Study to Evaluate Adverse Events, Change in Disease Activity, and How Intravenously Infused ABBV-291 Moves Through the Body in Adult Participants With Non-Hodgkin's Lymphoma

Non-Hodgkin's lymphoma (NHL) is a cancer that arises from the transformation of normal B and T lymphocytes (white blood cells). The purpose of this study is to assess the safety, tolerability, pharmacokinetics, and preliminary efficacy of ABBV-291 in adult participants in relapsed or refractory (R/R) NHL, including but not limited to diffuse large b-cell lymphoma (DLBCL), mantle cell lymphoma (MCL), and follicular lymphoma (FL). Adverse events will be assessed. ABBV-291 is an investigational drug being developed for the treatment of NHL. This study will include a dose escalation phase to determine the maximum administered dose (MAD)/Maximum tolerated dose (MTD) of ABBV-291 and a dose expansion/optimization phase to determine the change in disease activity in participants with R/R NHL. Approximately 165 adult participants with multiple NHL subtypes will be enrolled in the study in sites world wide In the dose escalation phase of the study participants will receive escalating Intravenously (IV) infused doses of ABBV-291, until the MAD/MTD is determined. In the dose expansion/optimization phase of the study participants receive IV infused ABBV-291, as part of the approximately 74 month study duration. There may be higher treatment burden for participants in this trial compared to their standard of care. Participants will attend regular visits during the study at an approved institution (hospital or clinic). The effect of the treatment will be frequently checked by medical assessments, blood tests, and side effects.