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

An AE was any untoward medical occurrence in a participant administered the study drug and which did not necessarily have a causal relationship with this treatment. TEAEs were defined as those AEs with onset after the first dose of randomized treatment or existing events that worsened in severity after the first dose of randomized treatment. A summary of all Serious Adverse Events and Other Adverse Events (nonserious) regardless of causality is located in the 'Reported Adverse Events' Section.

The UWDRS comprises 3 parts: UWDRS Part I (level of consciousness, item 1), UWDRS Part II (a patient-reported review of daily activity items [disability], items 2 to 11 [10 items in total]), and UWDRS Part III (a detailed neurological examination, items 12 to 34 [23 items in total]). The UWDRS Part II total score was calculated as the sum of Question 2 to Question 11 (each question has range 0 [none] to 4 [severe]). The UWDRS Part II total score ranges from 0 (no disability) to 40 (severe disability), with lower score indicating improvement in condition and a better outcome. Change from baseline was calculated as: postbaseline assessment value - baseline assessment value when both values were not missing.

The UWDRS comprises 3 parts: UWDRS Part I (level of consciousness, item 1), UWDRS Part II (a patient-reported review of daily activity items [disability], items 2 to 11 [10 items in total]), and UWDRS Part III (a detailed neurological examination, items 12 to 34 [23 items in total]). The UWDRS Part I and III was assessed by a neurologist who was blinded to the treatment randomization. The UWDRS Part III total score was calculated as the sum of Question 12 to Question 34. The UWDRS Part III total score ranges from 0 (normal) to 175 (severe disease), with lower score indicating improvement in condition and a better outcome. Change from baseline was calculated as: postbaseline assessment value - baseline assessment value when both values were not missing.

UWDRS Part III Functional Subscale consists of speech, handwriting, arising from chair, and gait from UWDRS Part III. The standardized score of the first 3 items ranges from 0 (normal) to 10 (worst), and standardized transformed score of gait ranges from 0 (normal) to 10 (worst). The average of these scores was used to create the Part III Functional Subscale with a range of 0 (normal) - 10 (worst) with higher scores indicating more functional disability.

UWDRS Part III individual items speech, handwriting, arising from chair, and gait are reported here. For speech (Question 12), original score ranges from 0 (normal) to 4 (unintelligible). For handwriting (Question 20), original score ranges from 0 (normal) to 4 (cannot hold a pen). For arising from chair (Question 27), original score ranges from 0 (normal) to 4 (unable to arise without help). For gait (Question 29), the original score (range: 0 [normal] to 10 [severe condition]) was calculated by summing subscores (0 [normal] to 4 [severe]) of Part A (Right and Left Leg dystonia), B (Ataxia), and C (Parkinsonism).

The CGI-I is a 7-point scale where the clinician assessed how much participant's illness improved or worsened relative to a Baseline state at the beginning of the intervention and rated as: 1, very much improved; 2, much improved; 3, minimally improved; 4, no change; 5, minimally worse; 6, much worse; or 7, very much worse.

The CGI-S is a 7-point scale where the investigator rated severity of participant's illness at the time of assessment, relative to the investigator's past experience with participants who have the same diagnosis. Considering total clinical experience, a participant was assessed on severity of illness at time of rating as: 1, normal, not at all ill; 2, borderline ill; 3, mildly ill; 4, moderately ill; 5, markedly ill; 6, severely ill; or 7, extremely ill.

The MELD score uses the participant's values for bilirubin, creatinine, and the international normalized ratio (INR). The initial MELD score (MELD[i]) is calculated according to the following formula: MELD(i) = 3.78*ln[serum bilirubin (mg/dL)] + 11.2*ln[INR] + 9.57*ln[serum creatinine (mg/dL)] + 6.43. Creatinine, bilirubin, and INR values less than 1.0 are set to 1.0 and creatinine values greater than 4.0 are set to 4.0 when calculating MELD(i). Additionally, creatinine, bilirubin, and INR are rounded to the 10th decimal place prior to performing the calculation. The initial MELD score is then rounded to the nearest integer. The MELD score ranges from 6 (least sick) - 40 (most sick), with higher values indicating more advanced disease.

cNCC = Plasma Total Copper (Cu) [micrograms (µg)/L]-(3.15*ceruloplasmin [milligrams (mg)/L])/63.5 [µg/µmol] For ALXN1840-treated participants, cNCC in plasma corrected for amount of Cu bound to ALXN1840 tripartite complex (TPC) cNCCcorrected = (√cNCC- 0.993)2√Mo, (Mo= molybdenum). In calculation of cNCC and cNCCcorrected following rules apply: - For plasma total Cu concentration <lower limit of quantification (LLOQ), cNCC was considered missing (LLOQ = 20 nanograms [ng]/mL); - Serum ceruloplasmin concentration values <LLOQ are set to 0 (LLOQ = 22.5 mg/L); - Plasma total Mo concentration values <LLOQ are set to 0 (LLOQ = 1 ng/L); - If cNCC calculation produces a negative result, cNCC was considered missing and cNCCcorrected was not derived; - cNCCcorrected was set to 0 when 0.993√Mo > √cNCC.

cNCC [µmol/L] = Plasma Total Cu [µg/L]-(3.15*ceruloplasmin [mg/L])/63.5 [µg/µmol] For ALXN1840-treated participants, cNCC in plasma was corrected for amount of Cu bound to the ALXN1840 TPC using square root-based cNCC correction method: cNCCcorrected = (√cNCC- 0.993)2√Mo, where Mo = molybdenum. In calculation of cNCC and cNCCcorrected following rules apply: - For plasma total Cu concentration values <LLOQ, cNCC was considered missing (LLOQ = 20 ng/mL); - Serum ceruloplasmin concentration values <LLOQ are set to 0 (LLOQ = 22.5 mg/L); - Plasma total Mo concentration values <LLOQ are set to 0 (LLOQ = 1 ng/L); - In cases where cNCC calculation produces a negative result, cNCC was considered missing and cNCCcorrected was not derived; - cNCCcorrected was set to 0 when 0.993√Mo > √cNCC.

cNCC/cNCCcorrected responder was defined as participants who achieved or maintained normalized cNCC/cNCCcorrected concentration (0.8-2.3 μmol) within (at or before) 48 weeks or reached a reduction of at least 25% in cNCC/cNCCcorrected within 48 weeks. Thus, a participant was considered a cNCC/cNCCcorrected responder if they met at least 1 of the following criteria: - Achieved normalized cNCC/cNCCcorrected concentration for 2 consecutive measurements within 48 weeks, for participants who had elevated cNCC concentrations at baseline; - Maintained normalized cNCC/cNCCcorrected concentration within 48 weeks, for participants who had normal cNCC concentrations at baseline; - Reached a reduction of at least 25% in cNCC/cNCCcorrected for 2 consecutive measurements within 48 weeks.