A Study of JNJ-80948543, a T-cell Redirecting CD79b x CD20 x CD3 Trispecific Antibody, in Participants With Non-Hodgkin Lymphoma (NHL) and Chronic Lymphocytic Leukemia (CLL)

Inclusion Criteria:

• Histologic documentation of disease: B-cell non-Hodgkin lymphoma (NHL) or chroniclymphocytic leukemia (CLL) requiring therapy.

All participants must have relapsed or refractory disease with no other approved therapies available that would be more appropriate in the investigator's judgment.

B-cell NHL as defined per the 2016 world health organization (WHO) classification. In addition, the following disease-specific criteria outlined below must be met:

If diffuse large B-cell lymphoma (DLBCL) or other high-Grade B-cell lymphoma: Received, or not eligible for high-dose chemotherapy and autologous stem cell transplantation with curative intent or deemed not eligible or fit for an alternative 2nd line therapy. Participants may be eligible if relapsing after chimeric antigen receptors (CAR-T) cell treatment or while waiting for a CAR-T cell treatment.

If transformed lymphoma from low Grade B-cell malignancies: Received or not a candidate for an approved first-line regimen for DLBCL and received or not eligible for high-dose chemotherapy and autologous stem cell transplantation with curative intent.

If follicular lymphoma (FL) (all grades): Previously treated with a minimum of 2 prior lines of systemic therapy, with at least one prior line containing an anti-CD20 antibody.

If mantle cell lymphoma (MCL), marginal zone lymphoma (MZL) (including nodal, extranodal/MALT, and splenic MZL subtypes): Previously treated with at least 2 lines of systemic therapy. H.pylori-positive gastric MALT lymphoma must have failed prior H. pylori eradication therapy as one of their prior lines .

Waldenstrom macroglobulinemia (WM): Previously treated with at least 1 line of systemic therapy.

small lymphocytic lymphoma/chronic lymphocytic leukemia (CLL/SLL): Relapsed or refractory with at least 2 prior lines of therapy, including a Bruton tyrosine kinase inhibitor (BTK) inhibitor or a BCL2 inhibitor, if eligible. In addition for part B Participants must have measurable disease as defined by the appropriate disease response criteria

• Eastern Cooperative Oncology Group (ECOG) performance status Grade of 0 or 1

• Cardiac parameters within the following range: corrected QT interval (QTc intervalscorrected using Fridericia's formula [QTcF]) less than or equal to (<=) 480milliseconds based on the average of triplicate assessments performed no more than 5 (plus minus [+-] 3) minutes apart

• A female participant of childbearing potential must have a negative highly sensitiveserum pregnancy test (beta- human chorionic gonadotropin) at screening and mustagree to further serum or urine pregnancy tests prior to the first dose, during thestudy and until 3 months after the last dose of study treatment

• A female participant must agree not to be pregnant, breastfeeding, or planning tobecome pregnant while enrolled in this study or within 3 months after the last doseof study treatment

Exclusion Criteria:

• Known active central nervous system (CNS) involvement; Lymphoma with CNS involvementmay be allowed in pharmacokinetic/ pharmacodynamic (PK/PD) and expansion cohorts ifapproved by the study evaluation team (SET)

• Prior solid-organ transplantation

• Autoimmune or inflammatory disease requiring systemic steroids or otherimmunosuppressive agents (example, methotrexate or tacrolimus) within 1 year priorto first dose of study drug

• Toxicity from prior anticancer therapy has not resolved to baseline levels or toGrade <= 1 (except alopecia, vitiligo, peripheral neuropathy, or endocrinopathiesthat are stable on hormone replacement, which may be Grade 2)

• Clinically significant pulmonary compromise, particularly the need for supplementaloxygen use to maintain adequate oxygenation