Brand Name(s)
US: Unloxcyt
Warning(s)
Cosibelimab is an immune checkpoint inhibitor. It can cause your immune system to attack healthy organs. Serious problems can happen during treatment or after it ends.
- Immune-related organ problems: lungs (pneumonitis), intestines (colitis), liver (hepatitis), kidneys (nephritis), pancreas (pancreatitis or diabetes), thyroid, pituitary, or adrenal glands (hormone changes), nerves and muscles (weakness or numbness), heart (inflammation), skin (severe rash), and eyes (vision changes).
- High blood sugar: New or worse diabetes can happen.
- Infusion reactions can occur during or soon after the IV infusion (for example, chills, fever, flushing, shortness of breath, rash, or wheezing).
- Transplants: Risk of organ or cornea graft rejection. Serious problems can also occur after an allogeneic (donor) stem cell transplant.
- Allergic reactions can be severe, including swelling of the face or throat and trouble breathing.
- Rare but serious immune over-activation (HLH) has been reported.
- Pregnancy and breastfeeding: This drug may harm an unborn baby. If you can become pregnant, a pregnancy test is usually done before starting. Use birth control during treatment and for 4 months after the last dose. Do not breastfeed during treatment or for 4 months after the last dose.
- Drug interactions: Tell your care team about all medicines, vitamins, and herbal products you use.
- Monitoring: You may need regular blood tests and checks for hormone levels, liver and kidney function, and blood sugar.
Get urgent medical help if you notice warning signs such as chest pain; trouble breathing or a persistent cough; severe stomach pain or bloody/black stools; yellow skin or eyes; fast or irregular heartbeat; confusion or severe headache; severe muscle weakness; swelling of the face, lips, or throat; a widespread rash or skin peeling; or sudden changes in vision.
Kind of Cancers It Is Used For (not a complete list)
- Cutaneous squamous cell carcinoma (cSCC) that has spread (metastatic) or cannot be cured with surgery or radiation (locally advanced).
Your cancer type, stage, and health history guide whether this medicine is right for you.
Mechanism of Action
Cosibelimab is a monoclonal antibody that targets PD-1, a brake on T cells. By blocking PD-1, it helps your immune system find and attack cancer cells.
Because it boosts immune activity, it can also cause the immune system to attack normal organs. This is why close monitoring and quick reporting of new symptoms are important.
Common Side Effects
- Headache
- Feeling tired or weak
- Diarrhea or constipation
- Upset stomach or nausea
- Infusion-related symptoms such as chills, fever, flushing, itching, rash, or shortness of breath
This is not a complete list. Side effects can be mild or serious. Keep track of how you feel and share new or worsening symptoms with your care team.
Official manufacturer site (Unloxcyt)
Last reviewed: 2025-12-17
