A recent study published in Clinical Rheumatology has found that ivarmacitinib 4 mg demonstrated consistent efficacy across a broad range of demographic and clinical subgroups of patients with active ankylosing spondylitis (AS). The findings from a post-hoc subgroup analysis suggest that the clinical benefits of ivarmacitinib were generally maintained irrespective of baseline patient and disease characteristics.
AS is a chronic inflammatory disease that primarily affects the axial skeleton and can result in persistent back pain, stiffness, impaired physical function, and progressive structural damage. Janus kinase (JAK) inhibitors represent an important class of targeted therapies that act by modulating the JAK/signal transducer and activator of transcription (STAT) signaling pathway, thereby suppressing signaling mediated by several cytokines involved in the pathogenesis and progression of autoimmune and autoinflammatory diseases.
Ivarmacitinib (SHR0302) is a novel selective JAK1 inhibitor. Previous clinical studies have investigated its therapeutic potential in several immune-mediated inflammatory diseases, including rheumatoid arthritis, atopic dermatitis, inflammatory bowel disease, and ankylosing spondylitis.
The subgroup analysis was based on data from a phase II/III randomized clinical trial (NCT04481139) involving patients with active AS. A total of 373 patients were included, with 187 receiving ivarmacitinib 4 mg and 186 receiving placebo during the initial 12-week placebo-controlled period. The investigators evaluated treatment responses across subgroups stratified according to age, sex, body mass index (BMI), AS duration, history of biological or JAK inhibitor use, C-reactive protein (CRP) levels, total back pain visual analogue scale (VAS) scores, and night pain VAS scores.
At week 12, Assessment of SpondyloArthritis international Society 20% improvement (ASAS20) response rates were significantly higher with ivarmacitinib than with placebo across subgroups defined by sex, BMI, AS duration, previous biological or JAK inhibitor use, total back pain VAS score, and night pain VAS score. In addition, ASAS5/6 response rates were higher in the ivarmacitinib group across all subgroups evaluated.
The benefits of treatment extended beyond categorical response measures. Patients receiving ivarmacitinib demonstrated greater improvements in the Bath Ankylosing Spondylitis Disease Activity Index (BASDAI) at week 12 across subgroups defined by age, sex, BMI, AS duration, total back pain VAS score, and night pain VAS score. Greater improvements in the Ankylosing Spondylitis Disease Activity Score (ASDAS) were also observed with ivarmacitinib across all subgroups examined.
The results are particularly relevant given the clinical heterogeneity of AS. Patients may differ substantially in disease duration, inflammatory activity, symptom severity, body composition, and previous exposure to advanced therapies. The consistency of the treatment response across these baseline characteristics suggests that the efficacy of ivarmacitinib was not limited to a specific patient profile.
The findings also align with results from the parent phase II/III trial, in which ivarmacitinib demonstrated significantly greater clinical improvement than placebo during the 12-week randomized treatment period. Improvements were observed across multiple measures of disease activity, symptoms, and treatment response, supporting the potential of selective JAK1 inhibition as a therapeutic approach for patients with active AS.
Efficacy outcomes continued to improve through week 24 across the evaluated subgroups. Patients who continued ivarmacitinib maintained or experienced further improvements, while those initially assigned to placebo demonstrated improvements after switching to ivarmacitinib at week 12. This pattern suggests that the clinical benefits of treatment can be sustained with continued therapy and may also be achieved in patients who initiate ivarmacitinib after an initial period without active treatment.
The subgroup analysis indicated that ivarmacitinib 4 mg improved treatment response rates and disease activity compared with placebo across multiple demographic and clinical subgroups. The benefits were sustained through 24 weeks of treatment, while patients who switched from placebo to ivarmacitinib also experienced subsequent improvements. As a post-hoc subgroup analysis, the findings should be interpreted as supportive evidence of consistency in treatment response rather than definitive proof of equivalent efficacy in every individual subgroup. Nevertheless, the results add to the growing clinical evidence supporting selective JAK1 inhibition as a potential treatment strategy for patients with active ankylosing spondylitis.
References
- Xu B, Ke Y, Xu L, Sun C, Chen W, Xu D, Sun Y, Cao H, Lin J. Ivarmacitinib in patients with active ankylosing spondylitis: subgroup analysis based on key baseline features from a phase II/III trial. Clin Rheumatol. 2026 Sep;45(9):5503-5511.
- Xu X, Wei H, Liu L, Yang R, Shi Q, Pang D. Ivarmacitinib improves patient-reported outcomes across multiple domains in patients with active ankylosing spondylitis: a post hoc analysis of a phase II/III trial. Front Pharmacol. 2025 Nov 20;16:1710434.