BCMA×CD3 Bispecific Antibody Pregnancy: Based on its mechanism of action, elranatamab may cause fetal harm when given to a pregnant woman; there are no data in pregnant women and no animal reproductive studies have been conducted. It causes T-cell activation and cytokine release, and immune activation may compromise pregnancy maintenance; based on B-cell depletion in non-pregnant animals it can cause B-cell lymphocytopenia in infants exposed in utero. Human IgG crosses the placenta after the first trimester. Elranatamab is associated with hypogammaglobulinaemia, so assessment of immunoglobulin levels in newborns of treated mothers should be considered. Advise women of the potential risk to the fetus.

Elranatamab

Brand names: Elrexfio

Elranatamab is a bispecific T-cell engaging antibody used in the treatment of relapsed or refractory multiple myeloma.

Auto-extracted from the source labelling — not yet independently clinician-verified. These values were distilled from the UK SPC (or the US label where noted) but have not had a clinician sign-off. Confirm against the current SmPC before prescribing.

Adult dose

Dose: Step-up dosing then a fixed treatment dose: step-up dose 1 of 12 mg on Day 1, step-up dose 2 of 32 mg on Day 4, then the first treatment dose of 76 mg on Day 8, followed by 76 mg for all subsequent treatment doses

Route: Subcutaneous injection only. Administered only by a qualified healthcare professional with appropriate medical support to manage severe reactions such as cytokine release syndrome (CRS) and neurologic toxicity including ICANS.

Frequency: 76 mg weekly from one week after the first treatment dose through week 24; then, in patients who have had at least 24 weeks of treatment and achieved a partial response or better maintained for at least 2 months, 76 mg every 2 weeks from week 25 through week 48; then, in patients who have maintained the response after 24 weeks of every-2-week dosing, 76 mg every 4 weeks from week 49 onwards. Continue until disease progression or unacceptable toxicity.

Max: 76 mg per dose (the labelled treatment dose; no higher dose is stated)

INDICATION: relapsed or refractory multiple myeloma (MagnetisMM-3). MANDATORY MONITORING: because of the risk of CRS, patients should be hospitalised for 48 hours after the first step-up dose and for 24 hours after the second step-up dose. MINIMUM INTERVALS: at least 2 days between step-up dose 1 (12 mg) and step-up dose 2 (32 mg); at least 3 days between step-up dose 2 (32 mg) and the first treatment dose (76 mg); at least 6 days between treatment doses. PRE-TREATMENT MEDICATIONS approximately 1 hour before each of the first three doses (step-up dose 1, step-up dose 2 and the first treatment dose): paracetamol/acetaminophen (or equivalent) 650 mg orally, dexamethasone (or equivalent) 20 mg orally or intravenously, and diphenhydramine (or equivalent) 25 mg orally. RESTARTING AFTER A DELAY: after step-up dose 1 (12 mg) — if 14 days or less, restart at step-up dose 2 (32 mg) with pre-treatment medications and, if tolerated, increase to 76 mg 4 days later; if more than 14 days, restart the step-up schedule at 12 mg. After step-up dose 2 (32 mg) — if 14 days or less, restart at 76 mg; if more than 2 weeks up to 4 weeks (15 to 28 days), restart at 32 mg and, if tolerated, increase to 76 mg 1 week later; if more than 28 days, restart the step-up schedule at 12 mg. Guidance for delays after a weekly 76 mg treatment dose was truncated out of the fetched extract (the row begins '8 weeks or less') — verify against the full prescribing information. PRESENTATIONS: 76 mg/1.9 mL and 44 mg/1.1 mL (40 mg/mL) single-dose vials. GERIATRIC: no overall differences in safety or effectiveness in patients 65-74 years; insufficient numbers of patients 75 years and older to determine a difference. PAEDIATRIC: safety and effectiveness in paediatric patients have not been established. SOURCE: no UK SPC was fetched in this bundle — this draft is distilled from the US ELREXFIO prescribing information and must be verified against the UK SPC.

Dose auto-extracted from US FDA prescribing information (openFDA / DailyMed) — cross-check; US labelling may differ from UK — not yet clinician-verified. Always confirm against the product SmPC and your local formulary before prescribing.

Contraindications

None — the US label section 4 Contraindications reads 'None'

Side effects

Cytokine release syndrome — occurred in 58% of patients at the recommended dosing schedule (Grade 1 in 44%, Grade 2 in 14%, Grade 3 in 0.5%); recurrent in 13%; most often after the first step-up dose (43%) or second step-up dose (19%); median time to onset 2 days (range 1 to 9)
Neurologic toxicity including ICANS
Infections — can be severe, life-threatening or fatal; includes upper respiratory tract infection and pneumonia; do not initiate treatment in patients with active infections
Neutropenia (monitor complete blood counts at baseline and periodically); Grade 3-4 laboratory abnormalities of decreased lymphocytes, neutrophils, haemoglobin, white cells and platelets each occurred in at least 30%
Hepatotoxicity — elevated ALT, AST and bilirubin
Fatigue, injection site reaction, diarrhoea, musculoskeletal pain, decreased appetite, rash, cough, nausea and pyrexia (each at least 20%)

Interactions

CYP substrates — elranatamab causes cytokine release, which may suppress CYP450 enzyme activity and increase exposure of CYP substrates; for CYP substrates where minimal concentration changes may lead to serious adverse reactions, monitor for toxicity or monitor drug concentrations
The risk of increased CYP substrate exposure is greatest after the first dose on Day 1, for up to 14 days after the 32 mg dose on Day 4, and during and after cytokine release syndrome

Clinical monograph

How it works

It binds B-cell maturation antigen (BCMA) on myeloma cells and CD3 on T cells, bringing them together to trigger T-cell-mediated killing of the malignant plasma cells.

Prescribing in practice

Can cause cytokine release syndrome and neurological toxicity including immune effector cell-associated neurotoxicity, so step-up dosing and monitoring in an appropriately equipped setting are required.
It increases the risk of serious infections, so infection prophylaxis and prompt treatment of infections are important.
Treatment should be initiated and supervised by clinicians experienced in managing myeloma and the toxicities of T-cell engaging therapies.

Monitoring

Monitor closely for cytokine release syndrome, neurological symptoms, infections and blood counts during and after dosing.

Counselling the patient

Report fever, breathlessness, confusion or any new neurological symptoms to your team straight away.
Tell your team about any signs of infection promptly, as these can become serious.

Evidence & guidelines

Bispecific BCMA-directed antibodies are used in relapsed or refractory multiple myeloma in line with their licensed indications and NICE appraisals.

Reference: MagnetisMM-3 trial (Lesokhin et al. NEJM 2023); MHRA SPC Elrexfio 2023; NICE appraisal in progress; Bahlis et al. ASH 2022; Drug verified in RxNorm (NLM); confirm dosing against the manufacturer SPC (eMC). Verify against your local formulary and current prescribing references before prescribing. The structured dose values shown have been reviewed by a clinician. Monograph status: clinician-reviewed (2026-07-04).

Curated clinical cross-links plus same-class fallbacks.

Drugs

Teclistamab · BCMA×CD3 Bispecific Antibody

Pathways