• Age ≥18 years and \< 70 years of age.

• Subjects must voluntarily sign a written informed consent and be willing and able to comply with all study requirements.

• Adequate hematologic, renal, liver, cardiac and pulmonary organ function.

• Subjects must agree to use acceptable methods of contraception.

• Willing and able to comply with scheduled visits, treatment plan, laboratory tests, contraceptive guidelines, and other study procedures.

• Diagnosis of systemic lupus erythematosus (SLE), systemic sclerosis (SSc) or idiopathic inflammatory myopathy (IIM).

⁃ For systemic lupus erythematosus (SLE) subjects:

⁃ \- Diagnosis of SLE by a board-certified rheumatologist that conforms with 2019 ACR/EULAR criteria. For lupus nephritis subjects, active, biopsy-proven proliferative lupus nephritis Class III or IV, either with or without the presence of Class V, and appropriate National Institutes of Health index activity score using the 2018 International Society of Nephrology/Renal Pathology Society criteria.

⁃ For Systemic Sclerosis (SSc) subjects:

⁃ \- Diagnosis of diffuse cutaneous systemic sclerosis (dcSSC) or SSc-ILD that conforms with 2013 ACR/EULAR criteria. Subjects should meet active skin or lung disease criteria.

⁃ For Idiopathic Inflammatory Myopathy (IIM) subjects:

⁃ \- Diagnosis with dermatomyositis (DM), polymyositis (PM) or myositis as part of rheumatologic overlap syndrome, antisynthetase (ASyS), or immune-mediated necrotizing myopathy (IMNM) that conforms with 2017 ACR/EULAR criteria for inflammatory myopathies. Subjects must meet moderate severe, skin, or lung involvement criteria.