This registry study will provide valuable evidence to assess and validate its effectiveness in the Chinese MM population, refine clinical application strategies, and support the optimization of BCMA BsAbs use in MM treatment in China.

Multiple myeloma (MM) is a malignancy characterized by the clonal proliferation of terminally differentiated plasma cells within the bone marrow. It is the second most common hematological malignancy, accounting for 10-15% of all hematological cancers. Over the past three to four decades, the incidence of MM has been increasing globally. Similar trends are observed in China, where the incidence of MM has also been rising. According to the GLOBOCAN database, in 2022, there were an estimated 30,300 new cases of MM and 18,662 deaths. The 5-year prevalence rate was approximately 6.0 per 100,000 people in China.

Remarkable progress in MM has been achieved in the past two decades. Proteasome inhibitors (PIs), immunomodulatory drugs (IMiDs), and anti-CD38 monoclonal antibodies (mAbs) are the cornerstone of MM therapeutics. After the incorporation of three class novel agents the clinical outcomes of patients with MM have improved significantly, however, MM remains incurable, as most patients eventually experience relapse/progression. Relapse and progression remain the primary causes of mortality in MM patients.

As relapses are common in MM, and patients often receive various drug combinations throughout the course of their disease, providing optimal therapy for patients already exposed to PIs, IMiDs, and anti-CD38 mAbs s (namely triple-class exposed [TCE]) and/or refractory to these drugs (triple-class refractory [TCR]) presents a significant therapeutic challenge. The LocoMMotion and MAMMOTH studies have highlighted the dismal outcomes of patients with TCE/TCR MM, with response rates of approximately 30% and a complete response (CR) or better (<1%). Furthermore, the progression-free survival (PFS) and overall survival (OS) for this patient subset are limited, with a median PFS of no longer than 6 months and median OS of less than 1 year. As a result, there is an urgent and increasing unmet need for novel therapies with new targets, mechanisms of action, and treatment strategies to extend the duration and durability of clinical responses, thereby improving survival outcomes for TCE/TCR MM patients.

BMCA is a member of the tumor necrosis factor (TNF) receptor superfamily and plays a crucial role in the survival of long-lived bone marrow plasma cells (PCs). Additionally, the overexpression of serum BCMA correlates with disease progression and shorter PFS and OS in patients with MM, making BCMA an ideal therapeutic target. Recently, immunotherapies targeting BCMA have shown promise in the treatment of relapsed or refractory multiple myeloma (RRMM). The chimeric antigen receptor (CAR) T cell and bispecific antibodies (BsABs) targeting BCMA are emerging as a new standard of care in TCE-RRMM population. To date, two bispecific antibodies targeting CD3 on T cells and BCMA on myeloma cells have been approved globally for the treatment of TCE-RRMM patients.

Elranatamab, a humanized BCMA-CD3 BsAB was granted accelerated approval by the FDA in August 2023 for the treatment of patients with TCE-RRMM, based on the results of the MagnetisMM-3 (NCT04649359) study. In the MagnetisMM-3 study (Cohort A), elranatamab led to an ORR of 61%, with a median PFS of 17.2 months in TCE-RRMM patients who had received a median of 5 prior lines of therapy. The median duration of response (DOR) was not reached, with a median follow-up of 33.9 months. Elranatamab was approved by the National Medical Products Administration (NMPA) in March 2025 in China. However, real-world data on its use in the Chinese population is currently lacking, and physicians have limited experience administering it outside of clinical trials.

Therefore, collecting real-world data on the effectiveness of Elranatamab in Chinese TCE-RRMM patients after its commercially available in China is crucial.

Inclusion Criteria:

Participants with TCE-RRMM who have received or are planning to start Elranatamab treatment according to the local Health Authority approved product label (routine-care).

Patients must meet the following criteria to be eligible for inclusion in the study:

In the retrospective part:

1. Male or female patients above 18 years old
2. Patients diagnosed with RRMM(IMWG)
3. Prior lines of therapy must include a proteasome inhibitor, an immunomodulatory drug and anti-CD38 monoclonal antibody in any order during the course of treatment
4. Patients received at least 1 treatment dose of Elranatamab treatment after commercial launch in China and according to the approved product label (routine-care) in China (consistent with the approved label in China)*
5. Patients understand and voluntarily sign an ICF .

In the prospective part:

1. Male or female patients above 18 years old
2. Patients diagnosed with RRMM (IMWG)
3. Prior lines of therapy must include a proteasome inhibitor, an immunomodulatory drug and anti-CD38 monoclonal antibody in any order during the course of treatment
4. Patients treated with elranatamab as monotherapy or a part of combination therapy and according to the approved product label (routine-care) in China (consistent with the approved label in China)*
5. Patient understand and voluntarily sign an ICF. *Note: If patients received Elranatamab treatment at a Hong Kong site,the treatment must consist the indications approved in Hong Kong.

Exclusion Criteria:

Patients meeting the following criteria will not be included in the study:

In the retrospective part:

1. Patients with documented diagnosis of other cancers prior to the diagnosis of MM
2. Patients enrolled in interventional clinical trials of any drug for MM treatment
3. Patients with incomplete medical records or missing clinical laboratory data that preclude effectiveness evaluation.
4. Patients who, in the opinion of the investigator, have other factors that make them unsuitable for study participation.

In the prospective part:

1. Patients with documented diagnosis of other cancers prior to the diagnosis of MM
2. Patients with contraindication listed in the package insert of elranatamab
3. Patients enrolled in interventional clinical trials of Elranatamab or any other drug for MM treatment

Participants with TCE-RRMM who have received or are planning to start Elranatamab treatment according to the local Health Authority approved product label (routine-care).

Patients must meet the Inclusion Criteria and the Exclusion Criteria to be eligible for inclusion in the study.

Unplanned