A Study Designed to Evaluate the Safety and Efficacy of Venetoclax Plus Dexamethasone (VenDex) Compared With Pomalidomide Plus Dexamethasone (PomDex) in Participants With t(11;14)-Positive Relapsed or Refractory Multiple Myeloma.

PFS is defined as the time in days from subject randomization to the date of the first documented progressive disease (PD) or death due to any cause, whichever occurs first.

ORR is defined as the percentage of participants with documented best response (sCR, CR, VGPR or partial response [PR]) prior to first documented PD.

VGPR or better response rate is defined as the proportion of participants with documented stringent complete response (sCR), complete response (CR), or VGPR.

OS is defined as the number of days from the date that the participant was randomized to the date of the participant's death.

MRD defined as the percentage of participants with MRD negativity status. MRD negativity will be defined at 10^-5 threshold as measured by centralized testing of bone marrow aspirate samples by next generation sequencing (NGS).

Time to deterioration in disease symptoms is measured by the disease symptom domain of the European Organization for Research and Treatment of Cancer Quality of Life Multiple Myeloma Module 20 (EORTC QLQ-MY20).

Time to deterioration in physical functioning is measured by the physical functioning domain of European Organization for Research and Treatment of Cancer Quality of Life Core 30 Question Questionnaire (EORTC-QLQ-C30).

Change from baseline in the Patient Reported Outcomes Measurement Information System (PROMIS) Fatigue Short Form 7a score.

Change from baseline in the Brief Pain Inventory - Short Form (BPI-SF) worst pain score.

EQ-5D-5L consists of 2 components: the EQ-5D descriptive system and the EQ visual analog scale (VAS). The EQ-5D descriptive system comprises 5 dimensions: mobility, self-care, usual activities, pain/discomfort and anxiety/depression. The EQ VAS records the participant's self-rated health on a vertical VAS where the endpoints are labelled "The best health you can imagine" and "The worst health you can imagine."

EORTC QLQ-C30 is a 30-item subject self-report questionnaire composed of both multi-item and single scales, including 5 functional scales (physical, role, emotional, social, and cognitive), 3 symptom scales (fatigue, nausea and vomiting, and pain), a global health status/quality of life scale, and 6 single items (dyspnea, insomnia, appetite loss, constipation, diarrhea, and financial difficulties).

EORTC QLQ-MY20 includes scales for disease symptoms, side effects of treatment, future perspective, and body image. Values for each scale range from 0 to 100.

DOR for a participant is defined as the number of days from the date of first documented response (PR or better) to the date of first documented PD or death due to multiple myeloma, whichever occurs first.

TTP for a participant is defined as the number of days from the date of randomization to the date of first documented PD or death due to multiple myeloma, whichever occurs first.

TTR for a participant is defined as the number of days from the date of randomization to the date of first documented response (PR or better).

Maximum plasma concentration (Cmax) of venetoclax

Observed plasma concentration at trough (Ctrough) of venetoclax.

An adverse event (AE) is defined as any untoward medical occurrence in a patient or clinical investigation participant administered a pharmaceutical product which does not necessarily have a causal relationship with this treatment. The investigator assesses the relationship of each event to the use of study.