What is elranatamab? A Bispecific Antibody for Multiple Myeloma

October 11, 2025 •

3 min read

The FDA granted accelerated approval to elranatamab (Elrexfio) in August 2023, making it a new, “off-the-shelf” treatment option for certain adults with heavily pretreated relapsed or refractory multiple myeloma. This innovative immunotherapy, part of a new class of bispecific T-cell engagers, provides a vital alternative for patients whose cancer has progressed after multiple prior therapies.

Quick Summary

Elranatamab is a bispecific T-cell engager antibody that targets both myeloma cells and immune cells, prompting T-cells to kill cancer cells effectively. It is indicated for patients with relapsed or refractory multiple myeloma after several prior treatment lines.

Key Points

Mechanism of Action: Elranatamab is a bispecific antibody that links T-cells to multiple myeloma cells, activating the T-cells to destroy the cancer.
Approved Indication: It is used for adults with relapsed or refractory multiple myeloma who have received at least four prior therapies.
Route of Administration: The drug is given via subcutaneous injection, which can be more convenient than intravenous infusions.
Safety Precautions: Because of the risk of serious side effects like Cytokine Release Syndrome (CRS) and neurotoxicity, it is available only through a restricted REMS program.
Efficacy in Clinical Trials: The Phase 2 MagnetisMM-3 trial demonstrated a high objective response rate and durable responses in a heavily pretreated patient population.
Dosing Schedule: Treatment involves a step-up dosing phase to mitigate risk, followed by regular and potentially less frequent maintenance dosing.
Off-the-Shelf Availability: As a pre-made product, elranatamab offers faster access to treatment compared to personalized cell therapies like CAR T-cells.

Understanding the Mechanism of Action

Elranatamab (Elrexfio) is a bispecific T-cell engager (BiTE) antibody designed to connect cancer cells with the body's immune T-cells. It achieves this by having two binding sites: one for B-cell maturation antigen (BCMA) on multiple myeloma cells, and another for the CD3 receptor on T-cells. This connection activates the T-cells to target and eliminate the myeloma cells. This mechanism is particularly beneficial for patients who have not responded to or have relapsed after conventional therapies.

Approved Indication and Administration

Elranatamab-bcmm is approved for adult patients with relapsed or refractory multiple myeloma. It is administered as a subcutaneous injection, offering a potentially more convenient option. A step-up dosing schedule is initially used.

Elranatamab Dosing:

Step-Up Doses: Treatment typically begins with lower doses during the initial phase to mitigate certain risks. Close monitoring is required, often necessitating hospitalization.
Treatment Schedule: Following the step-up phase, the medication is administered according to a specific schedule, which may be adjusted over time based on the patient's response and tolerability. For patients who respond well, the frequency of administration may be reduced to manage long-term treatment.

Important Safety Considerations

Due to the risk of severe adverse events, elranatamab is available through the restricted ELREXFIO Risk Evaluation and Mitigation Strategy (REMS) program, requiring close monitoring, especially initially.

Key Adverse Events

Cytokine Release Syndrome (CRS): A potentially serious immune system overreaction.
Neurologic Toxicity: Can range from mild symptoms to severe conditions like ICANS.
Infections: Increased risk of severe bacterial and viral infections.
Low Blood Counts: Decreased levels of various blood cells.
Liver Problems: Elevated liver enzymes and bilirubin.
Other common side effects: Injection site reactions, fatigue, diarrhea, musculoskeletal pain, and fever.

Elranatamab Compared to Other Myeloma Therapies

Elranatamab is a distinct treatment option for relapsed/refractory multiple myeloma. The table below highlights key differences between elranatamab and traditional CAR T-cell therapy.


Feature	Elranatamab (Bispecific Antibody)	CAR T-cell Therapy (e.g., cilta-cel)
Availability	"Off-the-shelf"; readily available.	Patient-specific; requires manufacturing.
Mechanism	Links existing T-cells to myeloma cells.	Uses engineered patient's T-cells to target cancer.
Administration	Subcutaneous injections.	Single intravenous infusion.
Side Effects	Risk of CRS, ICANS, infections; generally manageable with step-up dosing.	Higher rates of severe CRS and ICANS.
Logistics	Less complex and faster time-to-treatment.	More complex process with longer turnaround time.

Conclusion

Elranatamab offers a significant new treatment option for relapsed or refractory multiple myeloma, particularly for patients with limited alternatives. Its availability as an off-the-shelf bispecific antibody provides faster access compared to personalized cell therapies. Elranatamab's mechanism of engaging T-cells to kill cancer cells has demonstrated promising efficacy in clinical trials. However, managing potential serious side effects through the REMS program is crucial. Ongoing research into its use, potentially in combination with other drugs, offers hope for improved outcomes for patients with multiple myeloma. For more information, refer to the {Link: FDA website https://www.ons.org/publications-research/voice/news-views/08-2023/fda-grants-accelerated-approval-elranatamab-bcmm}.

Further Insights on Elranatamab

Elranatamab's efficacy and convenient subcutaneous administration make it a valuable addition to myeloma treatment. Ongoing studies continue to refine its optimal use. The potential for less frequent maintenance dosing for responders is a key benefit for long-term patient management.

The Efficacy of Elranatamab in Clinical Trials

The accelerated FDA approval was based on data from the Phase 2 MagnetisMM-3 trial. This study evaluated elranatamab in heavily pretreated patients with triple-class refractory multiple myeloma. It showed a high objective response rate (approximately 61%) in patients without prior BCMA-directed therapy, demonstrating its effectiveness in this difficult-to-treat group.

Frequently Asked Questions

Elranatamab (Elrexfio) is used to treat adults with relapsed or refractory multiple myeloma, a type of bone marrow cancer.

It is a bispecific antibody that binds to multiple myeloma cells and T-cells, bringing them together. This activates the T-cells to specifically target and kill the cancer cells.

Eligibility is for adult patients with relapsed or refractory multiple myeloma who have received at least four previous lines of therapy, including specific classes of drugs.

Common side effects include Cytokine Release Syndrome (CRS), neurologic toxicity, infections, low blood cell counts, injection site reactions, and fatigue.

No, elranatamab is a form of immunotherapy, specifically a bispecific antibody. It works by harnessing the body's immune system rather than directly killing all fast-growing cells like chemotherapy.

The treatment begins with a step-up dosing phase to minimize risk. This is followed by regular subcutaneous injections, and for responders, the schedule may be adjusted to less frequent administrations.

Due to the potential for serious adverse reactions like Cytokine Release Syndrome and neurotoxicity, elranatamab is only available through a Risk Evaluation and Mitigation Strategy (REMS) program.