A Study in Participants With Relapsed or Refractory Multiple Myeloma for QLS4131

Participants will receive QLS4131 injection until death, disease progression, initiation of new anti-tumor therapy, withdrawal of informed consent to participate in the study, or other reasons for discontinuation of study treatment, whichever occurs first.

QLS4131 will be administered subcutaneously.

Participants will receive DPd or PVd until death, disease progression, initiation of new anti-tumor therapy, withdrawal of informed consent to participate in the study, or other reasons for discontinuation of study treatment, whichever occurs first.

The DPd treatment regimen, one cycle every 28 days: Pomalidomide 4mg/d orally, on days 1-21;The PVd treatment regimen, one cycle every 21 days: Pomalidomide 4 mg/d orally, on days 1-14 of each treatment cycle.

The PVd treatment regimen, with one cycle every 21 days: Bortezomib on days 1, 4, 8, and 11 of cycles 1-8, and on days 1 and 8 from cycle 9 onwards.

The DPd treatment regimen, one cycle every 28 days: on days 1, 8, 15, and 22 of cycles 1 and 2; on days 1 and 15 from cycles 3-6; and on day 1 from cycle 7 onwards.

The DPd treatment regimen, one cycle every 28 days: Dexamethasone 20 mg orally, on days 1, 2, 8, 9, 15, 16, 22, and 23 (total 40 mg per week).

The PVd treatment regimen, one cycle every 21 days: Dexamethasone 20 mg orally, on days 1, 2, 4, 5, 8, 9, 11, and 12 of cycles 1-8, and on days 1, 2, 8, and 9 from cycle 9 onwards.

PFS is defined as the duration from the date of randomization to either PD or death, whichever comes first. Disease progression will be determined according to the IMWG 2016 response criteria.

PFS is defined as the duration from the date of randomization to either PD or death, whichever comes first. Disease progression will be determined according to the IMWG 2016 response criteria.

Very good partial response or better rate is defined as the percentage of participants who achieve very good partial response or better prior to subsequent antimyeloma therapy in accordance with the IMWG 2016 response criteria.

Defined as the proportion of participants achieving MRD-negative status.

Defined as the proportion of participants achieving MRD-negative status and maintaining it for at least 1 year.

The proportion of participants achieving a response of CR or better and MRD-negative status at 6 months post-randomization.

The proportion of participants achieving a response of CR or better and MRD-negative status at 12 months post-randomization.

Objective response rate is defined as the percentage of participants who achieve PR or better prior to subsequent antimyeloma therapy in accordance with the IMWG 2016 response criteria.

Complete response or better rate is defined as the percentage of participants who achieve CR or better prior to subsequent antimyeloma therapy in accordance with the IMWG 2016 response criteria.

DoR is defined as the time interval between the date of initial documentation of a response (PR or better) to the date of first documented evidence of progressive disease according to the IMWG 2016 response criteria or death from any cause.

Percentage of participants who remain alive and progression-free at 6, 12, and 18 months after randomization, as assessed by both the independent review committee (IRC) and the investigator according to IMWG 2016 response criteria.

OS is defined as the time from the date of randomization to the date of the participant's death due to any cause.

Percentage of participants who remain alive at 12 and 24 months after randomization.

Number of participants with AEs by Severity will be reported.

Change from baseline scores