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# CFTR modulators

Oral drugs that repair the faulty chloride channel behind cystic fibrosis, chosen according to the patient's CFTR mutations.

Updated Nov 1, 2026

## What they are

Small molecules that improve the function of the CFTR chloride channel, the protein that is defective in cystic fibrosis. Potentiators (ivacaftor) hold the channel open longer once it is at the cell surface. Correctors (lumacaftor, tezacaftor, elexacaftor) help the misfolded protein, typically the F508del variant, reach the membrane. They are prescribed by genotype: ivacaftor alone for gating variants such as G551D, and corrector–potentiator combinations for people with F508del.

## Mechanism of action

CFTR is an ATP-gated chloride channel on the apical surface of epithelial cells in the airways, pancreas, intestine, bile ducts and sweat glands. Chloride flow drives water movement and keeps mucus thin. In F508del the protein misfolds and is destroyed before reaching the membrane; in gating variants it reaches the membrane but rarely opens. Correctors bind the protein during folding and increase how much arrives at the surface; potentiators bind the channel and increase its open probability. Together they restore part of chloride transport.

Target: CFTR (cystic fibrosis transmembrane conductance regulator), an ATP-gated chloride channel

## Key points

- Potentiator = opens the channel (ivacaftor, G551D); corrector = brings the protein to the membrane (elexacaftor, tezacaftor; F508del).
- The choice depends on the patient's CFTR genotype; F508del is the most common variant.
- Liver injury can occur: liver tests are checked before and during treatment.
- Cataracts have been seen in children: eye examinations before and during treatment.
- Metabolised by CYP3A: strong inducers such as rifampicin and St John's wort reduce their effect; grapefruit and strong inhibitors raise levels.

## Drugs in this class

- [**Elexacaftor + tezacaftor + ivacaftor** A triple CFTR modulator: two correctors bring the faulty F508del channel to the cell surface and ivacaftor opens it. CFTR chloride channel (cystic fibrosis transmembrane conductance regulator)](https://durgical.com/en/pharmacology/elexacaftor-tezacaftor-ivacaftor/)
- [**Ivacaftor** The first CFTR potentiator: it opens the chloride channel more often in cystic fibrosis caused by gating variants such… CFTR chloride channel (cystic fibrosis transmembrane conductance regulator)](https://durgical.com/en/pharmacology/ivacaftor/)

## Others in the class

- Lumacaftor + ivacaftor
- Tezacaftor + ivacaftor

## Test yourself

Think of the answer, then tap the question to see it.

## What is the difference between a CFTR potentiator and a corrector?

A potentiator (ivacaftor) increases how often the channel at the surface opens; a corrector (tezacaftor, elexacaftor) helps the misfolded protein reach the membrane.

## Which CFTR variant is most common and which drugs treat it?

F508del; it is treated with corrector–potentiator combinations such as elexacaftor + tezacaftor + ivacaftor.

## Which organ is monitored with blood tests during CFTR modulator therapy?

The liver: transaminases and bilirubin, because liver injury can occur.

## Why can St John's wort make a CFTR modulator fail?

It induces CYP3A and lowers the drug levels.

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Educational content on how drugs work; not a prescribing guide and no substitute for a health professional's advice. No doses are given.

Sources: [Elexacaftor, Tezacaftor, and Ivacaftor: MedlinePlus Drug Information](https://medlineplus.gov/druginfo/meds/a619061.html) (MedlinePlus (U.S. National Library of Medicine), 2026); [CFTR gene: MedlinePlus Genetics](https://medlineplus.gov/genetics/gene/cftr/) (MedlinePlus (U.S. National Library of Medicine), 2026).

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Representative model, for educational purposes only.

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