Cosibelimab-ipdl (Unloxcyt™)

Author: Marisa Healy, BSN, RN
Content Contributor: Rachel Hatch, PharmD, BCOP
Last Reviewed: April 24, 2026

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Pronounce: koh-sih-BEH-lih-mab

Classification: Programmed death ligand-1 (PD-L1) blocking antibody

About Cosibelimab-ipdl (Unloxcyt™)

Your immune system works by making antibodies, which are proteins that attach to antigens found on the surface of a cell. The antibody “calls” your immune system to attack the cell it is attached to, causing your immune system to kill the cell. Monoclonal antibodies are created in a lab to attach to the antigens found on certain types of cancer cells. These antibodies can work in different ways, including stimulating (revving up) the immune system to kill the cell or by blocking cell growth and other functions needed for cell growth.

Cosibelimab-ipdl is a type of monoclonal antibody therapy that targets and blocks PD-L1, a protein found on some cancer cells, from interacting with PD-1 on immune cells. By blocking PD-L1, the immune system can attack and kill the cancer cells, slowing or stopping cancer growth.

How to Take Cosibelimab-ipdl (Unloxcyt™)

Cosibelimab-ipdl is given intravenously (IV, into a vein). Most often, you will receive this medication over 1 hour every 3 weeks.

Talk with your provider about other medical conditions you may have, including autoimmune diseases (Crohn’s disease, Lupus, rheumatoid arthritis, etc.) as these can get worse with immunotherapy. You should also tell your provider if you have had or plan on having a solid organ transplant, an allogeneic hematopoietic stem cell transplantation (HSCT), or any other surgery or condition that would lead to prolonged or lifelong use of immunosuppression.

Tell your provider if you have had radiation therapy to your chest area or if you have a condition that affects your nervous system, such as myasthenia gravis or Guillain-Barré syndrome.

Tell your provider about all medications (including prescription and over-the-counter), supplements, and vitamins you are taking. Steroids should be avoided while on immunotherapy unless directed by your provider.

Possible Side Effects

These are some of the most common or most serious side effects of this medication. Talk with your provider about the side effects you are having and how they can be managed.

Immunotherapy Side Effects

This medication helps your immune system become more active so it can attack cancer cells. However, as your immune system attacks these cancer cells, it can also affect normal organs and tissues in your body. This can cause serious or life-threatening problems. Tell your provider right away if you have any of the following symptoms:

Low Red Blood Cell Count (Anemia)

Anemia is when your red blood cell count is lower than normal. Red blood cells carry oxygen to the tissues in your body. When your red cell count is low, you may feel tired or weak. Tell your providers if you have shortness of breath, trouble breathing, or pain in your chest. If your count gets too low, you may receive a blood transfusion.

Low White Blood Cell Count (Leukopenia or Neutropenia)

White blood cells (WBC) help your body fight infection. While you are having treatment for cancer, your WBC count can drop, putting you at a higher risk of an infection. Tell your provider right away if you have a fever (temperature greater than 100.4°F or 38°C), sore throat or cold, shortness of breath, cough, burning with urination, or a sore that doesn't heal.

Tips for preventing infection:

  • Hand washing: both yours and your visitors is the best way to prevent the spread of infection.
  • Avoid large crowds and people who are sick (those who have a cold, fever, or cough, or live with someone with these symptoms).
  • When working outside, wear clothes that protect you, like long pants and gloves.
  • Do not handle pet waste.
  • Keep all cuts and scratches clean.
  • Shower or bathe daily. 
  • Brush your teeth at least twice a day.
  • Do not cut cuticles or ingrown nails. You may wear nail polish, but not fake nails.
  • Ask your providers before scheduling dental appointments or procedures.
  • Ask your providers before you or someone you live with has any vaccines

Low Platelet Count (Thrombocytopenia)

Platelets are blood cells that help your blood clot. Thrombocytopenia is when your platelet count is lower than normal, and you are at a higher risk of bleeding. Tell your providers if you have any bruising or bleeding, including nose bleeds, bleeding gums, or blood in your urine or stool. If your count gets too low, you may receive platelets from a donor. 

  • Do not use a razor (an electric razor is fine).
  • Do not do activities that can cause injury or bleeding.
  • Talk to your provider before taking any non-steroidal, anti-inflammatory medications (NSAIDs) like Motrin/Advil (ibuprofen), Aleve (naproxen), Celebrex (celecoxib), and others. These can raise the risk of bleeding. 
  • Use a soft-bristle toothbrush to brush your teeth. Ask your provider about flossing or using toothpicks. 

Electrolyte Abnormalities

This medication can affect your electrolytes (potassium, magnesium, sodium, calcium, etc.). Your electrolyte levels will be checked with blood tests. If your levels get too low, you may be given electrolytes by IV (intravenously through your vein) or by mouth. Talk to your provider before taking any supplements. 

Fatigue

Fatigue can cause exhaustion, feeling worn out and that your body is "heavy" and hard to move, or being unable to focus. It is common when you have cancer, and it is not the same as feeling tired. You may need to adjust your schedule to manage fatigue. Plan times to rest during the day and save your energy for more important activities. Exercise can help lessen fatigue. Talk to your providers about ways to deal with this side effect.

Muscle or Joint Pain/Aches and Headache

You may have joint or muscle pain/aches and headaches while taking this medication. Your provider can recommend medications and other ways to help relieve your pain.

Reproductive Concerns

There is a higher risk of health problems for your baby if you are pregnant, become pregnant, or get someone pregnant while on this medication. To lower the risk of birth defects, you should use birth control (contraception) to avoid pregnancy. Talk with your provider about what kind of birth control is safest for you and your partner.

If you can become pregnant, you will need to use non-hormonal birth control during treatment and for 4 months after the last dose of this medication, even if your menstrual cycle has stopped or changed.

If you can get someone pregnant, talk with your provider about the best birth control options for you, even if you believe you are not producing sperm.

You should not breastfeed during treatment and for 4 months after the last dose of this medication.

Important but Less Common Side Effects

Infusion-Related Side Effects

This infusion can cause a reaction that may lead to chills, fever, low blood pressure, dizziness, feeling like you are going to pass out, and difficulty breathing. Let your nurse know right away if you have any changes in how you are feeling.