What is Symdeko (Tezacaftor/Ivacaftor)?

Reviewed by: HU Medical Review Board | Last reviewed: May 2022

Symdeko® (tezacaftor/ivacaftor) is approved to treat cystic fibrosis (CF) in people who are 6 and older. They must have 2 copies of the F508del mutation or a single copy of one of dozens of other CFTR mutations for this drug to work.1

Cystic fibrosis (CF) is a genetically inherited disease that results in recurring lung infections and gastrointestinal issues that gradually damage many organs. It affects the lungs the most, but also the digestive system, including the pancreas, liver, intestines, and kidneys. CF may also impact the ears, nose and sinuses, sex organs, and the bones and joints.1

The full prescribing information includes a list of all the genetic mutations that Symdeko is known to treat.

How does Symdeko work?

People with CF inherit 2 copies of a defective or mutated CF gene, meaning each parent was a carrier for CF. Called the cystic fibrosis transmembrane conductance regulator (CFTR) gene, this mutation affects how the body makes the CFTR protein.

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A healthy CFTR protein helps cells move chloride, an element in salt, to the cell surface. In CF, the body creates a “broken” CFTR protein that cannot move chloride properly. Without chloride, water isn’t attracted to the cell surface, resulting in a thick, sticky mucus building up in the lungs and other organs.

Symdeko belongs to a class of drugs called CFTR modulators. These drugs target specific defects in the CFTR protein so it can work properly.1

Symdeko is a combination of 2 drugs that work in 2 different ways to help the CFTR protein move chloride across a cell surface. It is used to treat people with more than 154 specified CFTR mutations.1

Tezacaftor is what is known as a corrector. It helps the CFTR protein form the correct shape so it can move to a cell’s surface. Once there, not enough of the CFTR protein gets to the cell surface to move enough chloride to the surface. That is why another CFTR modulator, ivacaftor is added.2

Ivacaftor is a potentiator (which is a type of modulator), and it works differently than a corrector. Ivacaftor holds the “gate” on the cell surface open long enough for the chloride to pass through. Combined, these 2 modulators reduce the symptoms of CF by rehydrating the thick, sticky mucus which makes it thinner.2

Symdeko works only for a long as it is in the body, or about 12 hours. That is why it is taken every 12 hours. Tezacaftor/ivacaftor does not completely restore proper chloride flow in the cells or reverse lung damage, but it does reduce the symptoms of cystic fibrosis.1,2

Why genetic testing is important in cystic fibrosis

CFTR modulators are designed to correct the specific type of malfunction that certain CF mutations cause. If you do not have one of these mutations, Symdeko will not work to correct why your CFTR protein fails to carry chloride through cells. This is why it is important to know which genetic mutation for CF you have. If you do not know your mutation, the Cystic Fibrosis Foundation offers free genetic testing for people with cystic fibrosis.3

What are the possible side effects of Symdeko?

The most common side effects of Symdeko include:1

  • Headache
  • Nausea
  • Sinus congestion
  • Dizziness

These are not all of the possible side effects of Symdeko. Talk to your doctor about what to expect or if you experience any changes that worry you.

What are the ingredients in Symdeko?

The active ingredients in Symdeko are:

  • tezacaftor
  • ivacaftor

Things to know about Symdeko

Some younger people taking Symdeko have developed cataracts while taking one of the ingredients of Symdeko, ivacaftor. Before starting this drug, younger people may need a baseline eye exam and follow-up exams.1

Symdeko can be hard on the liver, so people taking it should be regularly tested for elevated transaminase (AST and ALT) These are enzymes that the liver leaks into the bloodstream at higher levels when it is damaged.1

Doctors do not know yet if Symdeko is safe to take during pregnancy or while breastfeeding. Before using this drug, tell your doctor if you are pregnant, plan to become pregnant, or are breastfeeding.1

Symdeko can interact with other drugs. Before taking it, tell your doctor about any other medicines you take, including over-the-counter vitamins and supplements.1

Symdeko should be taken with fat-containing foods. Examples of fat-containing foods include:

  • Eggs
  • Butter
  • Peanut butter
  • Whole milk dairy products

For more information, read the full prescribing information of Symdeko.