Baseline characteristics and secondary medication adherence among Medicare patients diagnosed with transthyretin amyloid cardiomyopathy and/or receiving tafamidis prescriptions: A retrospective analysis of a Medicare cohort

BACKGROUND: Transthyretin amyloid cardiomyopathy (ATTR-CM) is an underdiagnosed, life-threatening condition that mostly affects older persons. In May 2019, regulatory approval of tafamidis provided the first pharmacologic treatment of ATTR-CM. In the pivotal phase 3 Transthyretin Amyloidosis Cardiomyopathy Clinical Trial (ATTR-ACT), 97.2% of patients were classified as adherent(defined as taking >= 80% of scheduled doses). Given its recent approval, there is limited real-world evidence examining patient adherence to tafamidis. OBJECTIVE: To evaluate adherence patterns, demographics, and clinical characteristics of patients in the United States receiving tafamidis prescriptions through Medicare. Secondarily, we aimed to evaluate concomitant medications filled by this patient population. METHODS: We conducted a retrospective cohort study of US Medicare claims data, limited by the Health Insurance Portability and Accountability Act of 1996, in adult patients with an adjudicated pharmacy claim for tafamidis (tafamidis free acid 61-mg capsule once daily or tafamidis meglumine four 20-mg capsules once daily) between May 1, 2019, and June 30, 2021. Gaps in therapy were measured using day gaps between prescription refills and continuous measure of medication gaps. Implementation adherence was assessed through modified medication possession ratio (MPRm), medication refill adherence (MRA), and proportion of days covered (PDC). Patients were grouped based on Medicare coverage. Patients were analyzed by subgroups based on age and at the zip code level, via distressed communities index quartiles and rural-urban tiers. RESULTS: A total of 3,558 patients who received a prescription fill of a tafamidis formulation were identified using Medicare Fee-for Service (FFS) and Medicare Advantage (MA) claims data from May 1, 2019, to June 30, 2021. The characteristics of this patient population were consistent with published literature, as 98.6% were older than 65 years, 53.4% were between 75 years and 84 years, and 81.5% were male. In the patient population receiving tafamidis refills, adherence was high across all 3 measures, with mean MPRm greater than 90% and mean MRA greater than 80%, across all age groups. Mean PDC adherence rates were 79% or more across all age groups. Concomitant medications were generally indicated for heart failure and thrombosis. Among monotherapy groups with similar demographic makeup, adherence was significantly higher among users of tafamidis free acid vs tafamidis meglumine (P<0.0001 across all mean adherence measures). CONCLUSIONS: Our results demonstrate that real-world adherence to tafamidis in the Medicare population is high, regardless of age, zip code-level socioeconomic quartile, or geography. Adherence was higher among patients receiving tafamidis free acid, suggesting that the enhanced convenience of a single capsule once daily may positively contribute to adherence among patients with ATTR-CM.