A Study Evaluating the Efficacy of Venetoclax Plus Ibrutinib in Participants With T-cell Prolymphocytic Leukemia

* Adequate liver, kidney and hematology function per laboratory values as described in the protocol. * Diagnosis of T-cell prolymphocytic leukemia (T-PLL) that requires treatment. * Eastern Cooperative Oncology Group (ECOG) performance status less than or equal to 2. * Received prior alemtuzumab (unless unsuitable or unavailable). * Has no malignancies other than T-PLL that: * currently require systemic therapies; * were not previously treated with curative intention (unless the malignant disease is in a stable remission due to the discretion of the treating physician); or * developed signs of progression after curative treatment.

* History of or current decompensated cirrhosis including Child-Pugh class B or C, ascites, hepatic encephalopathy, or variceal bleeding. * Has human T-cell lymphotropic virus, type 1. * Prior allogeneic stem cell transplant within 6 months of study drug administration and requirement for graft versus host therapy. * Has an uncontrolled or active infection including severe acute respiratory syndrome- coronavirus-2 (SARS-COV-2). * Previously treated with a B-cell lymphoma (BCL)-2 inhibitor. * Received a prohibited therapy within the specified time frame as described in the protocol.