• General

‣ Subjects must understand and voluntarily sign an informed consent form, including written consent for data protection;

⁃ Adults aged ≥ 18 years and \< 65 years at time of consent;

⁃ Male subjects, unless surgically sterile, must agree to use two acceptable methods for contraception (e.g., spermicide and condom) during the trial and refrain from fathering a child starting from the time of signing the Informed Consent Form (ICF) until 12 months after dosing of the IMP;

⁃ Females of childbearing potential (FCBP) must have a negative urine pregnancy test at screening and must agree to use a highly effective contraceptive method (Pearl index \<1) starting from the time of signing the ICF and for 12 months after dosing of the IMP;

⁃ Must be able to adhere to the study visit schedule and other protocol requirements;

⁃ Double vaccination (2 doses) against SARS-CoV-2 or SARS-CoV-2 within the last 6 months.

• SLE subjects

• a) Fulfilling the 2019 ACR/EULAR classification criteria of SLE; b) Presence of anti-dsDNA, anti-histone, anti-nucleosome or anti-Sm antibodies; c) Active disease at screening, defined as ≥1 organ system with a British Isles Lupus Assessment (BILAG) A score (severe disease activity) or ≥2 organ systems with a BILAG B score (moderate disease activity); d) Insufficient response to glucocorticoids and at least 2 of the following treatments: hydroxychloroquine, mycophenolate mofetil, belimumab, methotrexate, rituximab.

• SSc subjects

‣ Fulfilling the 2013 ACR/EULAR classification criteria of SSc;

⁃ Diffuse SSc with respective autoantibody profile;

⁃ Signs for fast progression including i) disease duration ≤5 years (from onset of first non-Raynaud manifestation), ii) mRSS score 10-35 at screening, iii) elevated acute phase reactant levels (CRP ≥ 6 mg/L, ESR ≥ 28mm/h or platelet count ≥ 330 000/mm3), iii) mRSS increase ≥ 3 units or involvement of one new body area or mRSS increase ≥ 2 units in one body area or ≥1 tendon friction rub over 6 months;

⁃ Insufficient response to glucocorticoids and to at least 2 of the following treatments:

∙ mycophenolate mofetil, azathioprine, nintedanib, methotrexate, rituximab.

• DM/PM subjects

• a) Fulfilling the 2017 ACR/EULAR classification criteria for probable or definite DM or PM57, b) Muscle weakness as defined by MMT \< 142 and 2 of the following criteria: VAS patients Global ≥ 2 cm, VAS physician Global ≥ 2 cm, HAQ \> 0.25, at least one muscle enzyme \>1.3 times upper limit of normal, VAS global extra muscular activity ≥ 2 cm; c) Presence of at least one myositis-specific antibody; d) Insufficient response to glucocorticoids and to at least 2 of the following treatments: mycophenolate mofetil, ciclosporin A, tacrolimus, methotrexate, rituximab, and intravenous immunoglobulins.

• AAV subjects

‣ Fulfilling the 2022 ACR/EULAR classification criteria for MPA/GPA/EGPA,

⁃ Presence of ANCA to either proteinase 3 or myeloperoxidase;

⁃ At least one major or three non-major items or at least two renal items of hematuria and proteinuria on the BVAS;

⁃ Failure of at least 1 of the following treatments: glucocorticoids, cyclophosphamide, or B-cell targeting therapy.