This is an open-label study to assess the absorption, metabolism, excretion, and mass balance of a single oral dose of carbon-14 ([14C])-ALXN2050 in healthy adult males.

Inclusion Criteria:

1. No clinically significant medical history, physical or neurological examination findings, screening clinical laboratory profiles, or electrocardiogram findings.
2. Body mass index in the range of 18.0 to 32.0 kilograms (kg)/meter squared, inclusive, with a minimum body weight of 50.0 kg at screening.
3. Non-sterile participants must agree to abstinence or use a highly effective method of contraception.

Exclusion Criteria:

1. History of any medical or psychiatric condition or disease that might limit the participant's ability to complete or participate in this clinical study, confound the results of the study, or pose an additional risk to the participant by their participation in the study.
2. History or presence of drug or alcohol abuse within previous 2 years, current user of tobacco/any nicotine-containing product, or positive drugs-of-abuse screen or alcohol screen at screening or Day -1 of Period 1.
3. History or presence of seizures, head injury, or head trauma.
4. History of procedures that could alter absorption or excretion of orally administered drugs.
5. History of meningococcal infection, or has a first-degree relative with a history of meningococcal infection.
6. Body temperature ≥ 38.0°Celcius at screening or check-in.
7. Donation of whole blood from 3 months prior to first dosing or of plasma from 30 days before first dosing, or receipt of blood products within 6 months prior to first dosing.
8. Has less than 1 bowel movement every 2 days or has a recent history of abnormal bowel movements, such as diarrhea, loose stools, or constipation, within 2 weeks prior to dosing.
9. Has received radiolabeled substances or has been exposed to radiation sources within 12 months of dosing or is likely to receive radiation exposure or radioisotopes within 12 months of dosing such that participation in this study would increase their total exposure beyond the recommended levels considered safe.
10. Participation in any other investigational study drug trial in which receipt of an investigational study drug occurred within 5 half-lives (if known) or 30 days prior to dosing, whichever is longer.