Survival in a Contemporary, Real-World Cohort of Patients with Mixed-Phenotype Transthyretin Amyloid Cardiomyopathy Treated with Tafamidis: An Analysis from THAOS

Introduction: Tafamidis is approved to treat transthyretin amyloid cardiomyopathy (ATTR-CM). Many patients with ATTR-CM present with a mixed phenotype of both cardiac and neurologic symptoms, but real-world effectiveness studies of tafamidis in this population are lacking. This study assessed survival and other outcomes in a real-world, contemporary cohort of tafamidis-treated and untreated patients with mixed-phenotype ATTR-CM. Methods: The Transthyretin Amyloidosis Outcomes Survey (THAOS) was a longitudinal, observational, phase 4 study of patients with transthyretin amyloidosis and asymptomatic carriers of pathogenic transthyretin gene variants and was completed in June 2023. This analysis included a contemporary cohort of patients enrolled in THAOS in 2019–2023 who were characterized as having mixed-phenotype ATTR-CM at enrollment. The tafamidis-treated cohort received the approved dose of tafamidis (meglumine 80 mg/free acid 61 mg) throughout the study, and the untreated cohort never received tafamidis. Results: In tafamidis-treated (n = 116) and untreated patients (n = 223), respectively, median age at enrollment was 77.8 and 72.8 years, and 42.2% and 77.6% had variant ATTR-CM. Survival rates at 30 months were 81.5% (95% CI 66.7–90.2) in tafamidis-treated patients and 75.1% (95% CI 66.1–82.0) in untreated patients. Median yearly incidence of cardiovascular-related hospitalizations was 0.89 for tafamidis-treated and 1.70 for untreated patients, and median duration of cardiovascular-related hospitalizations was 7.0 and 11.5 days, respectively. There were 13 (11.2%) and 40 (17.9%) deaths in the respective groups. Conclusion: Patients with mixed-phenotype ATTR-CM treated with the approved dose of tafamidis had numerically higher survival rates, a numerically lower rate of cardiovascular-related hospitalizations, and fewer deaths than untreated patients. These data parallel recent results for patients with predominantly cardiac ATTR-CM from THAOS and extend results of ATTR-ACT to a contemporary, real-world, mixed-phenotype population. Trial Registration: ClinicalTrials.gov