Study of BTK Inhibitor LOXO-305 Versus Approved BTK Inhibitor Drugs in Patients With Mantle Cell Lymphoma (MCL)

Inclusion Criteria: * Confirmed MCL diagnosis * Previously treated with at least one prior line of systemic therapy for MCL * Measurable disease per Lugano criteria * Eastern Cooperative Oncology Group (ECOG) 0-2 * Absolute neutrophil count ≥ 0.75 × 109/L without granulocyte-colony stimulating factor support within 7 days of screening * Hemoglobin ≥ 8 g/dL not requiring transfusion support or growth factors within 7 days of screening * Platelets ≥ 50 × 109/L not requiring transfusion support or growth factors within 7 days of screening. * AST and ALT ≤ 3.0 x upper limit of normal (ULN) * Total bilirubin ≤ 1.5 x ULN. * Creatinine clearance of ≥ 30 mL/min according to Cockcroft/Gault Formula Exclusion Criteria: * Prior treatment with an approved or investigational BTK inhibitor * History of bleeding diathesis * History of stroke or intracranial hemorrhage within 6 months of randomization * History of allogeneic or autologous stem cell transplant (SCT) or chimeric antigen receptor modified T-cell (CAR-T) therapy within 60 days of randomization * Clinically significant cardiovascular disease * Prolonged QT interval corrected using Fridericia's formula (QTcF) \> 470 ms on 2/3 consecutive ECGs, and mean QTcF\>470 ms on all 3 ECGs * Known HIV infection or active HBV, HCV, or CMV infections. (Certain participants with controlled HBV infections may still be eligible) * Clinically significant active malabsorption syndrome or other condition likely to affect gastrointestinal (GI) absorption * Ongoing chronic treatment with strong cytochrome P450 3A4 (CYP3A4) inhibitors or inducers which cannot be stopped within 3-5 half lives of the CYP3A inhibitor therapy prior to start of study drug treatment. * Patients requiring therapeutic anticoagulation with warfarin or another Vitamin K antagonist. * Vaccination with live vaccine within 28 days prior to randomization