A Study of Zilovertamab Vedotin (MK-2140) as Monotherapy and in Combination in Participants With Aggressive and Indolent B-cell Malignancies (MK-2140-006)

The purpose of this study is to assess the safety and tolerability of zilovertamab vedotin as monotherapy and in combination in participants with select B-cell lymphomas including mantle cell lymphoma (MCL), Richter's transformation lymphoma (RTL), follicular lymphoma (FL), and chronic lymphocytic leukemia (CLL). This study will also evaluate zilovertamab vedotin as monotherapy and in combination with respect to objective response rate. * Cohort A: Participants with relapsed or refractory MCL relapsed or refractory disease after at least 2 prior systemic therapies including a Bruton's tyrosine kinase inhibition/inhibitor (BTKi), and post therapy chimeric antigen receptor T (CAR-T) cell therapy or ineligible for CAR-T cell therapy * Cohort B: Participants with relapsed or refractory RT disease after at least 1 prior systemic therapy * Cohort C: Participants with relapsed or refractory MCL relapsed or refractory disease after at least 1 prior systemic therapy and no prior exposure to a non-covalent BTKi * Cohort D: Participants with relapsed or refractory FL and CLL relapsed or refractory disease after at least 2 prior systemic therapies and have no other available therapy * Cohort E: Participants with relapsed or refractory FL after at least 2 prior systemic therapies and have no other available therapy The primary study hypothesis is that zilovertamab vedotin monotherapy has an increased Objective Response Rate (ORR) per Lugano Response Criteria as assessed by blinded independent central review (BICR). As of Amendment 07, Cohort D is closed to enrollment of participants with CLL and enrollment of participants into Arm 2 (zilovertamab vedotin at Dose 2 on Days 1 \& 8 of each 3 Week Cycle (Q2/3W)). As of Amendment 09, no additional participants with RT will be enrolled in Cohort B; however, those currently enrolled will continue with study intervention treatment (if applicable) until a protocol specified discontinuation criterion is met. Cohort E will be closed, as no participants with FL have been treated in this cohort.

The main inclusion criteria include, but are not limited to the following: Inclusion Criteria: * For aggressive B-cell malignancies mantle cell lymphoma (MCL): Has histologically confirmed biopsy according to the 2016 World Health Organization (WHO) classification of neoplasms of the hematopoietic and lymphoid tissues and has relapsed or refractory disease after at least 2 prior systemic therapies including a Bruton's tyrosine kinase inhibition/inhibitor(s) (BTKi), and is post chimeric antigen receptor T (CAR-T) cell therapy or is ineligible for CAR-T cell therapy. * For aggressive B-cell malignancies MCL Cohort C: Has histologically confirmed biopsy according to the 2016 World Health Organization (WHO) classification of neoplasms of the hematopoietic and lymphoid tissues and has relapsed or refractory disease after at least 1 prior systemic therapy and has no prior exposure to a non-covalent BTKi. * For aggressive B-cell malignancies Richter transformation lymphoma (RTL): Has histologically confirmed biopsy according to the 2016 World Health Organization (WHO) classification of neoplasms of the hematopoietic and lymphoid tissues and has relapsed or refractory disease. * For indolent B-cell malignancies follicular lymphoma (FL) and chronic lymphocytic leukemia (CLL): Has histologically confirmed biopsy and has relapsed or refractory disease after at least 2 prior systemic therapies and no other available therapy. * Participants who are hepatitis B surface antigen (HBsAg) positive are eligible if they have received hepatitis B virus (HBV) antiviral therapy for at least 4 weeks and have undetectable HBV viral load prior to randomization/allocation. * Have an Eastern Cooperative Oncology Group (ECOG) performance status of 0 to 2 assessed within 7 days before cycle 1 day 1. Exclusion Criteria: * Has received solid organ transplant at any time. * Has clinically significant (ie, active) cardiovascular disease: cerebral vascular accident/stroke (\