Comparative Analysis of Clinical Trials of Biologic Drugs for Patients with Primary Sjögren's Syndrome

Background/Objectives: To evaluate and compare the characteristics of clinical trials (CTs) involving patients with primary Sjögren's syndrome (pSS), using biologics, and focusing on the features of the patients recruited. Methods: This systematic review assessed pSS CTs evaluating biologic drugs published from 2010 to 2024 according to the Preferred Reporting Items for Systematic reviews and Meta-Analyses (PRISMA) guidelines. The literature search of the electronic databases was performed individually by the authors. The extracted variables regarding the baseline characteristics of participants and trial-related information were defined a priori, collected, and compared. Results: A total of 16 CTs were included in this review in line with the inclusion criteria. The trials were predominantly multicenter (75%) randomized controlled trials with a placebo arm (93.8%), with only five trials recruiting participants across multiple (≥3) continents. The search included a total of 1607 patients (mean age 51 years, 94% female) with a mean disease duration of 6.47 years. Race and ethnicity were underrepresented variables, found in 37.5% and 12.5% of the trials, respectively, with White patients comprising the majority (77.8%). The EULAR Sjögren's Syndrome Disease Activity Index (ESSDAI) was reported in 93.8% of the CTs. However, only recent studies have emphasized it as the primary outcome. Conclusions: Recent trials on biologics in pSS patients show better methodological quality, with a more standardized assessment of disease activity using ESSDAI, and an increased focus on patient-reported outcomes. Global participation is increasing, but limited racial and ethnic diversity, endpoint variability, and inconsistent biomarker reporting remain critical issues.