If you have a certain type of cancer, your doctor may suggest Imfinzi (durvalumab) or Keytruda (pembrolizumab) as a treatment option for you.

Imfinzi and Keytruda are immunotherapy medications, available only by prescription. They work by activating your immune system to recognize and attack cancer cells.

Imfinzi and Keytruda are also biologic drugs. A biologic is made from parts of living organisms. At this time, there are no biosimilar forms for Imfinzi or Keytruda. (Biosimilars are like generic drugs. But unlike generics, which are made for nonbiologic drugs, biosimilars are made for biologic drugs.) However, a biosimilar version of Keytruda is currently being developed.

Imfinzi and Keytruda can be used to treat some of the same types of cancer. You might wonder if one of these drugs could help your condition. This article highlights how these drugs are alike and different to help you decide which might work better for you.

Note: For more information about each drug, see these in-depth Imfinzi and Keytruda articles.

Imfinzi and Keytruda belong to a class of immunotherapy drugs called PD-L1 inhibitors. (A drug class is a group of medications that work in a similar way.) These medications aren’t chemotherapy drugs.

Imfinzi contains the active ingredient durvalumab.

Keytruda contains a different active ingredient, pembrolizumab.

Imfinzi and Keytruda are used to treat some of the same types of cancers in adults. These cancers are:

In addition, Keytruda is used to treat additional types of cancer in adults:

* Keytruda may also be used in children to treat some types of this cancer.

Imfinzi and Keytruda aren’t recommended for all types of each of the cancers listed above. Additional factors will decide whether Imfinzi or Keytruda are good options for you.

For more detailed explanations of each drug’s approved uses, see these in-depth Imfinzi and Keytruda articles.

Whether you have health insurance or not, cost may be a factor when you’re considering these drugs.

Keep in mind that what you’ll pay for either drug will depend on your treatment plan, health insurance, and the pharmacy you use.

Imfinzi and Keytruda are both biologic drugs. A biologic is made from parts of living organisms. Currently, these drugs aren’t available in biosimilar forms. (Biosimilars are like generic drugs. But unlike generics, which are made for nonbiologic drugs, biosimilars are made for biologic drugs.) However, a biosimilar version of Keytruda is currently being developed.

You may wonder whether Imfinzi or Keytruda would help your condition.

Imfinzi and Keytruda were shown to be effective in studies for treating certain types of cancer. If you’d like more details about how each drug performed in studies, see the prescribing information for Imfinzi and Keytruda.

You’ll receive Imfinzi or Keytruda at your doctor’s office or hospital. It’s given as an intravenous (IV) infusion. (With IV infusions, medications are slowly injected through a needle placed in your vein.)

Both drugs come in vials of solution that a healthcare professional uses to prepare your IV infusion.

Imfinzi infusions are generally repeated every 2, 3, or 4 weeks. Each Imfinizi infusion will take about an hour.

Keytruda infusions are typically given every 3 or 6 weeks. With Keytruda, each IV infusion will last around 30 minutes.

Your doctor will discuss the details of your dosage with you. Your schedule may depend on the type of cancer you’re getting treated for and if you’re also receiving chemotherapy.

You may feel some concern about what side effects can happen with Imfinzi and Keytruda if you’re considering either drug for your cancer.

Imfinzi and Keytruda may cause mild or serious side effects. Below, we’ll highlight the side effects that are similar and different between these drugs.

For more information about possible side effects, see the prescribing information for Imfinzi and Keytruda.

Mild side effects

Imfinzi and Keytruda may cause mild side effects in some people. The chart below lists examples of mild side effects that can occur with these drugs.

Fatigue (lack of energy)XX
Feeling weakXX
Muscle or bone painXX
Decreased appetiteXX
Swelling in arms or legsX
Urinary tract infection (UTI)X
Upper respiratory tract infectionX
Shortness of breathXX
Hair lossXX
Itchy skinX
Belly painXX

This chart may not include all mild side effects of these drugs. Other mild side effects may occur if you’re receiving Imfinzi or Keytruda with other cancer treatments.

For more information on mild side effects of these drugs, see the prescribing information for Imfinzi and Keytruda.

Serious side effects

In addition to the mild side effects described above, serious side effects may occur in people receiving Imfinzi or Keytruda. See the chart below for a list of possible side effects.

Allergic reactionXX
Severe immune system reactions*XX
Severe infusion reactionsXX
Serious infections, such as pneumoniaX
Severe skin rashXX

* Severe immune system reactions can occur because Imfinzi and Keytruda may trigger the immune system to attack your own body. The areas most often harmed are the lungs, liver, heart, intestines, skin, and glands that make hormones.

If you have questions about your specific risk for side effects of Imfinzi or Keytruda, talk with your doctor.

Imfinzi or Keytruda may not be right for you if you have certain medical conditions or other factors that affect your health. Talk with your doctor about your health history before you take either drug.

Before taking Imfinzi or Keytruda, talk with your doctor if you have any of the following conditions or health factors.

For more information about these warnings, see these in-depth Imfinzi and Keytruda articles.

The short answer: It’s not likely.

Details: There aren’t any studies on switching between Imfinzi and Keytruda. So it isn’t known if it’s safe and effective to switch between these drugs.

Imfinzi and Keytruda both stay in your system for several months after your last dose.It could be harmful to have both of these drugs in your system at the same time.

If you have a severe immune system reaction to one of these drugs, it’s possible that you would have a similar reaction to the other.Studies are needed to learn more about the safety of switching these medications.

Discuss the risks and benefits with your doctor if there’s a reason that you’re interested in switching your medication.

Reminder: You should not switch drugs or stop your current treatment unless your doctor tells you it’s fine to do so.

Imfinzi and Keytruda work in a similar way to treat several forms of cancer. However, they’re different in some of their side effects. And Keytruda is used to treat more types of cancer than Imfinzi.

If you have questions about which drug may be better for your treatment plan, talk with your doctor. Here are some questions you may want to ask during your conversation:

  • Is there a reason why Imfinzi may be better for me than Keytruda?
  • Would Imfinzi or Keytruda interact with any medications I’m taking?
  • How long would I receive treatments of Imfinzi or Keytruda?
  • Is it safe for me to receive vaccines while taking Imfinzi or Keytruda?


Can I continue taking my medical cannabis while receiving Imfinzi or Keytruda?

Anonymous patient


Before taking either Imfinzi or Keytruda, you need to inform your doctor and pharmacist about all medications you take. This includes medical cannabis.

One study suggests that cannabis may make immunotherapy drugs, such as Imfinzi and Keytruda, less effective. This study found that people who used cannabis were less likely to have their cancer respond to these medications.

Note that this was a small study. More research is needed to learn what effect cannabis use may have on Imfinzi or Keytruda treatment.

If you use medical cannabis, it’s important that you tell your doctor and pharmacist before taking Keytruda or Imfinzi. They’ll help you make the best treatment decisions.

The Healthline Pharmacist TeamAnswers represent the opinions of our medical experts. All content is strictly informational and should not be considered medical advice.
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Disclaimer: Healthline has made every effort to make certain that all information is factually correct, comprehensive, and up to date. However, this article should not be used as a substitute for the knowledge and expertise of a licensed healthcare professional. You should always consult your doctor or another healthcare professional before taking any medication. The drug information contained herein is subject to change and is not intended to cover all possible uses, directions, precautions, warnings, drug interactions, allergic reactions, or adverse effects. The absence of warnings or other information for a given drug does not indicate that the drug or drug combination is safe, effective, or appropriate for all patients or all specific uses.