Tafamidis

Tafamidis is an oral medicine classified as a transthyretin stabiliser. It is used to treat certain forms of transthyretin amyloidosis, a disease in which misfolded transthyretin protein forms amyloid deposits in tissues. Transthyretin is a transport protein produced mainly in the liver that carries thyroxine and retinol-binding protein in the blood. Normally, it circulates as a four-part structure called a tetramer. In transthyretin amyloidosis, this structure can become unstable, allowing the protein to separate into individual units that may misfold and form harmful deposits. Tafamidis binds to transthyretin and stabilises the tetramer, helping reduce its breakdown and the formation of amyloid. Depending on the approved indication and product, it is used for transthyretin amyloid cardiomyopathy, which affects the heart, or hereditary transthyretin amyloidosis with symptomatic polyneuropathy, which affects peripheral nerves. Tafamidis does not remove existing amyloid deposits or cure the underlying genetic condition, but it can slow disease progression and improve important clinical outcomes in eligible patients. Treatment is generally long term and requires specialist assessment, monitoring of symptoms and organ function, and continued management of associated cardiac or neurological complications.

Tafamidis was developed as a small-molecule stabiliser of transthyretin (TTR), targeting the protein instability that contributes to transthyretin amyloidosis. Its clinical development included studies in hereditary transthyretin amyloidosis with polyneuropathy and in transthyretin amyloid cardiomyopathy. The European Medicines Agency (EMA) authorised Vyndaqel in November 2011 for adults with stage 1 symptomatic hereditary transthyretin amyloidosis with polyneuropathy, based on clinical evidence including the Fx-005 study. In 2019, the United States Food and Drug Administration (FDA) approved tafamidis formulations for adults with wild-type or hereditary transthyretin amyloid cardiomyopathy to reduce cardiovascular mortality and cardiovascular-related hospitalisation. The ATTR-ACT phase 3 trial provided key evidence for this cardiac indication. In 2020, the European Union extended the Vyndaqel authorisation to include transthyretin amyloidosis in adults with cardiomyopathy. Approval, formulation and indication details vary between jurisdictions; prescribing decisions should follow the current product information applicable to the patient.

Tafamidis is used for approved forms of transthyretin amyloidosis. In adults with wild-type or hereditary transthyretin amyloid cardiomyopathy (ATTR-CM), it helps reduce cardiovascular mortality and cardiovascular-related hospitalisation. In the European Union, the 20 mg formulation is also authorised for adults with stage 1 symptomatic hereditary transthyretin amyloidosis with polyneuropathy (ATTR-PN), to delay peripheral neurological impairment. The authorised indication depends on the formulation and jurisdiction. Tafamidis is generally used alongside standard supportive care, such as treatment for heart failure and management of neurological symptoms, as appropriate. It is not a substitute for the assessment and treatment of other causes of cardiomyopathy or neuropathy. It is not established as a treatment for amyloidosis caused by proteins other than transthyretin.

Tafamidis is administered orally once daily. For adults with ATTR-CM, the recommended dose in the United States is either tafamidis 61 mg once daily or tafamidis meglumine 80 mg once daily, equivalent to four 20 mg capsules. These formulations are not interchangeable on a milligram-for-milligram basis. In the European Union, the recommended dose for ATTR-CM is generally tafamidis 61 mg once daily, while the authorised regimen for stage 1 ATTR-PN is tafamidis meglumine 20 mg once daily. The correct formulation and dose must be selected according to the indication and local prescribing information. Capsules should be swallowed whole and should not be crushed or cut. If a dose is missed, patients should follow the product instructions and should not take an extra dose to compensate. Treatment is usually continued long term while clinically appropriate, with regular specialist review of disease progression, tolerability and organ function.

Tafamidis is generally well tolerated in clinical studies, and adverse events in patients treated for ATTR-CM were broadly similar to those observed with placebo. Reported adverse effects vary by indication and study population. In patients treated for ATTR-PN, reported events have included diarrhoea, upper abdominal pain and urinary tract infections. Patients may also experience symptoms that arise from the underlying amyloidosis rather than from the medicine itself. Any persistent, severe or new symptom should be discussed with the treating clinician. Patients should not discontinue tafamidis independently, as ongoing treatment may be important for controlling disease progression.

Tafamidis has no formal contraindications listed in the United States prescribing information, apart from known product-specific considerations such as hypersensitivity where applicable. However, important precautions remain. Animal studies indicate that tafamidis may cause fetal harm, so pregnancy or plans to become pregnant should be discussed with the treating clinician. Breastfeeding is not recommended under the United States product information. Tafamidis does not reverse existing amyloid deposits, and patients may continue to experience progression of cardiac or neurological disease despite treatment. New or worsening breathlessness, swelling, fainting, chest discomfort, reduced exercise tolerance or neurological deterioration requires clinical assessment. Treatment decisions should consider the patient's overall clinical condition, the approved indication and the potential benefits and risks. Suspected adverse reactions should be evaluated promptly, and interruption or discontinuation should be guided by the treating specialist.

Before starting tafamidis, clinicians should confirm the diagnosis and determine whether the patient has wild-type or hereditary ATTR-CM, or an authorised form of ATTR-PN. Assessment may include cardiac imaging, laboratory investigations, neurological evaluation and genetic testing where appropriate. Pregnancy and breastfeeding require particular attention because of potential reproductive risks. Tafamidis can affect the disposition of certain medicines, including substrates of breast cancer resistance protein (BCRP); therefore, patients taking BCRP substrates such as methotrexate, rosuvastatin or imatinib may require monitoring for adverse effects and consideration of dose adjustment according to the relevant prescribing information. Patients should provide a complete list of prescription medicines, non-prescription products and supplements. Classic interactions are not extensive, but interaction checks remain important. Monitoring should be tailored to the underlying disease, associated conditions and other medicines being used.

Confirm the amyloidosis subtype and the locally approved indication before prescribing tafamidis, as dosing differs between ATTR-CM and ATTR-PN and between formulations. Explain that treatment stabilises transthyretin and aims to slow disease progression; it does not remove existing amyloid deposits or provide an immediate improvement in symptoms. Review the patient's cardiac or neurological status at baseline and periodically during treatment, coordinating care with cardiology, neurology, genetics and other specialists as appropriate. Check for potential interactions, particularly with BCRP substrates, and review pregnancy and breastfeeding considerations. Reinforce once-daily adherence and explain that the 61 mg tafamidis and 80 mg tafamidis meglumine regimens are not interchangeable on a milligram-for-milligram basis. Advise patients not to crush or cut capsules and not to double a dose after a missed dose. Continue appropriate supportive care and assess new or worsening symptoms rather than assuming that all changes are due to the underlying disease.