Copper Balance in Healthy Participants Administered ALXN1840

Inclusion Criteria:

1. Have regular bowel movements (at least once per day).
2. Adequate venous access in the left or right arm to allow collection of study-required blood samples.
3. Willing and able to adhere to all dietary requirements of the study.
4. Body weight between 50 to 70 kilograms (kg) (inclusive) for female participants, and 65 to 85 kg (inclusive) for male participants, and body mass index within the range 18 to 25 kg/meters squared (inclusive).
5. Willing and able to follow protocol-specified contraception requirements.
6. Capable of giving signed informed consent.

Exclusion Criteria:

1. Significant medical history (current or past).
2. History or presence of gastrointestinal conditions including chronic constipation and irritable bowel syndrome.
3. Supine blood pressure ≤ 90/60 millimeters of mercury (mmHg) or > 140/90 mmHg.
4. Lymphoma, leukemia, or any malignancy within 3 years.
5. Breast cancer within the past 10 years.
6. Alanine aminotransferase, aspartate aminotransferase, or total bilirubin > upper limit of normal at Screening.
7. Serum copper or serum ceruloplasmin below lower limit of normal on laboratory reference range at Screening.
8. History of anemia or hemoglobin < 130 gram (g)/Liter (L) for men and hemoglobin < 115 g/L for women at Screening.
9. History of benign ethnic neutropenia or absolute neutrophil count < 1500/microliter (uL); lymphocyte count below 1000/uL.
10. QTcF> 450 millisecond (ms) for men and QTcF> 480 ms for women.
11. Current or chronic history of liver disease or known hepatic or biliary abnormalities (except for asymptomatic gallstones).