Safety, Efficacy, and Pharmacokinetics of Tafamidis in Patients With Transthyretin-mediated Amyloidosis Post Orthotopic Heart Transplantation

Transthyretin cardiac amyloidosis (ATTR-CA) is a relentlessly progressive disease that can progress to end stage heart failure, at which point recently approved transthyretin production silencing or structure stabilizing therapies provide no clinical benefit. For well-selected individuals, heart transplantation is an excellent therapeutic option to improve survival. Historically, concomitant liver transplantation has been used to halt the progression of non-cardiac transthyretin amyloidosis (ATTR) manifestations, especially for individuals with TTR genotypes associated with significant neuropathy. However, despite this, patients continue to experience progressive non-cardiac manifestations, particularly gastrointestinal and neuropathic, which can have a substantial influence on post-heart transplantation morbidity. Concomitant liver transplantation is also associated with substantial morbidity and its future therapeutic role is questionable with recently established therapies for ATTR. Therefore, there is a clear unmet need to determine the utility and safety of ATTR targeted therapies for patients with recent heart transplantation for end-stage ATTR-CA. The central hypothesis of this proposal is that in patients who have received a heart transplantation for end-stage ATTR-CA, tafamidis therapy will be efficacious and well-tolerated. We aim to determine the safety and efficacy of tafamidis in stable patients who have undergone heart or combined heart/liver transplantation for ATTR (wild-type or variant) cardiac amyloidosis. The proposed study will be a single-arm intervention clinical trial with tafamidis. Because of the efficacy of tafamidis for both variant ATTR-CA and wild-type ATTR-CA, there is no clinical equipoise for an inactive-comparator placebo arm. The primary endpoint of this study will be serial change in plasma transthyretin (TTR) levels from baseline to 12 months at 3-month intervals. The secondary endpoints of this study will include serial changes in neuropathy assessments, modified body mass indices, incident transplant-specific adverse events, and pharmacokinetics of tafamidis. Observations from this study will establish the role of tafamidis use for the management of ATTR in patients after transplantation for end-stage ATTR-CA.