Study of Brexucabtagene Autoleucel (KTE-X19) in Participants With Relapsed/Refractory Mantle Cell Lymphoma (Cohort 1 and Cohort 2)

Key Inclusion Criteria: Up to 5 prior regimens for Mantle cell lymphoma. Prior therapy must have included: * Anthracycline or bendamustine-containing chemotherapy and * Anti-CD20 monoclonal antibody therapy and * Ibrutinib or acalabrutinib At least 1 measurable lesion Platelet count ≥ 75,000/uL Creatinine clearance (as estimated by Cockcroft Gault) \> or = to 60 mL/min Cardiac ejection fraction ≥ 50%, no evidence of pericardial effusion as determined by an echocardiogram (ECHO), and no clinically significant electrocardiogram (ECG) findings Baseline oxygen saturation \>92% on room air. Key Exclusion Criteria: * Known history of infection with human immunodeficiency virus (HIV) or hepatitis B (HBsAG positive) or hepatitis C virus (anti-HCV positive). A history of hepatitis B or hepatitis C is permitted if the viral load is undetectable per standard serological and genetic testing * History of a seizure disorder, cerebrovascular ischemia/hemorrhage, dementia, cerebellar disease, cerebral edema, posterior reversible encephalopathy syndrome, or any autoimmune disease with central nervous system (CNS) involvement * Presence of fungal, bacterial, viral, or other infection that is uncontrolled or requiring IV antimicrobials for management. Note: Other protocol defined Inclusion/Exclusion criteria may apply.