MTS109 in Patients With Refractory Autoimmune Diseases

This is the first-in-human trial of MTS109 (mRNA-LNP). The goal of this clinical trial is to evaluate the safety, tolerability of intravenous injection of MTS109 in moderate to severe autoimmune diseases.

Inclusion Criteria: 1\) The subject or his/her legal representative has voluntarily signed a written informed consent form and is willing and able to comply with study procedures. 2) Aged 18 to 65 years (inclusive) at the time of signing the informed consent form, with no gender restriction. 3\) Subjects with SLE must meet the following criteria: a) Meet the 2019 EULAR/ACR classification criteria for systemic lupus erythematosus (SLE); b) SLEDAI-2K score ≥6, with at least 1 BILAG-2004 organ domain score of Grade A (severe manifestation) or 2 Grade B (moderate manifestation), or both; or SLEDAI-2000 score ≥8; c) Meet the definition of refractory and relapsing disease: inadequate response to conventional therapy for more than 6 months, or disease flare after remission. Conventional therapy is defined as: glucocorticoids plus at least 2 of the following immunomodulatory agents: antimalarials, azathioprine, mycophenolate mofetil, methotrexate, leflunomide, tacrolimus, cyclosporine, and biologics including rituximab, belimumab, and telitacicept. 4\) Subjects with idiopathic inflammatory myopathy (IIM) must meet the following criteria: a) Meet the 2017 EULAR/ACR classification criteria for idiopathic inflammatory myopathies (including dermatomyositis \[DM\], polymyositis \[PM\], anti-synthetase syndrome \[ASS\], and necrotizing myopathy \[NM\]); b) Positive for myositis-specific antibodies; c) Moderate-to-severe IIM during screening, defined as: MMT-8 ≥142 with active interstitial lung disease (ILD) (ground-glass opacity on HRCT); OR MMT-8 \0.25; One or more muscle enzymes (CK, LDH, AST, ALT) ≥1.5 × upper limit of normal (ULN); d) Meet the definition of refractory, relapsing, or progressive disease: Refractory: inadequate response to conventional therapy for more than 6 months, or disease flare after remission; conventional therapy as defined for SLE; Progressive: worsening myositis or rapidly progressive interstitial lung disease. 5\) Subjects with systemic sclerosis (SSc) must meet the following criteria: a) Meet the 2013 ACR classification criteria for systemic sclerosis; b) Positive for SSc-related specific antibodies; c) Meet the definition of refractory or progressive disease: Refractory: inadequate response to conventional therapy for more than 6 months, or disease flare after remission; conventional therapy as defined for SLE; Progressive: rapid skin progression (increase in mRSS \>25%); or progressive lung disease (decrease in FVC ≥10%, or decrease in FVC \>5% with decrease in DLCO ≥15%). 6\) Subjects with ANCA-associated vasculitis (AAV) must meet the following criteria: a) Meet the 2022 ACR/EULAR classification criteria for ANCA-associated vasculitis, including microscopic polyangiitis, granulomatosis with polyangiitis, and eosinophilic granulomatosis with polyangiitis; b) Positive for ANCA-associated antibodies (MPO-ANCA or PR3-ANCA); c) Birmingham Vasculitis Activity Score (BVAS) ≥15 (total score 63), indicating active vasculitis; d) Meet the definition of refractory: inadequate response to conventional therapy for more than 6 months, or disease flare after remission; conventional therapy as defined for SLE. 7\) Subjects with Sjögren's syndrome (SS) must meet the following criteria: a) Meet the 2002 AECG criteria for primary Sjögren's syndrome or the 2016 ACR/EULAR classification criteria; b) Disease activity ESSDAI ≥6; c) Positive for anti-SSA/Ro antibody; d) Meet the definition of refractory: inadequate response to conventional therapy for more than 6 months, or disease flare after remission; conventional therapy as defined for SLE. 8\) Screening laboratory results meet the following criteria (excluding abnormalities related to the study disease): a) Neutrophil count ≥1.5 ×10⁹/L; b) Hemoglobin ≥80 g/L; platelet count ≥50 ×10⁹/L; c) Alanine aminotransferase (ALT) ≤3 × ULN; aspartate aminotransferase (AST) ≤3 × ULN (unless elevation is judged by the investigator to be related to PM or DM); total bilirubin (TBIL) \92% while breathing room air. 9\) Female subjects of childbearing potential: negative serum β-human chorionic gonadotropin (β-hCG) pregnancy test at screening. 10\) Male subjects with female partners and female subjects of childbearing potential agree to use effective contraceptive methods (e.g., oral contraceptives, intrauterine device, condom) from screening until at least 1 year after the last dose of MTS109. Exclusion Criteria: 1. SLE subjects: a) Drug-induced SLE; b) Subjects with lupus crisis, or who require medications prohibited by the protocol due to comorbidities, or who are considered ineligible by the investigator. 2. IIM subjects: a) Subjects with documented inclusion body myositis (IBM), drug-induced PM or DM, malignancy-associated PM or DM, or non-inflammatory myopathy (e.g., muscular dystrophy); b) Uncontrolled extramuscular involvement related to PM or DM: ILD: FVC \