A 58-year-old man presents with progressive dyspnea, orthopnea, and peripheral edema for 6 months. Echocardiography shows restrictive cardiomyopathy with biopsy-proven cardiac amyloidosis (transthyretin type). What is the drug of choice for slowing disease progression?

Explanation

## Management of Transthyretin (TTR) Amyloidosis **Key Point:** Tafamidis is a transthyretin stabilizer and the first-line disease-modifying therapy for both wild-type and hereditary TTR amyloidosis, particularly cardiac amyloidosis. ### Mechanism of Tafamidis Tafamidis binds to transthyretin and stabilizes the native tetrameric structure, preventing dissociation into monomers that misfold and aggregate into amyloid fibrils. This halts disease progression and improves cardiac function and survival in TTR-CA (cardiac amyloidosis). ### Clinical Evidence - **ATTR-ACT trial** demonstrated that tafamidis reduced all-cause mortality by 29% and cardiovascular hospitalizations by 32% in wild-type TTR-CA - Improves functional capacity (6-minute walk distance, NYHA class) - Well-tolerated with minimal adverse effects - FDA-approved and now standard of care in most developed health systems ### Role of Other Agents in TTR Amyloidosis | Agent | Indication | Role | |-------|-----------|------| | **Tafamidis** | TTR-CA (wild-type & hereditary) | First-line stabilizer | | **Diflunisal** | Hereditary TTR polyneuropathy | Alternative stabilizer (less effective than tafamidis) | | **Inotersen** | Hereditary TTR polyneuropathy | Antisense oligonucleotide (not for cardiac) | | **Patisiran** | Hereditary TTR polyneuropathy | siRNA therapy (not for cardiac) | | **Colchicine** | AA amyloidosis (secondary) | Reduces SAA production | | **Melphalan + ASCT** | AL amyloidosis | Chemotherapy + stem cell transplant | **High-Yield:** Tafamidis is disease-modifying for TTR-CA and reduces mortality — it is now preferred over supportive care alone. **Clinical Pearl:** In hereditary TTR polyneuropathy, inotersen and patisiran are alternatives, but tafamidis remains first-line for cardiac involvement due to superior cardiac outcomes data. ## Why Tafamidis Is Correct Tafamidis directly addresses the pathophysiology of TTR amyloidosis by stabilizing the transthyretin tetramer, preventing amyloid formation and disease progression. It is the only agent with proven survival benefit in cardiac amyloidosis and is guideline-recommended as first-line therapy.