Retifanlimab-dlwr injection is used to treat certain types of Merkel cell carcinoma (MCC; a type of skin cancer) and anal cancer (cancer that starts in the anus [the opening at the end of the digestive system]). Retifanlimab-dlwr is in a class of medications called monoclonal antibodies. It works by helping your immune system to slow or stop the growth of cancer cells.

Retifanlimab-dlwr comes as a solution (liquid) to be injected slowly into a vein over 30 minutes by a doctor or nurse. It is given once every 4 weeks for as long as your doctor recommends that you receive treatment.

Retifanlimab-dlwr injection may cause serious reactions during the infusion of the medication. You may be given other medications to treat or help prevent reactions to retifanlimab-dlwr. A doctor or nurse will monitor you carefully while you are receiving the medication. Tell your doctor or nurse immediately if you experience any of the following symptoms during the infusion: chills or shaking, itching, rash, flushing, shortness of breath, wheezing, dizziness, feeling faint, back or neck pain, or fever. Your doctor may need to slow down your infusion or delay or permanently stop your treatment if you experience these side effects.

Your doctor may permanently or temporarily stop your treatment, or treat you with other medications if you experience other side effects. Be sure to tell your doctor how you are feeling during your treatment with retifanlimab-dlwr injection.

You will be given you the Medication Guide. Read the information carefully and ask your doctor or pharmacist if you have any questions. You can also visithttps://www.fda.gov/Drugs/DrugSafety/ucm085729.htm to obtain the Medication Guide.

This medication may be prescribed for other uses; ask your doctor or pharmacist for more information.

Before receiving retifanlimab-dlwr injection,

• tell your doctor or pharmacist if you are allergic to this drug, any part of this drug, or any other drugs, foods or substances. Tell your doctor or pharmacist about the allergy and what symptoms you had.
• tell your doctor and pharmacist what other prescription and nonprescription medications, vitamins, nutritional supplements, and herbal products you are taking or plan to take. Your doctor may need to change the doses of your medications or monitor you carefully for side effects.
• tell your doctor if you have or have ever had an organ or bone marrow transplant and if you have or have ever had radiation therapy to your chest area; an autoimmune disease (condition in which the immune system attacks a healthy part of the body) such as Crohn's disease (condition in which the immune system attacks the lining of the digestive tract causing pain, diarrhea, weight loss, and fever), ulcerative colitis (condition which causes swelling and sores in the lining of the colon [large intestine] and rectum), or lupus (condition in which the immune system attacks many tissues and organs including the skin, joints, blood, and kidneys); diabetes; thyroid problems; any type of lung disease or breathing problems; any condition that affects your nervous system such as myasthenia gravis (a disorder of the nervous system that causes muscle weakness) or Guillain-Barré syndrome (weakness, tingling, and possible paralysis due to sudden nerve damage); or kidney or liver disease.
• tell your doctor if you are pregnant or plan to become pregnant. You should not become pregnant while you are receiving retifanlimab-dlwr injection. You may need to take a pregnancy test before you start treatment and use birth control to prevent pregnancy during your treatment and for 4 months after your final dose. Talk to your doctor about birth control methods that will work for you. If you become pregnant while receiving retifanlimab-dlwr injection, call your doctor immediately. Retifanlimab-dlwr injection may harm the fetus.
• tell your doctor if you are breastfeeding or plan to breastfeed. You should not breastfeed while receiving retifanlimab-dlwr injection and for 4 months after your final dose.

Unless your doctor tells you otherwise, continue your normal diet.

If you miss an appointment to receive retifanlimab-dlwr injection, call your doctor as soon as possible.

Retifanlimab-dlwr injection may cause side effects. Tell your doctor if any of these symptoms are severe or do not go away:

• muscle or bone pain
• nausea
• vomiting
• constipation
• headache
• unusual tiredness or weakness

Some side effects can be serious. If you experience any of these symptoms, call your doctor immediately or get emergency medical treatment:

• new or worsening cough or shortness of breath
• chest pain; shortness of breath; irregular heartbeat; or swelling of feet, ankles, or lower legs
• diarrhea; blood in stools; dark, tarry, sticky stools; or stomach area pain or tenderness
• yellowing of skin or eyes, dark-colored urine, bleeding or bruising more easily than normal, loss of appetite, decreased energy, or pain on right side of stomach area
• headaches that won't go away or unusual headaches; rapid heartbeat; increased sweating; voice changes; weight changes; feeling more hungry or thirsty than usual; dizziness or fainting; hair loss; changes in mood or behavior such as decreased sex drive, feeling irritable, confused, or forgetful; constipation; increased urination; or feeling cold
• changes in vision, including double vision or blurry vision; sensitivity to light; or eye pain
• confusion; sleepiness; stiff neck; problems with balance; or tingling and weakness in the feet, legs, hands, and arms
• decreased urination; blood in urine; swelling in ankles; or loss of appetite
• rash; itching; blistering or peeling skin; sores in mouth, nose, throat, or genital area; swollen glands; or fever or flu-like symptoms
• unusual bleeding or bruising

Retifanlimab-dlwr may cause other side effects. Call your doctor if you have any unusual problems while taking this medication.

If you experience a serious side effect, you or your doctor may send a report to the Food and Drug Administration's (FDA) MedWatch Adverse Event Reporting program online (https://www.fda.gov/Safety/MedWatch) or by phone (1-800-332-1088).

In case of overdose, call the poison control helpline at1-800-222-1222. Information is also available online athttps://www.poisonhelp.org/help. If the victim has collapsed, had a seizure, has trouble breathing, or can't be awakened, immediately call emergency services at 911.

Keep all appointments with your doctor and the laboratory. Your doctor will order certain lab tests to check your body's response to retifanlimab-dlwr injection.

Keep a written list of all of the prescription and nonprescription (over-the-counter) medicines, vitamins, minerals, and dietary supplements you are taking. Bring this list with you each time you visit a doctor or if you are admitted to the hospital. You should carry the list with you in case of emergencies.

• Zynyz^®