A biopsy-based pilot clinical study: monitoring the effectiveness of tafamidis treatment of patients with transthyretin amyloid cardiomyopathy

Abstract Background Transthyretin amyloid cardiomyopathy (ATTR-CM) is a rare and progressive disease associated with high mortality. It is caused by the accumulation of TTR amyloid protein in various tissues, including the myocardium. Tafamidis is currently the only approved therapy for ATTR-CM. The results of the phase III ATTR-ACT trial showed lower rates of mortality and hospitalization, besides lower rate of decline for both quality of life (QoL), and 6-minute walk test (6mwt) distance [1]. Whether the reported clinical outcomes represent a change in myocardial ATTR-accumulation and remodeling remains unclear. Here we monitor the clinical outcome and the corresponding myocardial histological changes of tafamidis-treated patients using endomyocardial biopsy (EMB). Methods Eleven patients with EMB-proven ATTR-CM, 10 wild type, 1 hereditary, 9 males, 2 females age= 77±9 years, were prescribed with 61 mg tafamidis once daily indefinitely. The course of the disease was evaluated via EMB, 99mTc-DPD scintigraphy, cardiac magnetic resonance imaging (cMRI), echocardiography, 6mwt, Minnesota QoL questionnaire and serum N-terminal pro brain natriuretic peptide (NT-proBNP) analysis, at baseline and after 321±72 days of treatment (ethics application number EA2/140/16). EMBs were examined via immunohistochemistry and Imaging mass spectrometry. All patients received standard heart failure medications. Paired clinical measurements were compared via paired t test for parametric data or Wilcoxon rank test for non-parametric data. Results Following the course of treatment, EMB ATTR-positive area measured via immunohistochemistry increased by 7.7±9.5% (p