Cemiplimab is an immunotherapy that helps your immune system find and attack cancer cells. It is given by IV infusion in a clinic. You and your care team will watch for side effects during and after treatment.
Brand Name(s)
- United States: Libtayo
- Canada: Libtayo
Warning(s)
Serious side effects can happen with cemiplimab. Some may be life-threatening or can occur after treatment ends. Tell your care team about all your health conditions and all medicines, vitamins, and herbs you take.
- Immune-related problems: Inflammation can affect many organs, including the lungs, bowels, liver, kidneys, pancreas, nerves, muscles, and hormone glands (thyroid, pituitary, adrenal). Severe skin reactions can also happen. Report new or worsening symptoms right away.
- Lung symptoms: Shortness of breath, cough, or fever may be signs of lung inflammation.
- Liver symptoms: Dark urine, yellow skin or eyes, severe tiredness, loss of appetite, nausea, or stomach pain can be signs of liver problems.
- Brain and nerve symptoms: Confusion, severe headache, stiff neck, seizures, hallucinations, sleepiness, or major weakness need urgent attention.
- Infusion reactions: Rash, itching, fever, chills, shaking, dizziness, fainting, wheezing, flushing, nausea, vomiting, back or neck pain, or swelling can occur during or shortly after the infusion.
- Infections and low white blood cells: Fever, chills, sore throat, burning with urination, pelvic pain, or skin redness/swelling may signal infection.
- Eye problems: Changes in vision, eye pain, or severe irritation require prompt care.
- Blood pressure and blood sugar: High blood pressure and high blood sugar (including new or worse diabetes) can occur. Your care team may check these regularly.
- Allergic reactions: Hives; trouble breathing; swelling of the face, lips, tongue, or throat need emergency care.
- Transplant risks: If you have had an organ, cornea, or donor stem cell transplant, there is a risk of graft rejection or other serious complications. Discuss this with your care team.
- Pregnancy and breastfeeding: Cemiplimab may harm an unborn baby. You may need a pregnancy test before starting. Use birth control while on treatment and for a time after the last dose. Do not breastfeed during treatment and for 4 months after the last dose.
- Tell all providers you receive cemiplimab, including dentists, pharmacists, and other specialists. Do not start, stop, or change any medicine without checking first.
Kind of Cancers It Is Used For (not a complete list)
- Cutaneous squamous cell carcinoma (advanced or metastatic)
- Basal cell carcinoma (certain advanced cases, often after a hedgehog pathway inhibitor)
- Non-small cell lung cancer (advanced). It may be used alone or with chemotherapy in some situations.
- Cervical cancer (recurrent or metastatic) in some cases after chemotherapy
Your exact use depends on your cancer type, stage, lab results, and prior treatments. Ask your care team how this applies to you.
Mechanism of Action
Cemiplimab is a monoclonal antibody that targets PD-1, a “brake” on immune cells. By blocking PD-1, it helps T cells see and attack cancer cells.
- Helps your immune system work better against the tumor.
- Can shrink tumors or slow their growth.
- Because it boosts immunity, it can also cause inflammation in healthy organs (immune-related side effects).
Common Side Effects
- Tiredness or weakness
- Diarrhea or constipation
- Stomach pain, nausea, or vomiting
- Decreased appetite
- Headache
- Cold-like symptoms (such as runny nose or sore throat)
- Back, bone, joint, or muscle pain
- Trouble sleeping
- Cough (more common in people treated for lung cancer)
These are not all the possible side effects. Side effects can range from mild to serious. Tell your care team about new, severe, or changing symptoms. Seek urgent help for symptoms of a severe reaction.
Learn more on the official Libtayo site
Last reviewed: 2025-12-17
