Long-term survival with tafamidis in patients with transthyretin amyloid cardiomyopathy
Abstract Background The Tafamidis in Transthyretin Cardiomyopathy Clinical Trial (ATTR-ACT), demonstrated that tafamidis was an effective treatment for patients with transthyretin amyloid cardiomyopathy (ATTR-CM). Tafamidis, at an 80 mg daily dose, was subsequently approved in several countries for the treatment of ATTR-CM. Patients who completed ATTR-ACT were eligible to enroll in an ongoing long-term extension study (LTE) which provides additional data on the long-term efficacy of tafamidis. Purpose To assess the long-term benefit of tafamidis in patients with ATTR-CM and to determine median survival times with treatment. Methods Patients with ATTR-CM who completed ATTR-ACT (in which they were randomized to tafamidis meglumine 80 mg, 20 mg or placebo for 30 months) could enroll in the ongoing LTE in which patients continued to be treated with the same dose of tafamidis or, if previously treated with placebo, were randomized to tafamidis meglumine 80 mg or 20 mg. Tafamidis free acid 61 mg is a new formulation (bioequivalent to tafamidis meglumine 80 mg) developed for patient convenience and all patients in the LTE transitioned to tafamidis free acid 61 mg as of 1 Aug, 2018. All-cause mortality (with heart transplant or cardiac mechanical assist device [CMAD] implantation counted as death) was assessed using a Cox proportional hazards model (as of 1 Aug, 2019). Patients treated with tafamidis meglumine 80 mg in ATTR-ACT and the LTE who transitioned to tafamidis free acid 61 mg (tafamidis 80/61 mg) were compared with patients treated with placebo in ATTR-ACT who transitioned to tafamidis in the LTE (placebo/tafamidis). Results There were a total of 176 tafamidis 80/61 mg patients and 177 placebo/tafamidis patients. Median treatment duration was 51.9 months with tafamidis 80/61 mg and 51.4 months with placebo/tafamidis. With tafamidis 80/61 mg, there were 75 (42.6%) all-cause deaths; consisting of 67 (38.1%) deaths, 6 (3.4%) heart transplants, and 2 (1.1%) CMAD implantations. With placebo/tafamidis, there were 108 (61.0%) all-cause deaths; consisting of 102 (57.6%) deaths and 6 (3.4%) heart transplants. There was a significant reduction of 41.1% in the risk of all-cause mortality with tafamidis 80/61 mg compared with placebo/tafamidis (hazard ratio [95% CI], 0.5888 [0.4370, 0.7931]; P=0.0004). Median survival time with placebo/tafamidis was 35.8 months but was not reached with tafamidis 80/61 mg. Conclusions Treatment with tafamidis significantly improves long-term survival in patients with ATTR-CM. The comparatively poorer survival in patients treated with placebo in ATTR-ACT who transitioned to tafamidis in the LTE highlights the importance of early diagnosis and treatment. Funding Acknowledgement Type of funding source: Private company. Main funding source(s): This study was sponsored by Pfizer.