MTS109 in Patients With Refractory Autoimmune Diseases

This is an open-label, single-arm, basket-designed clinical trial.A maximum of 10 subjects with moderate to severe autoimmune diseases (including but not limited to SLE, IIM, SSc, AAV, and SS) will be enrolled. Following enrollment, subjects will receive MTS109 via subcutaneous injection; each subject will be followed up for up to 26 weeks after the first dose administration.This study consists of three periods: Screening Period (Day -28 to Day -1), Treatment Period (Day 1 to Day 32), and Follow-up Period (Month 2 to Month 6).Screening Period: After signing the Informed Consent Form (ICF), subjects will complete general screening procedures and disease-specific baseline assessments corresponding to their autoimmune conditions.Treatment Period: Subjects will receive MTS109 via subcutaneous injection in a stepwise titration to the target dose on Day 1 (D1), Day 4 (D4), and Day 7 (D7), followed by maintenance doses of MTS109 at the target dose on Day 14 (D14), Day 21 (D21), and Day 28 (D28). During the treatment period, subjects will undergo safety assessments, sample collection for pharmacokinetics (PK), pharmacodynamics (PD), and immunogenicity analyses after each dose administration, and the first efficacy assessment will be completed on Day 30 (D30).Follow-up Period: Subjects will attend safety follow-up visits, provide samples for PD and immunogenicity analyses at Month 2 (M2), Month 3 (M3), Month 4 (M4), Month 5 (M5), and Month 6 (M6); efficacy assessments will be performed at M2, M3, and M6. Among these follow-up visits, M4 and M5 will be conducted remotely. An interim analysis will be conducted after a minimum of 5 enrolled subjects complete the Month 3 visit to ensure subject safety and evaluate the preliminary benefit-risk ratio of the drug. Details: 1. Timing: Initiated within 7 working days after all subjects complete M3 visit, with the statistician completing data cleaning, analysis and report for EC and sponsor review. 2. Population: Subjects who received at least one dose of MTS109, completed M3 visit with complete data; excluding those who failed screening, missed visit or had missing key data. 3. Content: Safety (incidence and correlation of AEs/SAEs), preliminary efficacy (therapeutic response and score changes), PK/PD (preliminary parameter analysis), immunogenicity (antibody positive rate at M3). 4. Decision: Reviewed by sponsor, collaborators, statistician and EC to determine trial continuation, suspension, termination or enrollment adjustment. 5. Statistics: Descriptive statistics, paired tests and Fisher's exact test (two-sided α=0.05); interim analysis for trial decision only, final efficacy based on M6 final analysis. 6. Data management: Clean data set verified by monitoring, data cleaning completed within 5 working days with retained statistical codes and logs.