A Study to Test CRT-402 in Refractory Autoimmune Disease

Inclusion Criteria: * Age 18 years or older. * Diagnosis of active, refractory systemic lupus erythematosus, systemic sclerosis, or idiopathic inflammatory myopathy meeting established classification criteria, with inadequate response or intolerance to standard therapy. * Adequate renal, hepatic, cardiac, and pulmonary function per protocol-defined criteria. * Participants of reproductive potential must agree to use protocol-specified contraception during the study and for a defined period after dosing. * Females of childbearing potential must have a negative pregnancy test before treatment. * Must be willing and able to attend study visits and follow all study requirements. Exclusion Criteria: * Clinical suitability for a less burdensome and/or approved therapeutic approach, as judged by the Investigator, * Any medical condition or laboratory abnormality that, in the Investigator's judgment, would place the participant at unacceptable risk or confound interpretation of study data, * Prior Cluster of differentiation 19 (CD19)-directed, cell, or gene therapy, * History of bone marrow/ hematopoietic stem cell or solid organ transplantation, * Active or inadequately treated infection, including Human immunodeficiency (HIV), hepatitis B or C, or tuberculosis, * Pregnancy or lactation.