Expert viewpoint on endpoints in systemic sclerosis: current and future outlook

Systemic sclerosis (SSc) is a rare, heterogeneous, systemic autoimmune rheumatic disease characterised by vasculopathy, immune dysregulation and fibrosis affecting multiple organ systems. The complexity and variability of SSc manifestations pose significant challenges for clinical trial design and endpoint selection. Historically, three types of trial concepts have emerged: studies focused on a single organ; studies suggesting disease modification by combining a primary single-organ endpoint with supportive secondary endpoints across other systems, and studies explicitly designed to demonstrate disease modification through combined endpoints.This expert review explores the current landscape and future directions of clinical endpoints in SSc trials. It highlights the growing importance of patient-reported outcomes, such as the Health Assessment Questionnaire-Disability Index and ScleroID, which provide valuable insights into patient experiences. The review also discusses the emergence of candidate composite endpoints, including the revised Composite Response Index in Systemic Sclerosis, which integrates clinical, functional and patient-centred measures to better reflect treatment efficacy.Despite progress, significant unmet needs remain. Many endpoints assess damage at advanced stages, underscoring the need for earlier indicators of disease progression. The review advocates for incorporating time-to-event analyses, imaging and biomarker-based assessments to enhance sensitivity and relevance. It also emphasises the importance of refining composite endpoints to include continuous measures and broader domains such as vascular and gastrointestinal involvement. These efforts aim to improve the design and interpretability of SSc clinical trials, ultimately enhancing therapeutic development and patient outcomes.