An Open-label, Study to Assess Safety, Efficacy and Cellular Kinetics of YTB323 in Severe, Refractory Systemic Lupus Erythematosus

Inclusion Criteria: * Signed informed consent * Adequate renal, hepatic, cardiac, hematological and pulmonary function * Men and women with SLE, aged ≥18 years and ≤65 years at screening, fulfilling the 2019 European League Against Rheumatism EULAR/ACR classification criteria for SLE. * Patient must be positive for at least one of the following autoantibodies at screening: antinuclear antibodies (ANA) at a titer of ≥1:80, or anti dsDNA (above the ULN); or anti-Sm (above the ULN) * Active (severe) disease as defined by SLEDAI-2K ≥ 8 (not including the SLEDAI-2K domains of lupus headache, cerebrovascular accident, organic brain syndrome) and at least one of the following significant SLE related organ involvements: * Renal * At least moderate or severe peri/myocarditis * At least moderate or severe pleuritis or other lung involvement * Vasculitis * Failure to respond to two or more standard immunosuppressive therapies (including one of mycophenolate or cyclophosphamide), unless contraindicated or having experienced documented adverse events or intolerance related to such immunosuppressive drugs not allowing their further use, in combination with glucocorticoids and failure to respond to at least one biological agent (unless contraindicated, the patient deemed ineligible by the Investigator or not available in a country). Exclusion Criteria: * Clinically significant active, opportunistic, chronic or recurrent infection confirmed by clinical evidence, imaging, or positive labor…