A Research Study to Look at How a New Medicine Called NNC6019-0001 Works and How Safe it is for People Who Have Heart Disease Due to Transthyretin (TTR) Amyloidosis

Inclusion Criteria:

   - Male or female.

   - Age greater than or equal to (>=) 18 to less than (<) 85 years at the time of signing
   informed consent.

   - Have an established diagnosis of Transthyretin amyloid cardiomyopathy (ATTR CM) with
   either wild-type transhyretin (TTR) or hereditary transthyretin (TTR) genotype as per
   local standards.

   - Expected to be on stable doses of cardiovascular medical therapy 6 weeks prior to the
   randomisation visit.

   - Known end-diastolic interventricular septal wall thickness greater than or equal to
   (>=) 12 millimeters (mm).

   - Presently classified as New York Heart Association (NYHA) Class II-III.

   - N-terminal-pro brain natriuretic peptide (NT-proBNP) concentration greater than or
   equal to (>=) 650 picograms per milliliter (pg/mL) in sinus cardiac rhythm and greater
   than (>) 1000 pg/mL in atrial fibrillation at screening.

   - Completed greater than or equal to (>=) 150 meters to less than or equal to (<=) 450
   meters on the 6-minute walk test (MWT) at screening.

   - Estimated glomerular filtration rate (eGFR) greater than or equal to (>=) 25
   milliliter per minute per 1.73 meter square (mL/min/1.73 m^2) at screening.

Exclusion Criteria:

   - Cardiomyopathy not primarily caused by transthyretin amyloid cardiomyopathy
   transthyretin amyloid cardiomyopathy (ATTR CM), for example, cardiomyopathy due to
   hypertension, valvular heart disease, or ischemic heart disease.

   - A prior solid organ transplant.

   - Planned solid organ transplant during the study.

   - Presence or history of malignant neoplasm (other than basal or squamous cell skin
   cancer, insitu carcinomas of the cervix, or in-situ/high grade prostatic
   intraepithelial neoplasia (PIN) or low-grade prostate cancer) within 5 years before
   screening.

   - Current treatment with calcium channel blockers with conduction system effects
   (example [e.g.], verapamil, diltiazem). The use of dihydropyridine calcium channel
   blockers is allowed. The use of digoxin will only be allowed if required for
   management of atrial fibrillation with rapid ventricular response.

   - Acute coronary syndrome, unstable angina, stroke, transient ischemic attack (TIA),
   coronary revascularization, cardiac valve repair, or major surgery within 3 months of
   screening.

   - Body weight >120 kilogram (kg) (264.6 pounds [lb]) at screening.

   - History of contrast allergy or adverse reactions to gadolinium-containing agents.