A Study to Assess the Adverse Events and Change in Disease Activity in Adult Participants With Relapsed or Refractory Multiple Myeloma Receiving Oral ABBV-453 Tablets

Inclusion Criteria:

Eastern Cooperative Oncology Group (ECOG) performance status <= 1.
Laboratory values meeting the criteria outlined in the protocol.
Documented diagnosis of multiple myeloma (MM) based on standard International Myeloma Working Group (IMWG) criteria.
Has measurable disease at screening as defined in the protocol.
Locally documented or centrally determined t(11;14) positive status and/or centrally determined BCL2high status. Note: If local testing for t(11;14) is discordant with central testing for t(11;14) status, a detailed review of central and local results for t(11;14) status is required to ensure the participants' safety.
Part 1 and Part 2, Arm 1 Only: Refractory to or intolerant of all established MM therapies that are known to provide clinical benefit and are triple class exposed to a proteasome inhibitors (PI), an Immunomodulatory drugs (IMID), and an anti-CD38 monoclonal antibody in previous line(s) of therapy.
Part 2, Arms 2 and 3 Only: Received 1 to 3 prior lines of therapy, including a PI or an IMiD.
Part 1 only: Permitted to be venetoclax or BCL-2 inhibitor exposed in previous lines of therapy.
Life expectancy >= 12 weeks.

Exclusion Criteria:

Clinically relevant or significant Electrocardiogram (ECG) abnormalities as outlined in the protocol.
Part 2 only: Previous treatment with venetoclax or BCL-2 inhibitor.
Part 2, Arms 2 and 3 only: Prior daratumumab or other anti-CD38 therapy exposure that meets any of the criteria outlined in the protocol.