Rate of Uptake of Ivacaftor Use after FDA Approval among Patients Enrolled in the United States Cystic Fibrosis Foundation Patient Registry

Abstract

Chronic cystic fibrosis (CF) therapies have variable rates of prescribed use, and therapies are rarely prescribed to more than 80% of eligible patients. Ivacaftor was approved in the United States in January 2012 for patients ages 6 years and older with a G551D mutation in their CF gene. To examine the rate of uptake and patterns of documented ivacaftor use among U.S. patients with CF during the first year after approval, to compare eligible patients with and without reported use, and to describe characteristics of early adopters of ivacaftor use. A cross-sectional study of patients in the U.S. Cystic Fibrosis Foundation Patient Registry in 2012 with at least one encounter in which ivacaftor use was documented. Ivacaftor-eligible patients were defined as any individual 6 years of age or older with a G551D mutation. We performed bivariate and multivariate regression analyses, stratified by age group, to compare clinical and demographic characteristics of (1) eligible patients with and without documented ivacaftor use in 2012 and (2) early (February-June) versus late (July-December) adopters in 2012. A total of 1,087 patients with CF with G551D mutations were in the U.S. Cystic Fibrosis Foundation Patient Registry in 2012. By June 2012, 64% of eligible patients had documented ivacaftor use, which increased to 81% by the end of 2012. Among eligible patients younger than 18 years of age, 85% were prescribed ivacaftor, with significantly lower odds among those with higher BMI percentile, fewer clinical encounters in 2011, and later age at diagnosis. Among eligible patients age 18 years or older, 79% were prescribed ivacaftor, with significantly lower odds in nonwhite patients and those with later age at diagnosis. Documented prescriptions of ivacaftor also varied by state of residence, with a range of 42-100% of eligible patients across states. The only association with early adoption of ivacaftor in 2012 was a decreased likelihood in adults with fewer than four encounters in 2011. Uptake of ivacaftor use among eligible patients in the United States was rapid, with the majority of use initiated within 4 months of regulatory approval. Differences in ivacaftor prescriptions appear to be related to patient age, older age at diagnosis, and less frequent clinical encounters. Nutritional status also appears to play a role in children, and race seems to have an association in adults.