A Phase 1 Study of FT819 in B-cell Mediated Autoimmune Disease

Key Inclusion Criteria: * Age: 12 to 70 years old. * Diagnosis: Must have active B-cell mediated autoimmune disease (SLE, AAV, IIM, or SSc) confirmed by standard criteria. * Disease Severity: Moderate to severe, requiring at least two prior treatments that were ineffective. * Health Status: Adequate organ function to tolerate treatment. * Consent: Able to provide informed consent or assent/obtain parental consent and comply with study procedures. Key Exclusion Criteria: * Pregnancy/Breastfeeding: Women must not be pregnant or nursing. * Severe Organ Dysfunction: Significant heart, lung, liver, or kidney impairment. * Active Infections: No recent or ongoing serious infections. * Recent Cancer or Prior Cell Therapy: No active/recent malignancies, prior CAR T-cell therapy, or organ transplant. * Allergies: No known allergies to study treatments. * Weight Restriction: Must weigh at least 50 kg (110 lbs).