Long-term treatment with Kalydeco (ivacaftor) in people with cystic fibrosis (CF) is associated with a better body mass index, lung function, and a lesser effort required to breath, a small study reports.
The single-site study, “Long‐term effects of ivacaftor on nonpulmonary outcomes in individuals with cystic fibrosis, heterozygous for a S1251N mutation,” was published in the journal Pediatric Pulmonology.
CF is caused by mutations in the CFTR gene, which results in the CFTR protein being made in a “faulty” way or not at all. The CFTR protein acts as an ion gate, and is located on the cell surface to allow the movement of chloride (a component of salt) in and out of a cell.
Some CFTR mutations are classified as gating mutations, because they cause this gate to lock in a closed position, so that chloride cannot get through.
Previous studies reported that while on Kalydeco, CF patients gained in body mass index (BMI, a measure based on height and weight to determine if a person’s weight is healthy), while lowering their resting energy expenditure (the amount of energy needed for normal body functions while resting). Patients’s exercise capacity and duration also seems to improved with Kalydeco’s use.
Researchers at University Medical Center Utrecht, in the Netherlands, now conducted a study to evaluate the effects of long-term Kalydeco treatment in CF patients who are heterozygous for the CFTR gene — meaning, carrying two different forms of the gene — of which one form has a gating mutation, identified as S1251N.
They enrolled seven patients, ages 9 to 26 (mean age of 15.4), including two adults (ages 18 or older). Researchers measured their BMI, lung function, exercise capacity, and resting energy expenditure before starting with Kalydeco (150 mg, two times a day), and again after at least 12 months of treatment.
Results showed that after using Kalydeco for a median of 15 months, CF patients had a higher BMI — mean 21.2 kg/m2 post-treatment versus mean 19.9 kg/m2 at the study’s start.
In this largely pediatric population, the increase in BMI was “attributed to weight gain of both fat mass and lean mass, but also to (height‐)growth in the pediatric individuals,” the scientists wrote.
Lung function, measured as percentage predicted forced expiratory volume in one second (ppFEV1), was found to improve by 16% compared to pre-treatment measures (81.7% ppFEV1 vs. 97.7% after treatment).
Data showed a lesser amount of oxygen being required to exercise during after treatment with Kalydeco, which was likely associated with a “lower work of breathing,” according to researchers. This measure refers to the energy needed to inhale and exhale.
The team believes this lesser effort required to breath indicates a “decrease of small airway disease” with the treatment’s use.
Resting energy expenditure was also seen to be reduced in most patients in the study, although the difference overall was not statistically significant from the study’s start. Yet, researchers believe that any potential differences in energy expenditure might be related to a great ease in breathing.
“The lower work of breathing … could explain the not statistically significant but clinically relevant, reduction of REE [resting energy expenditure] in most of our individuals,” they wrote.
“[T]his study demonstrates that 15 months of ivacaftor in a small group of CF individuals with the S1251N mutation improve BMI and pulmonary function,” the team wrote. “Oxygen uptake reduces after treatment, which may be due to a decrease in work of breathing.”
Given the changes in exercise capacity after Kalydeco treatment, “physical therapy and dietetic intervention should be intertwined adequately to guide and advise individuals with CF to achieve an optimal physical and nutritional status,” the researchers proposed.
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