CLN-978-SL-101; CLN-978 for SLE

Inclusion Criteria:
*  Diagnosis of SLE at least 24 weeks prior to Screening and meet 2019 EULAR / ACR Classification Criteria at screening.
*  Presence of one or more of the following autoantibodies documented during screening: positive anti-nuclear antibody (ANA) test (≥1:80); anti dsDNA above the upper limit of normal (ULN); anti-Sm above the ULN.
*  Active SLE disease, as demonstrated by a SLEDAI total score ≥8 at screening.
*  Inadequate response to at least 2 of the following treatments: oral corticosteroid, antimalarials, conventional immunosuppressants, or biologics. At least one of the failed treatments should be an immunosuppressive or biologic standard-of care agent.
*  If on corticosteroid and/or antimalarial, the dose must be stable prior to day 1.
*  Laboratory parameters including the following:
*  Absolute lymphocyte count (ALC) ≥0.5 x 109/L
*  Peripheral CD19+ B cell count ≥25 cells/µL
*  Absolute neutrophil count (ANC) ≥1.0 x 109/L
*  Hemoglobin ≥8 g/dL
*  Platelet count ≥75 x 109/L.
*  Estimated glomerular filtration rate (eGFR) (based on CKD-EPI formula) ≥30 mL/min/1.73m2
*  Total bilirubin ≤1.5 × ULN, except patients with confirmed Gilbert's Syndrome
*  Aspartate aminotransferase (AST) and alanine aminotransferase (ALT) ≤2.5 × ULN
*  Serum albumin \>2.8 g/dL
*  Part B only: For patients who were treated in Part A and did not experience dose-limiting toxicity (DLT) or discontinue CLN-978 treatment due to AEs are eligible for retreatment at a higher dose or longer schedule in Part B if they otherwise meet eligibility criteria and at least 90 days have passed since the last dose of CLN-978.

Exclusion Criteria:
*  Active inflammatory disease other than SLE. Thyroiditis or secondary Sjogren's syndrome is allowed.
*  Considered at high risk for thrombosis.
*  Rapidly progressive glomerulonephritis, and/or urine protein/creatinine \>3 mg/mg (339 mg/mmol).
*  Active severe neuropsychiatric/CNS manifestations of SLE.
*  Evidence of hepatitis B, hepatitis C (HCV) infection, human immunodeficiency virus (HIV), Epstein-Barr virus (EBV), or cytomegalovirus (CMV) infection.
*  History of splenectomy.
*  Prior treatment with the following:
*  Cellular or gene therapy product directed at any target.
*  Investigational therapy within 30 days or 5 drug-elimination half-lives (whichever is longer) prior to Day 1.
*  Any anti-CD19 or anti-CD20 therapy less than 3 months prior to Day 1.
*  Non-biologic DMARD within 14 days prior to Day 1.
*  Cyclophosphamide or a biologic immunomodulating therapy during 2 months prior to Day 1.
*  Live or attenuated vaccine within 28 days prior to screening or during screening.
*  Active, clinically significant bacterial, viral, fungal, mycobacterial, parasitic, or other infection, including SARS-CoV-2 infection, within 14 days before Day 1.
*  Active or latent tuberculosis (TB) evidenced by a positive or indeterminant Interferon Gamma Release Assay (IGRA), unless the patient has documented previous completion of TB treatment and no current clinical indication of TB.
*  Any condition for which, in the opinion of the Investigator and/or Sponsor, would not be in the best interest of the patient to participate in the study or that could prevent, limit, or confound any protocol-defined assessment.