Elranatamab

Say it: el-ran-AT-ah-mab · Brand names: Elrexfio

Elranatamab is an immunotherapy medicine that links your immune cells to myeloma cells so your body can attack the cancer.

What it is

It is a special antibody with two arms. One arm grabs a protein called BCMA on myeloma cells, and the other arm grabs a protein called CD3 on your T cells (a type of immune cell). This brings your immune cells right next to the cancer so they can attack it.

Often used for

• multiple myeloma that has come back or stopped responding after several other treatments

How you get it

You get elranatamab as a shot under the skin. The first 2 doses are smaller step up doses, and you stay in the hospital for a time after each one. After that, most people get it once a week, and some can switch to every 2 weeks later on. Your schedule may be different.

Common side effects and what helps

• Fever, often from cytokine release syndrome. Check your temperature and call as your team tells you.
• Feeling tired. Rest and short walks can help.
• Redness or soreness where the shot was given. A cool cloth may help.
• Diarrhea or nausea. Drink fluids and eat small meals.
• Colds, chest infections, and other infections. Wash your hands often.
• Muscle or bone pain. Ask your team what pain medicine is safe.
• Lower appetite. Small meals and snacks may be easier.
• Rash. Use gentle soap and unscented lotion.

Call your care team right away if you have

• Fever, chills, fast heartbeat, dizziness, or trouble breathing (possible signs of cytokine release syndrome, a strong immune reaction)
• Confusion, trouble speaking or writing, shaking, very bad sleepiness, seizures, or feeling not like yourself
• A fever of 100.4 degrees Fahrenheit (38 degrees Celsius) or higher
• Cough, burning when you pee, or other signs of infection
• Yellow skin or eyes, or dark urine
• Bleeding or bruising that is not normal for you

Before you start, tell your team

• If you have an infection now or get infections often
• If you have had hepatitis B, hepatitis C, or HIV
• If you have ever had a seizure or other nervous system problem
• If you are pregnant, may become pregnant, or are breastfeeding
• All the medicines, vitamins, and herbal products you take

Good to know

• This medicine can cause cytokine release syndrome, a strong immune reaction that causes fever, low blood pressure, and trouble breathing. It is most common after the first few doses and can be life threatening, so you will be watched closely.
• This medicine can cause nervous system problems, such as confusion, trouble speaking, or seizures. Do not drive or use heavy machines during the early doses and for as long as your team tells you.
• This medicine lowers your body's infection fighting cells and antibodies. Serious infections can happen. Your team may give you medicines or antibody infusions to help prevent them.
• You will have blood tests to check your blood counts and liver.
• Because of these risks, this medicine is only given through a special safety program at certified centers.

At home

• Carry the wallet card your team gives you and show it to any doctor or emergency room.
• Stay close to your treatment center after the first doses, as your team tells you.
• Have a caregiver with you during the early weeks who can watch for confusion or other changes.

Questions to ask

• How long will I need to stay in the hospital for the first doses?
• When can I drive again?
• Do I need medicines or antibody infusions to prevent infection?
• Who do I call after hours if I get a fever?

Side effect guides

• Fatigue (tiredness)
• Nausea and vomiting
• Diarrhea
• Appetite loss and weight loss
• Low white blood cells and infection risk
• Skin rash (including EGFR-inhibitor rash)
• Pain

Last updated: 2026-10-27. Medically reviewed by Veli Bakalov, MD, medical oncologist (October 2026). General education from Step by Step, the patient portal of HemeOncBuddy.