Business objectives have changed.

The purpose of this study is to evaluate the safety and preliminary efficacy of BMS-986403 in participants with relapsed and/or refractory chronic lymphocytic leukemia (R/R CLL) or small lymphocytic lymphoma (SLL).

Inclusion Criteria:

• Participants with chronic lymphocytic leukemia (CLL) or small lymphocytic lymphoma (SLL) and high-risk features must have failed at least 2 lines of prior therapy and participants with CLL or SLL and standard risk features must have failed at least 3 lines of prior therapy
• Eastern Cooperative Oncology Group (ECOG) performance status of ≤ 1
• Either currently has central vascular access or is a candidate to receive central vascular access or peripheral vascular access for leukapheresis procedure
• Has recovery to Grade ≤ 1 or baseline of any non-hematologic toxicities due to previous therapy, except alopecia (any Grade acceptable) and peripheral neuropathy (Grade ≤ 2 acceptable)

Exclusion Criteria:

• Any condition, including active or uncontrolled infection, or the presence of laboratory abnormalities, that places the subject at unacceptable risk if they were to participate in the study
• Systemic fungal, bacterial, viral, or other infection that is not controlled
• Active autoimmune disease requiring immunosuppressive therapy
• Progressive deep vein thrombosis or pulmonary embolism requiring treatment, but not yet on a stable anticoagulation regimen

Other protocol-defined inclusion/exclusion criteria apply