Pronunciation: ZYE-niz
Generic name: retifanlimab-dlwr
Dosage form: injection (500 mg/20 mL)
Drug class: Anti-PD-1 and PD-L1 monoclonal antibodies (immune checkpoint inhibitors)

Medically reviewed by Carmen Pope, BPharm. Last updated on May 20, 2025.

What is Zynyz?

Zynyz is a targeted cancer treatment used to squamous cell carcinoma of the anal canal (SCAC) and Merkel cell carcinoma (MCC). It is given as an IV infusion by a healthcare provider, usually once every 4 weeks.

Zynyz is a programmed death receptor-1 (PD-1)–blocking antibody (also called an immune checkpoint inhibitor) that works by binding to the PD-1 protein on immune T-cells to prevent the interaction with PD-L1, a protein that is often found on some cancer cells. When the PD-1 protein on an immune cell interacts with the PD-L1 protein on a cancer cell, the cancer cell is considered healthy and is left alone. By blocking the interaction with PD-1, Zynyz's mechanism of action removes the "brakes" on the immune system, allowing it to attack cancer cells more effectively.

Zynyz belongs to the drug class called immune checkpoint inhibitors. It may also be called an anti-PD-1 and PD-L1 monoclonal antibody.

Zynyz (retifanlimab) first gained FDA approval on March 22, 2023, for MCC. Approval was extended on May 15, 2025, to include SCAC. There is no generic or biosimilar.

FDA approvals and indications

Zynyz (retifanlimab) is FDA-approved for:

• Squamous cell carcinoma of the anal canal (SCAC).
  • It may be used in combination with carboplatin and paclitaxel, as your first treatment, when your anal cancer has returned and cannot be removed by surgery, or has spread.
  • Zynyz may be used alone when your anal cancer has returned or has spread, and you have received chemotherapy that contains platinum, and it did not work, is no longer working, or you could not tolerate it.

• Merkel cell carcinoma (MCC).
  • Zynyz may be used alone to treat your skin cancer when it has spread or returned.

It is not known if this medicine is safe and effective in children.

Side effects

The most common side effects of Zynyz when given with carboplatin and paclitaxel in people with SCAC are:

• tiredness
• numbness, pain, tingling, or burning in your hands or feet
• nausea
• hair loss
• diarrhea
• muscle and bone pain
• constipation
• bleeding
• rash
• vomiting
• decreased appetite
• itching
• stomach-area pain.

The most common side effects of Zynyz when used alone in people with SCAC are:

• tiredness
• muscle and bone pain
• diarrhea
• infection
• rectal or genital area pain
• bleeding
• urinary tract infection (UTI)
• rash
• nausea
• loss of appetite
• constipation
• stomach-area pain
• shortness of breath
• fever
• vomiting
• cough
• itching
• low levels of thyroid hormone
• headache
• decreased weight.

The most common side effects of Zynyz when used alone in people with MCC are:

• tiredness
• muscle and bone pain
• itching
• diarrhea
• rash
• fever
• nausea.

Serious side effects and warnings

Warning. Zynyz is a medicine that may treat certain types of cancers by working with your immune system. Zynyz can cause your immune system to attack normal organs and tissues in any area of your body and affect how they work. These problems can sometimes become severe or life-threatening and can lead to death. You can have more than one of these problems at the same time. These problems may happen anytime during treatment or even after your treatment has finished.

Call or see your healthcare provider right away if you develop any new or worsening signs or symptoms, including:

• Lung problems:
  • cough
  • shortness of breath
  • chest pain.
• Intestinal problems:
  • diarrhea (loose stools) or more frequent bowel movements than usual
  • stools that are black, tarry, sticky, or have blood or mucus
  • severe stomach-area (abdomen) pain or tenderness.
• Liver problems:
  • yellowing of your skin or the whites of your eyes
  • severe nausea or vomiting
  • pain on the right side of your stomach (abdomen)
  • dark urine (tea colored)
  • bleeding or bruising more easily than normal.
• Hormone gland problems:
  • headaches that will not go away or unusual headaches
  • eye sensitivity to light
  • eye problems
  • rapid heartbeat
  • increased sweating
  • extreme tiredness
  • weight gain or weight loss
  • feeling more hungry or thirsty than usual
  • urinating more often than usual
  • hair loss
  • feeling cold
  • constipation
  • your voice gets deeper
  • dizziness or fainting
  • changes in mood or behavior, such as decreased sex drive, irritability, or forgetfulness.
• Kidney problems:
  • decrease in your amount of urine
  • blood in your urine
  • swelling of your ankles
  • loss of appetite.
• Skin problems:
  • rash
  • itching
  • skin blistering or peeling
  • painful sores or ulcers in your mouth or nose, throat, or genital area
  • fever or flu-like symptoms
  • swollen lymph nodes.

Problems can also happen in other organs and tissues. These are not all of the signs and symptoms of immune system problems that can happen during treatment with Zynyz. Call or see your healthcare provider right away for any new or worsening signs or symptoms, which may include:

• chest pain, irregular heartbeat, shortness of breath, or swelling of the ankles
• confusion, sleepiness, memory problems, changes in mood or behavior, stiff neck, balance problems, tingling or numbness of the arms or legs
• double vision, blurry vision, sensitivity to light, eye pain, changes in eyesight
• persistent or severe muscle pain or weakness, muscle cramps
• low red blood cells, bruising.

Infusion reactions can happen with Zynyz, which can sometimes be severe. Tell your healthcare provider right away if you get any of these signs and symptoms during or soon after your infusion:

• chills or shaking
• itching or rash
• flushing
• shortness of breath or wheezing
• dizziness
• feel like passing out
• fever
• back or neck pain

Rejection of a transplanted organ or tissue, can happen in people receiving Zynyz who have had an organ/tissue transplant. Your healthcare provider should tell you what signs and symptoms you should report and monitor you, depending on the type of organ or tissue transplant that you have had.

Complications, including graft-versus-host disease, may occur in people who have received a bone marrow (stem cell) transplant that uses donor stem cells (allogeneic). These complications can be serious and can lead to death.

• These complications may happen if you underwent transplantation either before or after being treated with Zynyz.
• Your healthcare provider will monitor you for these complications.

Getting medical treatment right away may help keep these problems from becoming more serious.

Your healthcare provider will check you for these problems during your treatment with Zynyz. Your healthcare provider may treat you with corticosteroids or hormone replacement medicines. Your healthcare provider may also need to delay or completely stop treatment with Zynyz if you have severe side effects.

These are not all the possible side effects of Zynyz. Call your doctor for medical advice about side effects. You may report side effects to the FDA at 1-800-FDA-1088.

Related/similar drugs

Before you receive Zynyz

Before you start treatment, tell your healthcare provider about all of your medical conditions, including if you:

• have immune system problems such as Crohn’s disease, ulcerative colitis, or lupus
• have received an organ transplant
• have received or plan to receive a stem cell transplant that uses donor stem cells (allogeneic)
• have received radiation treatment to your chest area
• have a condition that affects your nervous system, such as myasthenia gravis or Guillain-Barré syndrome
• are pregnant or plan to become pregnant
• are breastfeeding or plan to breastfeed.

Pregnancy

Zynyz can harm your unborn baby. Females who can become pregnant:

• Your healthcare provider should do a pregnancy test before you start treatment.
• You should use an effective method of birth control during your treatment and for 4 months after your last dose. Talk to your healthcare provider about birth control methods that you can use during this time.
• Tell your healthcare provider right away if you become pregnant or think you may be pregnant during treatment.

Breastfeeding

Tell your healthcare provider if you are breastfeeding or plan to breastfeed. It is not known if Zynyz passes into your breast milk.

Do not breastfeed during treatment, and for 4 months after your last dose.

How will I receive Zynyz?

Your healthcare provider will give you Zynyz into your vein through an intravenous (IV) line over 30 minutes.

• Zynyz is usually given every 4 weeks.
• Your healthcare provider will decide how many treatments you will need.
• Your healthcare provider will do blood tests to check you for side effects.
• If you miss any appointments, call your healthcare provider as soon as possible to reschedule your appointment.

Dosing information

Usual Adult Dose of Zynyz for Squamous Cell Carcinoma of the Anal Canal (SCAC)

• 500 mg as an intravenous infusion over 30 minutes every 4 weeks.
• Continue until disease progression, unacceptable toxicity, or up to 24 months.

Usual Adult Dose of Zynyz for Merkel Cell Carcinoma

• 500 mg as an intravenous infusion over 30 minutes every 4 weeks.
• Continue until disease progression, unacceptable toxicity, or up to 24 months.

What other drugs will affect Zynyz?

Tell your healthcare provider about all the medicines you take, including prescription and over-the-counter medicines, vitamins, and herbal supplements.

What are the ingredients in Zynyz?

Active ingredient: retifanlimab-dlwr

Inactive ingredients: glacial acetic acid, polysorbate 80, sodium acetate, sucrose, and Water for Injection.

Available as a 500 mg/20 mL (25 mg/mL) solution for injection in a single-dose vial.

Manufacturer

Zynyz (retifanlimab-dlwr) is made by Incyte Corporation, Wilmington, DE 19803.

Zynyz Biosimilars

Biosimilar and interchangeable products are biological products that are highly similar to and have no clinically meaningful differences from the reference product.

Reference products

These are biological products that have already been approved by the FDA, against which biosimilar products are compared. There is 1 for Zynyz.

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Further information

Always consult your healthcare provider to ensure the information displayed on this page applies to your personal circumstances.

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