Systemic sclerosis (SSc) is a heterogeneous autoimmune disease characterized by immune dysregulation, microvascular injury, and progressive cutaneous and internal organ fibrosis. Despite advances in the understanding of SSc pathogenesis, effective disease-modifying therapies remain limited, and there is ongoing interest in targeted approaches that may modulate early inflammatory-vascular mechanisms linked to subsequent fibrotic remodeling. The IL-23/Th17 axis contributes to SSc biology, providing a rationale for IL-23p19 blockade as a potential therapeutic strategy. This focused narrative review summarizes currently available clinical signals of IL-23p19 inhibition in SSc, centered on guselkumab, and interprets reported outcomes using a domain-based framework. Published evidence remains confined to uncontrolled reports totaling 4 patients (one case report of early limited cutaneous SSc and a three-patient case series of early diffuse cutaneous SSc with comorbid psoriasis). Across these reports, investigators described improvements most consistently in the cutaneous domain (modified Rodnan skin score [mRSS], modified Rodnan total skin score [mRTSS], and the American College of Rheumatology Combined Response Index in Systemic Sclerosis [CRISS]) and in microvascular manifestations, including Raynaud’s phenomenon and nailfold microangiopathy, whereas pulmonary and gastrointestinal findings remain preliminary. We discuss key limitations of the current literature, including publication and reporting bias, the heterogeneity of phenotypes and endpoints, and confounding by comorbid psoriatic disease and natural disease fluctuation. Overall, IL-23p19 inhibition offers a pathway-specific approach in SSc, but establishing efficacy and defining responsive phenotypes requires adequately powered controlled evidence. Findings pertain specifically to guselkumab and cannot be generalized to IL-23 inhibition as a class.

Systemic sclerosis (SSc) is a heterogeneous autoimmune disease characterized by immune dysregulation, vasculopathy, and progressive fibrosis affecting the skin and internal organs. Although biologic therapies have expanded the therapeutic landscape of immune-mediated diseases, their impact in SSc has been uneven and remains difficult to interpret when viewed only on a drug-by-drug basis. This focused narrative review reappraises biologic therapies in SSc using a manifestation-based framework spanning cutaneous, pulmonary, vascular, gastrointestinal, musculoskeletal, and global or composite outcomes. Published evidence is most developed for selected cutaneous and pulmonary manifestations, particularly through B-cell depletion in selected cutaneous–pulmonary phenotypes and interleukin-6 blockade that attenuates pulmonary function decline in early inflammatory disease, whereas gastrointestinal and vascular manifestations have not yet shown comparable clinical evidence of benefit and remain insufficiently studied. We argue that this asymmetry not only reflects differences in trial design and endpoint selection, but also manifestation-specific pathobiology, disease stage, and the extent to which inflammatory, vascular, and fibrotic processes remain therapeutically modifiable. In particular, vasculopathy may represent an upstream pathogenic layer that constrains the disease-modifying capacity of biologics that primarily improve downstream inflammatory or fibrotic manifestations. We also highlight the relevance of Japanese contributions to the biologics literature in SSc and discuss future priorities, including manifestation-appropriate endpoint selection, early-disease enrichment, and biomarker-informed stratification. Overall, biologics have changed the treatment of SSc in a selective rather than global manner; embracing a manifestation-based view is now essential for both trial design and day-to-day therapeutic decision-making.