Transthyretin amyloidosis (ATTR) is a disease where the normally occurring transthyretin (TTR) protein falls apart and forms amyloid, a sticky plaque-like substance that accumulates in different organs in the body and can cause damage to the organ. There are two ways that the TTR protein can fall apart. One way occurs as a person ages, where the normal TTR protein can fall apart and form amyloid that may no longer be sufficiently cleared by the body. This type of ATTR is known as wild-type ATTR (ATTRwt). The other way occurs when a person inherits a defective TTR gene that causes the TTR protein to spontaneously fall apart. This form of the disease is known as variant ATTR (ATTRv) and can be detected in adults by a genetic test of their TTR gene before they age.

Amyloid build-up in the heart causes the heart wall to become thick and stiff and can result in heart failure and even death. Accumulation of TTR amyloid in the heart is known as transthyretin amyloid cardiomyopathy or ATTR-CM. Amyloid can also deposit in the nerve tissues leading to nerve problems. Accumulation of TTR in the nerves is known as transthyretin amyloid polyneuropathy or ATTR-PN.

Acoramidis is an experimental drug designed to bind tightly to TTR in the blood and stabilize its structure, so it does not form the harmful amyloid plaques that can cause damage to organs.

This study is intended to determine if treatment with acoramidis in participants with ATTRv who have not yet developed any symptoms of disease can prevent or delay the development of ATTR-CM or ATTR-PN disease. If adults with an inherited defective TTR gene are treated early before any of the symptoms of disease have developed, it may be possible to delay the onset or prevent the disease entirely.

The AG10-501 ACT-EARLY study is a randomized, multicenter, double-blind, placebo-controlled study of acoramidis for prevention of ATTR (with specific reference to either its cardiomyopathic or polyneuropathic manifestations). Participants will be stratified at randomization.

The study population will be asymptomatic carriers of a known pathogenic TTR gene variant. A participant must be 18 to 75 inclusive years of age, and the age of the participant must be within 10 years younger than or older than the predicted age of disease onset (PADO) based either on family history (pedigree analysis) or, if family history is insufficient, based on a TTR Variant Actuarial table from published literature. For example, if PADO for a given individual is found to be 50 years, the age of the participant must be between 40 and 75 years inclusive.

Key Inclusion Criteria:

• Male or female ≥ 18 to ≤ 75 years of age inclusive.
• Participants must have an established genotype (hetero- or homozygosity) through a medically-indicated genetic test of a TTR gene variant that is known to be pathogenic or likely pathogenic (eg, V30M/p.V50M, V122I/p.V142I, T60A/p.T80A, or all other pathogenic TTR variants).
• Participant's age is within 10 years younger than or older than PADO.

Key Exclusion Criteria:

• Evidence of ATTR-CM or ATTR-PN.
• Current or past (within last 1 to 12 months, depending on specific agent) treatment with other TTR modifying therapies.
• Contraindication to or inability to undergo cardiac magnetic resonance testing.
• Major organ dysfunction, including: kidney disease, liver disease, heart disease (including cardiomyopathy), neuropathy
• Other diseases or conditions such has cancer within 5 years, untreated hyperthyroidism or hypothyroidism, type 1 diabetes, active hepatitis B or C, HIV.
• Major surgery within the past 3 months or planned during the next 12 months.
• Known hypersensitivity to acoramidis.