|Systematic (IUPAC) name|
|Licence data||US FDA:|
|Half-life||12 hrs (single dose)|
|Mol. mass||392.490 g/mol|
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Ivacaftor (trade name Kalydeco, developed as VX-770) is a drug approved for patients with a certain mutation of cystic fibrosis, which accounts for 4–5% cases of cystic fibrosis. Ivacaftor was developed by Vertex Pharmaceuticals in conjunction with the Cystic Fibrosis Foundation and is the first drug that treats the underlying cause rather than the symptoms of the disease. It is one of the most expensive drugs, costing over $300,000 per year, and doctors who developed the drug have criticized Vertex for charging so much.
Cystic fibrosis is caused by any one of several defects in a protein, cystic fibrosis transmembrane conductance regulator (CFTR), which regulates fluid flow within cells and affects the components of sweat, digestive fluids, and mucus. One such defect is the G551D mutation, in which the amino acid glycine (G) in position 551 is replaced with aspartic acid (D). G551D is characterized by a dysfunctional CFTR protein on the cell surface. In the case of G551D, the protein is trafficked to the correct area, the epithelial cell surface, but once there the protein cannot transport chloride through the channel. Ivacaftor, a CFTR potentiator, improves the transport of chloride through the ion channel by binding to the channels directly to induce a non-conventional mode of gating which in turn increases the probability that the channel is open.
Ivacaftor is approved for use in cystic fibrosis patients in the US, Canada and across some European countries. The US Food and Drug Administration approved Ivacaftor in January 2012 and the European Medicines Agency (EMA) followed soon after.
The cost of ivacaftor is $311,000 per year, which an editorial in JAMA called "exorbitant", particularly because of the support by the National Institutes of Health and Cystic Fibrosis Foundation in its development. Vertex said it would make the drug available free to patients in the United States with no insurance and a household income of under $150,000. In 2012, 24 US doctors and researchers involved in the development of the drug wrote to Vertex, “We have invested our lives and careers toward the success of these inspiring therapeutic agents. We also write with feelings of dismay and disappointment that the triumph and honor that should be yours is diminished by the unconscionable price assigned to Kalydeco." In the UK, the company provided the drug free for a limited time for certain patients, then left the hospitals to decide whether to continue to pay for it for those patients. UK agencies estimated the cost per quality adjusted life year (QALY) at between £335,000 and £1,274,000 —way above the National Institute for Health and Care Excellence thresholds.
The drug was not covered under the Ontario Drug Benefit plan due to the elevated price until June 2014 when the Province of Ontario and the manufacturer negotiated for what "Ontario Health Minister Deb Matthews had called a “fair price” for taxpayers". The negotiations took 16 months and it was estimated that around 20 Ontarians required the drug at the time.
During Phase 3 clinical trials, the STRIVE study demonstrated a 10.6% mean absolute improvement in baseline lung function (FEV1) over a 24 week period and a 10.5% mean absolute improvement in lung function over 48 weeks among those who had the G551D mutation and were treated with Ivacaftor.
The most common adverse reactions experienced by patients who received ivacaftor in the pooled placebo-controlled Phase 3 studies were abdominal pain (15.6% versus 12.5% on placebo), diarrhoea (12.8% versus 9.6% on placebo), dizziness (9.2% versus 1.0% on placebo), rash (12.8% versus 6.7% on placebo), upper respiratory tract reactions (including upper respiratory tract infection, nasal congestion, pharyngeal erythema, oropharyngeal pain, rhinitis, sinus congestion, and nasopharyngitis) (63.3% versus 50.0% on placebo), headache (23.9% versus 16.3% on placebo) and bacteria in sputum (7.3% versus 3.8% on placebo). One patient in the ivacaftor group reported a serious adverse reaction: abdominal pain.
Ivacaftor is extensively metabolised in humans. In vitro and in vivo data indicate that ivacaftor is primarily metabolised by CYP3A. M1 and M6 are the two major metabolites of ivacaftor in humans. M1 has approximately one-sixth the potency of ivacaftor and is considered pharmacologically active. M6 has less than one-fiftieth the potency of ivacaftor and is not considered pharmacologically active.
Following oral administration, the majority of ivacaftor (87.8%) is eliminated in the faeces after metabolic conversion. The major metabolites M1 and M6 accounted for approximately 65% of total dose eliminated with 22% as M1 and 43% as M6. There was negligible urinary excretion of ivacaftor as unchanged parent. The apparent terminal half-life was approximately 12 hours following a single dose in the fed state. The apparent clearance (CL/F) of ivacaftor was similar for healthy subjects and patients with CF. The mean (±SD) of CL/F for the 150 mg dose was 17.3 (8.4) L/h in healthy subjects at steady state.
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- "Kalydeco: Annex I: Summary of product characteristics" (PDF). European Medicines Agency.
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- "FDA Approves KALYDECO™ (ivacaftor), the First Medicine to Treat the Underlying Cause of Cystic Fibrosis" (Press release). Cambridge, Massachusetts: Vertex Pharmaceuticals. 2012-01-31. Retrieved 2014-02-01.
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- FAQs About VX-770 from the Cystic Fibrosis Foundation