Efficacy and Safety of ALXN1840 Administered for 48 Weeks Versus Standard of Care in Participants With Wilson Disease

Key Inclusion Criteria:

• Established diagnosis of WD by Leipzig-Score ≥ 4

• Female participants of childbearing potential, if heterosexually active, must bewilling to follow protocol-specified guidance for highly effective contraceptionstarting at least 6 weeks before the Day 1 visit and continuing through 28 daysafter the last dose of either ALXN1840 or SoC

• Male participants, if heterosexually active, must be willing to followprotocol-specified guidance for highly effective contraception beginning at Day 1visit and continuing through 90 days after last dose of either ALXN1840 or SoC

Key Exclusion Criteria:

• Decompensated hepatic cirrhosis

• MELD score > 13

• Modified Nazer score > 7

• Clinically significant gastrointestinal bleed within past 3 months

• Alanine aminotransferase > 2 X upper limit of normal (ULN) for participants treatedfor > 28 days with WD therapy (Cohort 1)

• Alanine aminotransferase > 5 X ULN for treatment-naïve participants or participantswho have been treated for ≤ 28 days (Cohort 2)

• Marked neurological disease requiring either nasogastric feeding or intensiveinpatient medical care

• Hemoglobin < 9 grams/deciliter

• History of seizure activity within 6 months prior to informed consent

• Pregnant (or women who are planning to become pregnant) or breastfeeding women

• Active infection with hepatitis B virus (positive hepatitis B surface antigen) or Cvirus or seropositivity for human immunodeficiency virus (HIV)

• Previous treatment with tetrathiomolybdate

• Participants with end-stage renal disease on dialysis (chronic kidney disease stage

5. or creatinine clearance < 30 milliliter/minute