (Tremfya) in biologic-naïve adults with active psoriatic arthritis (PsA) and axial involvement, reporting significant improvements in axial symptoms and MRI-confirmed inflammation.

The company described STAR as the first dedicated randomized, double-blind, placebo-controlled study to prospectively evaluate an interleukin (IL)-23 inhibitor specifically in patients with PsA and MRI-confirmed axial involvement. Detailed efficacy and safety findings from the study have not yet been released and are expected to be presented at an upcoming scientific congress.

STAR Meets Primary and Major Secondary Endpoints

At week 24, guselkumab met the study's primary endpoint of improvement from baseline in the Bath Ankylosing Spondylitis Disease Activity Index (BASDAI) compared with placebo. BASDAI is a patient-reported composite measure incorporating symptoms including spinal pain, stiffness, fatigue, joint symptoms, and areas of tenderness.

The therapy also met major secondary endpoints, including significant improvement in axial symptoms measured using the Ankylosing Spondylitis Disease Activity Score with C-reactive protein (ASDAS-CRP) and a significant reduction in objective inflammation of the sacroiliac joints assessed by MRI. According to Johnson & Johnson, the safety profile was consistent with the established safety profile of guselkumab in PsA, with no new safety signals identified.

The topline announcement did not provide numerical changes in BASDAI or ASDAS-CRP, MRI inflammation scores, or between-group treatment differences.

Dedicated Study of Axial PsA

STAR (NCT04929210) is a phase 4, multicenter, randomized, double-blind, placebo-controlled trial enrolling 411 biologic-naïve adults with active PsA and axial involvement. Eligible patients were required to have objective evidence of axial inflammation confirmed by centrally read MRI, as well as elevated C-reactive protein despite previous treatment with nonbiologic disease-modifying antirheumatic drugs, apremilast, and/or nonsteroidal anti-inflammatory drugs.

The trial includes a 24-week placebo-controlled period followed by a 24-week active-treatment period. In addition to BASDAI and assessments of axial symptoms and MRI inflammation, secondary outcomes evaluate physical function, peripheral musculoskeletal manifestations, skin disease, and safety.

“What makes the STAR study particularly noteworthy is that, for the first time in a prospective, randomized, double-blinded, placebo-controlled PsA study, it evaluates MRI assessments for inclusion and provides a rigorous and objective measure of improvements in inflammation alongside clinical outcomes in axial PsA,” 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, said in the announcement.

For the first time in a prospective, randomized, double-blinded, placebo-controlled PsA study, it evaluates MRI assessments — Philip J. Mease, MD, MACR, FRCP

The company disclosed that Mease is a paid consultant for Johnson & Johnson but was not compensated for media work related to the announcement.

Addressing an Area of Unmet Need

Axial involvement in PsA affects the spine and sacroiliac joints and may present with inflammatory back pain, stiffness, fatigue, impaired mobility, and reduced physical function. Estimates of its prevalence vary considerably, ranging from approximately 5% to 28% among patients with early PsA and 25% to 70% among those with longer-standing disease.

Despite the clinical burden, axial PsA remains challenging to define and study. There are currently no universally accepted classification criteria specific to axial PsA, and relatively few prospective clinical trials have exclusively enrolled this patient population. Although axial PsA shares clinical features with axial spondyloarthritis, it is increasingly recognized as a distinct domain of PsA.

The MRI-based eligibility requirements and imaging outcomes in STAR are therefore notable because they provide objective evidence of axial inflammation alongside patient-reported clinical outcomes.

Expanding Evidence for Guselkumab in PsA

Guselkumab is a fully human monoclonal antibody targeting the IL-23 p19 subunit. It is currently approved in the US for several immune-mediated inflammatory diseases, including active PsA and moderate to severe plaque psoriasis in adults and children aged 6 years and older who weigh at least 40 kg, as well as moderately to severely active ulcerative colitis and Crohn disease in adults.

The STAR results follow a recent FDA-approved label expansion for guselkumab recognizing inhibition of the progression of structural joint damage in adults with active PsA.

Full efficacy and safety results from STAR, including detailed MRI findings, are expected to be presented at a future scientific meeting.

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. Published September 25, 2026.
2. ClinicalTrials.gov. A study of guselkumab administered subcutaneously in bio-naive participants with active psoriatic arthritis axial disease (STAR). NCT04929210. Accessed September 2026.
3. Gottlieb AB, Merola JF. Axial psoriatic arthritis: An update for dermatologists. J Am Acad Dermatol. 2021;84(1):92-101. doi:10.1016/j.jaad.2020.05.089.
4. Poddubnyy D, Jadon DR, Van den Bosch F, Mease PJ, Gladman DD. Axial involvement in psoriatic arthritis: An update for rheumatologists. Semin Arthritis Rheum. 2021;51(4):880-887.