Elexacaftor/tezacaftor/ivacaftor
Elexacaftor/tezacaftor/ivacaftor, sold under the brand names Trikafta (US) and Kaftrio (EU), is a fixed-dose combination medication used to treat cystic fibrosis. Elexacaftor/tezacaftor/ivacaftor is composed of a combination of ivacaftor, a chloride channel opener, and elexacaftor and tezacaftor, CFTR modulators.It is approved for use in the United States for people aged six years and older who have cystic fibrosis with a F508del mutation or other mutations in the CFTR gene. It is also approved for use in Canada, the European Union and Australia.

Medical uses
The combination is indicated for the treatment of people aged six years and older who have cystic fibrosis with a F508del mutation or other mutations in the CFTR gene.

Side effects
The most common side effects affecting more than 5% of patients are headache, upper respiratory tract infection, abdominal pain, diarrhea, rash, alanine aminotransferase increased, nasal congestion, blood creatine phosphokinase increased, aspartate aminotransferase increased, rhinorrhea, rhinitis, influenza, sinusitis and blood bilirubin increased.

Interactions
Concomitant use with CYP3A inducers is not recommended. Dosage must be adjusted with moderate or strong CYP3A inhibitors.Other drugs with the potential for interaction include: warfarin, digoxin, statins, glyburide, nateglinide, repaglinide.

Pharmacology
Cystic fibrosis and CFTR
Cystic fibrosis is an autosomal recessive genetic disorder of the CFTR protein which reduces chloride and sodium ion transport through the cell membrane, causing thicker than normal mucus secretions. The CFTR protein is found in epithelial cells of the lung, liver, pancreas, digestive tract, and reproductive tracts. CFTR has a role in the production of mucus, sweat, and digestive fluids. The thickened mucus can lead to inflammation, respiratory infections, and clogged ducts.

Mechanism of action
Elexacaftor/tezacaftor/ivacaftor is a tridrug treatment in which the medications work together to increase the transport of chloride and sodium ions, and reducing thick mucus production.

CFTR channel potentiator
Ivacaftor is a selective small-molecule potentiator of the CFTR protein that increases the proteins ability to open chloride channels. Its effectiveness is highly dependent on the amount of CFTR protein at the cell surface and the responsiveness of the mutant CFTR protein. Ivacaftors primary target is to treat class III CFTR gating mutations like G551D as well as other less common mutations. In the crystalline figure, you can see ivacaftor, shown as a gray ball and stick model on the bottom-right, bound to CFTR docked in a cleft formed by transmembrane helices at the protein-lipid interface.

CFTR correctors
Elexacaftor and Tezacaftor act as CFTR correctors to repair F508del processing by binding to the CFTR protein to increase the availability of CFTR protein on the cell surface. They work by modulating the position of the CFTR protein into the right position on the cell surface.The combination of increased CFTR protein in the correct position on the cell surface with ivacaftors potentiation of chloride channel opening results in increased transport of chloride and thinned mucus secretions.

Pharmacokinetics
Elexacaftor/tezacaftor/ivacaftor is primarily metabolized by CYP3A4 /5. This medication should be taken with a high fat meal to improve absorption through the gut. It is excreted as metabolites or unchanged mainly through feces and to a smaller extent urine. The mean effective half-life of elexacaftor, tezacaftor, and ivacaftor is 27.4 hours, 25.1 hours, and 15 hours, respectively.

History
A phase III trial showed people treated with elexacaftor/tezacaftor/ivacaftor improved in FEV1 at four weeks with sustained improvement at 24 weeks. Rate of pulmonary exacerbation was 63% lower and sweat chloride concentration was 41.8 mmol/L lower. Its effectiveness is dependent on the type of CF mutations the patient has.

Society and culture
Legal status
United States
The combination was approved for use in the United States in 2019 for people twelve years and older with cystic fibrosis who have at least one F508del mutation in the cystic fibrosis transmembrane conductance regulator (CFTR) gene, which is estimated to represent 90% of the cystic fibrosis population. In December 2020, after an additional clinical trial was completed, and FDA approval was expanded for 177 other cystic fibrosis mutations. FDA approval for children aged 6–11 was added in January 2021, after a third clinical trial was completed.The U.S. Food and Drug Administration (FDA) granted the application priority review, in addition to fast track, breakthrough therapy, and orphan drug designations. The drugs manufacturer Vertex Pharmaceuticals will receive a rare pediatric disease priority review voucher for having developed this therapy.

Australia
In March 2021, health regulators in Australia approved trikafta for patients aged 12 years and older with at least one copy of the F508del mutation. At the end of April 2022, it was placed on PBS, thus reducing the cost from tens of thousands of dollars a month, to tens of dollars a month.

Canada
In June 2020, Health Canada approved Trikafta for patients ages 12 and up. In September 2021, the provinces Alberta and Saskatchewan announced they will join Ontario in funding the medication. They will determine coverage on a case-by-case basis using criteria that has not yet been announced.

European Union
In June 2020, the Committee for Medicinal Products for Human Use (CHMP) of the European Medicines Agency (EMA) recommended its approval for the treatment of cystic fibrosis. It was approved for medical use in the European Union in August 2020.

Norway
On 25 April 2022, Beslutningsforum for nye metoder approved Kaftrio for treatment of cystic fibrosis.

New Zealand
In February 2022, Pharmac recommended, with medium priority, funding for patients age 12 and above.

Spain
In November 2021, the Spanish government approved the reimbursement of Kaftrio for patients ages 12 and older with at least one copy of the F508del mutation.

Economics
United States
The list price of a years treatment in the US is US$311,000. However, a 2020 report by Institute for Clinical and Economic Review found that the price has made the treatment not cost effective and that "an appropriate health-benefit price would range from $67,900–$85,500 per year".

Australia
Following the listing of Trikafta on the Pharmaceutical Benefits Scheme in 2022, the cost for CF patients 12 years or older who have at least one F508del mutation in the cystic fibrosis transmembrane conductance regulator gene is $42.50 per month, or $6.80 for concession card holders.

Research
CFTR mutations that are responsive to elexacaftor/tezacaftor/ivacaftor were determined by an in-vitro study of Fischer Rat Thyroid (FRT) cells that expressed mutant CFTR. Elexacaftor/tezacaftor/ivacaftor showed effectiveness with mutations where the CFTR protein was being successfully delivered to the cell surface.

References
External links
"Elexacaftor". Drug Information Portal. U.S. National Library of Medicine.
"Ivacaftor regimen with Tezacaftor". Drug Information Portal. U.S. National Library of Medicine.